Aviral Report

8/17/2019 Aviral Report

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1. INTRODUCTION

As we need food,water ,air shelter etc. for living, we also need electricity in stable and

continuous form. In modern civilization we cannot think of life without electricity as it has

acquired its place next to oxygen.

The network of electricity supply to the consumer is very complex one comprising of

generating plant, transmission and subtransmission lines, grid substation etc .each element

of the network has got direct bearing on the quality and continuance of electric power so as

now a time in industrial sector the maintenance section also plays a important part as in the

industrial sector the input supply is !!"# and so heavy equipments are connected so thesupply should be continued and there all the equipments are employed as capacitor

bank,transformer ,diesel generator ,battery room etc. $o in this section of my report it%s all

related to the maintenance of industrial sector.

1.1 SODEXO INDIA:-

In 1966, Pierre Bellon launched Sodexo, in Marseilles (France),

founded on the Bellon family's exerience of more than 6!

years in maritime caterin" for luxury liners and cruise shis#

$erations initially ser%ed sta& restaurants, schools andhositals#

$odexo is now the worldwide leader in &uality of 'ife services. (or over )* years, we have

developed unique expertise, backed by nearly )+*,*** employees in * countries across the

globe.

In combining the diverse talents of our teams, $odexo is the only company to integrate a

complete offer of innovative services, based on over !** professions. -e develop, manage

and deliver a unique array of nsite $ervices, /enefits 0 1ewards $ervices and 2ersonal

and 3ome $ervices for all our clients to improve the &uality of 'ife.

ur experiences with our over 45 million customers each and every day enable us to develop

&uality of 'ife services that reinforce the wellbeing of individuals, improving their

effectiveness and helping companies and organizations to improve performance...every day.

1.2 ($M Soft*ororate Ser%ices) :-

In IFM we provide all technical services for utilities and soft and corporate

services essential for thesuccess of the customer’s core business.Servicesare oered on a deployment or lump sum basis.

1

http://www.sodexo.com/en/services/quality-life-services.aspxhttp://www.sodexo.com/en/services/on-site/offer.aspxhttp://www.sodexo.com/en/services/benefits-rewards/offer.aspxhttp://www.sodexo.com/en/services/personal-home/concierge-services.aspxhttp://www.sodexo.com/en/services/personal-home/concierge-services.aspxhttp://www.sodexo.com/en/services/quality-life-services.aspxhttp://www.sodexo.com/en/services/on-site/offer.aspxhttp://www.sodexo.com/en/services/benefits-rewards/offer.aspxhttp://www.sodexo.com/en/services/personal-home/concierge-services.aspxhttp://www.sodexo.com/en/services/personal-home/concierge-services.aspx


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1.3 (TFM & Managed Servie!" :-

Total Facilities management TFM! is the new concept that has evolvedout of the "ustomer’s need to outsource all non#core activities to a single

vendor. $nder this scenario Sode%o&Mac'ellan is able to oer a

comprehensive and complete solution to meet our customer’s needs. TFM

will enable our customers to pass the full responsibility of managing its

facilities to Sode%o&Mac'ellan for a (%ed price.

1.# $r%e' anageen' :-

$odexo67ac'ellan offers deployment based services in which we provide highly qualified

managers, engineers, technicians and assistants to assist the customer in their pro8ects

implementation. -e typically structure this work on a cost plus basis. -e provide turnkey

pro8ect management solutions for the management of small capital and engineering pro8ects.

This model is very attractive option for the customer because of the substantial cost

reductions made possible due to our familiarity of the plant and facility environment. This

can be done on a rate contract or cost plus basis.

)


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1.) SER*ICES :-

• Electrical installations & distribution

• Emergency power systems

• Mechanical & HVAC

• Building Management Systems

• Fire & Safety systems

• Hydraulics & waste water systems

• tilities Management

*


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2. CIRUIT +REA,ER

2.1INTRODUCTION :-

The circuit breaker is one of the important equipment in power system. It protects the system

by isolating the faulty section while the healthy one is keep on working. 9very system is

susceptible to fault or damages while can be caused due to overloading, shortcircuiting, earth

fault etc. thus to protect the system and isolate the faulty section :./. are required. Apart

from breaking and making contacts, a :./. should be capable of doing.

• :ontinuously carry the maximum current at point of installation.

• 7ake and break the circuit under abnormal and normal condition.

• :lose or open the faulty section only where fault exists.

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

electrical circuit from damage caused by overload or short circuit .It;s basic function

is to detect fault condition and interrupt current flow .

The circuit breaker contacts must carry the load current without excessive heating and

must also withstand the heat of the arc produced when interrupting the circuit

.:ontacts are made of copper or copper alloys or highly conductive materials .3igh

voltage circuit breakers have replaceable contacts

-hen a current is interrupted ,an arc is generated .This arc must be contained cooled

and extinguished between the contacts .


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FOR AC

These breakers use magnetic and thermal magnetic circuit breakers as magnetic use solenoid

whose pulling force increases with current. The circuit breaker contacts are held closed by a

latch some employ a hydraulic time delay feature using viscous fluid as thermal magnetic

:/ are the type found in most


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-


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2.3.2 MCC+ (M%ded a!e ir/i' 0reaer" :-

The rating of 7::/ is rated current up to +5**A.Thermal or thermal magnetic

operation. Trip current may be ad8ustable in larger rating. 7::/ can also be

termed as next level of 7:/ as has high rating then that and there is also resetoption.

2.3.3 RCC+ (Re!id/a /rren' ir/i' 0reaer" :-

The 1::/ detects the current imbalance, but does not provide over current

protection. The 1::/ is also available as 1:/>residual current breaker with

over current protection? as 1::/ and 7:/ in one package.

2.3.# C%%n 'ri 0reaer (T4% and '5ree %e T$N" :-

-hen supplying a branch circuit with more than one live conductor, each live

conductor must be protected by breaker pole. To ensure that all live conductors

are interrupted when any pole trips, a common trip breaker must be used. These

either contain two or three tripping mechanisms within one case ,or for small

breakers.


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2.3.) AC+ (Air ir/i' 0reaer" :-

The 1ating of air circuit breaker is upto !*,***A.Their characteristics are fully

ad8ustable including configurable trip thresholds and delays. These :/ use air

alone to extinguish the arc, have metal plates to divide and cool the arc .7agnet

blowout coils or permanent magnets deflect the arc into the arc chute.

2.3.6 *C+ (*a// ir/i' 0reaer" :-

1ated current is up to B***A these breakers interrupt the current by creating and

extinguishing arc in vacuum container. These are generally applied for voltages

up to B5***# which corresponds roughly to the medium voltage range of power

systems have longer life than A:/

2.3.7 OC+ (Oi ir/i' 0reaer" :-

In the oil circuit breaker the fixed and moving contacts are immerged inside the

insulating oil. -henever there is a separation of current carrying contacts in the

oil, the arc initialized at the movement of separation of contacts, and due to this

arc the oil is vaporized and decomposed in mostly hydrogen gas and ultimately

creates a hydrogen bubble around the arc it prevents restriking of arc after

current reaches zero crossing of the cycle. The rating of :/ is ++*"#,and

maximum rated current is B.+"A.

/


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2.3.8 SF6 C+ :-

( S/5/r 5e9a/%ride ir/i' 0reaer"

$ulfur 3exafluoride >$(? is an excellent gaseous dielectric for high voltage

power applications. It has been used extensively in high voltage circuit breakersand other switchgears employed by the power industry. Applications for $(

include gas insulated transmission lines and ;gas insulated power distributions.

1ated voltage for $( :/ is 4.+"#B"#,1ated current value is B*A+5**A.

$ome of the outstanding properties of $( making it desirable to use in power

applications areF

3igh dielectric strength

Gnique arcquenching ability

9xcellent thermal stability

Hood thermal conductivity

0


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3. REA;S

1elay is a device which detect fault current and energize trip circuit of circuit breaker.1elays

must be able to evaluate a wide variety of parameters to establish that corrective action is

required. bviously, a relay cannot prevent the fault. Its primary purpose is to detect the fault

and take the necessary action to minimize the damage to the equipment or to the system. The

most common parameters which reflect the presence of a fault are the voltages and currents at

the terminals of the protected apparatus or at the appropriate zone boundaries. The

fundamental problem in power system protection is to define the quantities that can

differentiate between normal and abnormal conditions. This problem is compounded by the

fact that normalJ in the present sense means outside the zone of protection. This aspect,

which is of the greatest significance in designing a secure relaying system, dominates the

design of all protection systems.

( Rea! "

1


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3.1 IN*ERSE TIME-DEA; O*ERCURRENT REA;

The principal application of timedelay over current relays >T


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3.) Te! O Di!'ane rea:-

a. Iedane Rea:-

The impedance relay has a circular characteristic centred. It is non directional and is used

primarily as a fault detector.

0. Adi''ane Rea:-

The admittance relay is the most commonly used distance relay. It is the tripping relay in

pilot schemes and as the backup relay in step distance schemes. In the electromechanical

design it is circular, and in the solid state design, it can be shaped to correspond to the

transmission line impedance.

. Rea'ane Rea:-

The reactance relay is a straightline characteristic that responds only to the reactance of the

protected line. It is non directional and is used to supplement the admittance relay as a

tripping relay to make the overall protection independent of resistance. It is particularly

useful on short lines where the fault arc resistance is the same order of magnitude as the line

length.

d. DIFFERENTIA REA;

A differential relay operates when the vector difference of current in circuit in which relay is

connected , exceed a set value.

3.7 Te O Dieren'ia Rea:-

C/rren' Dieren'ia Rea:-

In this type, relay compares the current entering a section of the system and the current

leaving the section. Gnder fault condition,these currents are different.

*%'age Diern'ia Rea:-

In this type of relay two transformer are used.The secondaries of the transformer in series

with the relay in such a way that the induced e.m.f. are in opposition under normal

condition.under fault condition , primaries carry current due to which induced e.m.f.s no

longer remain in opposition and the relay operates.

1)


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#. +US-+ARS

A 0/! 0ar >sometimes pronounced Kbuzz barsK? in electrical power distribution refers to thick

strips of copper or aluminium that conduct electricity within a switchboard, distribution

board, substation, or other electrical apparatus.

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

be safely carried. /us bars can have a crosssectional area of as little as !* mmL but electrical

substations may use metal tubes of 5* mm in diameter >!,MB mmL? or more as bus bars.

/us bars are typically either flat strips or hollow tubes as these shapes allow heat to dissipate

more efficiently due to their high surface area to crosssectional area ratio.

The skin effectmakes 5*N* 3z A: bus bars more than about mm >!=B in? thick inefficient,so hollow or flat shapes are prevalent in higher current applications. A hollow section has

higher stiffness than a solid rod of equivalent currentcarrying capacity, which allows a

greater span between bus bar supports in outdoor switchyards.

A bus bar may either be supported on insulators, or else insulation may completely surround

it. /us bars are protected from accidental contact either by a metal enclosure or by elevation

out of normal reach. @eutral bus bars may also be insulated. 9arth bus bars are typically

bolted directly onto any metal chassis of their enclosure. /us bars may be enclosed in a metal

housing, in the form of bus duct or bus way, segregatedphase bus, or isolatedphase bus.

/us bars may be connected to each other and to electrical apparatus by bolted or clampconnections. ften 8oints between highcurrent bus sections have matching surfaces that are

silverplated to reduce the contact resistance.

A bus bar must have its own protection, although they have high degrees of reliability.

/earing in mind the risk of unnecessary trips, the protection should be dependable, selective

and should be stable for external faults, called ;through faults;.

The most common fault is phase to ground, which usually results from human error. There

are many types of relaying principles used in bus bar.

#.1 +US-+AR ARREN


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+US +AR ARRENIC>

IS +EIN< ADO$TED +; R.R.*.$.N..:-

!. $ingle bus bar arrangement

+.


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SU$$;

).1 INTRODUCTION :-

An G2$ system is an alternate or backup source of power with the electric utility company being

the primary source. The G2$ provides protection of load against line frequency variations,elimination of power line noise and voltage transients, voltage regulation, and uninterruptible

power for critical loads during failures of normal utility source. An G2$ can be considered a

source of standby power or emergency power depending on the nature of the critical loads. The

amount of power that the G2$ must supply also depends on these specific needs. These needs

can include emergency lighting for evacuation, emergency perimeter lighting for security, orderly

shut down of manufacturing or computer operations, continued operation of life support or

critical medical equipment, safe operation of equipment during sags and brownouts, and a

combination of the preceding needs.

+% diagra % U$S :-

).2 Te! % U$S :-

Main '5ere are '5ree 'e! % U$S are avaia0e:-

).2.1 Oie U$S T5e ain! '% 0a''er 5ange%ver 'ie %r 0a''er '% ain! 5ange%ver 'ie in %ine

U$S i! ver %4 a! %ared '% inver'er.

Tia@ 5ange%ver 'ie in inver'er! i! ) ii!e%nd! & Oine U$S 5a!

5ange%ver 'ie % 3-8 ii!e%nd!.

In a 'ie@ 45en ain! a i! re!en'@ Inver'er r%vide! '5e %/'/' a! i! '5e in/'

ain!.

=5ie@ Oine U$S 5a! 0/i' in A/'%a'i *%'age Reg/a'%r (A*R" '% reg/a'e '5e

%/'/' v%'age %!e '% 22* a. Oine U$S! are n%ra 4eig5' U$S! and are 4ide /!ed %r d%e!'i %/'er!.

1,


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+% diagra % Oine U$S :-

).2.2 ine in'era'ive U$S :- In '5i! de!ign@ '5e 0a''er '% AC %4er %nver'er (inver'er" i! a4a! %nne'ed

'% '5e %? % '5e U$S.

+a''er 5arging i! d%ne d/ring 'ie! 45en '5e I?$ AC %4er i! n%ra 45en

'5e I?$ AC ai!@ 'ran!er !4i'5 %en! and '5en '5e inver'er !'ar'! /n'i%ning '%

r%vide %4er '% %ad iedia'e.

+% diagra % ine In'era'ive U$S :-

).2.3 Onine U$S :-

1-


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In '5i! 'e % U$S@ '5e !!'e a4a! reain! %n 0a''er@ 45e'5er ain! a i!

re!en' %r n%'.

=5en ain! a i! re!en'@ i' r%vide! %4er '% DC !/ % inver'er !e'i%n a!

4e a! 5arge! '5e 0a''er !i/'ane%/!.

=5en ain! a i! n%' re!en'@ i' 4i r/n '5e %nne'ed %ad 'i '5e 0a''er 5a! a

re%ended di!5argea0e eve.

+% diagra % Onine U$S :-

6. CONTRO ROOM

1


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At @23 not only remote control carry the appropriate means by which circuit breaker may be

open or close but also necessary indicating devices, indicating lamps, isolating switching,

protective relays, secondary circuit and wires are located here and most important @o load

tap changerJ for transformer is available. There is a panel for synchronizing.


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7aster relay gives the signal to the trip coil of circuit breaker and thus faulty feeder is

disconnected from supply. 7eter section includes different types of meter.

(C%n'r% $ane! In C%n'r% R%%"

7. +ATTER; ROOM

)


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As the system connected is so sensitive for its protection separate dc supply is maintained for

signalling remote position control, alarm circuit etc as if the supply discontinues so system

may get damage or any minor fault can occur to it so a separate battery room is made.


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this example, the electrons go through the wire, lighting the light bulb along the way. This is

one

way of describing how electrical potential causes electrons to flow through the circuit.

3owever, these electrochemical processes change the chemicals in anode and cathode to

make them stop supplying electrons. $o there is a limited amount of power available in a

battery.-hen a battery is recharged, the direction of the flow of electrons is changed, The

electrochemical processes happen in reverse, and the anode and cathode are restored to their

original state and can again provide full power.

Ce *%'age :-

9ach cell element of the battery produces approximately +.!,regardless of the quantity or size

of the plates. The battery shown have six cells that are connected in series ,which total

produces voltage of !+. #olts.

+a''er aai' :-

The quantity A

is defined as the current that discharges the battery in ! hour,so that the battery capacity can be said to be C Amperehours >units confusion?

))


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If we discharge the battery more slowly, say at a current of C =!*, then we might

expect that the battery would run longer >!* hours? before becoming

discharged.

In practice, the relationship between battery capacity and discharge current is not linear, and

less energy is recovered at faster discharge rates. 2eukert%s 'aw relates battery capacity to

discharge rateF A3 P Ik t where A3 >amphour? is capacity at a ! A discharge rateI is thedischarge current in Amperes t is the discharge time, in hours k is the 2eukert coefficient,

typically !.! to !.B

(ollowing precautions are taken in a battery roomF

• The conductor connecting the cells are greased and coated with electrolyte

resisting varnish.

• 2roper care is taken so that acid vapours do not accumulate in the room to avoid

risk of explosion, smoking, winding etc.

• Any arc is prohibited in the room.

• The windows of battery are of forested glass to avoid the batteries from directaction of sun light.

8. AUTO TRANSFORMER

)*


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/asically autotransformer comprises of only one winding per phase, part of which is used by

both primary and secondary winding. This arrangement results into an appreciable saving in

cost as well as higher operating efficiency is achieved, but their extensive use is not being

favored by power utilities due to certain inherent disadvantages which are as followsF

!. It has got low inherent reactance as such is sub8ected to severe short circuit conditions.

+. $ince primary and secondary side uses same windings, there is always possibility of

imposition of higher voltage on secondary in case of fault.

B. /oth the windings make use of common neutral, as such neutral is required to be earthed

or isolated on both sides.

). 2rovision of additional insulation on secondary side and increased frame size when

ad8ustable taps are provided erodes the initial advantage of low cost.

8.1 C%n!'r/'i%na $ar':-

The chief elements of the construction are F

!. Magne'i Cir/i'!: "omprising limbs2 yo3es and clamping structures.

+. Ee'ria Cir/i'!: The primary, secondary and >if any? tertiary windings, formers,

insulation and bracing devices.

B. Terina!: Tapings, tapping switches, terminal insulators and leads.

). Tan: oil, cooling devices, conservators, dryers and auxiliary apparatus.

)+


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>A/'% Tran!%rer"

C%re C%n!'r/'i%n:-

$pecial alloy steel of high resistance and low hysteresis loss is used almost exclusively in

transformer;s cores. Induction densities up to !.B5 !.55 wb=m+ are possible. The limit for

5* c=s is being the loss and the magnetizing current.

As the flux in the cores is a pulsating one, the magnetic circuit must be laminated and the

separate laminations insulated in order to retain the advantages of subdivision. 2aper, Qapan,

#arnish, :hina clay or phosphate may be used.

/urring of edges of plates may cause a considerable increase in a core loss by providing paths

for eddy currents should the sharp edges cut through the insulation and establish contacts

between ad8acent plates. /urrs are removed before core assembly. $ilicon alloy steel are

hard, and cause wearing of the punching tools, so that the removal of burrs needs special

attention.

),


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Transformer shut sheet are cut as far as possible along the grain which is in the direction in

which the material has a higher permeability.

C%n!'r/'i%na Frae =%r:-

:onsiderable use is made of channel and angle section rolled steel in the framework of core

type transformers. a typical construction is to clamp the top and bottom yokes between

channel sections, held firmly by tieholts. The bottom pair of channels has cross channels as

feet. The upper pair carries clamps for the high and low voltage connections.

=inding! :-

:lassification of windings maybe done as >a? :ircular or rectangular 0 >b? :oncentric or sandwiched.

In core type circular or rectangular type of windings are used and in shell type generally

sandwiched type windings are used.

n account of easier insulation facilities, the low voltage winding is placed nearer to the

core. In the case of core type and on the outside positions in the case of shell type

transformers. The insulation spaces between low and high voltage coils also serve to

facilitate cooling.

In!/a'i%n:-

The insulation between the 3.#. and I.#. windings, and between I.#. winding and

core, compresses /akelite paper cylinders or elephantine wrap.

The insulation of the conductors may be of paper, cotton or glass tape being used for

air insulated transformers. The paper is wrapped round the conductor in a suitable machine,

preferably without overlap of ad8acent turns. In the power transformers, owing to strain on

the insulation between turns t the line end of the high voltage winding, about 5 percent of the

turns are reinforced with the extra insulating material.

ead! And Ma'eria:-

The connections to the windings are copper rods or bars, insulated wholly or in part,

and taken to the bus bars directly in the case of oil cooled transformers. The shape and size

of the conductors are of importance in very high voltage systems, not on account of the

)-


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current carrying capacity, but because of dielectric stresses, corona, etc. at sharp bends

corners with such voltages.

+/!5ing!:-

Gp to voltages of BB k#, ordinary porcelain insulators can be used. Above this voltage the use

of conductor and of oil filled terminal bushings, or, for certain cases, a combination of the

two has to be considered. f course, any conductor can be effectively insulated by air

provided that it is at a sufficient distance from other conducting bodies and sufficiently

proportioned to prevent corona phenomena. $uch conditions are naturally G@obtainable

with transformers where the conductor has to be taken through the cover of the containing

tank, although common enough with over head transmission lines.

The oil filled bushing consists of a hollow porcelain cylinder of special shape with a

conductor >usually a hollow tube? through its centre.

The space between the conductor and the porcelain is filled with oil, the dielectric strength of

which is greater than that of air. The dielectric field strength is greatest at the surface of the

conductor, and this breaks down at a much lower voltage in air than in oil. il is fed into the

bushing at the top, act as an expansion chamber for the oil when the bushing temperature

rises.

Gnder the influence of the electric field, foreign substances in the form of dust, moisture or

metallic particles have a tendency to arrange themselves in radial lines giving rise to paths of

low dielectric strength, with constant danger of breakdown. To prevent such action by

unavoidable impurities in the oil /akelite tubes are used to surround the conductor

concentrically. The effect is to break up radial chains of semiconducting particles.

Tan!:-

$mall tanks are constructed from welded sheet steel, and larger ones from plain boilerplates.

The lids may be cast iron, or waterproof gasket being used at the 8oints. The fittings include

thermometer pockets, drain cock, rollers or wheels for moving the transformer into position,

eye bolts for lifting, conservators and breathers, cooling tubes are welded in, but separate

radiators are individually welded and afterwards bolted on.

)


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Teera'/re India'%r!:-

7ost of the transformer >small transformers have only TI? are provided with indicators that

displace oil temperature and winding temperature. There are thermometers pockets provided

in the tank top cover which hold the sensing bulls in them. il temperature measured is that of

the top oil, where as the winding temperature measurement is indirect. This is done by addingthe temperature rise due to the heat produced in a heater coil >known as image coil? when a

current proportional to that flowing in windings is passed in it to that or top oil. (or proper

functioning or TI 0 -TI it is essential to keep the thermometers pocket clean and filled with

oil.

(=inding And Oi Teera'/re India'%r"

Siia


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C%n!erva'%r :-

:onservators are required to take up the expansion and contraction of the oil to come in

contact with the air, from which it is liable to take up moisture. The conservator may consist

of an airtight cylindrical metal drum supported on the transformer lid or on a neighboring

wall, or of a flexible flat corrugated disc drum. The tank is filled when cold and the

expansion is taken up in the conservator.

The figure conservator is as shown belowF

(C%n!erva'%r"

Tran!%rer Oi:-

il in transformer construction serves the double purpose of cooling and insulating. In the

choice of oil for transformer use the following characteristics have to be considered.

• #iscosity

• Insulating property

• (lash point

• (ire point

• 2urity

• $lugging

• Audity

. CA$ACITATI*E *OTA


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A capacitor voltage transformer >:#T? is a transformer used in power systems to stepdown

extra high voltage signals and provide low voltage signals either for measurement or to

operate a protective relay. In its most basic form the device consists of three partsF two

capacitors across which the voltage signal is split, an inductive element used to tune thedevice to the supply frequency and a transformer used to isolate and further stepdown the

voltage for the instrumentation or protective relay. The device has at least four terminals, a

highvoltage terminal for connection to the high voltage signal, a ground terminal and at least

one set of secondary terminals for connection to the instrumentation or protective relay.

:#Ts are typically singlephase devices used for measuring voltages in excess of one

hundred kilovolts where the use of voltage transformers would be uneconomical. In practice

the first capacitor, :!, is often replaced by a stack of capacitors connected in series.

This results in a large voltage drop across the stack of capacitors that replaced the first

capacitor and a comparatively small voltage drop across the second capacitor, : +, and hencethe secondary terminals.

( C*T "

The porcelain in multi unit stack, all the potentials points are electrically tied and suitably

shielded to overcome the effect of corona 1I# etc. :apacitive voltage transformers are

available for system voltage.

1. CURRENT TRANSFORMER

*

http://en.wikipedia.org/wiki/File:Cvt.png


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As you all know this is the device which provides the predecoded fraction of the primary

current passing through the line=bus main circuit. $uch as primary current *A, 45A, !5*A,

+)*A, B**A, )**A, to the secondary output of !A to 5A.

@ow a day mostly separate current transformer units are used instead of bushing mounting:T%s on levelled structure they should be for oil level indication and base should be earthed

properly. :are should be taken so that there should be no strain as the terminals.

-hen connecting the 8umpers, mostly secondary connections is taken to three unction boxes

where star delta formation is connected for three phase and final leads taken to protection

=metering scheme. There should be no chance of secondary circuit remaining opens as it leads

to extremely high voltage which ultimately damage the :T itself.

(C/rren' Tran!%rer!"

It can be used to supply information for measuring power flows and the electrical inputs for

the operation of protective relays associated with the transmission and distribution circuit or for power transformer. These current transformers have the primary winding connected in

series with the conductor carrying the current to be measured or controlled. The secondary

winding is thus insulated from the high voltage and can then be connected to low voltage

metering circuits.

:urrent transformers are also used for street lighting circuits. $treet lighting requires a

constant current to prevent flickering lights and a current transformer is used to provide that

constant current. In this case the current transformer utilizes a moving secondary coil to vary

the output so that a constant current is obtained.

11. $OTENTIA TRANSFORMER

*1


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A potential transformer >2T? is used to transform the high voltage of a power line to a lower

value, which is in the range of an ac voltmeter or the potential coil of an ac voltmeter.

( $%'en'ia Tran!%rer"

The voltage transformers are classified as underF

!.:apacitive voltage transformer or capacitive type

+.9lectromagnetic type.

:apacitive voltage transformer is being used more and more for voltage measurement in high

voltage transmission network, particularly for systems voltage of !B+"# and above where it

becomes increasingly more economical. It enables measurement of the line to earth voltage to

be made with simultaneous provision for carrier frequency coupling, which has reached wide

application in modern high voltage network for telemetering remote control and telephone

communication purpose.

The capacitance type voltage transformers are of twp typeF

• :oupling :apacitor type

• 2ushing Type

he performance of :#T is affected by the supply frequency switching transient and

magnitude of connected /urdon. The :#T is more economical than an electromagnetic

voltage transformer when the nominal supply voltage increases above "#.

The capacitor connected in series act like potential dividers, provided, the current taken by

burden is negligible compared with current passing through the series connected capacitor.

12. CA$ACITOR +AN,

*)


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The capacitor bank provides reactive power at grid substation. The voltage regulation

problem frequently reduces so of circulation of reactive power.

Gnlike the active power, reactive power can be produced, transmitted and absorbed of course

with in the certain limit, which have always to be workout. At any point in the system shunt

capacitor are commonly used in all voltage and in all size.

(Caai'%r +an"

/enefits of using the capacitor bank are many and the reason is that capacitor reduces the

reactive current flowing in the whole system from generator to the point of installation.

:apacitor bank is used following purpose

!.Increased voltage level at the load

+. 1educed system losses

B. Increase power factor of loading current

). 1educe loading on source generator and generators.

5. 1educe system investment per "- of load.

13. CONCUSION

**


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I' 4a! a ver g%%d e9eriene % 'aing v%a'i%na 'raining in SODEXO FASCIITIESMANA


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1#. REFERENCES

/adriramF $witch gear protection system

/. 1. HuptaF Transmission 0


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