7449867 Distribution Power Transformer

8/14/2019 7449867 Distribution Power Transformer

http://slidepdf.com/reader/full/7449867-distribution-power-transformer 1/29

11

Distribution TransformersDistribution Transformers

Reference Standard: IS 1180 --1989Reference Standard: IS 1180 --1989

Types of Distribution TransformersTypes of Distribution Transformers

a) Non-Sealed typea) Non-Sealed typeb) Sealed typeb) Sealed type



22

Non-Sealed type DistributionNon-Sealed type Distribution

TransformersTransformers

Reference StandardReference Standard

IS 1180 (Part 1) : 1989IS 1180 (Part 1) : 1989

This standard specifies the requirementsThis standard specifies the requirementsand tests for oil immersed 3-and tests for oil immersed 3-ΦΦ Non-Non-

Sealed type Distribution TransformersSealed type Distribution Transformers

of ratings up to and including 100KVAof ratings up to and including 100KVA

and voltage class up to and includingand voltage class up to and including

11KV11KV



33

IS 1180 (Part 1) : 1989IS 1180 (Part 1) : 1989

This standard coversThis standard covers RatingsRatings No load voltage ratiosNo load voltage ratios

Winding connections and vectorsWinding connections and vectors Tapping rangesTapping ranges FittingsFittings

Terminal arrangementTerminal arrangement Losses and Impedance valuesLosses and Impedance values TolerancesTolerances



44

IS 1180 (Part 1) : 1989IS 1180 (Part 1) : 1989

Rating :Rating :

KVA Rating – 16, 25, 63 and 100KVA Rating – 16, 25, 63 and 100

Frequency – 50HzFrequency – 50Hz

System Voltage – 3.3, 6.6 and 11KVSystem Voltage – 3.3, 6.6 and 11KVSecondary Voltage – 433 and 250Secondary Voltage – 433 and 250



55

IS 1180 (Part 1) : 1989IS 1180 (Part 1) : 1989

TappingTapping

±2.5% and±5%

+5%Tappings at

52Number of tappings

PrimarySecondaryWindingtapped

Above 25 KVAUp to andIncluding 25 KVA



66

FittingsFittingsOil level indicatorOil level indicator

Lifting lugsLifting lugs

BreatherBreatherDrain cum sampling valveDrain cum sampling valve

Rating and terminal marking platesRating and terminal marking plates

IS 1180 (Part 1) : 1989IS 1180 (Part 1) : 1989



77

IS 1180 (Part 1) : 1989IS 1180 (Part 1) : 1989

40140Phase toearth

75255Phase tophase

L.V SideH.V Side

Clearances in mm



88

IS 1180 (Part 1) : 1989IS 1180 (Part 1) : 1989 Limits of temperature rise :Limits of temperature rise :

Winding 55°CWinding 55°C

Top oil 45°CTop oil 45°C

Losses and Impedance valuesLosses and Impedance values

1760260100

123518063

685100254758016

Load loss (W)at 75°C

No load loss (W)Rating (KVA)



99

TestsTests

Measurement of winding resistanceMeasurement of winding resistance

Measurement Voltage ratio andMeasurement Voltage ratio and

check of voltage vector relationshipcheck of voltage vector relationship

Measurement of impedance voltage,Measurement of impedance voltage,

short circuit impedance and load lossshort circuit impedance and load loss

Measurement of no-load loss andMeasurement of no-load loss andcurrentcurrent

Measurement of insulation resistanceMeasurement of insulation resistance



1010

TestsTests

SSVW testSSVW test

IOVW testIOVW test

Lightning impulse testLightning impulse test Temperature rise testTemperature rise test

SC testSC test

Air pressure test (35KPa 30min)Air pressure test (35KPa 30min)



1111

Permissible flux density andPermissible flux density and

overfluxingoverfluxing

BBmaxmax – 1.69 Tesla– 1.69 Tesla

No load current in terms of %of fullNo load current in terms of %of full

load currentload current

52.5100

6363

73.5258416

At 112.5%rated voltage

At 100% ratedvoltage

KVA Rating



1212

Mounting arrangementsMounting arrangements

The under-base of all theThe under-base of all the

transformers shall be provided withtransformers shall be provided with

two 75x40mm channels 460mmtwo 75x40mm channels 460mm

long.long.

415mm

415±2mm



1313

Sealed type DistributionSealed type Distribution


Reference StandardReference Standard IS 1180 (Part 2) : 1989IS 1180 (Part 2) : 1989 This standard specifies theThis standard specifies the

requirements and tests for oilrequirements and tests for oilimmersed 3-immersed 3-ΦΦ Sealed typeSealed typeDistribution Transformers of ratingsDistribution Transformers of ratings

up to and including 100KVA andup to and including 100KVA andvoltage class up to and includingvoltage class up to and including11KV11KV



1414

IS 1180 (Part 2) : 1989IS 1180 (Part 2) : 1989

No TapsNo Taps

No conservatorNo conservator

Air pressure test is to be conductedAir pressure test is to be conductedat 80KPa for 30minutes.at 80KPa for 30minutes.



1515

IS 1180 (Part 2) : 1989IS 1180 (Part 2) : 1989

402014076Phase toearth

7545255127

Phase to

phase

externalInternalexternalInternal

L.V SideH.V Side

Clearances in mm



1616

Power TransformersPower Transformers

Reference StandardsReference Standards

IS 2026 Part IIS 2026 Part I 1977– General1977– General

IS 2026 Part IIIS 2026 Part II 1977– Temperature Rise1977– Temperature Rise

IS 2026 Part IIIIS 2026 Part III 1981– Insulation Levels1981– Insulation Levels

and Dielectric Testsand Dielectric Tests

IS 2026 Part IVIS 2026 Part IV 1977– Terminal markings,1977– Terminal markings,

Tappings and ConnectionsTappings and Connections IS 2026 Part VIS 2026 Part V 1994–1994– Transformer/Transformer/

Reactor Bushings- Minimum externalReactor Bushings- Minimum external

clearance in airclearance in air



1717

IS 2026 Part IIS 2026 Part I

This standard coversThis standard covers Service conditionsService conditions RatingRating

Requirements to withstand Short CircuitRequirements to withstand Short Circuit Dimensions of Neutral ConnectionDimensions of Neutral Connection TolerancesTolerances

Rating platesRating plates FittingsFittings TestsTests



1818

RatingRating

Rated KVARated KVA

Operation at other than ratedOperation at other than rated

voltagevoltage: The transformer can be: The transformer can be

operated at its rated KVA at anyoperated at its rated KVA at any

voltage with in ±10%voltage with in ±10%

Rated frequencyRated frequency: 50Hz ± 1.5: 50Hz ± 1.5



1919

TOLERANCESTOLERANCES

+10%

+15%±0.5%

±10%

+30

Total Losses

Component LossesVoltage ratio

Impedance Voltage

No-load current

TolerancesItem



2020

TESTSTESTS

Measurement of winding resistanceMeasurement of winding resistance

Measurement Voltage ratio andMeasurement Voltage ratio and

check of voltage vector relationshipcheck of voltage vector relationship

Measurement of impedance voltage,Measurement of impedance voltage,

short circuit impedance and load lossshort circuit impedance and load loss

Measurement of no-load loss andMeasurement of no-load loss andcurrentcurrent

Measurement of insulation resistanceMeasurement of insulation resistance



2121

TESTSTESTS

Dielectric testsDielectric tests Temperature riseTemperature rise Measurement of Zero Sequence impedance of Measurement of Zero Sequence impedance of

three phase transformersthree phase transformers Short-circuit testShort-circuit test Measurement of acoustic Noise levelMeasurement of acoustic Noise level Measurement of harmonics of no-load currentsMeasurement of harmonics of no-load currents Measurement of power taken by fans and oilMeasurement of power taken by fans and oil

pumpspumps



2222

IS 2026 Part IIIS 2026 Part II

This standard covers temperatureThis standard covers temperature

rise requirements of Powerrise requirements of Power


Identification according to coolingIdentification according to cooling

methods. Ex. ONAN,OFAFmethods. Ex. ONAN,OFAF

Limits of temperature riseLimits of temperature rise

Procedure for temperature rise test.Procedure for temperature rise test.



2323

Temperature rise limits for OilTemperature rise limits for Oil

Immersed Type TransformersImmersed Type Transformers

Part Temp. Rise in °CPart Temp. Rise in °C

Winding 55 ONAF 60 ONWFWinding 55 ONAF 60 ONWF

Oil 50 (with conservator)Oil 50 (with conservator)45 (without conservator)45 (without conservator)

Core, Should not damage coreCore, Should not damage core

Metallic parts itself Metallic parts itself



2424

This standard specifies the requirementsThis standard specifies the requirements

relating to insulation levels andrelating to insulation levels and

Dielectric tests for Power TransformersDielectric tests for Power Transformers

Insulation requirementsInsulation requirements

Dielectric withstand tests i.eDielectric withstand tests i.e

a) Short duration power frequencya) Short duration power frequency

withstand voltage testwithstand voltage test

b) Lightning impulse withstand voltage testb) Lightning impulse withstand voltage test

c) Induced Over voltage withstand Testc) Induced Over voltage withstand Test

IS 2026 Part IIIIS 2026 Part III



2525

Short duration power frequencyShort duration power frequency

withstand voltagewithstand voltage

--

20

40

60

7595

145

250

325

3

10

20

28

3850

70

95

140

1.1

3.6

7.2

12

17.524

36

52

72.5

Lightning impulsewithstand voltage (KV)

power frequencywithstand voltage (KV)

Voltageclass



2626

IS 2026 Part IVIS 2026 Part IV

This standard covers TerminalThis standard covers Terminalmarkings, Tappings and Connectionsmarkings, Tappings and Connectionsfor power transformersfor power transformers

Identifying Terminal and tappingIdentifying Terminal and tappingmarkingsmarkings

a) Charactera) Character

b) End points of phase windingb) End points of phase windingc) Line and Neutral terminalsc) Line and Neutral terminals

d) Marking of Tappingsd) Marking of Tappings



2727

ConnectionsConnections

Connections of phase windingsConnections of phase windings

Phase displacement betweenPhase displacement between

windingswindings



2828

IS 2026 Part VIS 2026 Part V

This standard specifies clearances inThis standard specifies clearances in

air between live parts of bushings onair between live parts of bushings on

oil immersed power transformer andoil immersed power transformer and

to object at earth potential.to object at earth potential.



2929

Bushing clearanceBushing clearance

--

--

60

90

125

170

275

450

630

< 1.1

3.6

7.2

12

17.5

24

36

52

72 5

Minimum clearance(mm)

Voltage class (KV)

Documents

7449867 Distribution Power Transformer