7449867 Distribution Power Transformer

Distribution Transformers Reference Standard: IS 1180 --1989 Types of Distribution Transformers a) Non-Sealed type b) Sealed type

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Non-Sealed type Distribution Transformers Reference Standard  IS 1180 (Part 1) : 1989 This standard specifies the requirements and tests for oil immersed 3-Φ NonSealed type Distribution Transformers of ratings up to and including 100KVA and voltage class up to and including 11KV 2

IS 1180 (Part 1)

: 1989

This standard covers  Ratings  No load voltage ratios  Winding connections and vectors  Tapping ranges  Fittings  Terminal arrangement  Losses and Impedance values  Tolerances 3

IS 1180 (Part 1)

: 1989

Rating :  KVA Rating – 16, 25, 63 and 100  Frequency – 50Hz  System Voltage – 3.3, 6.6 and 11KV  Secondary Voltage – 433 and 250

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IS 1180 (Part 1)

: 1989

 Tapping

Up to and Including 25 KVA

Above 25 KVA

Winding tapped

Secondary

Primary

Number of tappings

2

5

+5%

±2.5% and ±5%

Tappings at

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IS 1180 (Part 1)

: 1989

Fittings  Oil level indicator  Lifting lugs  Breather  Drain cum sampling valve  Rating and terminal marking plates

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IS 1180 (Part 1)

: 1989

Clearances in mm H.V Side

L.V Side

Phase to phase

255

75

Phase to earth

140

40

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IS 1180 (Part 1)

: 1989

 Limits

of temperature rise : Winding 55°C Top oil 45°C  Losses and Impedance values Load loss (W) Rating (KVA) No load loss (W) at 75°C 16 80 475 25 100 685 63 180 1235 100 260 1760 8

Tests  Measurement

of winding resistance  Measurement Voltage ratio and check of voltage vector relationship  Measurement of impedance voltage, short circuit impedance and load loss  Measurement of no-load loss and current  Measurement of insulation resistance 9

Tests  SSVW

test  IOVW test  Lightning impulse test  Temperature rise test  SC test  Air pressure test (35KPa 30min)

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Permissible flux density and overfluxing B

max

– 1.69 Tesla

 No

load current in terms of %of full load current

KVA Rating

At 100% rated At 112.5% voltage rated voltage

16

4

8

25

3.5

7

63

3

6

100

2.5

5

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Mounting arrangements  The

under-base of all the transformers shall be provided with two 75x40mm channels 460mm long.

415mm

415±2mm

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Sealed type Distribution Transformers Reference Standard  IS 1180 (Part 2) : 1989  This standard specifies the requirements and tests for oil immersed 3-Φ Sealed type Distribution Transformers of ratings up to and including 100KVA and voltage class up to and including 11KV 13

IS 1180 (Part 2)

: 1989

 No

Taps  No conservator  Air pressure test is to be conducted at 80KPa for 30minutes.

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IS 1180 (Part 2)

: 1989

Clearances in mm H.V Side

L.V Side

Internal external Internal

external

Phase to phase

127

255

45

75

Phase to earth

76

140

20

40 15

Power Transformers Reference Standards  IS 2026 Part I 1977– General  IS 2026 Part II 1977– Temperature Rise  IS 2026 Part III 1981– Insulation Levels and Dielectric Tests  IS 2026 Part IV 1977– Terminal markings, Tappings and Connections  IS 2026 Part V 1994– Transformer/ Reactor Bushings- Minimum external clearance in air 16

IS 2026 Part I This standard covers  Service conditions  Rating  Requirements to withstand Short Circuit  Dimensions of Neutral Connection  Tolerances  Rating plates  Fittings  Tests 17

Rating  Rated

KVA  Operation at other than rated voltage: The transformer can be operated at its rated KVA at any voltage with in ±10%  Rated frequency: 50Hz ± 1.5

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TOLERANCES Item

Tolerances

Total Losses Component Losses Voltage ratio Impedance Voltage No-load current

+10% +15% ±0.5% ±10% +30

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TESTS  Measurement

of winding resistance  Measurement Voltage ratio and check of voltage vector relationship  Measurement of impedance voltage, short circuit impedance and load loss  Measurement of no-load loss and current  Measurement of insulation resistance 20

TESTS Dielectric tests  Temperature rise  Measurement of Zero Sequence impedance of three phase transformers  Short-circuit test  Measurement of acoustic Noise level  Measurement of harmonics of no-load currents  Measurement of power taken by fans and oil pumps 

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IS 2026 Part II  This

standard covers temperature rise requirements of Power Transformers  Identification according to cooling methods. Ex. ONAN,OFAF  Limits of temperature rise  Procedure for temperature rise test.

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Temperature rise limits for Oil Immersed Type Transformers Part Winding Oil

Temp. Rise in °C 55 ONAF 60 ONWF 50 (with conservator) 45 (without conservator) Core, Should not damage core Metallic parts itself

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IS 2026 Part III This standard specifies the requirements relating to insulation levels and Dielectric tests for Power Transformers Insulation requirements Dielectric withstand tests i.e a) Short duration power frequency withstand voltage test b) Lightning impulse withstand voltage test c) Induced Over voltage withstand Test 24

Short duration power frequency withstand voltage Voltage power frequency Lightning impulse class withstand voltage (KV) withstand voltage (KV) 1.1 3 -3.6 10 20 7.2 20 40 12 28 60 17.5 38 75 24 50 95 36 70 145 52 95 250 72.5 140 325 25

IS 2026 Part IV  This

standard covers Terminal markings, Tappings and Connections for power transformers  Identifying Terminal and tapping markings a) Character b) End points of phase winding c) Line and Neutral terminals d) Marking of Tappings 26

Connections  Connections

of phase windings  Phase displacement between windings

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IS 2026 Part V  This

standard specifies clearances in air between live parts of bushings on oil immersed power transformer and to object at earth potential.

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Bushing clearance Voltage class (KV) < 1.1 3.6 7.2 12 17.5 24 36 52 72.5

Minimum clearance (mm) --60 90 125 170 275 450 630

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