07 transformer

7/31/2019 07 Transformer

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TRANSFORMER PROTECTION

Slide 1Issue A


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Slide 2Issue A

Causes of failure:

Environment

System

Mal operation

Wrong design

Manufacture

Material

Maintenance


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2. External failure2. External failure2. External failure2. External failure

Causes:Causes:Causes:Causes:

Issue A Slide 4

-Abnormal operating conditionAbnormal operating conditionAbnormal operating conditionAbnormal operating condition

- sustained or unclear faultssustained or unclear faultssustained or unclear faultssustained or unclear faults

Transformer failures classification :Transformer failures classification :Transformer failures classification :Transformer failures classification :


5/81

Issue A Slide 5

Vector GroupsVector GroupsVector GroupsVector Groups

Phase displacementPhase displacementPhase displacementPhase displacement0000

Group 1Group 1Group 1Group 1

Phase displacementPhase displacementPhase displacementPhase displacement180180180180


Lag phase displacementLag phase displacementLag phase displacementLag phase displacement30303030


Lead phase displacementLead phase displacementLead phase displacementLead phase displacement30303030


Yy0Yy0Yy0Yy0Dd0Dd0Dd0Dd0Zd0Zd0Zd0Zd0

Yy6Yy6Yy6Yy6Dd6Dd6Dd6Dd6Dz6Dz6Dz6Dz6

Yd1Yd1Yd1Yd1

Dy1Dy1Dy1Dy1Yz1Yz1Yz1Yz1

Yd11Yd11Yd11Yd11Dy11Dy11Dy11Dy11

Yz11Yz11Yz11Yz11


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Slide 10Issue A

Fault current distribution

Earth fault on Transformer winding

V2

R

T 2 T 1

V1

X

Fig.3 If

Fig.N


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Slide 13Issue A

Differential

Basic Protection

Restricted Earthfault

Overfluxing

Overcurrent & Earthfault


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Slide 14Issue A

Differential Protection

Where protection co-ordination is difficult /notpossible using time delayed elements

For fast fault clearance

Applied

Works on Merz-price current comparisonprinciple

Relays with bias characteristic should only beused

For zone of protection


10/81

Slide 15Issue A

Differential Protection

Consideration for applying differential

protection

Phase correction

Filtering of zero sequence currents

Ratio correction

Magnetizing inrush during energisation

Overfluxing


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Slide 16Issue A

Differential Protection - Principle

R I diff = 0I diff = 0I diff = 0I diff = 0

Nominal current through the protected equipmentNominal current through the protected equipmentNominal current through the protected equipmentNominal current through the protected equipment

I Diff = 0 :I Diff = 0 :I Diff = 0 :I Diff = 0 : No trippingNo trippingNo trippingNo tripping


12/81

Slide 17Issue A

Differential Protection -

Principle Through fault currentThrough fault currentThrough fault currentThrough fault current

I Diff = 0 :I Diff = 0 :I Diff = 0 :I Diff = 0 : No trippingNo trippingNo trippingNo tripping



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Slide 18Issue A

Differential Protection -

Principle

TrippingTrippingTrippingTripping

Internal FaultInternal FaultInternal FaultInternal Fault

I Diff = 0 :I Diff = 0 :I Diff = 0 :I Diff = 0 :



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Slide 19Issue A

Biased differential protection

Fast operation

Adjustable characteristic

High through fault stability

CT ratio compensation

Magnetising inrush restraint

Overfluxing 5th harmonic restraint


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Slide 20Issue A


1 A

100/50 KV100 / 1 200 / 1

1 A

0 A

LOAD

= 200 A

Why bias characteristic ?

OLTC Setting is at mid tap

R

I1I2


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Slide 21Issue A

Biased differential protection100/50 KV100 / 1 200 / 1

0.9 A 1 A

0.1 A

Relay pickup setting = O.2 A, So the Relay restrains

LOAD= 200 A

OLTC SETTING IS AT 10%

Differential current = 0.1 A

R


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Slide 22Issue A


100/50 KV100 / 1 200 / 1

9 A10 A

1 A

Relay Pickup Setting is O.2 AOLTC SETTING IS AT 10%

2000 A

R

OperatesSo the Relay


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Slide 24Issue A

Based on Current operated relay with an external stabilising resBased on Current operated relay with an external stabilising resBased on Current operated relay with an external stabilising resBased on Current operated relay with an external stabilising resistoristoristoristor

Requires matched current transformers of low reactance design,Requires matched current transformers of low reactance design,Requires matched current transformers of low reactance design,Requires matched current transformers of low reactance design,typically class X or equivalenttypically class X or equivalenttypically class X or equivalenttypically class X or equivalent

Equal CT ratiosEqual CT ratiosEqual CT ratiosEqual CT ratios NonNonNonNon----linear resistor may be required to limit voltage across relaylinear resistor may be required to limit voltage across relaylinear resistor may be required to limit voltage across relaylinear resistor may be required to limit voltage across relaycircuit during internal faultscircuit during internal faultscircuit during internal faultscircuit during internal faults

Suitable for zones up to 200Suitable for zones up to 200Suitable for zones up to 200Suitable for zones up to 200 ---- 300 metres (typically)300 metres (typically)300 metres (typically)300 metres (typically)

High Impedance Principle


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Slide 25Issue A


TC satur

M

RCT

ZM

RCT2RL 2RL

A

M

ZM

RCT

2RL

2RL

RCT


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Slide 26Issue A


RCT

ZM

RCT

ZM

2RL 2RL

A

M

M


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Slide 27Issue A


RCT

ZM

RCT

ZM

2RL 2RL

TC satur

A

M

M


23/81

Slide 28Issue A


RCT

ZM

RCT

ZM

2RL 2RL

A

M

M


24/81

Slide 29Issue A


RCT

ZM

RCT

ZM

2RL 2RL

TC satur

A

M

M


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Slide 30Issue A


RCT

ZM

RCT

ZM

2RL 2RL

A

M

M


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Slide 31Issue A


RCT

ZM

RCT

ZM

2RL 2RL

TCsatur

A

M

M


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Slide 32Issue A


RCT

ZM

RCT

ZM=0

2RL 2RL

TC satur

RCT

2RL

2RL

RCT

A

M

MCT Saturation

False tripping


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Slide 33Issue A


RCT

ZM

RCT

ZM=0

2RL 2RL

TC satur

RCT

2RL

2RL

RCT

A

RS

M

M


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Slide 34Issue A


RCT

ZM

RCT

ZM=0

2RL 2RL

TC satur

RCT

2RL

2RL

RCT

A

RS

M

M

Stabilising resistorStabilising resistorStabilising resistorStabilising resistor


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Slide 35Issue A

RCT

ZM

RCT

ZM

2RL 2RL

A

RS

M

M

RCT

2RL

2RL

RCT Vset



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Slide 36Issue A

RCT

ZM

RCT

ZM=0

2RL 2RL

RCT

2RL

2RL

RCT

A

RS

M

M

ZM = 0(CT "shortcircuited" )

Vset



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Slide 37Issue A

A

RCT

ZM

RCT

ZM

2RL 2RL

2RL

RCT

2RL

RCT

RS

M

M

Vset



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Slide 38Issue A


2RL

RCT

2RL

RCT

M

Vset

A

RCT

ZM

RCT

ZM

2RL 2RL

RS

M


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Slide 39Issue A


M

A

RCT

ZM

RCT

ZM

2RL 2RL

RS

M

Vset

MetrosilMetrosilMetrosilMetrosil may bemay bemay bemay berequired for voltagerequired for voltagerequired for voltagerequired for voltage

limitationlimitationlimitationlimitation2RL

RCT

2RL

RCT

M

f


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Slide 40Issue A

Restricted Earthfault

Protection

Increased sensitivity for earth faults

REF elements for each transformer winding

CTs may be shared with differential element

Uses high impedance principle

6464

64

R t i t d E thf lt P t ti


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Slide 41Issue A

Restricted Earthfault Protection

P1P1P1P1

S1S1S1S1

P2P2P2P2

S2S2S2S2P1P1P1P1

S1S1S1S1

P2P2P2P2

S2S2S2S2

P1P1P1P1S1S1S1S1

P2P2P2P2S2S2S2S2

P1P1P1P1

P2P2P2P2

S1S1S1S1

S2S2S2S2

Stability level : usually maximum through fault level of tranStability level : usually maximum through fault level of tranStability level : usually maximum through fault level of tranStability level : usually maximum through fault level of transformersformersformersformerREF Case I : Normal Condition

Under normal conditions no current flows thro Relay

So, No Operation


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Slide 42Issue A


REF Case II : External Earth Fault

External earth fault - Current circulates between the phase & neutral CTs;

no current thro the relay

So, No Operation


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Issue ASlide 43

Issue A


REF Case III : Internal Earth Fault

For an internal earth fault the unbalanced current flows thro the relay

So, Relay Operates


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Slide 44Issue A


Restricted Earth Fault Protection SettingRestricted Earth Fault Protection SettingRestricted Earth Fault Protection SettingRestricted Earth Fault Protection Setting

1MVA(5%)11000V 415V

1600/1RCT = 4.9

80MVA

RS1600/1RCT = 4.8

MCAG14IS = 0.1

Amp2 Core 7/0.67mm(7.41/km)100m Long

Setting will requireSetting will requireSetting will requireSetting will requirecalculation of :calculation of :calculation of :calculation of :

1)1)1)1) Setting stabilitySetting stabilitySetting stabilitySetting stabilityvoltage (Vvoltage (Vvoltage (Vvoltage (V

SSSS))))

2)2)2)2) Value of stabilisingValue of stabilisingValue of stabilisingValue of stabilisingresistor requiredresistor requiredresistor requiredresistor required

3)3)3)3) Peak voltagePeak voltagePeak voltagePeak voltage

developed bydeveloped bydeveloped bydeveloped by CTCTCTCTssssfor internal faultfor internal faultfor internal faultfor internal fault

i d hf l i


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Slide 45Issue A


Example : Earth fault calculation :Example : Earth fault calculation :Example : Earth fault calculation :Example : Earth fault calculation :----

Using 80MVA baseUsing 80MVA baseUsing 80MVA baseUsing 80MVA base

Source impedance = 1 p.u.Source impedance = 1 p.u.Source impedance = 1 p.u.Source impedance = 1 p.u.

Transformer impedance = 0.05 x 80 = 4 p.u.Transformer impedance = 0.05 x 80 = 4 p.u.Transformer impedance = 0.05 x 80 = 4 p.u.Transformer impedance = 0.05 x 80 = 4 p.u.1111

Total impedance = 14 p.u.Total impedance = 14 p.u.Total impedance = 14 p.u.Total impedance = 14 p.u.

I1111 = 1 = 0.0714 p.u.= 1 = 0.0714 p.u.= 1 = 0.0714 p.u.= 1 = 0.0714 p.u.14141414

Base current = 80 x 10Base current = 80 x 10Base current = 80 x 10Base current = 80 x 106666

3 x 4153 x 4153 x 4153 x 415

= 111296 Amps= 111296 Amps= 111296 Amps= 111296 Amps IFFFF = 3 x 0.0714 x 111296= 3 x 0.0714 x 111296= 3 x 0.0714 x 111296= 3 x 0.0714 x 111296

= 23840 Amps (primary)= 23840 Amps (primary)= 23840 Amps (primary)= 23840 Amps (primary)= 14.9 Amps (secondary)= 14.9 Amps (secondary)= 14.9 Amps (secondary)= 14.9 Amps (secondary)

1 P.U.1 4

I1

4

I2

4

I0

1

1

R i d E hf l P i


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Slide 46Issue A


(1)(1)(1)(1) Setting voltageSetting voltageSetting voltageSetting voltage

VVVVSSSS ==== IFFFF (R(R(R(RCTCTCTCT + 2+ 2+ 2+ 2RLRLRLRL))))

AssumingAssumingAssumingAssuming earthearthearthearth CT saturates,CT saturates,CT saturates,CT saturates,

RRRRCTCTCTCT = 4.8 ohms= 4.8 ohms= 4.8 ohms= 4.8 ohms

2222RLRLRLRL = 2 x 100 x 7.41 x 10= 2 x 100 x 7.41 x 10= 2 x 100 x 7.41 x 10= 2 x 100 x 7.41 x 10----3333 = 1.482 ohms= 1.482 ohms= 1.482 ohms= 1.482 ohms

Setting voltage = 14.9 (4.8 + 1.482)Setting voltage = 14.9 (4.8 + 1.482)Setting voltage = 14.9 (4.8 + 1.482)Setting voltage = 14.9 (4.8 + 1.482)

= 93.6 Volts= 93.6 Volts= 93.6 Volts= 93.6 Volts

(2)(2)(2)(2) Stabilising Resistor (RStabilising Resistor (RStabilising Resistor (RStabilising Resistor (RSSSS))))

RRRRSSSS ==== {Vs - [VA/(Is^2)]} /Is

WhereWhereWhereWhere ISSSS = relay current setting= relay current setting= relay current setting= relay current setting RRRRSSSS = {93.6= {93.6= {93.6= {93.6 ---- [[[[ 1/0.1^2]}/0.1 = 836 ohms1/0.1^2]}/0.1 = 836 ohms1/0.1^2]}/0.1 = 836 ohms1/0.1^2]}/0.1 = 836 ohms

R t i t d E thf lt P t ti


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Slide 47Issue A


3)3)3)3) Peak voltage = 2Peak voltage = 2Peak voltage = 2Peak voltage = 22222 VVVVKKKK(V(V(V(VFFFF ---- VVVVKKKK))))

VVVVFFFF = 14.9 x V= 14.9 x V= 14.9 x V= 14.9 x VSSSS = 14.9 x 936 = 13946 Volts= 14.9 x 936 = 13946 Volts= 14.9 x 936 = 13946 Volts= 14.9 x 936 = 13946 VoltsISSSS

ForForForFor EarthEarthEarthEarth CT, VCT, VCT, VCT, VKKKK = 1.4 x 236 = 330 Volts (from= 1.4 x 236 = 330 Volts (from= 1.4 x 236 = 330 Volts (from= 1.4 x 236 = 330 Volts (fromgraph)graph)graph)graph)

VVVVPEAKPEAKPEAKPEAK = 2= 2= 2= 22222 330 (13946330 (13946330 (13946330 (13946 ---- 330)330)330)330)

= 6kV= 6kV= 6kV= 6kV

Thus,Thus,Thus,Thus, metrosilmetrosilmetrosilmetrosil voltage limiter will be required.voltage limiter will be required.voltage limiter will be required.voltage limiter will be required.


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Slide 48Issue A

Magnetising Inrush

Transient condition - occurs when a

transformer is energised

Normal operating flux of a transformer is close to saturation

level

Residual flux can increase the mag-current

In the case of three phase transformer, the point-on-wave at

switch-on differs for each phase and hence, also the inrush

currents


44/81

Slide 49Issue A

Transformer Magnetising CharacteristicTransformer Magnetising CharacteristicTransformer Magnetising CharacteristicTransformer Magnetising Characteristic

TwiceTwiceTwiceTwiceNormal FluxNormal FluxNormal FluxNormal Flux

NormalNormalNormalNormalFluxFluxFluxFlux

NormalNormalNormalNormalNo Load CurrentNo Load CurrentNo Load CurrentNo Load Current

No Load Current atNo Load Current atNo Load Current atNo Load Current atTwice Normal FluxTwice Normal FluxTwice Normal FluxTwice Normal Flux

Magnetising Inrush


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Slide 50Issue A

Magnetising Inrush

m+

SWITCH ON AT VOLTAGE

ZERO - NO RESIDUAL FLUX

m-

m2

STEADY STATE

V

mI

mI

V

Inrush Current


46/81


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Slide 52Issue A

Magnetising Inrush

Appears on one side of transformer only

- Seen as fault by differential relay

- Transient magnetising inrush could cause

relay to operate

Makes CT transient saturation

- Can make mal-operation of Zero sequence

relay at primary

Effect of magnetising currentEffect of magnetising currentEffect of magnetising currentEffect of magnetising current


48/81

Slide 53Issue A

P1P1P1P1

S1S1S1S1

P2P2P2P2

S2S2S2S2P1P1P1P1

S1S1S1S1

P2P2P2P2

S2S2S2S2P1P1P1P1

S1S1S1S1

P2P2P2P2

S2S2S2S2

IRIRIRIR

ISISISIS

ITITITIT

IR + IS + IT = 3Io = 0IR + IS + IT = 3Io = 0IR + IS + IT = 3Io = 0IR + IS + IT = 3Io = 0

Magnetising Inrush

M i i I h


49/81

Slide 54Issue A

Effect of magnetising currentEffect of magnetising currentEffect of magnetising currentEffect of magnetising current

Example ofExample ofExample ofExample of disurbancedisurbancedisurbancedisurbance recordsrecordsrecordsrecordswith detailwith detailwith detailwith detail

Magnetising Inrush

M ti i I h R t i


50/81

Slide 55Issue A

2nd (and 5th) harmonic restraint2nd (and 5th) harmonic restraint2nd (and 5th) harmonic restraint2nd (and 5th) harmonic restraint

Makes relay immune to magnetisinginrush

Slow operation may result for genuine

transformer faults if CT saturationoccurs

Magnetising Inrush Restrain

O fl i B i Th


51/81

Slide 57Issue A

Overfluxing - Basic Theory

Low frequency High voltage

Geomagnetic disturbances

Causes

Overfluxing = V/F


52/81


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Overfluxing Protection


54/81

Slide 60Issue A

V Kf

Trip and alarm outputs for clearing prolonged overfluxing

Alarm : Definite time characteristic to initiate correctiveaction

Trip : IT or DT characteristic to clear overfluxing condition

Overfluxing - Protection

BUCCHOLZ PROTECTION


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Slide 60Issue A

Oil conservatorOil conservatorOil conservatorOil conservator

BucholzBucholzBucholzBucholz RelayRelayRelayRelay

BUCCHOLZ PROTECTION

BUCCHOLZ PROTECTION


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Slide 60Issue A

Buchholz Relay InstallationBuchholz Relay InstallationBuchholz Relay InstallationBuchholz Relay Installation

5 x internal pipe5 x internal pipe5 x internal pipe5 x internal pipediameter (minimum)diameter (minimum)diameter (minimum)diameter (minimum)

3 x internal pipe3 x internal pipe3 x internal pipe3 x internal pipediameter (minimum)diameter (minimum)diameter (minimum)diameter (minimum)

TransformerTransformerTransformerTransformer

76 mm typical76 mm typical76 mm typical76 mm typical

To oil conservatorTo oil conservatorTo oil conservatorTo oil conservator

BUCCHOLZ PROTECTION


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BUCCHOLZ PROTECTION


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Slide 60Issue A

Accumulation of gazAccumulation of gazAccumulation of gazAccumulation of gazOilOilOilOil LeakageLeakageLeakageLeakageSevereSevereSevereSevere windingwindingwindingwinding faultsfaultsfaultsfaults

BuccholzBuccholzBuccholzBuccholz Protection ApplicationProtection ApplicationProtection ApplicationProtection Application

BUCCHOLZ PROTECTION

BUCCHOLZ PROTECTION


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Slide 60Issue A

InterturnInterturnInterturnInterturn faultsfaultsfaultsfaults

WindingWindingWindingWinding faultsfaultsfaultsfaults totototo earthearthearthearth withwithwithwith lowlowlowlow

power (power (power (power (faultfaultfaultfault close toclose toclose toclose to neutralneutralneutralneutral forforforforexampleexampleexampleexample))))

Accumulation of GazAccumulation of GazAccumulation of GazAccumulation of Gaz

BUCCHOLZ PROTECTION

BUCCHOLZ PROTECTION


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Slide 60Issue A

Inter-Turn Fault

Nominal turns ratio

Fault turns ratioCurrent ratio

: 11,000 / 240

: 11,000 / 1: 1 / 11,000

Shortedturn

Load

Primary Secondary

CTCTCTCTEEEE

BUCCHOLZ PROTECTION

BUCCHOLZ PROTECTION


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Slide 60Issue A

Nominal turns ratio

Fault turns ratioCurrent ratio

: 11,000 / 240

: 11,000 / 1: 1 / 11,000

CTCTCTCTEEEE

Shortedturn

Primary Secondary

Inter-Turn Fault

BUCCHOLZ PROTECTION


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Slide 60Issue A

Interturn Fault Current / Numberof Turns Short Circuited

5555 10101010 15151515 20202020 25252525

Turn shortTurn shortTurn shortTurn short----circuitedcircuitedcircuitedcircuited(percentage of(percentage of(percentage of(percentage ofwinding)winding)winding)winding)

Primary currentPrimary currentPrimary currentPrimary current(multiples of(multiples of(multiples of(multiples ofrated current)rated current)rated current)rated current)

Fault currentFault currentFault currentFault current(multiples of(multiples of(multiples of(multiples ofrated current)rated current)rated current)rated current)

100100100100

80808080

60606060

40404040

20202020

BUCCHOLZ PROTECTION


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Slide 60Issue A

Interturn Fault Current / Numberof Turns Short Circuited

5 10 15 20 25

Primary current

(multiples of

rated current)

Fault current

(multiples of

rated current)

100

80

60

40

20

Fault current very high

Primary phase current very low

Detected by Bucholz relay

Not detected by current

operated relays

BUCCHOLZ PROTECTION


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Slide 60Issue A

InterturnInterturnInterturnInterturn faultsfaultsfaultsfaults

WindingWindingWindingWinding faultsfaultsfaultsfaults totototo earthearthearthearth withwithwithwith lowlowlowlow

power (power (power (power (faultfaultfaultfault close toclose toclose toclose to neutralneutralneutralneutral forforforforexampleexampleexampleexample))))


BUCCHOLZ PROTECTION


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Slide 60Issue A

Earth Fault Current / Number ofEarth Fault Current / Number ofEarth Fault Current / Number ofEarth Fault Current / Number ofTurns Short CircuitedTurns Short CircuitedTurns Short CircuitedTurns Short Circuited

5555 10101010 15151515 20202020 25252525

Turn shortTurn shortTurn shortTurn short----circuitedcircuitedcircuitedcircuited(percentage of(percentage of(percentage of(percentage ofwinding)winding)winding)winding)

Primary currentPrimary currentPrimary currentPrimary current

Fault currentFault currentFault currentFault current

100100100100

80808080

60606060

40404040

20202020

multiples ofmultiples ofmultiples ofmultiples ofmax fault currentmax fault currentmax fault currentmax fault current

BUCCHOLZ PROTECTION


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Slide 60Issue A

OperatingOperatingOperatingOperating principleprincipleprincipleprinciple


BUCCHOLZ PROTECTION


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Slide 60Issue A

Buchholz RelayBuchholz RelayBuchholz RelayBuchholz Relay

AccumulationAccumulationAccumulationAccumulationofofofof gazgazgazgaz

BUCCHOLZ PROTECTION


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Slide 60Issue A



BUCCHOLZ PROTECTION


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Slide 60Issue A



BUCCHOLZ PROTECTION


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Slide 60Issue A

ColorColorColorColor ofofofof gazgazgazgaz indicatesindicatesindicatesindicatesthe type of faultthe type of faultthe type of faultthe type of fault

White or Yellow :White or Yellow :White or Yellow :White or Yellow :Insulation burntInsulation burntInsulation burntInsulation burnt

Grey :Grey :Grey :Grey :Dissociated oilDissociated oilDissociated oilDissociated oil


BUCCHOLZ PROTECTION


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Slide 60Issue A

AccumulationAccumulationAccumulationAccumulation

ofofofof gazgazgazgaz

GazGazGazGaz can be extracted fcan be extracted fcan be extracted fcan be extracted fdetailleddetailleddetailleddetailled analysisanalysisanalysisanalysis


BUCCHOLZ PROTECTION


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Slide 60Issue A

After oil maintenance, falsetripping may occur because Oil

aeration

Effects of Oil MaintenanceEffects of Oil MaintenanceEffects of Oil MaintenanceEffects of Oil Maintenance

BucholzBucholzBucholzBucholz relay tripping inhibited duringrelay tripping inhibited duringrelay tripping inhibited duringrelay tripping inhibited duringsuitable periodsuitable periodsuitable periodsuitable period

Need of electrical protectionNeed of electrical protectionNeed of electrical protectionNeed of electrical protection

BUCCHOLZ PROTECTION


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Slide 60Issue A


BucholtzBucholtzBucholtzBucholtz Protection ApplicationProtection ApplicationProtection ApplicationProtection Application

BUCCHOLZ PROTECTION


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Slide 60Issue A

Oil LeakageOil LeakageOil LeakageOil LeakageBuchholz RelayBuchholz RelayBuchholz RelayBuchholz Relay

BUCCHOLZ PROTECTION


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Slide 60Issue A


BUCCHOLZ PROTECTION


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Slide 60Issue A


BUCCHOLZ PROTECTION


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Slide 60Issue A


BUCCHOLZ PROTECTION


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Slide 60Issue A


BuccholzBuccholzBuccholzBuccholz Protection ApplicationProtection ApplicationProtection ApplicationProtection Application

BUCCHOLZ PROTECTION


79/81

Slide 60Issue A

Severe winding faultSevere winding faultSevere winding faultSevere winding faultBuchholz RelayBuchholz RelayBuchholz RelayBuchholz Relay


80/81

BUCCHOLZ PROTECTION


81/81

Slide 60Issue A

Severe winding faultSevere winding faultSevere winding faultSevere winding faultBuchholz RelayBuchholz RelayBuchholz RelayBuchholz Relay

07 transformer

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