Maintenance of Distribution network under DHBVNdhbvn.org.in/staticContent/tender/Manual_Handbook_Maintenance-2017.pdfCircuit breaker can be reset (either manually or automatically)

Draft Handbook for Maintenance of Distribution

network, under DHBVN

MAINTENANCE PROCEDURES

Proper maintenance of electrical systems helps in minimizing/preventing unwarranted breakdowns

of Equipment / lines improving the reliability and generating revenue. Periodical or preventive

maintenance is normally followed to keep the equipment continuously in service for desired output.

Condition based maintenance is the most accepted and adopted concept in maintenance now a day’s

which helps in providing advance information about the health of the equipment to take corrective

action in advance.

As the system is growing, it is getting more and more complex. Due to stringent regulations the

utility cannot afford to have breakdowns in the system resulting in interruption of power supply to

the consumer. On the other hand equipment are getting older and are more prone to failure.

Equipment overhaul and major maintenance are also expensive and need to be planned based on the

condition of the equipment rather than on a periodic basis as a routine.

SLD OF 33/11KV SUBSTATION

MAJOR EQUIPMENTS INSTALLED AT 33/11 KV SUBSTATION 1. POWER TRANSFORMER

2. CIRCUIT BREAKER

3. CURRENT TRANSFORMER

4. POTENTIAL TRANSFORMER

5. LIGHTNING (SURGE) ARRESTERS

6. 33 KV LINE ISOLATORS & EARTH SWITCHES

7. BATTERY BANK & BATTERY CHARGERS

8. 11 KV VCB PANELS

9. 33 KV C&R PANELS

10. 33 KV OUT DOOR BUS

11. 11 KV INDOOR BUS

12. APFC PANELS

13. ACDB ( AC-DISTRIBUTION BOARD)

14. ISOLATORS

15. POWER AND CONTROL CABLE

16. CAPACITOR BANK

1. POWER TRANSFORMERS

A transformer is an electrical device that transfers electrical energy between two or more circuits

through electromagnetic induction. Electromagnetic induction produces an electromotive force

within a conductor which is exposed to time varying magnetic. It constitutes the single most

expensive item in a substation.

In order to provide long and trouble free service, it is important that a careful and regular

supervision and maintenance of the transformer and its components is carried out. The frequency

and extent of such a supervision and maintenance is dependent on the experience, climatic

conditions, environment, service conditions, loading pattern etc. All work done on transformers

should be recorded in maintenance register / checklist.

POWER TRANSFORMER USED IN DHBVN

S.

No. RATING

PRIMARY

CURRENT SECONDARY

CURRENT

CURRENT

TRANSFORMR

RATIO 33 KV SIDE

CURRENT

TRANSFORMR

RATIO 11 KV SIDE

1 4 MVA 69.98 Amp 209.94 Amp 200-100/1-1-1 Amp 300-150/5-5-5-5 Amp 2 5 MVA 87.48 Amp 262.44 Amp 200-100/1-1-1 Amp 300-150/5-5-5-5 Amp 3 6.3 MVA 110.22 Amp 330.67 Amp 400-200/1-1-1 Amp 600-300/5-5-5-5 Amp 4 8 MVA 139.97 Amp 419.90 Amp 400-200/1-1-1 Amp 600-300/5-5-5-5 Amp 5 10 MVA 174.96 Amp 524.88 Amp 400-200/1-1-1 Amp 600-300/5-5-5-5 Amp 6 12.5 MVA 218.70 Amp 656.10 Amp 400-200/1-1-1 Amp 900-450/5-5-5-5 Amp

Alarms & Trippings provided for Power Transformers being used in Sub Stations under

DHBVN

S. No. Alarm / Tripping Ratings of Power Transformers

4 MVA 5 MVA 6.3 MVA 8 MVA 10 MVA 12.5 MVA

1 Differential relay

2 Pressure Release Valve

(PRV)

3 Oil Temperature Alarm

(OTA)

4 Oil Temperature Trip

(OTT)

5 Winding Temperature

Alarm (WTA)

6 Winding Temperature Trip

(WTA)

7 Low Oil Level Alarm

(LOLA)

8 Buchholz Alarm (BA)

9 Buchholz Trip (BT)

10 Over Current Relay (O/C)

11 Earth Fault Relay (E/F)

General Supervision in 33/11 Power transformer 1. Dirt and Dust: The external transformer surfaces shall be inspected regularly; and when

required cleaned of dust, insects and other air borne dirt etc.

2. Rust and Treatment: A regular inspection is to be done on the external surface of the

transformer tank and radiators.

3. Mechanical Damage: Checks must be carried out for mechanical damage to the fabrications

and associated equipment. Particular attention should be given to vulnerable areas such as

radiators.

4. Check out all Joints for Signs of Leakage: All joints, both welded and gasketted, must be

checked for signs of oil leakage. If there is any doubt of a leak, the area must be cleaned of oil,

using a suitable solvent (methyl alcohol) and sprayed with liquid chalk.

5. Check for Oil Level: All oil levels associated with the equipment including oil conservator

and all oil filled bushings shall be checked. Also the oil in the oil seal should be maintained.

6. After completing all the checks ensure that all materials or tools, used for maintenance work,

have been removed. All clothes and other debris must be disposed of. The transformer

compound should be left in a clean and tidy condition.

7. Silica Gel Breather: In open breathing transformer, the breather plays active role in

maintaining- the transformer dry by admitting dry air when transformer breathes. In

transformers having air cell or diaphragm, the breather ensures dry air inside the air cell or

above the diaphragm. The silica gel inside the breather becomes pink from bottom to top over a

period of time.

TESTS OF POWER TRANSFORMERS Following test should be carried out before the installation of Power transformer

Polarization index (by Digital Meggar) or Insulation resistance (by Analog meggar)

a) Connect the one lead of meggar at HV side of Transformer and Other one at LV

terminal.

b) Take the IR of 60 Sec and 10 minutes. The ratio of both the results should be greater

than 1 and less than 5.

c) Repeat the same procedure between HV terminal to earth and between LV terminals to

earth.

d) If analog meggar available then just measure the IR of all three condition mentioned

above. It should me 5000MOhm or above for new transformer.

Ratio Test.

a) Connect the ratio meter if available.

b) Connect the one terminal of meter at HV side other at LV side to confirm the ratio.

c) If ratio meter is not available then just connect the supply of 440V to HV side and

measure the voltage at LV side with respect to the ratio of PTR (33/11 kv). The

deviation should not be more than 0.5 %.

Magnetic Balance Test.

a) This test preferably conducted on LV side of Transformer.

b) Connect the supply of 250 volt between (r) phase and neutral (N).

c) Measure the voltage between y-N and b-N. The sum should be equal to supply voltage

d) Repeat the same procedure between y-N and b-N and conform the results.

Vector group test ( for Dyn11)

a) Short the R phase of HV side with r phase of LV side

b) Supply the voltage (440 V) at HV side.

c) Measure the voltage between R-N, N-Y, B-b, B-y, Y-b and Y-y

d) Condition for confirming vector group of Dyn11 is

1) RN + NY = RY

2) Bb < By

3) Yy = Yb.

Transformer Oil Analysis

Dissolved gas Analysis (DGA)

IEC gas ratio analysis

Dual Triangle method

GENERAL LIMITS OF TRANSFORMER OIL TEST

2. CIRCUIT BREAKERS: A circuit breaker is an automatically-operated electrical switch designed to protect an electrical

circuit from damage caused by faults. Circuit breaker can be reset (either manually or

automatically) to resume normal operation.

OPERATING PRINCIPLE

Under fault conditions, current intensity increases multiple times the normal current flow. This

current senses by relay and energized tripping coil of breaker to isolate the system. Circuit breaker

also used to isolate the section manually

Type of circuit breakers used in DHBVN

At 33 KV level 1. Oil circuit Breakers

2. Vacuum circuit breaker

At 11 KV level

1. Vacuum circuit breakers

CIRCUIT BREAKER RATING:The breaking capacity of a circuit breaker depends on

(i) Symmetrical breaking capacity

(ii) Asymmetrical breaking capacity

Symmetrical breaking capacity

It is the rms. Value of the ac component of the fault current that the circuit breaker is capable of

breaking under specified conditions of recovery voltage.

Asymmetrical breaking capacity

It is the rms value of the total current comprising of both ac and dc components of the fault current

that the circuit breaker can break under specified conditions of recovery voltage.

Making Capacity of circuit breakers

The rated making current is defined as the peak value of the current (including the dc component) in

the first cycle at which a circuit breaker can be closed onto a short circuit.

Testing of circuit breakers

BREAKER TIMING

CONTACT RESISTANCE MEASUREMENT

Testing Procedure:

De- energize, discharge the equipment which is to be tested as a safety precaution. .

Check whether Timer leads and associated clips that are to be connected to the breaker

poles are good & tight.

Make the test connections on the lines of circuit diagram

Switch on the power supply to the timer and issue Close command from the timer. Note

down the close timing displayed on the timer

After recommended time interval (3 seconds), issue Open command from the timer.

Note down the open timing displayed on the timer.

Now issue Close-Open (CO) command from the timer. Note down the CO timing

displayed on the timer.

Confirmation of Test:

Breaker opening time should be less than the closing time of the breaker, it should

come in the range of 30-45 ms. while closing time should be 40-60 ms.

CO- time breaker should at the middle of the closing and opening time.

Opening time < closing -Opening time < closing time

Please refer GTP Details of the Breaker for confirmation of the Timing Results.

Inference/Recommendation:

If the specimen breaker satisfies the respective condition then the respective breaker is considered

to be satisfactory. If any deviation is observed from above mentioned condition then corrective

action should be taken with the help of the manufacturer /OEM.

3. CURRENT TRANSFORMERS:

A current transformer (CT) is a type of instrument transformer designed to provide a current in

its secondary winding proportional to the alternating current flowing in its primary. They are

commonly used in metering and protection circuits

Principle

The current transformer works on the principle of variable flux. In the "ideal" current transformer,

secondary current would be exactly equal (when multiplied by the turn’s ratio) and opposite of the

primary current

4. POTENTIAL TRANSFORMERS

http://en.wikipedia.org/wiki/Transformer

http://en.wikipedia.org/wiki/Electric_current

Voltage transformers (VT) or potential transformers (PT) are another type of instrument

transformer, used for metering and protection in high-voltage circuits. Typically the secondary of a

voltage transformer is rated for 110 V at rated primary voltage, to match the input ratings of

protective relays. Ratio test is a routine test of potential transformer, ratio test is recommended during overhaul and

maintenance to check the expected ratio of potential transformer. Limit level of the tests is +- 3 %.

5. LIGHTNING (SURGE) ARRESTERS:

Lightning is one of the most serious causes of over voltage. A lightning rod provides a cone of

protection, which has a ground radius approximately, equal to its height above the ground. The

typical lightning arrester also known as surge arrester has a high voltage terminal and a ground

terminal.

LA voltage rating Corresponding to the system voltage

RATED SYSTEM VOLTAGE

(KV)

HIGHEST SYSTEM VOLTAGE

(KV)

ARRESTER RATING IN KV

FOR EFFECTIVE EARTHED

SYSTEM

11 12 9

33 36 30

66 72.5 60

132 145 120/132

220 245 198/216

400 420 336

Surge Arrestors installed in the substation are intended to divert surges to earth and thus protect

costly switchyard equipment. Proper insulation coordination is necessary for enhancing life span of

costly substation equipment.

6. ISOLATORS & EARTH SWITCHES

Disconnectors have main current carrying arms and operating mechanism for connection and

disconnection. Being off-line devices, they are normally air break type. Normally horizontal double

break, Horizontal center break, Pantograph, Vertical break Disconnectors are in use in EHV

substations.

The alignment of Disconnectors is very important for smooth operation. The limit switches, the

healthiness of auxiliary contacts needs to be checked periodically. The main contacts are to be

inspected and made smooth if any pitting marks seen. All moving parts are to be lubricated for

smooth operation. The gear mechanism and motor normally do not require any maintenance and

manufacturer's' recommendation should be referred for maintenance of gears.

Earth Switches: The earth switch is a safety device and smooth operation is to be ensured by

proper alignment. The earth blade contacts are to be cleaned properly for proper contact and contact

resistance to be measured to ensure healthiness. The earth connection from blade to earth is to be

carefully checked. All the joints should be tightened. Flexible copper braid connections are

provided and healthiness ensured. All moving parts should be lubricated for smooth operation.

7. BATTERY AND BATTERY CHARGERS:

In substation DC supply has equal importance. All protection & indication circuits enable with DC

supply only. Substations generally use Lead Acid batteries / Nickel-Cadmium batteries for DC

supply. Now a days valve regulated lead acid batteries (maintenance free batteries) are also in use

for substation applications.

Battery Chargers: Battery charger is to be maintained for keeping the battery always charged and

also to supply normal DC load for operation.

Rating of Battery bank along with VA capacity used

BATTERY CHARGER DETAIL USED IN DHBVN

VOLTAGE LEVEL VA CAPACITY OPERATING VOLTAGE

33 KV 150 24 Volt/ 50 Volt

8. 11 KV VCB CONTROL AND RELAY PANELS

A circuit breaker is an automatically-operated electrical switch designed to protect an electrical

circuit from damage caused by faults. Circuit breaker can be reset (either manually or

automatically) to resume normal operation.

9. 33 KV CONTROL & RELAY PANELS

33 KV relay & control panels are used to operate 33 KV outdoor circuit breakers. It also used to get

all the monitoring information like breaker on /off status, spring charge, local remote status, trip

circuit healthy information, DC & AC voltage related information etc.

33 KV control panels also include relays for protection & master trip relays also.

10. 33 KV OUT DOOR BUS

33 KV outdoor bus is used to connect incoming lines, power transformers, and outgoing lines etc.

33 KV outdoor bus works as the most visual architecture of a grid substation to interconnect various

substation equipment.

11. 11 KV INDOOR BUS

11 KV indoor bus system includes circuit for LT side of power transformer to 11 KV bus system.

11 KV bus includes 11 KV incomer as the source of power and outgoing feeders as supply source

of energy to the system.

The size of the bus-bar is important in determining the maximum amount of current that can be

safely carried. The bus-bar should be able to carry the expected maximum load current without

exceeding the temperature limit. The capacity of bus should also be checked for maximum

12. APFC PANELS (AUTOMATIC POWER FACTOR CONTROLLERS)

APFC consists of a number of capacitors that are switched by means of contactors. These

contactors are controlled by a controller that measures power factor in an electrical network.

Depending on the load and power factor of the network, the power factor controller will switch the

necessary blocks of capacitors in steps to make sure the power factor a selected value. Power factor

reduce due to high inductive load in system. Presence of this high inductive load power factor

reduces.

Generally on any supply system power demand is varying, power factor also varies as a function of

load requirement. Hence it is difficult to maintain consistent power factor by using fixed

compensation i.e. fixed capacitors. Thus under light load condition it may cause leading power

factor, which results over voltage, Saturation of transformer, Mal-operation of relays, Penalty by

electrical authority .

13. ACDB (AC-DISTRIBUTION BOARD):-

AC supply is required at grid substation for various purpose. It includes.

Supply to ac motor of breakers.

Charging of battery banks

Switch yard lighting system.

Panel lighting system.

Sources of supply for grid auxiliaries.

Normally a local transformer is used for such type of supply. Also a temporary sources also

available at grid level to supply in case of maintenance of local transformer.

EARTHING SYSTEM AT SUBSTATION An earthing system in a sub-station is to provide under and around the sub-station a surface which

shall be at a uniform potential and near zero or absolute earth potential as possible .This provision

ensures that no human being in sub-station is subjected to a shock or injury on occurrence of a short

circuit or development of other abnormal conditions in the equipment

Installed in the yard.

Ground mat is provided below ground level. Earth electrodes are driven into ground at several

points and are connected to grounding mat to form earth mesh. All the structures, Transformers &

other power equipment are connected to this mesh by galvanized steel strips (40x5 mm).

Earth Electrodes is a metal plate, pipe or a conductor electrically connected to earth. Copper,

Aluminum, mild steel, galvanized iron are generally used for electrodes.Generally 40mm dia, 2.6m

long GI/MS rods are used

EARTH MAT: It is formed by steel 75/8 flats laid horizontally at a depth of 0.5 m below surface of ground to form

a mesh of rectangular formation & are welded together. The spacing of earth rods is determined by

required touch & step potential. In addition to earth mat, earth electrodes are used these are also

connected to the mesh. Solid bar risers are welded to mesh and brought up near the equipment

foundations.

BASIS FOR DESIGN OF GROUNDING SYSTEM

Magnitude of fault current

Transient Over voltage

Lightning Protection

Application of Protective devices for selective ground fault protection

Type of load served viz. Motor, Generator etc.

GENERAL GUIDELINES FOR EARTHING

An effective grounding system must satisfy the following conditions:

Provide a low impedance path to ground for personnel and equipment safety.

Withstand and dissipate repeated faults and surge currents

Provide ample corrosion allowance to various chemicals to ensure continuous service during

life of the equipment being protected.

Provide rugged mechanical properties for easy driving of earth electrodes with minimum

difficulty.

All non-current carrying metal parts associated with installation shall be effectively earthed

to a grounding system or mat which will limit the touch and step potential to tolerable

values.

BASIC REQUIREMENT FOR EARTHING:

The current carrying path of earthing system should have enough capacity to carry

maximum fault current.

The resistance of earth & current path should be low enough so as to prevent voltage rise

between N & E.

Step & Touch potential should be within the safe limits.

Systematic survey of earth resistivity should be carried out.

The earth electrodes should be driven in the ground to a sufficient depth.

To obtain sufficient low earth resistance ,

The area of earth mesh is increased.

The spacing of buried rods is reduced.

Soil is kept wet.

The number of earth electrodes are increased.

Earth resistance is reduced by means of Nacl (Common salt), CaCl2 (Calcium chloride),

Na2CO4 (sodium carbonate), CuSO4 (Copper Sulphate), charcoal, soft coal etc.

Method of improving Grounds:

Increasing number of electrodes, creating parallel path.

Increasing depth of driven rod (2.44 m is economical depth).Volume of soil contact

increases. Moisture contact at depth also increases.

Increasing size of driven rod.

Soil treatment with salts. These are effective up to the soil of resistivity 300 ohm

meters. After that other methods are used. One of the most suitable substance for

chemical treatment of soil of very high resistivity for reducing the earth resistance is

Natural Clay, also called Bentonite. It is non corrosive, stable & has a resistivity of 2

Ohm.m at 300% moisture.

33 KV Transmission lines

In DHBVN, HVPNL is the main source of supply, all 33 KV lines come to substations via rail or

RCC pole structure.

Following conductors have been used

S. NO. CONDUCTOR

TYPE AREA

RATED CURRENT

UNDER NORMAL

CONDITION

MVA LOADING (33 KV

LEVEL)

1 WOLF 150 532 26.6

2 LEOPORD 130 386 19.3

3 DOG 100 368 18.4

4 RACCOON 80 344 17.2

5 RABBIT 50 251 12.55

6 WEASEL 30 186 9.3

ITEMS USED IN 33 KV LINES

PCC Pole 11.0M Long.

ACSR Conductor 150mm2

33 KV Pin insulators with pin

11 KV Disc insulators 45KN B&S type

Disc Fitting B&S type

Single Tension Fittings for 130mm2 ACSR Conductor

Suspension Fittings for 130mm2/ 150 mm2 ACSR conductor

U- Bolt for suspension Fitting

PG Clamps for 130mm2 / 150 mm2 ACSR conductor

33 KV Top Brackets / hamper

MS X Arm (Single Pole) 100x50x6 mm (2200mm)

M.S. Channel (X-Arm) 100x50x6mm 3050mm (for H pole)

M.S.Channel 75x40x6 3350mm (for earth wire)

M.S. Angle 50x50x6mm-2860mm (Bracing H. Pole)

M.S Angle 50x50x6mm-2200mm (Belting for H-pole)

Half Clamps

Full Clamps

Stay Sets 8' long complete with X-Plat 460mm of Angle 65x65x6 Elbow & rod with

Disc

Stay wire 7/8 SWG

G.I. Pipe 40 mm dia 6 mtr. Long for earthing

Earthing with Earth rod as per Drawing

GSL 8 SWG

MS Nuts & Bolts

Danger Plates (Enameled)

Number Plates (Enameled)

Phase plate for each phase set of 3 (on each H-Pole & 4-Pole)

Eye Screw Bolts 9”x5/8"

Barbed Wire

"G.I. Strip 25x6 mm 9 meter. For earthling

Knee Bracing - MS Flat 50x6

Catenary wire 7/14 SWG

CI pipe 250 mm diameter 14 mm thick for highway crossing

S/C 630mm2 33kV XLPE cable

End termination kit for S/C 630 sq. mm Cable

33KV Isolators (630 Amps), with clamps

ACSR Conductor 150mm2 (Leopard)

33 KV AB cable 3 Core 185+240 mm2

End termination kit for AB cable 3 Core 185+240 mm2

Dead end calm p assembly with eye hook

Trench (with angle and MS sheet cover) for laying 33 KV XLPE cable in yard

MAINTENANCE OF 33 KV LINES

Normal ground patrolling of lines should be conducted by lines maintenance crew periodically.

Periodicity will be decided on the basis of importance of the line, terrain condition, and proximity

of the line to habitations, forests, gardens, water borne areas etc. and environmental impact on the

line.

During ground patrolling of the line, the patrolman should check for the following

Location no; type of poles (PCC/Rail pole etc.), location address.

Clearances of the line, both to ground and in air.

Availability of all poles and their condition. Obstructions in the proximity of the line

(within line corridor) like trees, branches, structures etc. location wise should be noted.

Observing the condition of insulators, conductors, earth wire, jumpers, clamps,

dampers, spacers etc., with binoculars, from ground level/nearest possible elevated

level.

Special patrolling of the line should be done after momentary tripping of the line on fault, for any

defects. Defects noticed shall be rectified immediately if this can be attended while the line is live

or at the earliest by availing shutdown, anyway, before the defect develops into a major one causing

breakdown. Proper planning of materials and manpower is required in order to carryout rectification

under shutdown in minimum time to avoid/minimize interruption to loads.

Break down maintenance: When a permanent/semi-permanent fault occurs on the line, the line

may break down causing interruption of longer duration. The faults could be snapping of

conductors, disconnection of jumpers, cross-arms/ pole twisting or pole collapse with or without

damage to foundation. This may be due to various reasons like heavy wind due to storms,

weakening of pole due to aging, accidents, thefts etc.

BEST PRACTICES FOR PERSONNEL SAFETY

Electrical Safety Clearance (Live Metal clearance)

Rated Voltage Safety Clearance (meters)

Up to 33kV 0.8

66kV 1

MINIMUM CLEARANCE (IN M) BETWEEN LINES WHEN CROSSING EACH OTHER

MINIMUM CLEARANCE (IN M) BETWEEN LINES WHEN CROSSING EACH OTHER

11-66 KV 110-132 KV 220 KV 400 KV 800 KV

LOW AND MEDIUM 2.44 3.05 4.58 5.49 7.94

11-66 KV 2.44 3.05 4.58 5.49 7.94

110-132 KV 3.05 3.05 4.58 5.49 7.94

220 KV 4.58 4.58 4.58 5.49 7.94

400 KV 5.49 5.49 5.49 5.49 7.94

800 KV 7.94 7.94 7.94 7.94 7.94

GUARDING SYSTEM Guarding means safe guard. This is below the line. In case of conductor snapping, it will touch the

guarding wire before laying on ground or will lay on guarding. The guarding is always earthed. The

line protection will operate and will switch off the line. Snapped conductor will not remain charged.

In absence of guarding, conductor will fall on ground and as no protection is operated, conductor

will remain charged. This will cause accidents. Hence the guarding is very essential.

Types of Guarding:-

P. V. C. Guarding.

Lecing guarding.

11 KV LEVEL

DISTRIBUTION TRANSFORMER

Scope:

This operational guideline is intended to carry out the fundamental checks on Transformer for its

maintenance and while taking it into service. This requires that the concerned SDO should prepare

the action plan and ensure the availability of necessary tools and tackles to carry out this activity.

Prerequisites:

Ensure that necessary permit has been taken. Feeding Sub-station is responsible for providing

outage and PTW. The working party is responsible for ensuring isolation. Ensure that the

transformer is de-energized, isolated & grounded.

Working party should ensure the availability of proper tools and accessories, safety apparels, spares

and consumables required for carrying out the work.

UNDERGROUND CABLES: the underground cable network of any electricity distribution utility

is a vital component of the LV/HV network of the system. It has a several unique benefits over

overhead networks. In particular, they have:

Lower transmission losses.

Can absorb emergency power loads.

Have lower maintenance costs.

Emit no electric field and can be engineered to emit a lower magnetic field than an overhead

line;

Require a narrower band of land to install.

They are less susceptible to the impacts of severe weather.

The reliability of the underground distribution network directly affects the reliability of the overall

system and ultimately the overall customer satisfaction.

Directives & Checks

Abnormality Causes/ Effect Preventive-Corrective action plan

Electrical Stress

1. Flash over due to Phase to phase & Phase

to earth clearance at cable termination Ensure sufficient clearance

2. Termination failure due to Core crossing

above cut back area at cable termination

Ensure core crossing below cut back area

at cable termination

3. Termination failure due to Contaminated

surface of terminations Ensure cleanliness of terminations

4. Cable failure due to Cable testing at high

voltage(DC)

Ensure Testing at Recommended Voltage

(Refer table2)

Mechanical

Stress

1. Stress develop due to Improper Bending

Radius

Ensure Proper Bending radius

(Refer table1)

2. Stress develop due to Mechanical

vibrations

Ensure proper depth

(Refer table3)

3. Stress develop due to Improper cable

supports Ensure proper span length

Thermal Stress 1. Insulation degradation due to overloading Ensure Recommended Loading

Abnormality Causes/ Effect Preventive-Corrective action plan

(Refer table4)

2. Insulation degradation due to Hot spot at

joints & Terminations

Ensure proper Tightening/crimping of

Lugs & Ferrules

3. Insulation degradation due to Improper

Earthing connections

Ensure Cable earthing connected with

Sub-station earthing

External damage Insulation Damaged by external agency Ensure Patrolling of cable routes

Water ingress

Leakage current through the cable insulation/

cable failure, Corrosion in cable conductor

&Armour due ingress of water

Ensure Lug seal to be intact at outdoor

termination.

Minimum permissible Bending radius (Table1)

PILC XLPE

1C 3C 1C 3C

Upto 1.1 KV 20D 15D 15D 12D

1.1 KV to 11 KV 20D 15D 15D 15D

Above 11 KV 25D 20D 20D 15D

‘D’ Diameter of the cable

Table 2: Tests on Cable during Fault Localization, After Repair or when Network Modification is done.

S. No Test UG Cable

1 Meggar Phase toGround and Phase to Phase to be tested with 2.5/5.0 KV

meggar for one minute or till reading stabilized. Minimum IR value

should be 50 M ohms.

2 Hi pot Each phase to be tested @ 6.5 KV DC for 5 minute with respect to

ground with other two phases grounded. The cable must with stand

the test voltage & leakage current should not exceed 2mA

Depth of the cable (Table-3)

Voltage Level Depth of cable

LT cable (1.1kv) 0.6 m

HV cable (11kv) 0.9 m EHV cable (33kv) 1.2 m

EHV cable (66kv) 1.5 m

Current Rating (Table4)- 11 KV XLPE UG Cable

S. No.

Nominal Size of Cable

(Sqmm)

for 11 kV level

Current Carrying Capacity (Amps)

In Ground at 30˚C In Duct at 30˚C In Air at 30˚C

1 3x95 190 165 230

2 3x120 220 190 260

3 3x150 245 210 295

4 3x185 275 240 335

5 3x240 315 275 395

6 3x300 355 310 450

S. No.

Nominal Size of Cable

(Sqmm)

for 11 kV level

Current Carrying Capacity (Amps)

In Ground at 30˚C In Duct at 30˚C In Air at 30˚C

7 1x630 560 480 840

8 1x1000 680 580 1070

HT OVERHEAD LINES

Introduction:

Overhead lines are the most cost effective and frequently used carriers for electric energy. Exposure

to environment accelerates deterioration; if this not detected and repaired quickly, some of it will

degenerate into serious problems with time. To increase line loading and increase quality of power

supply, frequent inspection programs is required to locate and repair any significant failure at the

earliest possible stage.

Frequent failure in the Overhead lines can cause extensive damage to the insulator and other

electrical & earth joints which not only interrupts electricity supply but also results in large revenue

losses. Poor/inadequate maintenance in the areas of pole, span length, non-tension electrical joints,

conductor spacing, line stay leads to the instability in the electrical and mechanical parameter which

reduce the life of the line. With appropriate on site actions, like proper maintenance procedure, the

useful life of the overhead lines can be extended.

Scope:

This operational guideline is intended to carry out the fundamental Line Survey / Checks for its

maintenance and while taking it into service. This requires that the concerned engineer should

prepare the action plan and ensure the availability of required materials, tools and tackles to carry

out this activity.

Prerequisites:

Ensure that necessary permit has been taken from feeding sub-station officer who is responsible for

providing outage and PTW.

The Operating personnel is responsible for ensuring de-energization, isolation and properly

grounding the network where the activity has to be carried out.

Properly Grounding means

All conductor of the isolated working zones, should be shorted with earth by shorting

links at both ends.

The end of the shorting links which are to be connected with conductor & earth terminal

should be fitted with crocodile clip. (Presently all conductor are shorted with safety

chain without earth.A thin layer of Aluminium oxide form on conductor as it expose in

air which behaves like insulator. Due to small surface contact area by the safety chain

&conductor may cause high resistance at the chain contact point causing unusual

behavior. Shorting links should Better performance than safety chain)

If there be any branch line within the working zones, should be isolated/all conductor to

be shorted in similar manner.

If there be any DT within the working zones, the G.O (Gang Operated Switch) of all

DT’s should be OFF to avoid any back feeding from downstream.

During fixing the crocodile clip of shorting links to the conductor, it should be careful :

Before connection the shorting clip to the conductor, the earthing terminal of

the shorting clip should be earth.

Before connecting the shorting clip to a conductor, it (conductor) should be

earth by earth stick & holding the earth stick on the said conductor, the

crocodile clip of shorting links should be fastened with the conductor by

wearing safety gloves & then the earth stick to be removed. Repetition of the

same process of other too conductors must also be ensured.

The Working personnel should ensure the availability of proper tools and accessories, safety

apparels, spares and consumables required for carrying out the work.

Clearance

LV 11 KV

Minimum clearances from any accessible point

The vertical clearance from the highest point 2.5 m 3.7 m

The horizontal clearance from the nearest point 1.2 m 1.2 m

Minimum Ground Clearance Across the street 5.8 m 6.1 m

Along the street 5.5 m 5.8 m

Line erected elsewhere 4.6m 4.6m

Line with Insulated Conductor 4 m 4m

Line crossing 11 KV & LT line 2.4 m

Current carrying capacity of conductor

Size of conductor Current currying capacity in Amp

Dog (100 sqmm/ 1 SWG) 312

Raccoon (80 sqmm/3 SWG) 297

Rabbit (50 sqmm/ 6SWG) 247

Weasel (30 sqmm/ 8 SWG) 114

Maintenance Activity:

General Maintenance

Check visually, the condition of Pole base & alignment of pole. If the pole tilted, should be

straighten & rammed the pole base with brick bats after digging the earth around the pole base. If

any bend occurred at the mid of the pole, has to be changed & pole to be erected as per drawing

attached.

Check visually the condition of existing stay

Check the Condition & size of GI wire. It should be 7/10 SWG.

Check the Condition of Guy/Egg Insulator, if any damage or missing observed, should

be fix/replace.

Check the Condition of tension screw, if any damage observed , it has to be changed

otherwise to tighten the turn buckle ,if required

Check the condition of anchor hook

Check visually the Line Hardware

Condition of Disc Insulator, if there is any crack, flash mark on the surface of the disc,

disc should to be change.

Condition of strain clamp of disc insulator, If any crack or flash mark on surface, it has

to be change.

Condition of Pin insulator, if there be any flash mark on the insulator surface, it has to

be change otherwise check the tightness with the spindle.

Condition of Pin insulator spindle, if any damage or bend, to be change otherwise check

the tightness of the fixing nuts.

Condition of Top hamper; if any tilt observed at top hamper, it has to be straight or any

damage occurred to the metal part, it is to be change, otherwise check the tightness of

fixing nuts bolts.

Condition of the V-arm. if any damage occurred on V-arm or on the fixing clamp, it is

to be changed otherwise check the tightness of the fixing Nuts, bolts

Condition of channel-arm, if any damage occurred on channel-arm or on the fixing

clamp, it is to be changed otherwise check the tightness of the fixing Nuts, bolts.

All metal part to be painted by Primer &Aluminium paint for increasing the durability of

life span. Further all metal parts on the pole of line should be connected to proper earth.

Visual inspection of bare conductor -if any damage occurred on the conductor, it is to be

replaced the damaged portion by same conductor with sleeve joint & the joint is limited

to maximum 2 nos.per span. If any loose, conductor to be re-sagged from section to

section. Also maintain spacing between the conductors.,

Span length should be maximum 40 meter for urban & rural residential area & 60 meter

for rural field area if the length larger than above so mid pole to be provided.

Line should be sectioned at every 4/5 span apart.

Components of an Overhead 11 KV (H.T.) Line of O/H Lines 1. Reinforced cement concrete poles (R.C.C. Poles)

2. Double pole structure

3. Cross – arms

4. Line conductors

5. Pin-type insulators

6. Strain insulators

7. Earth wires

8. Angle iron for earth wire

9. Hooks for earth wire

10. Top hamper

11. Stay wire

12. Stay insulators

13. Anchor rod

14. Dead end clamps

15. Parallel grooved clamp (P.G. Clamp)

16. Earthing

17. Lightning arrestors

18. Danger plates

19. Anti –climbing device

20. Tie wire

HT AERIAL BUNCHED CABLE

The AB cable network of any electricity distribution utility is a vital component of the HV network

of the system. The reliability of the AB cable distribution network directly affects the reliability of

the overall system and ultimately the overall customer satisfaction.

Scope

The operational guidelines apply to DHBVN& any of Business Associates involved in Testing

& Repairing of Cable faults being carrying out for maintenance of electricity distribution

system.

Prerequisites

Ensure that necessary permit has been taken. Sub-divisions are responsible for ensuring

isolation of the faulty cable for both ends & providing the PTW. Ensure that the cable is

de-energized, isolated & grounded.

Patrolling of AB cable feeder may be conducted to identify & removal of unauthorized

tappings before starting of the work.

Copper Screen of HT ABC must be shorted along with messenger wire at starting & End

points and joints with crocodile clamp shorting’s. So that all conductive paths may be

kept at zero potential/ Earth potential

AB cable joints should be made properly. AB cable should not be jointed temporarily. In

case of emergency, proper joints must be made the next day. For jointing of Messenger

wire, mid span joint sleeve should be used instead of binding wires.

The Business Associates should ensure the availability of proper tools and accessories,

safety apparels, spares and consumables required for carrying out the work.

Laying of AB Cables

It may be ensure that AB cable should not be dragged on roads/ footpaths etc. It must be laid by

use of rollers & pulleys. In case AB cable is laid through trees/ vegetation area, branches may

be trimmed to avoid abrasion on AB cables.

Reason of Failure:

Design Snags-

Induction of high voltage at copper screen.

Under rated fault withstand capacity of Cu screen.

Manufacturing defects

Installation snags -

Improper connection between Cu screen & Messenger

Mechanical damage during installation.

Correctives Measures for Design snags:

HT ABC with revised specs. (AL wire screen)

Current Rating

HT ABC (Standard Sizes of Single core cable)

S. No. HT AB Cable Size (SqMM) Max. Continuous Load (Amps.)

1 35 106

2 50 150

3 70 190

4 95 230

5 120 265

6 150 300

7 185 345

Cable jointing Process

Power cables

Cablesare used for the transmission/distribution of electrical power and consist of three major

components:

Conductors

Insulation

Protective jacket

For cables operating at or above 6,000 volts between conductors, a conductive shield surrounds

each insulated conductor to equalize the electrical stress on the cable insulation. The construction

and requirements are specified in standards such as IS7098 and IEC 60502, IEC6084.

The important steps in the cable jointing of medium voltage XLPE insulated screened

armoured cable

a. Strip the jointing ends of both the cables to be done i.e. stripping of outer sheath, armour, inner

sheath, insulation screen, core insulation and conductor screen. Longer end will be 1050mm and

other end 750mm for 33Kv XLPE 3*400 sq. mm cable. Park the tubes 1000mm and 500mm then

1000mm at the longest side of the cable.

b. All the conductor cores shall be joint with the help of jointing ferrule/mechanical connector and

its crimping by suitable crimping tool.

c. Fill up the space between the ferrule and the core insulation and the crimped portion in ferrule

with semi conducting clay, so that it forms a smooth and round profile with 2 mm.

d. Measure a distance of 20 mm on both sides of the semi-conducting tape. Apply stress grading pad

of 30mm width over the core covering 10mm of the semi conducting tape.

e. Keeping conducting layer of core, wrap the self-amalgamating insulating tape so that the required

insulation thickness is built up. Ensure a tapered profile of the tape towards the semi conducting

layer of the insulation, the self-amalgamating tape should be stretched to 2/3rds of its original width

while applying.

f. Fill up the gap 5mm between self-amalgamating insulating tape and semi conducting layer of core

by stress grading pad of 30mm width.

g. Apply semi conducting tape one layer half over lapped about 10mm on one side of metallic

shielding to the other end in the same manner.

h. Wrap 2 layers of self-amalgamating insulating tape, each half overlapped to cover the semi

conducting tape. Stretch the tape 2/3rds of width while applying as shown in figure given below.

i. Wrap one layer of copper wire mesh on the core to connect the copper tape from end to another

over the tapes.

j. Place the black stress control tube centrally over the joint. Starting at the centre shrink the tube

towards one end and then towards the other end until fully shrunk. Apply heat evenly throughout

the process. When completed adhesive will flow from the ends, wipe off excess.

Role of Earthing in Power DistributionEarthing In Electrical System

Earthing means making an electrical connection to general mass of earth.

Earth forms an intrinsic part of electricity System.

Earthing of electrical installation is primarily concerned with ensuring safety.

Soil conductivity is an important consideration. Lower the resistivity, easier to get good

earth.

The ground is more effective conductor than copper wire used in electrical circuit.

Earth provides the shortest path for fault current to travel.

Short circuits allows electrical current to by-pass its normal route. Under short circuit,

current follows the least resistance fault to ground.

Reason for Poor Earthing Practices:

Inadequate understanding about technical requirement of earthing & Standards.

Earthing has no role to play during normal conditions.

Lack of compatibility between earthing requirement of electronic equipments & power

system.

Lack of motivation & importance to engineers for keeping earthing & connections in

proper state.

Why Earthing Important?

Earthing in a substation is extremely important for the safety of operating personnel as well as for

proper system operation.

It provides safe passage to earth fault current to flow. E/F current flow through the earth

and may readily cause operation of fuse or E/F relay.

It provides low resistance path to fault current to ensure prompt & consistent operation

of protective devices under fault current.

It protects the equipment other than live parts from attaining potential. Under fault

conditions, frames & enclosures etc may attain high potential w.r.t ground. So these

non-current carrying parts should be connected to ground for the safety of the operating

personal & other human beings for discharging electrical energy to earth.

It protects the equipment from over voltages, HV surges resulting from lightning &

other causes.

It ensures safety of life from electric shocks by grounding all metallic structures and also

avoid hazardous voltage gradients by suitably designing the grounding system. The

potential of earthed body does not reach to dangerously high values during fault.

It ensure that ground potential rise does not have any dangerous effect on

communication system.

It plays an important role in increasing the reliability & continuity of supply service and

stabilizing the voltage conditions.

It has means of discharging feeders & equipments to ground before proceeding with

maintenance.

Attributes Of Good Earth Connection

Lowest soil resistivity.

Low electrical resistance to earth.

Good corrosion resistance.

Ability to carry high current repeatedly.

A reliable life of at least 30 years.

Low loop impedance path of earthing.

Limits of Earthing Resistance

Following are values of earth resistance considered appropriate for different electrical

installation

FUSES

A switching device, which by the fusion of one or more of its specially designed and proportioned

components open the circuit, in which it is inserted and breaks the current, when the same exceeds a

a) Large HV and EHV s/stns - 0.5 ohms

b) Industrial and Distribution s/stns - 2.0 ohms

c) Medium voltage systems(415 V) - 5.0 ohms

d) Large HV and EHV s/stns - 0.5 ohms

e) Industrial and Distribution s/stns - 2.0 ohms

f) Medium voltage systems(415 V) - 5.0 ohms

given value for a sufficient time. The term fuse covers all the parts forming the complete switching

device.

Principle of operation

The operation of fuse depends upon the heating effect of an electric current. When the electric

current is increased in a circuit due to short circuits or over loads, it increases the rate of heat

generation, which will increase the temperature of the fuse wire and thereby the rate of heat

dissipation increases from the exposed surface of the fuse wire. The final temperature reaches to

such stage that the heat generation will be equal to the rate dissipation. If this temperature happens to

be above the melting point of the material for fuse wire, fuse must have operated

Selection of fuse wire

To select the proper fuse wire to be inserted in a circuit two factors viz. (a) maximum current rating

of the circuit (b) current rating of the smallest size of wire of accessories is to be seen, the fuse wire

inserted should be of size so that when the current with reference to factors (a) and (b) is increased, it

should blow out. The type of wire to be selected to use as a fuse wire depends upon the type of load

connected to the circuit i.e. steady load and fluctuating loads. The steady load covers the heating

loads and the fluctuating load consists of motor, capacitor and transformer loads, all of which take

transient over current when they are switched into the circuit. In steady load circuits, the fuse forms

only the protection part of the circuit. Therefore, the fuse rating should be equal to or next greater

than the ratings of the smallest cable used in the circuit. But if a number of fuse wires are run in

parallel to augment the rating of fuse, total rating should not be equal to the product of rating of and

strand and number of strands used. In fluctuating load circuits, fuse should allow the short time over

current to flow without blowing. For this, it is necessary to select fuses of rated current greater than

that of the cable of the circuit. The fuse wire should always be inserted in live wires or phase of the

circuit, or otherwise even if the fuse blows out, the faulty circuit will be fade and would cause

considerable damage in case of leakage fault.

LT UNDERGROUND CABLES The underground cable network of any electricity distribution utility is a vital component of the

LV/HV network of the system. The reliability of the underground distribution network directly

affects the reliability of the overall system and ultimately the overall customer satisfaction.

Scope:

The operational guidelines involved in Testing & Repairing of Cable faults being carrying out for

maintenance of electricity distribution system.

Prerequisites:

Ensure that necessary permit should be taken. Site In-charge is responsible for ensuring

isolation of the faulty cable for both ends & providing the PTW. Ensure that the cable is

de-energized, isolated & grounded.

The workman should ensure the availability of proper tools and accessories, safety

apparels, spares and consumables required for carrying out the work.

Minimum permissible Bending radius

PILC PVC XLPE

Type of Core 1C 3C 1C 3C 1C 3C

Upto 1.1 KV 20D 15D 15D 12D 15D 12D

‘D’ Diameter of the cable

Tests on Cables during fault localization, after repairs or when network modification is done

Test 230/440 V

Megger Test Phase to ground and phase to phase to be tested with 1KV Megger

for 1 Minute/or till reading stabilizes. Minimum IR values should be

50M Ohms.

Depth of the cable

LT cable (1.1kv) 0.6 m

LT Cables Current Rating

S No. No. of

Cores

Size

(Sqmm)

Current Rating of AL

PVC cables in Amp

Current Rating of AL XLPE

cables in Amp

AIR Ground AIR Ground

1 2 2.5 19 22 37 37

2 2 10 42 48 64 62

3 2 25 70 78 111 104

4 4 25 63 66 91 82

5 4 50 94 96 135 116

6 4 95 139 144 210 171

7 3.5 95 139 144 210 171

8 3.5 150 184 183 277 217

9 4 150 184 183 277 217

10 3.5 240 252 239 379 284

11 4 240 252 239 379 284

12 4 300 283 265 432 319

LT OVERHEAD LINES

Overhead lines are the most cost effective and frequently used carriers for electric energy. Exposure

to environment accelerates deterioration; if the fault is not detected and repaired quickly, some of it

will degenerate into serious problems with time. To increase line loading and quality of power

supply, frequent inspection program is required, to locate and repair any significant failure at the

earliest possible stage.

Frequent failure in the Overhead lines can cause extensive damage to the insulator and other

electrical & earth joints which not only interrupts electricity supply but also results in large revenue

losses. Poor/inadequate maintenance in the areas of pole, span length, non-tension electrical joints,

conductor spacing, pole stay leads to the instability in the electrical and mechanical parameter

which reduce the life of the line. With appropriate on site actions, like proper maintenance

procedure, the useful life of the overhead lines can be extended.

Scope

This operational guideline is intended to carry out the fundamental Line Survey / Checks for its

maintenance and while taking it into service. This requires that the concerned engineer should

prepare the action plan and ensure the availability of required materials, tools and tackles to carry

out this activity.

Prerequisites:

Ensure that necessary permit has been taken from SDO/JUNIOR ENGINEER who is

responsible for providing outage and PTW.

The PTW has to transfer to Working personnel after ensuring de-energization, isolation

and properly grounding the network where the activity has to carry out.

The Working personnel should ensure the availability of proper tools and accessories,

safety apparels, spares and consumables required for carrying out the work.

Clearance

Minimum clearances from any accessible point

1 The vertical clearance from the highest point 2.5 m

2 The horizontal clearance from the nearest point 1.2 m

Minimum Ground Clearance

1 Across the street 5.8 m

2 Along the street 5.5 m

3 Line erected elsewhere (Bare) 4.6 m

4 Line erected elsewhere (Insulated) 4 m

5 Line crossing 11 KV & LT line 2.4m

Maintenance Activity

General Maintenance

Check visually, the condition of Pole base & alignment of pole. If the pole is tilted,

should be straighten & rammed the pole base with brick bats after digging the earth

around the pole base. If any bend occurred at the mid of the pole, should be changed &

new pole to be erected.

Check visually the condition of existing stay

Check the Condition & size of GI wire. It should be 7/10 SWG.

Check the Condition of Guy/Egg Insulator-if any damage observed or is missing, it

should be fixed/replaced.

Check the Condition of tension screw-if any damage observed, it has to be changed.

Tighten the turn buckle if required.

Check the condition of anchor hook.

Check visually the Line Hardware

Condition of Shackle Insulator-if there is any crack, flash mark on the surface of the

insulator, it should be changed.

Condition of Pin insulator spindle- if any damage or bend happened, it needs to be

changed. Check the tightness of the fixing nuts.

Condition of Top hamper- if any tilt observed at top hamper or any damage occurred to

the metal part, it has to be change. Check the tightness of fixing nuts bolts.

Condition of the Double line X-arm. if any damage occurred on X-arm or on the fixing

clamp, it has to be changed. Check the tightness of the fixing Nuts, bolts

All metal parts to be painted by Primer &Aluminium paint for increasing the durability

& life span of the same.

Visual inspection of bare conductor -if any damage occurred on the conductor, it to be

replaced with the same conductor through sleeve joint & the nos. of joint is limited to

maximum 2 per span.

Use of Line Spacer to avoid fall of snapped conductor to ground & also maintaining

equal conductor spacing.

Span length should be maximum 40 m. If the length longer than it, a mid span pole

should be provided.

Line should be sectioned at every 4/5 span, if more, it should be reduced to 4/5 span.

Visual inspection of Earthing should be carried out. If any damage occurred on GI wire,

it has to be replaced with a new complete earth electrode. If there is any joint observed

at earth wire, either the wire or the complete earth electrode has to be changed. Also,

tighten all joints on earth set. Resistance value of earth shall be measured &It’s value

would be < 1 Ohm.

Visual inspection of Earth wire- if any damage/broken happened, it would be re-drawn

by 4 SWG GI wire.

Inspection of Joints – Jumpering should be done by same conductor & will be jointed by

suitable C-wedge connector. Mid span joint has to be done by Suitable Sleeves & the

joint is limited to 2 no per span.

Cable mounting on OH feeder-The cable should be mounted on pole structure through

GI pipe and must be mounted with clamps/STP. Cable be taken upto top of line and

jumper at cable end be through properly crimped lugs and fitted with C-wedge

connector with line.

Service line should be limited to 8 nos.perpole,if the above exceeds the latest instruction

followed by DHBVNsalescircular.

During connection of service cable with the distribution box, the cable/conductor surface

(after opening the insulation) should be cleaned properly and should apply anti corrosive

grease before termination on distribution box.

Configuration of line

LT ARIAL BUNCHED CABLE (ABC)

The AB cable network of any electricity distribution utility is a vital component of the LV network

of the system. The reliability of the AB cable distribution network directly affects the reliability of

the overall system and ultimately the overall customer satisfaction.

Laying of AB Cables

It may be ensure that AB cable should not be dragged on roads/ footpaths etc. It must be laid by use

of rollers & pulleys. In case the AB cable is laid through trees/ vegetation area, branches may be

trimmed to avoid abrasion on AB cables. OH distribution box (3-Φ /1-Φ) should be mounted on

pole for giving service connection. Incoming cable of suitable size for Distribution box should be

jointed with ABC by Mini wedge connector/IPC.

LT ABC (Values as per IS : 6474 – 71 & IS : 7098(1) 88 )

Clearly checking the phase of cable 1 line for R phase, 2 line for Y phase and 3 for B phase.

S. No LT AB Cable Size Current Rating @ 40 deg C

1 3x150+1x120 Sqmm 273A

2 3x95+1x95 Sqmm 235A

3 3x70 +1x70 Sqmm 190A

4 3x50 +1x35 Sqmm 149A

5 3x25 +1x25 Sqmm 99A

6 3x16 +1x25 Sqmm 60A

LT FUSE BOARD

LT fuse board shall be installed on One Pole for Plinth/Pole Mounted DT/H-Pole of the ratings

required at site. Insulated cable from LV side of DTs shall be connected to one side of fuse board

through proper size lug/thimble.

RECOMMENDATIONS

1. Regular Trainings/Seminars shall be organized for field staffs as a part of policy for

improving the capabilities for maintenance of distribution network.

2. Frequently breakdown of feeders shall be thoroughly checked for analyzing the reason of

fault and action shall be taken for minimizing the breakdown.

3. JE/SDO should maintain the Log Book of breakdowns in his area and all the details of

breakdowns must be recorded.

4. Phase balancing of feeders shall be regularly carried out as the balanced distribution

network have less interruptions, no heating of any one conductor and ageing/breaking of

conductors shall be minimized. A balanced network has less technical losses than an un-

balanced network.

5. Analysis of weak and strong area of every sub-division on the basis of data recorded in Log

Book, shall be carried out. After ascertaining the reason of weak area, action should be

taken to make it a strong area.

6. Reasons should be identified for frequent breakdowns of following equipments and

immediate action should be taken: -

Distribution Transformers

Line conductors

U/G cables

Jumpers

Insulators

Overloading of any feeder

7. Tree trimming shall be done on regular basis and the same should be taken as a preventive

maintenance.

Various Faults / Point of concern with Probable Causes and Remedial Actions

S. No. Fault / Point of Concern Probable Cause of Fault /

Point of Concern Remedial Action

1 Overhead Conductor

Faults

1. Flashed /Punctured or

broken insulators

2. Damaged jumper/Conductor

3. Fault due to Tree Contact

4. Faults due to Birds

5. Fault due to Cracked Pole

6. Improper Earthing

7. Unwanted wire b/w two

phase

1. Plan for Flashed /Punctured

or broken insulators

checking and replacement.

2. Plan for Jumper Repairing,

either of same conductor

size or next higher size of

conductor size.

3. Plan for Tree Pruning /

Trimming by using Tree

pruner instrument.

4. Plan to reduce Faults due to

Birds by installing bird

repellent/ falpper .

5. Proper Earthing should be



done

2 Under Ground Cable

Faults

1. Insulation Degradation

i. Electrical Stress

ii. Mechanical Stress

iii. Thermal Stress

2. External damage

i. Water Ingression

ii. Joint Failures

1. Plan to minimize insulation

failure by using proper

meggering instead of Hi-

pot, By usage of HS tape &

end caps to prevent from

moisture.

2. Plan to reduce joint failures

by not using sub-standard

joints kits, by

qualified/skilled jointers.

3. Plan to reduce external

damage by proper

patrolling.

4. Plan to reduce burning of

cables by proper load

balancing.

3

Distribution

Transformer Trippings /

Interruptions

1. Defective Bushing: HV/LV

& Oil Leakage

2. Condition of Breather &

Conservator

3. High unbalancing current

4. Continuous overloading of

DT

5. Frequent LT cable faults

6. Improper protection of

both HT and LT side

7. Development of hot spots

due to passage of time

8. Poor/defective earthing of

neutral & body of DT and

of LT feeders

9. Birds / Animal

electrocution

10. Poor maintenance of DT

11. High rating fuse used

1. HT and LT connections

should be tight

2. Proactive thermo-scanning

3. Earth value should be

checked during Planned

shutdown & earthing

connections should be

tightened

4. Earthing checked and

provided new earthing

where ever required.

5. Proactive patrolling, Drain

valves should be sealed

Segregate multiple LT

feeders that feed from one

ACB.

6. Top fence covering in

monkey/domestic animal

prone s/s, provision of HT

insulation caps.

7. Overhauling of the

DT/replacement with

new/repaired one.



4 Power transformer

Tripping

Differential Protection

operation

1. Inter-turn fault/ Aging

2. LT joints & HT bushing

failures

3. Short circuit at in-zone of

both sides CTs.

4. IED Failure

5. CTs wiring problem

6. CT Saturation

7. Fault at cable box before

LV

1. Complete visual Inspection

of power transformer.

2. Rectifying the root cause of

breakdown

3. Stability test of power

transformer.

5

Oil temperature

indicator tripping /

alarm

1. High temperature of oil

due to heavy loading.

2. Relay mal-function.

3. Low intensity Inter turn

fault.

1. Checking of OTI meter &

WTI meter for variation.

2. Check loading condition

3. Winding resistance of

power transformer.

6 Winding temperature

indicator tripping /alarm

1. High temperature of

winding due to heavy

loading.

2. Relay mal-function.

3. Low intensity Inter turn

fault.

1. Checking of OTI meter &

WTI meter for variation

2. Check loading

3. Winding resistance of

power transformer.

7 11 KV incomer tripping

1. Due to fault in 11 Bus

system.

2. Fault near to substation or

very high intensity of fault.

3. High breaker timer of

outgoing breaker

1. Checking of tripping of any

outgoing feeder along with

intensity of fault

2. Check breaker timing of

tripped breaker.

8 11 KV outgoing breaker

tripping

1. Due to over loading.

2. Due to phase fault /earth

fault

1. Check Relay’s tripping

parameters for analysis.

2. Line inspection is required

before again charging.

9 Failure of Lighting

arrestor

1. Due to heavy voltage

fluctuation.

2. Aging of lighting arrestors

1. Replace the faulty LA.

2. Check other installed LAs.

10 Low voltage at DC

system

1. Due to charging problem.

2. Battery issues in existing

system.

1. Check charger at location.

2. Impedance test of battery

11 DC leakage at

substation

Earthing of any one of the

terminal with ground it may

occur at yard's equipment of in

VCBs

Isolate DC supply at every

section and check DC leakage

in system and rectified the

same.

12 Poor earthing at grid

substation

Due to aging / Soil condition

& improper installation

1. Check earthing resistance at

every pit of yards & neutral

of transformer.



2. In case of poor earthing go

for parallel earthing concept

and connect it with old

earthing PIT.

Distribution transformer failure analysis & corrective actions.

1. Defective Bushing: HV/LV & Oil Leakage

CORRECTIVE ACTION & PREVENTIVE ACTION: Check bushings for cracks, chippings, over heating marks, flashover marks, replace the effected bushing.

Oil leakages if any then keep an eye on

a. tightness of nuts

b. tightness of oil seal caps/replace oil seal & gasket if required

Don’t apply M-seal or other material on HV/LV bushing to stop oil leakage as this may causing

flashover.

Check the HT/LT rod and replace if required.

OIL LEAKAGE FROM TOP PLATE

Oil leakage from top plate can be attended by tightening nuts & bolts diagonally

Replace gasket if required.

2. Condition of Breather & Conservator

Poor condition of breather like cracks on its body, improper coupling of Cup, absence of oil in

cup cause rust formed due to moisture ingress through breather

CORRECTIVE ACTION & PREVENTIVE ACTION:

BREATHER

Moisturized (Pink) Silica gel should be replaced with new / re activated (blue) Silica Gel.

In case of new Breather, ensure to remove seal from breathing hole of oil cup.

Re-activation of used silica gel to avoid excessive consumptions

After filling silica gel, Breather should be tight properly.

Pour oil in Breather oil cup, if required.

Breather should be tightly fixed to breather pipe.

Due to improper coupling of breather bottle and flange, breathing points may be formed,

thereby creating a passage for moisture, which leads to condensation and rusting of the

conservator tank from inside.

During maintenance , the breather size and type to be checked & non transparent breather

should be replaced by transparent breather of recommended size as below:

< 400 KVA- 0.5 Kg

> 400 -990 KVA- 1 Kg

CONSERVATOR & OIL

Oil sample for BDV test should be taken in proper oil sample bottle. In case of low BDV

value take necessary action.

Check the cap and surface of conservator tank for rusting/holes.

Check oil level from oil gauge.

Oil topping should be done if required.

Check Oil Gauge for leakage.

Explosion Vent Diaphragm

Check the Diaphragm, if it is torn then replace it by a new one

3. High unbalancing current :

Higher unbalance current cause rise in winding temperature. This overheating of winding may

damage the inter-winding insulation level and so as to distribution transformer failure.


Monthly load recording and balancing of DT as well as LT feeders.

Unbalance Current should not exceed 10% of Full Load/ Running Load.

4. Continuous overloading of DT

Distribution Transformers are generally not recommended for continuous overloading. However

overloading for a short duration cannot be avoided. It is one of the prime responsibilities of the

utilities to keep a check on the loading of a transformer and should record the loading Patton on a

history card. In case of overloading the additional loss generates more heat, which effects the

burning of winding insulation, causing ultimate failure of the transformer.


Transfer the load to nearby DT (If possible)

Augment or swap the overloaded DT

Provide additional DT.

5. Frequent LT cable faults

More the cable faults, more the fault current travels towards the transformer.


Replace sick cables and reduce length of LT feeders

Tree trimming should be done to avoid transient faults.

6. Improper protection of both HT and LT side

Improper protection system always invites the risk of damage of equipment. As Distribution

Transformers are one of Costliest & vital part of Distribution System, Special care must be

taken while selecting switching & protecting devices. Preferably at HT Side Ring Main unit

(RMU) / breaker should be used with appropriate Protective Relays in case of small DTs Drop

down Fuses (DD fuses) of appropriate ratings can also be used. At LT Side of Distribution

Transformers Appropriate rating of ACBs / MCCBs can be used.

In case of absence of proper protecting devices or installation of improper Rating / Size of fuses

the risk of DT failure became very high. This could be the due to:

Installation of RMU / Breakers with defective / inappropriate Relay or relay setting

Installation of inappropriate Rating / Size of fuses

Consistent overloading.

Lightning Arrestors (LAs) are not installed.

Inappropriate Earthing of DT / Neutral / Las


Get relay setting checked from M&P department

replace defective LT Fuse Board/ LT ACB

Segregate multiple LT feeders that feed from one LT fuse Board

7. Development of hot spots due to passage of time

Development of Hot spots in the system are mainly due to Loose nut bolt connection at HT/LT side,

Improper Lugs crimping, underrated wires & nut bolts, improper alignment of blades of G.O switch,

loose binding of conductor etc . Prolonged Hot spots causes breakdown the system which further

loss of reliability & revenue. Also it will make the equipment deteriorated day by day.


HT and LT connections should be tight.

Proper size of lugs & nut bolts should be used.

Proactive thermo-scanning and urgent compliance to the observations should be done.

Proper crimping of lugs should be carried out. Minimum 3-4 crimping required for each

lugs

8. Poor/defective earthing of neutral & body of DT and of LT feeders

In electricity supply systems, an earthing system or grounding system is circuitry which connects

parts of the electric circuit with the ground, thus defining the electric potential of the conductors

relative to the Earth's conductive surface.

Poor earthing of neutral will not allowed to pass the fault/ unbalance current though the ground.


Check earthing of DT neutral & body, Fence, LT/HT frames.

Earth resistance values must be below 1Ω. If the test values are greater than 1Ω, then new

earthing must be provided as soon as possible.

Proper earthing of LT feeder should be checked & provided new earthings where ever

required.

Total 5 earthings should exist in pole mount DT.

2 for DT neutral

1 body & fence for DT

2 for LA.

Earth value should be checked during planned shut down and earthing connections should be

tightened.

9. Cat/monkey electrocution

In many case, unnecessary trippings and DT bushings failures noticed due to Cat/ Monkey/ Birds

electrocution.


Top covering of fence of monkey/domestic animal prone substation.

Provision of HT insulation caps

10. Poor maintenance of DT

Transformer failure can also stem from poor O&M practices. For example, in addition to normal full

load, continuous over-heating and higher no-load losses may reduce the life of the transformer due to

reduction in the life of insulating papers, oil, etc. Other improper O&M practices leading to

transformer failure are mentioned below:

Negligence to Low BDV value of oil.

Negligence to Megger process & its results.

Low oil level.

Non-usage of Cleats at HT & LT sides.

Poor handling of LT cables associated with DT LT side.

Negligence to HV/LV connection CORRECTIVE ACTION & PREVENTIVE ACTION:

Pre inspection of scope of work to ensure less down time of PSD and material

requirement.

Proper LT Cable end terminations to be installed in order to prevent it from ingression of

water during to rains which turns in Cable fault.

LV/HV CONNECTION (Palm Connectors)

Nuts, bolts & clamps of H.V. & L.V. connections should be tight.

Proper size of lugs should be used on LV/HV cable as to maintain proper voltage.

Defected palm connectors should be replaced. (Pitting on the surface causes HOT

SPOT)

Check HT & LT cable cleats to avoid mechanical stress on transformer bushing.

LT leads & Neutral earth wire should not touch radiators.

During the maintenance palm & lug contact surface to be cleaned properly and

petroleum jelly to be applied to avoid rusting and hot-spots.

Power Transformers

Best practices at substation level maintenance

Note down the temperature and record the maximum daily ambient temperature.

Check that temp rise is reasonable. In case of any abnormal variation, check the cooling

system of T/F. If the same is not found in order. Shut down the T/F for further

investigation.

Check against transformer oil level/ temperature. Top up with dry oil, if necessary.

Check for any oil leakage.

Check for any abnormal sound or excessive chattering. Shut down the T/F in case of

abnormal noise, for further investigation

Examine relays and alarm contacts and their operation, fuses etc. Check for relays

functioning clean or replace the contacts if required

Measure earth resistance of the (a) T/F body, neutral and other body parts, (b) Keep

proper record of test results. (Earth testing to be done during driest part of the season)

Examine Firefighting equipments and ensure that these are in order.

In case of bushing -Test oil for dielectric strength Dehydrate or replace the oil, if

necessary.

Use LT sleeve on 11 KV side

Earthing of panels

In case of cooler fan & pump bearing all Lubricate bearings, check gear box. Examine

Contacts, Check Manual control and interlocks. Replace burnt or worn out contacts or

other parts.

I.R. values with 2.5KV rating meggar. Convert it at 700 C and compare the values with

the value taken at the time of commissioning.

Earth resistance of the (a) T/F body, neutral and other body parts, Keep proper record of

test results. (Earth testing to be done during driest part of the season)

Avoid leakage/seepage of oil from main tank to OLTC tank.

Continuously monitoring of DGA test to keep close eye on transformer condition.

To reduce eddy current, proper earthing of transformer body top cover with body is

must.

TYPES OF UNDERGROUND CABLE FAULTS

Cables are generally laid directly in the ground or in ducts in the underground distribution system.

For this reason, there are little chances of faults in underground cables. However, if a fault does

occur, it is difficult to locate and repair the fault because conductors are not visible. Nevertheless,

the following are the faults most likely to occur in underground cables:

1. Open-circuit fault

2. Short-circuit fault

3. Earth fault.

Following are the main causes of Under Ground Cable failure.

1. Insulation Degradation

2. Joint Failure

PREVENTIVE & CORRECTIVE ACTION PLAN

1. PLAN TO MINIMIZE INSULATION FAILURE

2. PLAN TO REDUCE JOINT FAILURES

3. PLAN TO REDUCE EXTERNAL DAMAGE

4. PLAN TO REDUCE BURNING OF CABLES

Overhead Circuits (O/H Lines) Fault in Overhead Lines

Overhead lines are the main part of electrical power distribution system. These are used to carry the

electrical power from generating station / Sub-station to load centers/ consumer’s point. There are

several types of faults occurs at lines and there are several causes of fault occurrence at Over head

lines.

There are mainly two types of faults in the electrical power system. Those are symmetrical and

unsymmetrical faults.

Causes of Overhead Line faults 1. Flashed /Punctured or broken insulators

2. Damaged jumper/Conductor

3. Fault due to Tree Contact

4. Faults due to Birds

5. Fault due to Cracked Pole

6. Improper Earthing

Corrective & Preventive Action 7. Action Plan for Flashed /Punctured or broken insulators:

8. Plan for Jumper Repairing

9. Plan for Tree Pruning / Trimming

10. Plan to reduce Faults due to Birds

11. Plan to Replace Cracked Pole

12. Plan for Proper Earthing.

Aerial Bunched Cable (ABC)

Symptoms prior to failure

At initial stage:

In Majority of cases, sparking &Hissing sound is developed between Copper screen & Messenger

wire of HT ABC.

Later stage:

Outer Sheath burnt along the Messenger wire & damage of XLPE insulation due to heat of

sparking.

Cause of Sparking

The design of ABC is such that a substantial voltage induced at copper screen and is capable to

puncture the outer sheath along the messenger wire which is at earth potential resulted in sparking

& discharging sound.

Symptoms prior to failure:

At initial stage: In Majority of cases, sparking & hissing sound is developed between Copper screen

& Messenger wire of HT ABC because of improper connection between copper screen &

Messenger wire.

Later stage: Outer Sheath burnt along the Messenger wire & damage of XLPE insulation due to

heat of sparking.

Reason of Failure:

Design snags- a) Induction of high voltage at copper screen.

b) Under rated fault withstand capacity of Cu screen.

c) Manufacturing defects

Installation snags - Improper connection between Cu screen & Messenger.

Mechanical damage during installation.

Mechanical stress

Stress develop due to Improper Bending Radius

o Ensure Proper Bending radius

Stress/ Abrasion develop due to improper clearance between poles & AB cable

suspended on suspension clamps

o Ensure proper clearance between poles & ABC

Stress develop due to Improper Span length

o Ensure proper span length

o Span Length should be depend on the size of the conductor/ABC cable and

pole height/type to maintain min. Sag & specified ground clearance

o It would be 30-35 m for PCC pole

External damage

Insulation Damaged during installation due to improper Laying practices.

o Ensure use of Rollers/ Pulleys during installations.

SN CHECK LIST DESCRIPTION ANNEXURE

1 CHECK LIST FOR MAINTENANCE OF 33/11KV POWER

TRANSFORMER ANNEXURE-PTR/MAIN/01

2 CHECK LIST FOR MAINTENANCE OF ON-LOAD TAP

CHANGER ANNEXURE-PTR/OLTC/MAIN/01

3 CHECK LIST FOR MAINTENANCE OF 33 & 11KV CIRCUIT

BREAKERS ANNEXURE-CB/MAIN/01

4 CHECK LIST FOR MAINTENANCE OF CURRENT

TRANSFORMERS ANNEXURE-CT/MAIN/-01

5 CHECK LIST FOR MAINTENANCE OF POTENTIAL

TRANSFORMERS ANNEXURE-PT/MAIN/01

6 CHECK LIST FOR MAINTENANCE OF LIGHTNING

(SURGE) ARRESTERS ANNEXURE-LA/MAIN/01

7 CHECK LIST FOR MAINTENANCE OF LINE ISOLATORS

& EARTH SWITCHES ANNEXURE-ISOL/MAIN/01

8 CHECK LIST FOR MAINTENANCE OF BATTERY BANK &

BATTERY CHARGERS ANNEXURE-BAT/MAIN/01

9 CHECK LIST FOR 11 KV VCB CONTROL PANEL ANNEXURE-11KV VCB CONTROL

PANEL/MAIN/01

10 CHECK LIST FOR 33 KV OUT DOOR BUS ANNEXURE-33KV BUS/MAIN/01

11 CHECK LIST FOR 11 KV OUT DOOR BUS ANNEXURE-11 KV BUS/MAIN/01

12 CHECK LIST FOR APFC CONTROLLERS ANNEXURE-11 KV APFC /MAIN/01

13 CHECK LIST FOR AC DISTRIBUTION BOARD ANNEXURE-ACDB /MAIN/01

14 CHECK LIST FOR MAINTENANCE OF EARTHING

SYSTEM AT GRID SUBSTATION ANNEXURE-EARTHING/MAIN/01

15 CHECK LIST FOR MAINTENANCE OF 33 KV LINES ANNEXURE-33 KV LINES /MAIN/01

16 CHECK LIST FOR MAINTENANCE OF 11 KV LINES

17 CHECK LIST FOR MAINTENANCE OF LT LINES

18 Annexure- AR-1 HT Auto-recloser

19 Annexures DT-1 Distribution Transformer








27 Annexure RMU-1 Ring Main Unit

28 Annexure RMU-2 Ring Main Unit

29 Annexure UG-1 Under Ground Cable

30 Annexure ABC-1 HT AB Cable

31 Annexure-ERT-1 HT Earthing

32 Annexure- G.O.-1 G.O. Switch

33 Annexure- OH-1 HT O/H Conductor

34 Annexure LT ACB LT ACB

SN CHECK LIST DESCRIPTION ANNEXURE

35 Annexure- LT UG Cable LT UG Cable

36 Annexure LT OH Conductor LT OH Conductor

37 Annexure LT ABC LT ABC

38 Annexure LT Earthing LT Earthing

39 Annexure LT Metering & Service Cable LT Metering & Service Cable

40 Annexure LT Feeder Pillar LT Feeder Pillar

41 Annexure LT Fuse Board LT Fuse Board

ANNEXURE-PTR/MAIN/01

CHECK LIST FOR MAINTENANCE OF 33/11KV POWER TRANSFORMER

Name of Grid: Date &

Time

Season

Pre-requisite for Maintenance

Caution Order/PTW No.

T&P/material/PPEs

Safety Cotton Rag

S.

NO.

ITEM TO BE

INSPECTED BRIEF DESCRIPTION OF WORK

FREQUEN

CY

PERMISSI

BLE

VALUES

STATU

S

ACTIO

N

TAKE

N

1 Ambient Temp

Note down the temperature and record the

maximum daily ambient temperature. Hourly NA

2

Winding/Oil Temp

Check that temp rise is reasonable. In case of

any abnormal variation, check the cooling

system of T/F. If the same is not found in order.

Shut down the T/F for further investigation.

Hourly 100° C

3 Load/Voltage

Check against rated figures. In case of any

variation, check the TPI. Hourly NA

1 Oil level in transformer

Check against transformer oil level/

temperature. Top up with dry oil, if necessary.

Daily each

shift

Above from

Min level

2 Oil level in bushings Check for any oil leakage.

Daily each

shift

Above from

Min level

3 Relief Vent diaphragm

Check for cracked or broken. Replace if

necessary.

Daily each

shift NA

4

For internal abnormal

noise.

Check for any abnormal sound or excessive

chattering. Shut down the T/F in case of

abnormal noise, for further investigation.

Daily each

shift NA

5

Heaters in Junction Box Check for proper working, if provided. Replace,

if found defective/damaged.

Daily each

shift NA

6

External connection

(Leads/Jumpers)

Check visually for tightness and sparking on

jumpers, bushings etc. on complete darkness.

Attend it, if required.

Daily each

shift

NA

7

Bus bar and cable boxes

and cables

Check for any damage and signs of overheating

at their joints. Check for overheating of back

covers and attend, if found excessive heated.

Daily each

shift

NA

1

Dehydrating breather

Check for condition/colour of Silica gel.

Recondition or replace as necessary.

Monthly

NA

2 Monthly

3 Monthly

4 Monthly

5 Monthly

6 Ensure for free air passage Monthly NA

7

Tight, lid of the breather for air tightness to

avoid entry Monthly NA

8

Check oil level in oil cup and make up oil, if

required. Monthly NA

9

Remove oil from dash pot and pour in fresh oil

where required. Monthly NA

10

Bushing and gaskets

Examine for cracks, Paint and dirt deposits and

gap settings. clean or replace it. Check gaskets

for leakage.

Monthly NA

11

Cooler fan and pump

bearings, motors and

operating mechanism

Lubricate bearings, check gear box. Examine

Contacts, Check Manual control and interlocks.

Replace burnt or worn out contacts or other

parts.

Monthly NA

12

On load tap changer

driving mechanism

Lubricate bearings, Check gear box oil level and

examine contacts. Clean/Replace burnt or worn

out contacts

Monthly NA

13

On load tap changer

automatic control

Check all circuits independently. Check step by

step operation including limit switches. Attend

if found faulty.

Monthly NA

14

Insulation resistance

Check the I.R.values with 2.5KV rating meggar.

Convert it at 70 0 C and compare the values

with the value taken at the time of

commissioning.

Monthly > 50 M-

ohm

15

Relays alarms,

temperature alarm and

their circuits

Examine relays and alarm contacts and their

operation, fuses etc. Check for relays

functioning clean or replace the contacts if

required.

Monthly NA

16 Arcing Horns

Set the rods for alignment and for proper gap

adjustment. Monthly NA

17

Measuring/Protection

CT’s

Check for sparking and tightness of connection

and oil level. Monthly NA

18 Remote/Manual Switch Check for proper functioning Monthly

NA

19 Firefighting equipments Examine them and ensure that these are in order. Monthly

NA

20 Bucholtz’s relay

Note the oil level in the inspection glass of

Bucholtz’s relay. Monthly NA

1

Oil in T/F and tap

changer

Check for dielectric strength. Dehydrate the oil,

if necessary. Keep continuous record of test

results.

Quarterly NA

2 Ventilators Check that air passages are free. Quarterly NA

3 Bucholtz’s relay Check proper operation by lowering the oil Quarterly NA

4 Forced cooling system Megger testing of motors(pumps) Quarterly NA

5

Checking transformer ground connections for

tightness. Quarterly NA

6 ThermoSyphen Filters Quarterly NA

7 Earth Resistance Check for tightness of earth connections. Quarterly NA

8

Measure earth resistance of the (a) T/F body,

neutral and other body parts, (b) Keep proper

record of test results. (Earth testing to be done

during driest part of the season)

Quarterly NA

1 On load tap

Inspect all moving parts, contacts, brake shoes,

motor etc. Clean, adjust or replace as required. half yearly NA

2 Oil in T/F

Check acidity, PPM & BDV & compare with

standard results. half yearly NA

1

Oil in T/F

Check Tan delta,,Sp.Resistively , sludge

contents, DGA test, compare it with standard

results.

yearly NA

2 Oil filled bushing

Test oil for dielectric strength Dehydrate or

replace the oil, if necessary. yearly NA

3 Cable box

Check for sealing arrangements for filling holes.

Examine compound for cracks. yearly NA

4 Surge diverter and gaps

Examine for cracks and dirt deposits. Clean or

replace if necessary. yearly NA

5 Gasket joints

Check for tightness of bolts to avoid uneven

pressure. Replace damaged gasket. yearly NA

6 Pipe connections

Check oil pipes valves and plugs for tightness

and proper functioning. yearly NA

7 Foundations Check for cracks, if any and setting. yearly NA

8 Bushings Test the bushings with a Hipet bushing tester yearly NA

and compare with previous figures.

9 Temperature indication

Pockets holding thermo-meter should be

checked. Oil to be replenished, if required. yearly NA

10 Dial type oil gauge

Check pointer for free operation. . Adjust, if

required. yearly NA

11 Paint work Should be inspected yearly NA

12

Conservator tank

Check for proper communication of the

conservator with T/F tank by draining some oil

through drain off valve and watching the oil in

gauge glass to drop.

yearly NA

13

In case, the oil does not drop, investigate and

remove the sludge or other obstructions after

dis-assembling the tank.

yearly NA

14

Check for leakage of oil from glass side. Clean

the inspection glass. yearly NA

1

Diverter switches for

tap changer having non-

arcing selector switch

Check for worn out contacts. Filter oil

irrespective of all test. Replace worn out parts.

Yearly or

after 5,000

operations

NA

2 Oil conservator

Internal inspection Clean the conservator

thoroughly Two years NA

3 Buchholtz relay

Mechanical inspection. Adjust floats, switches

etc. if required. Two years NA

4

Non-arcing selection

switch of on load tap

changer

General inspection. Replace worn out parts and

filter the oil.

3 years or

after 15,000

operations

NA

5

Overall inspection including lifting of core and

coils 7 to 10 years NA

6 Major overhauls (complete) of transformers. 7 to 10 years NA

7

3000KVA and below (once in 7 yrs.) Above

3000KVA (once in 10 yrs.)

Once in 7

years

once in 10

years

NA

NA

NA

Note:Insulation resistance measurement, tan δ of winding/bushings, winding resistance at all taps to

be carried out once before expiry of warranty period and then to be continued as per schedule.

Visual observation of transformers and Reactors by going round, should be made daily to check for

any variations in noise, vibrations and any abnormality/leakages from cooler fans, oil pumps,

radiators, valves etc.

WITNESSED BY:- JE/SDO SIGNATURE

ANNEXURE-PTR/OLTC/MAIN/01

CHECK LIST FOR MAINTENANCE OF ON-LOAD TAP CHANGER

Name of Grid: Date & Time

Season



T&P/material/PPEs

Cotton Rag

Sr.

no.

ITEM TO BE


FREQUENC

Y

Permissibl

e Values

STATU

S

ACTIO

N

TAKEN

1

ON LOAD TAP

CHANGER

ON LOAD TAP

CHANGER

Check leakage/seepage of oil from main tank to

OLTC tank DAILY N/A

2 Oil leakage from OLTC. DAILY N/A

1 Silica gel breather MONTHLY N/A

2 Colour of silica gel crystals MONTHLY N/A

3 Oil in oil cup in silica gel breather MONTHLY N/A

4 Vermin proofing of OSR to avoid moisture ingress MONTHLY N/A

5 All unused wires are insulated MONTHLY N/A

1 Prismatic oil gauge in OLTC conservator tank QUARTERL

Y N/A

2 OSR oil glasses. QUARTERL

Y N/A

3 Drain / filer valves QUARTERL

Y N/A

4 Cracks / any abnormality in barrier board QUARTERL

Y N/A

5 Local electrical operation of OLTC QUARTERL

Y N/A

6 Step by Step operation of OLTC QUARTERL

Y N/A

7 Electrical end limit (both upper and lower) QUARTERL

Y N/A

8 Operation of OLTC QUARTERL

Y N/A

9 Space heater / thermostat/illumination lamp in

drive mechanism

QUARTERL

Y N/A

1 OSR relay HALF

YEARLY N/A

2 Oil BDV for OLTC tank HALF

YEARLY

>40KV at

2.5 mm gap

3 Oil DGA HALF

YEARLY

4 OSR trial operation HALF

YEARLY Positive

5 OLTC operation manual/auto/local/remote HALF

YEARLY Positive

1 Complete OLTC YEARLY N/A

2 OLTC drive mechanism cubicle YEARLY N/A

3 Diverter switch tank and barrier board YEARLY N/A

4 Fixed contacts in diverter switch YEARLY N/A

5 Moving contacts in diverter switch tank YEARLY N/A

6 Transition moving contact YEARLY N/A

7 Tightness of internal connections YEARLY N/A

8 Braided flexible/collector ring/pre selector YEARLY N/A

9 Tap lead connection (for out tank OLTC only) YEARLY N/A

10 OSR connections YEARLY N/A

11 All gasketted joints YEARLY N/A

1 Transformer turn ratio / voltage ratio

5 years or

after

replacement

of any

primary part

of OLTC

As per pre

comm

values

1 Winding resistance of HV winding on all taps

At the time of

OLTC

maintenance

As per pre

comm

values

WITNESSED BY:- JE/SDO SIGNATURE -

ANNEXURE-CB/MAIN/01

CHECK LIST FOR MAINTENANCE OF 33 & 11KV CIRCUIT BREAKERS


Time

Season



T&P/material/PPEs

Safety Cotton Rag

Sr.

no.

ITEM TO BE


FREQUEN

CY

Permissi

ble

Values

STATU

S

ACTIO

N

TAKE

N

1 General cleanliness Examine that switchgear premises doors, circuit

breaker etc. for general cleanliness. Daily

N/A

2 Oil Check oil leakage, if so level be also ascertained. Daily

N/A

3 Tank Check for temperature by touch and for any unusual

noise and smell. Daily

N/A

4

Alarms and lamp indication

circuit etc.

Test the alarm circuit for continuity and lighting

circuit and earthing system. Daily

N/A

5 Safety aids Check safety aids for proper operation/condition. Daily N/A

6 Load

Check for load conditions on 3 phases, adjust relay

setting. If necessary. Daily

N/A

7 Indicating and measuring

instruments

Check, indicating and measuring instruments for

correct reading and being in proper working order Daily

N/A

1 Auxiliary fuses Check that auxiliary fuses are intact. Weekly

N/A

2 Oil level and gauges Check oil level in gauges of the tank/poles/oil filled

bushing. Replenish oil if found below normal. Weekly

N/A

3 Bushing or insulators

Check for chipped or broken insulator, excessive

dirt film. Weekly

N/A

4 Closing solenoid of air

cylinder, motor or spring

Visual inspection to see that equipment is in

operating conditions Drain condensation from air

cylinder.

Weekly

N/A

5 Latch and trip mechanism

Visual (or otherwise) inspection to see that

mechanism is in operating condition. Weekly

N/A

6 Tripping solenoid Visual inspection to see that solenoid trip device is

in operating condition. Weekly

N/A

7

Cabinet lights and heaters

Check cabinet heaters and see that they are in

service during cold weather. Replace burnt out

lamps.

Weekly

N/A

8 Power supplies and wiring See that all power control circuit switches are closed Weekly N/A

9 Breathers and vents

Check for external obstructions to breathers and

vents and condition of silica gel. Weekly

N/A

1 Nuts, bolts & Jumpers etc. Check whether nuts and bolts are tight and jumpers

are properly connected. Monthly

N/A

2 Drain plug Check that drain plug is tight. Monthly

N/A

3 Operation counter Observe and record reading of operation counter. Monthly N/A

1 Local remote operation

Check that breaker can be operated locally and in

remote control operation. Quarterly

N/A

2 Exhaust pipes Check and clean the exhaust pipes. Quarterly N/A

3 Dash pot Check the working of dash pot. Quarterly

N/A

4

Shutter mechanism and

trolley alignment for 11KV

breakers

To check for proper working of shutter mechanism

and to verify the alignment of trolley. Quarterly

N/A

5

Manual operating device

Check that manual operating lever or jack is kept on

hand and is in visible condition. See that breaker is

closable with it.

Quarterly

N/A

6 Latch and trip mechanism

Observe mechanism during general tripping

operations to see that everything is in working order.

Check pins, bearings and latch for wear, binding and

misalignment. Clean and lubricate the moving

parts. Check latch carefully to see that it is not

becoming worn so as to unlatch from vibration or

stick or fail to trip. Tighten bolts and screws.

Quarterly

N/A

7

Tripping solenoid

Observe operation during electrical tripping. See

that full energy, snappy action of plunger is

obtained. Check plunger for sticking in guide Check

oil and insulation resistance.

Quarterly

N/A

8

Indicating and measuring

instruments

Check for satisfactory operation, adjust where

necessary Quarterly

N/A

1

IR values

Check IR value in ON and OFF positions between

contacts in off position. Check IR value of control

cable with 500V megger.

Half yearly

N/A

2 Earth resistance Check earth resistance of body. Half yearly

N/A

3

Slow closing test This test may be conducted and also check that all

the three contacts are made simultaneously. Half yearly

N/A

4

Adjustment of gap (for

MOCB)& other type to

check the prescribed items

by the manufacturer

The gap may be checked and adjusted to the

required value. Half yearly

N/A

5

Wiring connections

Check and tighten wiring connection at terminal

points. Inspect wiring for open circuit, short circuit

and damaged insulation.

Half yearly

N/A

6 Aux.Switches

Check condition of contacts and refinish with fine

file if burnt or corroded. Check contact springs,

operating rods and levers. Check closing and

operating position with respect to main contacts

while breaker is slowly closed and opened manually.

Half yearly

N/A

7

Control and protection

chamber of 11KV switch

To check for alignment of front door

opening/closing for loose fitting, loose wiring of

opening in 11KV switchgear.

Half yearly

N/A

8 Insulated, jumpers CT and

PT in 11KV switchgear

To check for tightness of connections, proper

insulation and proper geometry. Half yearly

N/A

9 11KV cable connections

Check for overheating and proper connection and

insulation. Half yearly

N/A

1 Foundation

Check foundation for cracks and settings. Settings of

the breaker tank may break bushings or cause

misalignment of contacts or bindings of operating

mechanism.

Annual

N/A

2

Oil valves and plugs

Check condition of paint. Inspect oil valves and

plugs. Flush out oil and clean the oil

tank/quenching chambers.

Annual

N/A

3 Oil levels and gauges

Clean dirty gauge glasses and connections into tank.

Drain out and replace bushing oil if found dirty or

discoloured.

Annual

N/A

4

Breathers and Vents Check to see that screens and baffles in vents or

breathers are not obstructed or broken. Annual

N/A

5 Panels and cabinets

Check air circuit breaker or other panels of

insulating material for cracks and cleanliness. Check

condition of enclosing cabinets including hinges,

latches, locks door gaskets and paint.

Annual

N/A

6

Bushings or insulators

Clean porcelain with water, chloroethene or other

suitable cleaner. Repair chipped spots by painting

with lacquer such as red clay paint. Inspect gaskets

for leaks, tighten bolts. Check insulation resistance

with contacts closed and (Tan delta for condenser

type). Check oil sample from bottom of bushing for

dielectric strength and moisture. Replace or

replenish oil if necessary. Check and clean interior

at least once every five years.

Annual

N/A

7 Main terminals and ground

connections

Tighten all nuts and ground connections. Refinish

joint mating surface, if they have been overheated.

Inspect ground cable to see that it is not loose or

broken.

Annual

N/A

8

Main contacts

Remove the tanks or drain out oil, so that the

contacts can be inspected, dress contacts, if rough

with a fine file. Check contacts voltage drop with

millivolt meter after inspecting reasonable current.

Frequency of contact maintenance should be based

on numbers and severity of faults interrupted, rather

than a definite period. Check adjustment of gap

when required.

Annual

N/A

9 Contact pressure spring

Check for loss of temperature damage or other

deterioration. Annual

N/A

10 Flexible shunt

Check flexible shunts of contact hinges for

overheating or damages. Tighten connections. Annual

N/A

11 Magnetic, air or oil below

out devices

Check arc-rupturing blow out coils, magnetic circuit

arc chutes, de ion grids, oil blasts or other

interrupters for proper operations.

Annual

N/A

12

Cross heads Check contact cross head for misalignment breaks

bends or looseness on lift rods. Annual

N/A

13 Lift rods and guides

Check contacts for lift rods or brakes, weakening or

wrapping and pulling out at ends. Checks adequacy

of guides.

Annual

N/A

14

Operating rods shafts and

bell cranks

Check for loose locknuts, set screws, keys, bearing

bent rods or twisted shafts etc. clean moving parts of

rust, dirt and accumulated grease and oil, wash out

bearings, pivots and gears with chloromethane or

other suitable cleaner and operate breaker several

times to work out dirt and old lubricant. Lubricate

with new grease or oil.

Annual

N/A

15 Closing solenoid air

cylinder, meter or spring

Observe mechanism during several operations to see

that everything is in proper working order. Check

solenoid plunger for sticking in guides. Check coil

resistance and insulation resistance. Dismantle air

cylinder and clean and lubricate. Check spring for

proper tension and closing energy.

Annual

N/A

16

Solenoid valves

Check for condition of valve, and refit as necessary.

See that moving parts are free to operate. Check

resistance and insulation resistance of solenoid coil.

Annual

N/A

17 Operation counter

Check that the operation counter is properly

registering the breaker operations. Annual

N/A

18 Position indicator

Check that position indicator is properly registering

the breaker operations. Annual

N/A

19 Dashpots Check for proper setting and adjust as necessary.

Clean out and replenish liquid in liquid dashpot. Annual

N/A

20

Mechanism cabinets

Check condition of metal and hardware. Repaint as

necessary. See that door gaskets are tight and

properly dust and vermin proof.

Annual

N/A

21 Power supply and wiring

Inspect fuses of circuit breakers in all power and

control supply circuits, check in insulation

resistance of wiring with devices connected.

Annual

N/A

22

Oil dielectric test and

acidity test dependent on

actual tripping

Check dielectric strength of the insulating oil in the

main tanks and oil filled bushings. Oil should be

filtered or replaced if dielectric strength is found to

below 25 KV, or if there is a noticeable amount of

carbon in suspension on the bottom of the tanks.

Also check ratio and phase angle adjustments, the

acidity of the oil.

Annual

N/A

23 Operation

Some breakers particularly those carrying high

values of current have a tendency to develop contact

heating if left closed for long periods. Operating and

closing the breakers several times at intervals, as

system operation permit, may alleviate the heating

by wiping the oxide from the contact surfaces, as

well as demonstrate that the breaker is in operating

condition.

Annual

N/A

24

Bushing current

transformers and potential

devices

Check tap setting and adjustments at terminal board

to see that they agree with diagrams. Check

insulations resistance of wiring with devices

connected. Check of potential devices if changes

have been made in secondary connection and

burden. Tighten connections, including potential

devices top into bushing.

Annual

N/A

1

Testing of oil in oil filled

bushings

Once in two

years

N/A

2

Cleaning blast tube

internally and checking

clamping down nuts.

Once in two

years

N/A

3

Overhaul and checking

efficiency of main

compressor. Complete

overhaul of the O.C.B.

(The period can be changed

depending upon the lead

cycle of the equipment and

manufactures

recommendations).

Once in two

years

N/A


ANNEXURE-CT/MAIN/-01

CHECK LIST FOR MAINTENANCE OF CURRENT TRANSFORMERS


Season



T&P/material/PPEs

Earth resistance Tester

Cotton Rag

Sr.

no. ITEM TO BE INSPECTED

BRIEF DESCRIPTION OF

WORK

FREQUENC

Y

Permissible

Values

STATU

S

ACTION

TAKEN

1

CURRENT TRANSFORMER

Visual Damages & Deterioration

if any WEEKLY N/A

2 Oil Leakage if any WEEKLY N/A

3 Oil Level in CT WEEKLY N/A

6 Check condition of the Structure WEEKLY N/A

7 All unused wire are insulated in

CT WEEKLY N/A

8 All cables entry into CT is through

cable gland WEEKLY N/A

9 Check any abnormal sound with

Ultra probe 15000 WEEKLY N/A

1 CT Bushing MONTHLY N/A

2 Secondary Terminals MONTHLY N/A

3 CT Junction Box MONTHLY N/A

4 Oil Inspection Window MONTHLY N/A

6 Primary Connections MONTHLY N/A

7 Secondary Connections MONTHLY N/A

8 Mounting Frames MONTHLY N/A

9 Earthing CT/Frame/JB MONTHLY N/A

10 JB Connections MONTHLY N/A

11 Vermin Proofing of CT Junction

Box/Sec Terminal MONTHLY N/A

1 IR value of Primary to Earth HALF

YEARLY >200M Ohm

2 IR value of Secondary to Earth HALF

YEARLY >200 M Ohm

3 IR Value of Primary to Secondary HALF

YEARLY >200M Ohm

4 Tan Delta HALF

YEARLY <5%

1 CT Analysis YEARLY As per CT

Type


ANNEXURE-PT/MAIN/01

CHECK LIST FOR MAINTENANCE OF POTENTIAL

TRANSFORMERS


Season



T&P/material/PPEs

Safety Cotton Rag

Sr.

no.

ITEM TO BE

INSPECTED BRIEF DESCRIPTION OF WORK FREQUENCY

Permissible

Values

STAT

US

ACTIO

N

TAKE

N

1

POTENTIAL

TRANSFORMERS

Check any abnormal sound with

ultrasonic detector DAILY N/A

2 Visual damages and deterioration if any DAILY N/A

1 Oil Level sight Glass Weekly N/A

2 Earthing PT/Frame/JB Weekly N/A

3 JB Connections Weekly N/A

4 Oil Leakage if any Weekly N/A

5 Check condition of fuses & that all fuses

are intact Weekly N/A

1 PT Bushing Quartarly N/A

2 PT Junction Box Quartarly N/A

3 Secondary Connections Quartarly N/A

4 IR value of Primary to Earth Quartarly >200M Ohm

5 IR value of Secondary to Earth Quartarly >200 M Ohm

6 Oil Level in PT Quartarly N/A

7 Vermin Proofing of PT Junction Box/Sec

Terminal Quartarly N/A

1 Secondary Terminals Annually N/A

2 Primary Connections Annually N/A

3 Mounting Frames Annually N/A

4 IR Value of Primary to Secondary Annually >200 M Ohm

5 Correct Rating of PT Fuse, up to C&R

Panel Annually N/A

6 Check condition of the Structure Annually N/A

7 Check all unused wires are insulated Annually N/A

1 PT Analysis Once in 3 Yrs. As per pre

common values


ANNEXURE-LA/MAIN/01

CHECK LIST FOR MAINTENANCE OF LIGHTNING (SURGE)

ARRESTERS


Time

Season



T&P/material/PPEs


Cotton Rag

Sr.

no.

ITEM TO BE


FREQUE

NCY

Permissibl

e Values

STATU

S

ACTIO

N

TAKE

N

1 Surge Counter Note and record operation indicator reading along

with leakage current. DAILY

N/A

2 Base & support Usual inspection to detect cracking setting or shifting

of base of supports.

MONTHL

Y

N/A

3 Surge Monitor Check that surge monitor is properly connected and is

in working order and shows a leakage current.

MONTHL

Y

N/A

1 Jumpers and

clamps Check jumpers and clamps for tightness.

HALF

YEARLY

N/A

2

Porcelain

shells and

insulators

Clean porcelain insulators and arrestor unit shells.

Repair chipped spots on porcelain with lacquer such

as red clay paint.

HALF

YEARLY

N/A

3 Grading rings Check and tighten grading rings on high voltage

arrestors.

HALF

YEARLY

N/A

4 Gaps Check external gaps. Smooth off burnt spots and

readjust spacing.

HALF

YEARLY

N/A

1 Weather sheds

and hooks

See that weather sheds and hooks of oxide film

arrestors are securely fastened in place, repaint if

necessary.

ANNUAL

N/A

2 Line and Ground

connection

Check and tighten line and ground connections.

Check ground lead for corrosion or damage below

ground line. Check ground resistance. See that all leads

are as short and direct as possible.

ANNUAL

N/A

3

Operation tests

(Surge

generating

equipment

under

procurement)

To check the general working of lightening

arrestors by M&P Divisions. ANNUAL

N/A


ANNEXURE-ISOL/MAIN/01

CHECK LIST FOR MAINTENANCE OF LINE ISOLATORS & EARTH

SWITCHES


Time

Season



T&P/material/PPEs

Cotton Rag

Sr. no. ITEM TO BE


FREQUEN

CY

Permissi

ble

Values

STAT

US

ACTION

TAKEN

1 Insulators

Check for cracked or broken porcelain and

excessive dirt film and to undertake repair of

chipped spots by painting with lacquer such as red

clay paint.

WEEKLY

N/A

2

Blades and

contacts

Check that blades are properly seated in the

contacts.. WEEKLY

N/A

3

Blades and

latches and

stops

Check that blade latches where provided are

engaged.

WEEKLY

N/A

4

Locks and inter

locks

Check that switches are properly locked in the open

or closed position as required by padlocks or other

key type locks or interlocks.

WEEKLY

N/A

1 Bolts, Nuts &

Jumpers

Check bolts, nuts and jumpers for tightness. Apply

petroleum jelly on male and female contacts. Quarterly

N/A

1

I.R,value and

earth

resistance

Check IR, value with 2.5KV megger and earth

resistance. Check that double earthing is provided.

HALF

YEARLY

N/A

2 Auxiliary &

limit switches

Check condition of contacts and refinish with fine

file if burnt or corroded. Check contact spring

operating rod and lever. Check closing and opening

position with respect to main switch contacts or

travel or motor mechanism.

HALF

YEARLY

N/A

3

Manual

operating Rod

To check for proper engagement of emergency

operating handle and further its operation is smooth

and satisfactory.

HALF

YEARLY

N/A

4 Line & ground

ANNUALL

Y

N/A

5

Blades and

contacts

ANNUALL

Y

N/A


ANNEXURE-BAT/MAIN/01

CHECK LIST FOR MAINTENANCE OF BATTERY BANK & BATTERY

CHARGERS Name of

Grid:

Date &

Time

Season


Caution

Order/P

TW No.

T&P/mat

erial/PP

Es

Cotton

Rag

Sr. no. ITEM TO BE


FREQUEN

CY

Permissibl

e Values

STATU

S

ACTIO

N

TAKE

N

1 Battery room

and ventilation

See that battery room entrance doors are kept

closed and that ventilation to outside air are open

and air is circulated by running of the exhaust

fan

DAILY

N/A

2 Operation

Check charging rate hourly. Check and record

pilot cell specific gravity, temperature and

floating

voltage

DAILY

N/A

3

Bulb for dry

rectifier

element

Check for burnt bulb and replace when

necessary.

DAILY

N/A

4 Operations

Checking specific gravity and voltage of each

cell of lead acid cells. (before and after

charging) (weekly when trickle charge exists)

DAILY

N/A

5

Leakage test

Perform leakage test by lamp or

voltmeter method.

DAILY

(EACH

SHIFT)

N/A

1

Cleaning of terminals, applying Vaseline and

topping up with distilled water. (for lead acid

batteries)

WEEKLY

N/A

1 Cell Jars and

covers

Check for cracked or leaking jars or covers and

replace when necessary. Keep jars and covers

clean.

MONTHLY

N/A

2 Plates

Inspect plates(in case of transparent containers

only) carefully for signs of deterioration due to

improper charging. Note quantity, colour

and texture of sediment.

MONTHLY

N/A

3

Separators

See that the separators remain in place and are

keeping the plates properly spaced(in case of

transparent containers only)

MONTHLY

N/A

4 Electrolyte

Check electrolyte level and add distilled

water when required. MONTHLY

N/A

5

Acid and

distilled water

storage

See that enough distilled water and acid are kept

in storage to meet current needs. Check

containers for cleanliness.

MONTHLY

N/A

6 Operation

Check and record specific gravity and voltage of

each cell. MONTHLY

N/A

7 Transformer or

reactor

Check general condition and operating

temperature of transformer or reactor used in

bulb or dry type rectifiers.

MONTHLY

N/A

1 Connections

Checking all connections of charger and battery

for tightness. Quarterly

N/A

1

Discharging

and charging

cycle

This is required to be carried out as prescribed by

the manufacturer in order to prolong the life of

the battery.

Half yearly

N/A

2

Bulb or dry

rectifier

element

See the copper oxide or selenium rectifier

elements are not operating too hot, this will

shorten their life.

Half yearly

N/A

3 Rheostat

Check that sliding mechanism of the rheostat is

in order and clean the sliding contacts, if

required. Check contact heating and spring

pressure.

Half yearly

N/A

1

Battery room

and ventilation

Check metallic structures/parts located in the

room for corrosion and clean and paint

as necessary, check ventilation system fan etc.

for proper operation to make sure that no

explosive gases are being accumulated in the

battery room due to excessive gassing or poor

ventilation.

Annual

N/A

2

Base or rack

Inspect concretes base or wooden racks for

deterioration. Repair and repaint with acid

resistant paint as necessary.

Annual

N/A

3 Case pad

Check base pad of sheet rubber, or other material

for deterioration from acid or other causes. Annual

N/A

4 Inter cell

connectors

and terminals

Clean acid corrosion from connectors and

terminals should be lead coated. Tighten

terminals and apply petroleum jelly for exposed

surface.

Annual

N/A

5

Hydrometer and

thermo

meter

Check condition of hydrometer and

thermometers used for daily and monthly

readings against spare units held in reserve.

Annual

N/A

6 Sink funnel

and filters

See that the sink, funnels, fillers and other

distilled water and acid handling facilities kept

clean and in good useable conditions.

Annual

N/A

7 Water still

Check still for proper operation, adequacy

and purity of distilled water delivered. See

that equipment is kept clean

Annual

N/A

8

Complete overhauling of the battery. (as

recommended by manufacturer) Annual

N/A

N/A

N/A

N/A

N/A

N/A


ANNEXURE-CONTROL PANEL/MAIN/01

CHECK LIST FOR CONTROL PANEL Name of Grid: Date & Time

Season


Caution

Order/PTW No.

T&P/material/PP

Es

Cotton Rag

Maintenance Activities

S.NO. BRIEF DESCRIPTION OF WORK Frequency Permissib

le Values Status

Action

Taken

1 Check all indication lamps for working DAILY N/A

2 Check illumination lamp / power socket for working DAILY N/A

1 Vermin proofing of panel and door interlock switch MONTHLY N/A

2 Check & ensure that L/R switch is at remote position. MONTHLY N/A

3 Check fuse / MCB rating MONTHLY N/A

4 Check rating of fuses/MCB MONTHLY N/A

1 Control Panel Interior. HALF

YEARLY N/A

2 Control Panel external surface. HALF

YEARLY N/A

3 Relay / Contactors with air blower (from distance) HALF

YEARLY N/A

4 All Control Connections. HALF

YEARLY N/A

5 Earthing Connection wherever provided HALF

YEARLY N/A

6 Inter panel Coupling. HALF

YEARLY N/A

7 Multicore Cable Glands. HALF

YEARLY N/A

8 Check cubicle heater / thermostat for correct operation HALF

YEARLY N/A

9 Dressing of wiring. HALF

YEARLY N/A

10 Check door bidding for dust proofing. HALF

YEARLY N/A

11 Check & ensure that all multicore cables are earthed at

switchyard side only.

HALF

YEARLY N/A

12 Check and ensure that relay healthy indication is

glowing.

HALF

YEARLY N/A

13 Check that all unused wires are insulated. HALF

YEARLY N/A

1 All Protection Connections. At the time of

Prot checking N/A

1 All Communication Connections. At the time of

Com checking N/A

1 Insulation resistance of Multicore cables At the time of

commissioning

>50 M

Ohm


ANNEXURE-EARTHING/MAIN/01

CHECK LIST FOR MAINTENANCE OF EARTHING SYSTEM AT GRID

SUBSTATION Name of

Grid: Date & Time

Season


Caution

Order/PTW

No.

T&P/materia

l/PPEs

Maintenance Activities

S.NO. BRIEF DESCRIPTION OF WORK Frequency Permissible

Values

Stat

us

Action

Taken

1 All Earth pits MONTHLY N/A

1 All Earth connections at Earth pits. HALF

YEARLY N/A

2 Check all equipments for double earthing HALF

YEARLY N/A

3 Check all earthing conductors for adequacy & proper tightness. HALF

YEARLY N/A

4 Check proper clamping of earthing pipe and earthing

conductor.

HALF

YEARLY N/A

5 Check numbering of all earth pits. HALF

YEARLY N/A

6 Check availability of Cast Iron lid for each earthing pit. HALF

YEARLY N/A

7 Check exposed portion of earth conductor for Galvanizing or

painting

HALF

YEARLY N/A

8 Check & ensure painting of Earth isolator box with Green

colour for fast identification

HALF

YEARLY N/A

9 Check that each multicore cable is grounded through cable

gland.

HALF

YEARLY N/A

10 Check and ensure that all power cables are earthed at one end

only

HALF

YEARLY N/A

11 Check and ensure all multicore cables are earthed at switchyard

end only or alternatively at one end only.

HALF

YEARLY N/A

12

Check and ensure that Substation building earth is connected to

separate earth pit / pits and then the same is extended to mesh

earthing in switchyard.

HALF

YEARLY N/A

13

Check and ensure that individual Transformer neutral is

connected to separate earth pit and then the same is extended to

mesh earthing in switchyard.

HALF

YEARLY N/A

14 All Earth connections at equipment mounting frames HALF

YEARLY N/A

15 All Earth pits resistance for Power / Distribution Transformer

neutral YEARLY < 5 Ohm

16 All Earth pits resistance for LAs YEARLY < 5 Ohm

17 Resistance of earth mesh YEARLY < 1 Ohm

18 Final Status and Remarks


ANNEXURE-33 KV LINES /MAIN/01

CHECK LIST FOR MAINTENANCE OF 33 KV LINES

Sr.

no.

ITEM TO

BE

INSPECT

ED

BRIEF DESCRIPTION OF WORK FREQUEN

CY

Permissi

ble

Values

STAT

US

ACTI

ON

TAKE

N

1

Poles-

Steel

Wood

Cement

Damages/broken poles or for ground level erosion and

corrosions where the pole is not capable of safely

supporting its load.

Quarterly NA

2 Bowed or leaning poles due to improper guying or

overloading. Quarterly NA

3 Unauthorized attachments such as fencing, aerial wires

etc. Quarterly NA

4 Poles which are very much exposed to hitting/striking

of animals and bumping and scrapping by vehicles Quarterly NA

5 If the pole Number plate is still distinct Quarterly NA

6 Check the condition of foundation and attend it, if

necessary. Quarterly NA

7 Examine if pole requires painting of in case of

steel/wood poles Quarterly NA

1

Stays

Correct direction and proper angle of the stay Quarterly NA

2 Loose broken or any other damage done to stays Quarterly NA

3 Whether stay insulator is intact/whether stay is properly

earthed Quarterly NA

4 If stay rods are corroded. Attend the same if required. Quarterly NA

1

Cross

arms and

pole top

steel

works

If the cross-arms/clamps/knee has/have slipped. Quarterly NA

2 Bending of cross arms due to uneven tension Quarterly NA

3 Excessive rusting of the cross arms bracings etc. Quarterly NA

4 Cracked or splitting or the wooden cross-arms Quarterly NA

5 Loose or damaged bracings. Attend the same, if

required. Quarterly NA

1

Insulators

Broken or chipped porcelain flashover marks Quarterly NA

2 Tilted insulators Quarterly NA

3 Excessive deposit of dust/salt/coal and other pollution

clean the same. Quarterly NA

4 Excessive rusting of fittings, replace the same, if

required. Quarterly NA

1

Conductor

s and earth

wire

Examine, if securely tied to the insulator/pole/cross-

arms Quarterly NA

2 Proper sag, set right the same, if required. Quarterly NA

3 Proximity of trees and other objects including building

etc. Quarterly NA

4 Sufficient clearance between conductors and earth wire

and also from the ground Quarterly NA

5 Sufficient clearance from other electric/telephone lines

passing along below or above it. Quarterly NA

6 Earth wire is properly supported Quarterly NA

7 All the line guards are intact and installed where

necessary Quarterly NA

Sr.

no.

ITEM TO

BE

INSPECT

ED


CY

Permissi

ble

Values

STAT

US

ACTI

ON

TAKE

N

8

Conductor

s and earth

wire

If joints in the jumpers and conductors appear all right Quarterly NA

9 Broken conductors strands Quarterly NA

10 Nicking near insulator neck/or near conductor clamps Quarterly NA

11 Bindings wire has not become lose and open Quarterly NA

12 Mid span joints have not cracked. Quarterly NA

13

All joints and jumpers of aluminum conductors have

proper clamps/jointing sleeves. Straight the same, if

required.

Quarterly NA

1

Jumpers

and other

line

accessorie

s

Proper supporting and jointing two ends of the jumpers

with suitable clamps. Quarterly NA

2 Sufficient clearance between jumpers on the 3-phases Quarterly NA

3 Sufficient clearance of jumpers from metal Quarterly NA

4 Provision of proper insulation of jumpers Quarterly NA

5 Signs of over-heating and burnings on jumpers and

other fittings. Quarterly NA

6 Loose/defective clamps jointing sleeves, bolts and nuts,

and other fittings. Quarterly NA

1

Tree

trimming

and bird's

nests etc.

Cut off the trees branches where necessary to maintain

a minimum clearance of 1.8m on each side of the line Half yearly NA

2 Remove all dead wood. Half yearly NA

3

Remove all bird's nests. (once before the monsoons or

earlier, if necessary) Half yearly NA

1

Stays

Tighten the loose stays. Annually NA

2 Replace the broken/damaged stays and stay bows Annually NA

3 Replace the broken stay insulator/recondition the Earth Annually NA

4

Provide sufficient barbed wire/cattle guards on the stay

to avoid rubbing of cattles Annually NA

1

Cross

arms

Replace the broken/splitted/cracked/bent cross arms

by new ones. Annually NA

2

Bring in position the slipped cross

arms/clamps/bracings. Annually NA

3

Paint the steel cross arms and bracings etc. If

excessively rusted. Annually NA

1

Insulators

and

fittings

Clean and check for cracked/chipped and

punctured insulators. Replace, where necessary. Annually NA

2

Examine for the surface contamination and

remove it by wiping with a soft cloth (do not use cotton

waste). If the deposit has set hard, a weak acidic

solution may be used.

The insulators be checked twice a year preferably or

before and after (monsoons) Annually NA

1 Conductor

s and

earth

wires

Tighten loose bindings and replace damaged ones. Annually NA

2

Examine for corrosion at the joints of

conductors and insulators. Clean and renew, where

necessary. Annually NA

Sr.

no.

ITEM TO

BE

INSPECT

ED


CY

Permissi

ble

Values

STAT

US

ACTI

ON

TAKE

N

3 Examine closely for broken strands

particularly at the clamps and insulators due to

vibration and repair, where necessary. Annually NA

4

Examine general condition of the conductor

and earth wires i.e. for kinks, crushed spots over/under

tensioning, etc., and recondition, where necessary. Annually NA

5

Examine for any loose/cracked joints of

conductors in the mid span and recondition where

necessary. Annually NA

6

Examine for any loose/cracked joints slipping

of conductors from the clamps. Tighten all clamps and

fittings. Annually NA

1

Lightening

arrestor

Clean and examine insulators for cracks or

flashover. Replace, where necessary. Annually NA

2

Perform impulse voltage spark over test and

leakage current test to know the condition of

the arrester; replace in case of unsatisfactory

results. Annually NA

3 Keep records of test results. Annually NA

4

Check and tighten all line connections and

earth leads Annually NA

1 Earthing

System

Replace all broken earth leads and tighten others.

Measure earth resistance of various earths with

earth. Tester. In case of low values, recondition

them. Annually NA

2

Anti-

climbing

devices

and

danger

plates

etc.

Recondition the anti-climbing devices such as barbed

wire, locks, etc., paint and reprint the danger plated if

defaced. Annually NA


CHECK LIST FOR MAINTENANCE OF 11 KV LINES

Sr.

no.

ITEM TO

BE

INSPECTE

D

BRIEF DESCRIPTION OF WORK FREQUE

NCY

Permiss

ible

Values

STAT

US ACTION TAKEN

1

Poles

Steel

Wood

Cement

Stays

Cross arms

Conductor

Insulator

Earthwire

Lightning

arrestor

Earthing

System

Same as recommended for the items as 33

KV lines in addition to the followings

Quarterly

/

Half

year/

Year

1

G.O.

Switchs

(with fuse

unit)

Check for the following:

A method for field

testing for switch

contacts with live line

consists in using an

insulated rod (for 11

KV) adjustable height

having at its upper end

a tallow candle fixed in

a clip Hold the candle

against the hot contact

for a few seconds &

then examine. If the

grease slightly melts,

mark the contact for

attention. If the grease

runs, the switch

requires early attention

and if it smokes,

dangerous condition is

assumed, the switch

required immediate

attention.

2 For smooth operation Quarterly

3

Evidence of over-heating burning,

corrosion/pitting on the switch contacts.

Quarterly

4 Broken or damaged insulators. Quarterly

5 Proper and tight earth connections. Quarterly

6

Fuse links for continuity, tightness of

connections and correct rating.

Quarterly

7 Proper locking arrangement. Quarterly

8 Proper alignment of switch contracts. Quarterly

9

Proper and complete fitting of male contacts

into the female ones.

Quarterly

10 Arcing horns are intact.

Quarterly

1

11 KV

Cable and

Cable

boxes.

Check for the following:

2 Proper supporting of the cable and the cable

boxes. Quarterly

3 Damaged insulators. Quarterly

4 Oil and compound leaks and that the cable

box is properly tippe up with the compound. Quarterly

5 Tight and intact connections. Quarterly

6 Proper earthing. Quarterly

7 Overall condition of the cable and joint. Quarterly

1 G.O.

Switch

(with fuse

unit)

Cleanliness: Clean all dust and other

deposits with neat and dry cloth.

Half-

yearly

(its

maintena

nce may

be done

even

earlier as

These points should be

particularly checked

when contacts are

replaced.

2

Switch contacts: (1) Check for the aliment,

adequate pressure and smooth operation and

adjust, where necessary. (2) Examine for

burning/over-heating or other damages.

Fixed and moving

contacts may be

dressed by using fine

file/fine sand paper.

Sr.

no.

ITEM TO

BE

INSPECTE

D

BRIEF DESCRIPTION OF WORK FREQUE

NCY

Permiss

ible

Values

STAT

US ACTION TAKEN

Recondition or replace, where necessary. the

functioni

ng of GO

Switches

is

generally

in

disorder

and is

always a

source of

trouble).

Use of rough sand

paper be avoided.

3

Insulators: (1) Check for cracks, chipping

and other defects, replace, where necessary.

(2) Remove dirt, coal and other pollutions

by wiping with soft cloth. Use weak acidic

solution, if the deposit has set hard.

Petroleum jelly/ white

Vaseline or other

suitable contact

lubricant should

applied on contacts

grease should be

applied on all the

moving parts.

4 Arcing Herms : Check if those are intact

and replace, if damaged/burnt.

5

Mechanism: Clean, examine and renew

worn out parts. Re-lubricate and check for

correct operation.

6 Fuse unit: Replace old fuses with new ones

of right type and capacity and proper length.

7

Main connections and Earthing: proceed as

described under separate heading of

‘Jumpers’ and ‘Earthing devices’.

8 General : check all hardware and tighten, if

needed.

1

11 KV

Cable and

cable

boxes

Clean and examine for damaged bushings Annually

2 Check for compound level, if there is

leakage.

Annually

3 Perform insulation resistance test,

recondition or replace, where necessary.

Annually

4 Keep continuous records of insulation

resistance.

Annually

CHECK LIST FOR MAINTENANCE OF LT LINES

Sr.

no.

ITEM TO

BE

INSPECT

ED

BRIEF DESCRIPTION OF WORK FREQUENC

Y

Permiss

ible

Values

STA

TUS ACTION TAKEN

1

Pole

Stay

Cross

arm

Conductor

Insulator

Connectors

Cable

Boxes

etc.

Same as recommended for these items under schedule

for HT Lines (Whether cobwebs, kite strings, etc.,

hanging on the conductor)

Four

Monthly

This becomes

source of heavy

leakage when wet.

1

LT

Switch

Check for the flowing:

2 If the switch with cover is intact. Monthly

3 If the cable/switch running hot. Monthly

4 Broken cut-outs. Monthly

5 Signs of over-heating/burning on contacts. Monthly

6 Proper size of fuse wire. Monthly

7 If the switch is properly earthed. Monthly

8 Safety from rain water etc. Monthly

1

LT

Switch

Check lead on the LT circuit and replace the LT

cable/LT switch by higher capacity one, where

necessary.

Half-Yearly

2 Replace the damaged LT Cable with new one of right

capacity. Half-Yearly

3 Examine the switch for smooth operation. Half-Yearly

4 Replace the burnt/cracked cut-outs. Half-Yearly

5 Recondition the switch contacts Half-Yearly

6 Replace the old fuses with new ones of right capacity. Half-Yearly

7 Tighten all connections. Half-Yearly

8

Ensure that the inlet of the cable into the switch is

plugged with plastic compound to avoid entry of rain

water. Refill, where necessary.

Half-Yearly

9 Clean off the cob-web and other nests etc., from the

inside of the switch. Half-Yearly

1

Poles

Stays

Cross

arm

Conductor

Insulator

Connectors

Cable

boxes etc.

Same as recommended for these items under schedule

for HT Lines.

One to two

yearly

(depending

upon the

volume of

work)

Annexure- AR-1

(To be filled by JUNIOR ENGINEER/Project Engineer)

1 Operational checks Status

i Switchgear ON/OFF through PTCC OK Not OK

ii Switchgear ON/OFF manual (in 'Sectionaliser/ RL series' only) OK Not OK

iii Mechanical Interlocks OK Not OK

iv

Switchgear tripping through Emergency Lever (in U Series

only) OK Not OK

v Position Indicator (Mechanical) OK Not OK

2 Electrical Test

a Local / Remote - ON / OFF OK Not OK

b LED indication on PTCC Breaker Close OK Not OK

c LED indication on PTCC Breaker Open OK Not OK

d

Electrical interlock - Enable / Disable switch OK Not OK OK

Not OK OK Not OK

e Battery voltage ( Aux supply should be turn off ) ( 24VDC ) OK Not OK

f Auxiliary supply Normal Abnormal

g Check/ Download WSOS history logs Yes No

h Current values on PTCC ( After switch ON ) OK Not OK

i

Voltage values on PTCC ( After switch ON ) OK Not OK OK

Not OK OK Not OK

j Pressure reading of SF6 on PTCC ( RL Type only ) OK Not OK

k Check PT fuse intactness and continuity OK Not OK

l ON / OFF operation through Battery OK Not OK

3 Environmental checks

a Visual inspection for missing parts OK Not OK

b Cleaning of PTCC panel, ACR ( dust etc ) OK Not OK

c Connection Check of Plugs and CAPM compartment OK Not OK

d Cable entry point sealed in PTCC OK Not OK

E Stress on bushing due to cable/conductor connection OK Not OK

f Method of Conductor connection on bushing OK Not OK

g Tie / clamp support to umbilical cable (control cable) OK Not OK

h Terminal Connectors OK Not OK

i Visual inspection of any damages OK Not OK

j Presence of Earthing OK Not OK

k Earthing ( Pit ) Resistance test results OK Not OK

l Tightening of Cable clamps / connectors to bushing OK Not OK

m Condition of Male/Female Pins on plugs (PTCC / S/G) OK Not OK

n Clearance of PT with Guard wire OK Not OK

o Presence of PT bushing insulated Caps OK Not OK

4 PTCC panel door intactness (window + Main door) OK Not OK

5 Lock of PTCC panel door OK Not OK

6 Condition of Electronic Module - OK Not OK

a. CAPM / SCEM / CCEM / OCPM OK Not OK

b. MDIM3 / MDIM2 OK Not OK

7 Status of battery cells terminals, links OK Not OK

8 Modem Functionality OK Not OK

Remarks:

Witnessed by:

Junior Engineer: S.D.O

Annexures DT-1

Check List for oil filled Distribution Transformers: Checked

(To be filled by Junior Engineer)

1) Check that the colour of the silica gel in the breather is blue.

2) Check the breather for any cracks, holes, transparency and oil in the oil cup.

3) Check for any signs of No arcing/pitting mark on Bus-bar & palm connector.

4) Ensure that there is no leakage of oil from gaskets, flanges, valves, radiators,

bushings etc. Ensure oil level of conservator & cleaning of glass of conservator.

5) Check that the bushing surface is clean.

6) Check the bushings for any crack or any chipping of porcelain.

7) Check the earthing of the tank cover to tank.

8) Check the condition of neutral & transformer body grounding

9) Ensure that the surface of radiator is clean.

10) Check the earthing of fencing (enclosure) with two separate earths.

Witnessed by:

Junior Engineer: SDO:

Annexures DT-2

Test Results:


Test

Parameters

Limits Date of

Test

Actual value Remarks

IR test.

1. IR value shall be

equal for all three

phases for HT-E,

LT-E, HT-LT.

2. Normally IR value

shall be minimum

100 MΩ for HV &

50 MΩ for LV

windings at the the

temp of 50°C.

BDV

> 30 kV(avg) at 2.5mm

gap

Earth

resistance

Earth resistance shall be

less than 1Ω

Witnessed by:


Annexures DT-3

Check List for Dry type Distribution Transformer: Checked


1) Check that no dust on enclosure, doors & marshalling box.

2) Check the enclosure & marshalling doors are closed properly.

3) Check for working/setting for thermostat in marshalling.

4) Check for working and physical condition of DT energy meter.

5) Check for working of lamp in marshalling box.

6) Check the no dust deposition over active part.

7) Check the earthing of the enclosure at two places with separate earthing point.

8) Check the earthing of the neutral with two separate earthing points.

9) Check for working of exhaust fan.

10) Check there should not be any open space.

Witnessed by:


Annexures DT-4

Test Results:


Test

Parameters

Limits Date of

Test


IR test.

1. IR value shall be

equal for all three

phases for HT-E,

LT-E, HT-LT.

2. Normally IR value

shall be minimum

100 MΩ for HV &

50 MΩ for LV

windings at the the

temp of 50°C.

Earth

resistance


less than 1Ω

Witnessed by:


Annexures DT-5

Pre commissioning checks for oil filled Distribution Transformers: Checked


1) Check that the colour of the silica gel in the breather is blue.

2) Check the breather for any cracks, holes, transparency and oil in the oil cup.

3) Check for any signs of No arcing/pitting mark on Bus-bar & palm connector.

4) Ensure that there is no leakage of oil from gaskets, flanges, valves, radiators,

bushings etc.

5) Check that the bushing surface is clean.

6) Check the bushings for any crack or any chipping of porcelain.

7) Check the earthing of the tank cover to tank.

8) Check the condition of neutral & transformer body grounding

9) Ensure that the surface of radiator is clean.

10) Check the earthing of fencing (enclosure) with two separate earths.

Witnessed by:


Annexure DT-6

Test Results:


Test

Parameters

Limits Date of

Test


IR test.

1 IR value shall be

equal for all three

phases for HT-E,

LT-E, HT-LT.

2 Normally IR value

shall be minimum

100 MΩ for HV &

50 MΩ for LV

windings at the the

temp of 50°C.

Ratio Transformer turn

ratio test

MBT Magnetic Balance

test

BDV

> 30 kV(avg) at 2.5mm

gap

Earth

resistance


less than 1Ω

Witnessed by:


Annexure DT-7

Pre commissioning checks for Dry type Distribution Transformer: Checked


1) Check that no dust on enclosure, doors & marshalling box.

2) Check the enclosure & marshalling doors are closed properly.

3) Check for working/setting for thermostat in marshalling.

4) Check for working and physical condition of DT energy meter.

5) Check for working of lamp in marshalling box.

6) Check the no dust deposition over active part.

7) Check the earthing of the enclosure at two places with separate earthing point.

8) Check the earthing of the neutral with two separate earthing points.

9) Check for working of exhaust fan.

Witnessed by:


Annexure DT-8

Test Results:


Test

Parameters

Limits Date of

Test


IR test.

1 IR value shall be

equal for all three

phases for HT-E,

LT-E, HT-LT.

2 Normally IR value

shall be minimum

100 MΩ for HV &

50 MΩ for LV

windings at the the

temp of 50°C.

Ratio Transformer turn

ratio test

MBT Magnetic Balance

test

Earth

resistance


less than 1Ω

Witnessed by:


Annexure RMU-1

Check list –RMU

Sub-Division

Item Description Status

A Type of Substation

B 11 kV Switchgear/RMU

1 Make

2 Physical Condition

(a) RMU Covers

(b) Earth Bus Bar Status

3 SF6 Preassure Gauge Indication

4 Voltage Indicating LED's

5 Grounding

6 Rubber Mat

7 Fault Passage Indicator

Witnessed by:


Annexure RMU-2

Check List:

(To be filled by JUNIOR ENGINEER/Project Engineer

1) Check the manometer for any signs of SF6 gas leakage.

2) Check the functioning of the breaker, isolator & earth switch.

3) Check the functioning of FPI.

4) Check the functioning of VPIS

5) Check the Earth Resistance

6) Check the cable tightness

Witnessed by:


Annexure UG-1

Check List during Cable Testing Checked

1. Ensure cable is not live by Neon Tester.

2. The cable earthing is properly connected to Panel earth

3. The Panel earthing is properly connected to S/S Earth.

4. Ensure Cable Terminations are cleaned properly

5. Ensure Cable cores are earthed other than testing core

6. Ensure cable testing at Recommended voltage

Check during Rectification

1. Ensure caution tape, warning lights Boards & barricading

Provided at work site

2. Ensure cable laid at recommended depth

3. Ensure docketing done on cable & joints

4. Ensure backfilling done properly

Witnessed by:

JUNIOR ENGINEER/PO: SDO:

Annexure ABC-1

Check List


1. Ensure AB cable is not live by use of Neon Tester.

2. Ensure AB cable earthing is properly connected to Messenger

3. Ensure Messenger earthing is properly connected to Pole Earth.

4. Ensure AB Cable Terminations are cleaned properly


6. Ensure cable testing at recommended voltage


1. Ensure caution tape, warning lights, barricading


2. Ensure proper jointing done at fault sites.

3. Ensure Plastic Cable Ties are used to hold the joint

Witnessed by:


Annexure-ERT-1

Check list- Earthing

Pre-requisite for Routine Maintenance


T&P/material/PPEs


Cotton Rag

Routine Maintenance Activities

NATURE OF WORK Freq Permissible

Values Status

Action

Taken

Check and Clean

All Earth pits Twelve Months N/A

Check and Tight

All Earth connections at equipment

mounting frames Twelve Months N/A

All Earth connections at Earth pits. Twelve Months N/A

Measurement

All Earth pits resistance for HT/LT Feeder

Neutral Twelve Months < 5 Ohm

All Earth pits resistance Twelve Months < 5 Ohm

Resistance of Pole Twelve Months < 1 Ohm

General Checks

Check all equipments for double earthing Twelve Months N/A

Check all earthing conductors for

adequacy & proper tightness. Twelve Months N/A

Check proper clamping of earthing pipe

and earthing conductor. Twelve Months N/A

Check numbering of all earth pits. Twelve Months N/A

Check availability of Cast Iron lid for

each earthing pit. Twelve Months N/A

Check exposed portion of earth conductor

for Galvanizing or painting Twelve Months N/A

Check & ensure painting of Earth isolator

box with Green color for fast

identification

Twelve Months N/A

Check that each multicore cable is

grounded through cable gland. Twelve Months N/A

Final Status and Remarks

Witnessed by:


Annexure- G.O.-1

Check List- G.O Switch

Sr No. Particulars Ok Not OK

1 Alignment of Male Female Contact

2 Condition of Post Insulator

3 Operating Rod

4 Earthing of G.O Switch

5 Condition of Arcing Horn

6 Condition of Operating Handle

7 Locking Arrangement

Witnessed by:


Annexure- OH-1

Check List –OH Lines

Sr

No. Parameters Observations

1 Condition & size of GI wire. It should be 7/10 SWG OK Not OK Remarks

2

Condition of Guy/Egg Insulator, if any damage or

missing observed, should be fix/replace. OK Not OK

3

Condition of tension screw, if any damage observed

, it has to be changed otherwise to tighten the turn

buckle ,if required OK Not OK

4 condition of anchor hook OK Not OK

Visual Inspection

5

Condition of Disc Insulator, if there is any crack,

flash mark on the surface of the disc, disc should to

be change. OK Not OK

6

Condition of strain clamp of disc insulator, If any

crack or flash mark on surface, it has to be change OK Not OK

7

Condition of Pin insulator, if there be any flash

mark on the insulator surface, it has to be change

otherwise check the tightness with the spindle. OK Not OK

8

Condition of Pin insulator spindle, if any damage

or bend, to be change otherwise check the tightness

of the fixing nuts. OK Not OK

9

Condition of Top hamper, if any tilt observed at top

hamper it has to be straight or any damage occurred

to the metal part, it is to be change, otherwise check

the tightness of fixing nuts bolts. OK Not OK

10

Condition of the V-arm. if any damage occurred on

V-arm or on the fixing clamp, it is to be changed

otherwise check the tightness of the fixing Nuts,

bolts OK Not OK

11

Condition of channel-arm, if any damage occurred

on channel-arm or on the fixing clamp, it is to be

changed otherwise check the tightness of the fixing

Nuts, bolts OK Not OK

12

All metal part to be painted by Primer &Aluminium

paint for increasing the durability of life span OK Not OK

13 Visual inspection of bare conductor OK Not OK

14

Span length should be maximum 40m /50 m (Urban

/Rural) if the length larger than it , mid pole to be

provided. OK Not OK

15

Line should be sectioned at every 4/5 span apart, if

more it to be reduced to 4/5 span OK Not OK

16 Visual inspection of Earthing OK Not OK

17

Visual inspection of Guard wire- if any

damage/broken happened, it would be drawn by 4

SWG GI wire. OK Not OK

18

Inspection of Joints – all jumpers should be done by

conductor same as line conductor or higher rating &

joints to be done by suitable C-wedge connector/ PG

Clamp/D-clamp. Mid span joint to be to be done by

Suitable Sleeves & the joint is limited to 2 no per

span. OK Not OK

19 Anti-climbing device OK Not OK

Witnessed by:


Annexure LT ACB

SN Parameter Points to be checked Finding

1 Physical

Condition

a) check ACB have cover and locked.

b) Check for any visual deformity/ flash

mark/ crack/ dust on arc chutes, arcing

contacts and moving contacts.

c)Check the point of entry of busbars into

the enclosure (The busbars should be

properly tapes and the entry should be

sealed with sealants like silicon grease)

d) Check tripping circuit, CTs, release (

if applicable).

e) Status of Enclosure to be checked (

damage/ rusting, etc)

2 Alignment

and Support

Structure

The ACBs placed on level structure and

secured properly to be checked-

3 Dressing and

Crimping of

Main &

Looping

cables

All incoming and out going cables to be

crimped and connected properly to the

incoming and outgoing busbars.

4 ACB

Earthing

Earthing to be checked

5 Safeguarding

of Bare

Terminals

Bakelite/ FRP separator plats used where

clearance are reduced are to be checked

Witnessed by:

JUNIOR ENGINEER SDO:

Annexure- LT UG Cable


1. Ensure cable is not live by Neon Tester.

2. The cable earthing is properly connected to Panel earth

3. The Panel earthing is properly connected to S/S Earth.

4. Ensure Cable Terminations are cleaned properly




1. Ensure caution tape, warning lights Boards & barricading


2. Ensure cable laid at recommended depth

3. Ensure labelling done on cable & joints

4. Ensure backfilling done properly

Witnessed by:


Annexure LT OH Conductor

SN Parameter Points to be checked Finding

1 Physical

Condition

(Visual

Checking for

Stay and

Line support)

a.Check the Condition & size of GI wire

(It should be 7/10 SWG)

b.Check the Condition of Guy/Egg

Insulator-

c. Check the Condition of tension screw

d.Check the condition of anchor hook

e. Check the Condition of Shackle

Insulator

f. Check the Condition of Pin insulator

spindle

g. Check the Condition of Top hamper

h. Check the Condition of the Double

line X-arm

i. Check all metal part to be painted by

Primer &Aluminium paint

2 Conductor

Inspection

j. Check if any damage occurred on the

conductor

k. Check for use of Line Spacer

l. Check for use of cradles

3 Earthing check for proper earth wire & Earthing

4 Joints &

Jumpers

check for proper Joints and Jumpers

5 Pole

Connections

i. Check for Cable mounting on over head

feeder

ii. Check for no of service cable form one

single pole & dressing of service cable

6 Configuratio

n of Line

Check for configuration of Line-

Vertical Configuration

Delta Configuration

Witnessed by:


Annexure LT ABC


1. Ensure AB cable is not live by use of Neon Tester.

2. Ensure AB cable earthing is properly connected to Messenger

3. Ensure Messenger earthing is properly connected to Pole Earth.

4. Ensure AB Cable Terminations are cleaned properly




7. Ensure caution tape, warning lights, barricading

provided at work site

8. Ensure proper jointing done at fault sites.

9. Ensure Plastic Cable Ties are used to hold the joint

Witnessed by:


Annexure LT Earthing

Name of LT Feeder:

Date & Time

Pole No-

Season - Summer/Winter:

Pre-requisite for Routine Maintenance Caution Order/PTW No. T&P/material/PPEs Earth resistance Tester Cotton Rag Routine Maintenance Activities

NATURE OF WORK Freq Permissible

Values Status

Action

Taken Check and Clean All Earth pits Twelve Months N/A Check and Tight All Earth connections at equipment

mounting frames Twelve Months N/A

All Earth connections at Earth pits. Twelve Months N/A Measurement All Earth pits resistance for LT Feeder

Neutral Twelve Months < 5 Ohm

All Earth pits resistance for LT ACB Twelve Months < 5 Ohm Resistance of Pole Twelve Months < 1 Ohm General Checks Check all equipments for double earthing Twelve Months N/A Check all earthing conductors for

adequacy & proper tightness. Twelve Months N/A

Check proper clamping of earthing pipe

and earthing conductor. Twelve Months N/A

Check numbering of all earth pits. Twelve Months N/A Check availability of Cast Iron lid for each

earthing pit. Twelve Months N/A

Check exposed portion of earth conductor

for Galvanizing or painting Twelve Months N/A

Check & ensure painting of Earth isolator

box with Green color for fast identification Twelve Months N/A

Check that each multicore cable is

grounded through cable gland. Twelve Months N/A

Final Status and Remarks

Witnessed by:


Annexure LT Metering & Service Cable

Name of Consumer:

Date &

Time

Account No-

Sub-Division -

NATURE OF WORK Frequency Permissible

Values Status

Action

Taken

Any visible Cut mark or Puncture on

service cable 24 Months N/A

Checking all required information

written on meter box and are visible. 24 Months N/A

Whether Meter/MCCB is tightly fixed

or hanging 24 Months N/A

All Seals on MCCB & Terminals are

proper and not tampered 24 Months N/A

Consumer cable is at adequate height

while crossing the street/road (from

ground)

24 Months Min 5.8

Meters

Accuracy of Meter 24 Months ±3%

Witnessed by:


Annexure LT Feeder Pillar

Name of Feeder Pillar Date

Type of Feeder Pillar Time

Feeder Name


Values Status

Action

Taken

Cable connection tightness 12 Months N/A

Replacement of sockets 12 Months N/A

Tagging of outgoing & incoming

feeders 12 Months N/A

Earthing of Feedar& Service

Pillar (values to be provided) 12 Months N/A

Proper Cable earthing 12 Months N/A

Locking of doors 12 Months N/A

Replacement of fuse 12 Months N/A

Replacement of fuse base 12 Months N/A

Cleaning of Feeder Pillar 12 Months N/A

Condition of Plinth 12 Months N/A

Danger Plate 12 Months N/A

Witnessed by:


Annexure LT Fuse Board

Name of DT Date

DT Rating Time

Feeder Name


Values Status

Action

Taken

LV cable from DT shall be routed

through palm/bi-metallic connector. 12 Months N/A

Insulated cable from DT to fuse board

shall pass through DT meter CTs rings. 12 Months N/A

Only insulated cable shall be used for

connecting LV side of transformer to

fuse board.

12 Months N/A

Laying of cable from LV side of DT to

fuse board shall be separated using cleat

(wooden/PVC).

12 Months N/A

Proper size thimbles/Lugs used at cable

end to join it to fuse board. 12 Months

N/A

Lugs/Thimbles shall be fixed using

proper size crimping tool (hammering of

Lugs/Thimbles must be avoided because

this leads to weakening/breaking of

strands of cable).

12 Months

N/A

Proper color tape being used for taping

at lugs/thimbles. 12 Months N/A

Fuse Board shall be installed on Bakelite

sheet. 12 Months N/A

Height of fuse board 12 Months Min 6 Feet

Check for tightness of fuse wire.

12 Months N/A

Check for any oil & dust from fuse wire

and aluminum parts

12 Months N/A

Only insulated cable shall be used for

connecting fuse board to feeder line. 12 Months N/A

Laying of insulated cable form fuse

board to feeder line shall be properly

routed using clamps to fix it from

hanging.

12 Months N/A

Measurement of load of LT side of DT

(Phase wise) 12 Months

As per rating

of DT

R Phase

Y Phase

B Phase

Fuse wire Detail

Size

Rating (Amp)

Witnessed by:


Documents

Maintenance of Distribution network under DHBVNdhbvn.org.in/staticContent/tender/Manual_Handbook_Maintenance-2017.pdfCircuit breaker can be reset (either manually or automatically)