400 kv swyd FOR DOJ

7/31/2019 400 kv swyd FOR DOJ

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Understanding basics of switchyard

Switchyard equipments and schemes

Functions of various equipments

Brief description of modes of transmission


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What is a Switchyard ?What is a Switchyard ?It is a switching station which has the following credits :It is a switching station which has the following credits :

(i) Main link between Generating plant and(i) Main link between Generating plant and

Transmission system, which has a large influence onTransmission system, which has a large influence on

the security of the supply.the security of the supply.

(ii) Step-up and/or Step-down the voltage(ii) Step-up and/or Step-down the voltage

levels depending upon the Network Node.levels depending upon the Network Node.

(iii) Switching ON/OFF Reactive Power Control(iii) Switching ON/OFF Reactive Power Control

devices, which has effect on Quality of power.devices, which has effect on Quality of power.


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Power evacuation from switchyardPower evacuation from switchyard

400 KV LINES400 KV LINES

VINDHYACHAL-JABALPUR # 1VINDHYACHAL-JABALPUR # 1 VINDHYACHAL-JABALPUR # 2VINDHYACHAL-JABALPUR # 2

VINDHYACHAL-JABALPUR # 3VINDHYACHAL-JABALPUR # 3 VINDHYACHAL-JABALPUR # 4VINDHYACHAL-JABALPUR # 4 VINDHYACHAL- SATNA # 1VINDHYACHAL- SATNA # 1 VINDHYACHAL- SATNA # 2VINDHYACHAL- SATNA # 2

VINDHYACHAL- SATNA # 3VINDHYACHAL- SATNA # 3 VINDHYACHAL- SATNA # 4VINDHYACHAL- SATNA # 4 VINDHYACHAL- KORBA # 1VINDHYACHAL- KORBA # 1 VINDHYACHAL- KORBA # 2VINDHYACHAL- KORBA # 2


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POWER ALLOCATIONPOWER ALLOCATION

Stage I & II Stage IIIStage I & II Stage III

Gujrat 23.6% 23.9%Gujrat 23.6% 23.9% MH 36.1% 31.9%MH 36.1% 31.9%

MP 29.5% 23.1%MP 29.5% 23.1%

CG 3.4% 4.2%CG 3.4% 4.2% Goa, daman, dadar 7.4% 1.9%Goa, daman, dadar 7.4% 1.9%

& nagar haweli& nagar haweli


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Type of

Clearance

400 KV

Phase toEarth

clearance

3800mm

Phase to

Phase

clearance

4000 mm

Section

clearance

6500 mm

The minimum clearances for 400 KV switchyard are as follows:

Clearances


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400 KV

Highest System Voltage 420 KV RMS

Lightning Impulse Voltage 1425 KVp

Switching Impulse Voltage 1050 KVp

Power Freq withstand

voltage for 1 minute

630 KV RMS

MaximumFault Level (for1 second) 40 KA

Minimum Creepage dist 10500 mm

parameters


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OUTGOING LINE


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PICTORIAL VIEW OF 400KV SWITCHYARD AT

VSTPS
http://var/www/apps/conversion/current/tmp/scratch17457/sld%20of%20all%20stages%20switchyard.pdfhttp://var/www/apps/conversion/current/tmp/scratch17457/sld%20of%20all%20stages%20switchyard.pdf


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Bay DetailsBay DetailsThere are 38 nos. of 400 KV bays in VSTPSThere are 38 nos. of 400 KV bays in VSTPS

switchyard.switchyard.

1) 10 Nos. of 400 KV, GT Bay1) 10 Nos. of 400 KV, GT Bay2) 3 Nos. of 400/132 KV, 200 MVA ICT Bay2) 3 Nos. of 400/132 KV, 200 MVA ICT Bay

3) 10 Nos. of 400 KV Line Bay3) 10 Nos. of 400 KV Line Bay

4) 4 Nos. of 400 KV Bus Sections4) 4 Nos. of 400 KV Bus Sections

5) 3 Nos. of Bus Coupler Bay5) 3 Nos. of Bus Coupler Bay6) 3 Nos. of Transfer Bus Coupler6) 3 Nos. of Transfer Bus Coupler7) 2 Nos. of HVDC bay7) 2 Nos. of HVDC bay


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Equipments commonly found in switchyard :Equipments commonly found in switchyard :

Circuit breakerCircuit breaker IsolatorIsolator Instrument transformerInstrument transformer

Surge arrestorSurge arrestor Shunt reactorShunt reactor Wave trapWave trap Inter connecting transformerInter connecting transformer Neutral grounding reactorNeutral grounding reactor Post insulatorPost insulator DC systemDC system EarthingEarthing


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Functions of various equipments :Functions of various equipments :

Circuit breakers :Circuit breakers :

-- Makes or automatically breaks the electrical circuits underMakes or automatically breaks the electrical circuits underLoaded condition.Loaded condition.

Isolators :Isolators :

-- Opens or closes the electrical circuits under No-loadOpens or closes the electrical circuits under No-loadconditions.conditions.

Instrument transformers :Instrument transformers :-- For stepping-down the electrical parameter (Voltage orFor stepping-down the electrical parameter (Voltage or

Current) to a lower and safe value for Metering andCurrent) to a lower and safe value for Metering andProtection logics.Protection logics.

Lightning arrestorsLightning arrestors

-- Safe guards the equipment by discharging the high currentsSafe guards the equipment by discharging the high currentsdue to Lightning.due to Lightning.

Earth switch :Earth switch :

-- Used to connect the charged body to ground to dischargeUsed to connect the charged body to ground to dischargethe trapped charge to have a safe maintenance zone.the trapped charge to have a safe maintenance zone.


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Post insulatorPost insulator::

-- used for supporting bus bars, CTs, PTs, CBs etc.used for supporting bus bars, CTs, PTs, CBs etc.

ICTICT::-- used to interconnect two grids/system operating at twoused to interconnect two grids/system operating at twodifferent voltages.different voltages.

NGRNGR::

-- used for low impedance grounding of high voltage systemused for low impedance grounding of high voltage systemto limit the line to ground fault current under system faultto limit the line to ground fault current under system faultconditions.conditions.

DC systemDC system::

-- required for control and protection supply for switchgear,required for control and protection supply for switchgear,

indications, annunciation system and also for emergencyindications, annunciation system and also for emergencylighting.lighting.


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Overhead earth wireOverhead earth wire ::

-- Protects the O/H transmission line from Lightning strokes.Protects the O/H transmission line from Lightning strokes.

Bus barBus bar ::

-- Conductors to which a number of circuits are connected.Conductors to which a number of circuits are connected.

Wave Traps/Line trapsWave Traps/Line traps ::

-- Used in PLCC circuits for Communication and telemetering.Used in PLCC circuits for Communication and telemetering.

Reactive Power control devicesReactive Power control devices ::

-- Controls the reactive power imbalance in the grid byControls the reactive power imbalance in the grid by

switching ON/OFF the Shunt Reactors, Shunt Capacitors etc.switching ON/OFF the Shunt Reactors, Shunt Capacitors etc.

Current Limiting ReactorsCurrent Limiting Reactors ::

-- Limits the Short circuit currents in case of fault.Limits the Short circuit currents in case of fault.


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Can break or make the circuit on load and even on faults.

SF6gas is used for arc quenching medium since it has outstanding arc-

quenching properties and very good dielectric strength .

Each pole of breaker consists of 2 interrupter unit, a bell crank

mechanism with grading capacitors & PIR.

Bell Crank Mechanism converts the vertical movement of operating

rod into linear horizontal movement of moving parts of interrupter &

PIR.

Grading Capacitor ensures uniform voltage distribution in open


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400 KV Circuit Breaker parameters

Rated Voltage 420 kV (rms)

Rated continuous current minimum 2000A/3150A

Rated short ckt breaking current 40 kA

Rated short ckt making current 2.5 x 40 kA

Rated short ckt current duration 3 sec

Closing time 100 ms (max)

Opening time 22 ms (max)


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Operates on no load.It is not meant for breaking load currents. It merely acts as a

disconnecting switch for isolation of equipments from live parts

when required for maintenance purpose.

It can be opened only when Circuit Breaker is in open position.

Types of Isolators:-

Horizontal Centre Break isolator

Pantograph Isolator


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Pantograph Isolator:-

TECHNICAL PARAMETERS


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400KV ISOLATOR

Rated voltage 420 kV (rms)

Rated continuous current 2000 A/3150 A

Rated insulation level

1) Rated one minute power frequency withstand voltage

520 KVrms (between live terminals and earth)

610 KVrms (across isolating distance)

2) Rated lightning impulse withstand voltage1425 KV

P(between line terminals and earth)

1425 KVP

impulse on one terminal and 240 KVP

power

frequency voltage of opposite polarity on other terminals.


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Instrument transformers are used for measurement and

protection purposes.Types :-

1) Current Transformer:-

Steps downs current from high to low value.

Connected in series with the main circuit

2) Capacitor Voltage Transformer:-

Capacitor voltage divider type with electromagnetic unit

(EMU). EMU comprises of compensating reactor,

intermediate transformer, protective and damping devices.


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400KV CLASS CT


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400KV CLASS CVT


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ECHNICAL PARAMETERS

00KV CT (OIL FILLED TYPE)

Rated current 2000A(peak)

Number of cores 5(Four for protection

& one for metering)

Rated frequency 50 Hz

System neutral earthing effectively earthed

Rated system voltage 420 kV (rms)


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CAPACITOR VOLTAGE TRANSFORMER (CVT)

PARAMETERS 400kV

Rated frequency 50 Hz

System neutral earthing effectively earthed

Rated voltage 420 kV (rms)

Rated total thermal burden 750 VA

Number of cores 5(five)

Installation outdoor Rated insulation level

1) 1.2/50 microsecond impulse 1425 kVP


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2.4 SURGE ARRESTOR

Provides protection against lightning or any surge developing.

Discharges high frequency over voltages to the ground.

Non linear characteristics.



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Particular 400 kV

Rated system voltage 420 kV

Rated arrestor voltage 390 kV

Minimum discharge capability 8 kJ/kV corresponding to minimum

discharge characteristic

Switching surge residual voltage (1kA) 730 kVP- minimum

780 kVP maximumOne minute power frequency withstand

voltage of arrestor housing

630 kV(rms)

Impulse withstand voltage of arrestor 1425 kVP

Maximum residual voltage at

1) 10 kA nominal discharge current

2) 20 kA "

900 kVP

975 kVP


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2.5 SHUNT REACTOR

Provided at sending & receiving end of long transmission line Switched on when the line is to be charged or line is on low load to

avoid Ferranti Effect by neutralizing shunt capacitance of such lines.


Rated voltage 420 kV Rated MVAR 50 at rated voltage Number of phases 3 System fault level 40 kA

Connection with neutral through load


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Insulation level

1) Lightning impulse 1.2/50 1300 kV(peak)

microsecond withstand voltage

2) Switching surge withstand voltage 1050 kV(peak)

3) One minute power frequency 630 kV(rms)

withstand voltage

Cooling system ONAN

Ratio of zero sequence reactance


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400KV CLASS SHUNT REACTOR


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2.6 POST INSULATOR

It is used for supporting bus bars, CTs, PTs, CBs etc. in the

switchyard. Post type insulator consists of a particular part

permanently secured in a metal base to be mounted on the

supporting structure.


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2.7 WAVE TRAP

Wave trap is inserted into high voltage transmission line to prevent

undue loss of carrier signal for all power system conditions.

Its impedance is negligible at power frequency so as not to disturb

power transmission but is relatively high over the frequency band of

carrier .


Rated power frequency 50 Hz

Rated system voltage 400 kV

Rated continuous current 2000 A/3150 A

Type of tuning Broad band


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2.8 INTERCONNECTING TRANSFORMER:-

Are normally autotransformer

Used to interconnect two grids/system operating at two differentsystem voltages (ie.400/132 KV).

Characterized by wide tapping range & an additional tertiary

winding which may be loaded or unloaded. Unloaded tertiary

winding acts a stabilizing winding by providing a path for the thirdharmonic currents.

TECHNICAL PARAMETRS:-

MVA Rating 200/120/80

Voltage Ratio 400/132/33 KV


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Insulation level:

HV winding-

1. Lightning impulse withstand voltage 1425 KVp

2.CW Impulse withstand voltage 1570 KVp

LV winding-

1.Lightning impulse withstand voltage 250 KVp

2.CW Impulse withstand voltage 90 KVrms

MV winding-

1. Lightning withstand voltage 650 KVp

2. Magnetizing inrush current (Amps) 4 times the rated

current


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ICT


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2.9 NEUTRAL GROUND REACTOR(NGR):-

Neutral grounding reactors are used for lowimpedance grounding of high voltage systems.

They limit the line to ground fault current undersystem fault conditions by providing additionalreactance which neutralizes the capacitive currents.

RatingUnder balanced operating conditions, there isessentially no continuous current flowing through theneutral grounding reactor. Therefore, the rated

current of this reactor is considered to be the thermalshort time current under fault conditions . Theduration of the short time rating is time dependent,and is specified as 10 sec or 1minute


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2.10 DC SYSTEM

DC is required for control and protection supply forswitchgear, indications, annunciation system, communication

system etc. DC supply is also required for emergency lighting.

The commonly used voltage levels are 220 V for motors, for

controls & protection schemes and 48 V for communication.


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Modes

of

Transmission


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-- Power can be generated at high voltages.Power can be generated at high voltages.

- Step-up/Step-down is possible.- Step-up/Step-down is possible.

-- Requires more copper.Requires more copper.- Due to Skin effect, the effective- Due to Skin effect, the effectiveresistanceresistance is increasedis increased

- Continuous loss of power due to charging current even- Continuous loss of power due to charging current even

when the line is open.when the line is open.

- Requirement of Transposition of conductors.- Requirement of Transposition of conductors.


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-- Low cost due to less copper requirementLow cost due to less copper requirement

- No Stability and synchronizing problems.- No Stability and synchronizing problems.

- Asynchronous lines (Interregional ties)- Asynchronous lines (Interregional ties)

- No increase in Fault level if interconnected.- No increase in Fault level if interconnected.- Less Corona and RI.- Less Corona and RI.

- Better Voltage regulation due to absence of- Better Voltage regulation due to absence ofInductance.Inductance.

- Requires less insulation as the potential stress is less.- Requires less insulation as the potential stress is less.

-- Higher generation is not possible due toHigher generation is not possible due tocommutationcommutation

- Step-up/Step-down is not possible.- Step-up/Step-down is not possible.


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km

Cost

100 300 1100500 700 900

Break Even distance

HVDC Preferred

EHVAC Preferred

Cost of

Substation

HVDC

Line

EHVAC

Line


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400 kv swyd FOR DOJ