testing transf diff relays with single phase test currents - 03302015

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Methods for Testing

 Transformer DierentialRelays Applied to Delta-Grounded Wye Transformers

Using Single-Phase TestCurrents

 Tom rnstG Digital nergy

Craig Tal!otMinnesota Po"er

 Te#as A$M Relay Conferen%e &'()

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Agenda

*ntrodu%tion Traditional +-phase testing method

 Traditional (-phase testing method

Alternate (-phase testing methodAppli%ation e#amples

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*ntrodu%tion,

+-Phase testing %an !e %hallengingStraight for"ard magnitude $ phaseangles

Reuires . high-%urrent test set %hannels

(-phase testing

Reuires only & high-%urrent test set%hannels

Reuires non-o!/ious multipliers

Does not simulate real-"orld loading on

Delta-"ye transformers

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 There is al"ays a "ay to do this

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*ntrodu%tion,

Alternate (-phase testing methodReuires only & high-%urrent test set%hannels

Simulates real-"orld (-phase loading%onditions

0o phase shifts

0o non-o!/ious multipliers

Suita!le for %ommission testing, tests thetransformer installation not the relaysettings

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 Traditional +-phase testing,

Reuires simultaneous in1e%tion of test%urrents into a minimum of & relay"indings

Some test sets do not in%lude . high-%urrent %hannels

Magnitude relationship of the %urrents!ased on the transformer +-phase/oltage ratio

Slope %hara%teristi% tests

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 Traditional +-phase testing,

Phase shift !et"een test %urrents %an!e %hallenging for delta 2 grd "yetransformers

3un%tion of the transformer internal ande#ternal %onne%tions, phases A4 5 $ C

might not !e on !ushings (4 & $ +Reuires thorough understanding of +-phase po"er

Same transformer %an !e +'6 lag or +'6lead

Slope %hara%teristi% tests

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 Traditional +-phase testing,

 Typi%aldelta - grd"ye

transformerandasso%iated+-phasetest%urrents

7+'6 lag8

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 Traditional +-phase testing,

 Typi%aldelta - grd"ye

transformer"ith rolledphasingandasso%iated+-phasetest

%urrents

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 Traditional +-phase testing,

+-Phasetesting%onne%tion

s for a +'6lagtransformer

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 Traditional (-phase testing,

Che%9s the fun%tionality of ea%h phase

:nly reuires & %urrent %hannelsMay reuire multipliers and phaseshifts that are not o!/ious 7Delta 2 GrdWye transformers8

Slope %hara%teristi% tests

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 Traditional (-phase testing,

(-Phase

testing%onne%tions

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Somealternateideas are!etter than

others

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Alternate (-phase testing,

Conne%tions are related to thetransformer internal and e#ternal +-line diagrams

;ery ae%ti/e for %ommissioning

Simulates real-"orld load and short

%ir%uit %onditions0o non-o!/ious multipliers

0o non-o!/ious phase shifts

Slope %hara%teristi% tests

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Alternate (-phase testing,

Dierentially!alan%ed (-phase

through-%urrent for adelta - grd

"ye transf7+'6 lag8

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Alternate (-phase testing,

Dierentially!alan%ed (-phase test

%onne%tionsfor a delta -grd "ye

transf 7+'6lag8

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Alternate (-phase testing,

Dierentially!alan%ed (-phase

through-%urrent for adelta - grd

"ye transf7+'6 lead8

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Alternate (-phase testing,

Dierentially!alan%ed (-phase test

%onne%tionsfor a delta -grd "ye

transf 7+'6lead8

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Alternate (-phase testing,

 Test %urrents %al%ulated !ased on0(<0& turns-ratio not /oltage ratio

=+ multiplier inherent

0o '-se >ltering multiplier reuired

Currents al"ays (?'6 apart

 Test results %learly indi%ate ifdierential phase shift is set %orre%tly

Slope %hara%teristi% tests

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Alternate (-phase testing,

Dierentially !alan%ed through-%urrent

%ondition "ith %orre%t phase shift setting

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Alternate (-phase testing,

Dierentially !alan%ed through-%urrent

%ondition "ith in%orre%t phase shift

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Alternate (-phase testing,

Slope /eri>%ation "ith angle of "inding &

rolled until relay trips@ S '@(+<'@)'

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Alternate (-phase testing,

TestID

Winding 1(delta)connections

Winding 2 (wye)connections

A *n on A $ out on C AB *n on 5 $ out on A 5C *n on C $ out on 5 C

 Test %onne%tions for a & "inding +'degree lag delta-"ye %onne%tion

transformer

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Alternate (-phase testing,

TestID

Winding 1(delta)connections

Winding 2 (wye)connections

A *n on A $ out on 5 AB *n on 5 $ out on C 5C *n on C $ out on A C

 Test %onne%tions for a & "inding +'degree lead delta-"ye %onne%tion

transformer

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Wa9e up@ This is theinterestingpart

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Appli%ation #ample (, +'6ag

 Transformernameplate

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Appli%ation #ample (, +'6ag

+-line

installationdiagram-dierentially

!alan%ed (-phase load

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Appli%ation #ample (, +'6ag

 Test de>nitions

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Appli%ation #ample &, +'6ead

 Transformer

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Appli%ation #ample &, +'6ead

+-line

installationdiagram-dierentially

!alan%ed (-phase load

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Appli%ation #ample &, +'6ead

 Test de>nitions

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*n%orre%t :peration Analysis

 Transformer dierential tripped one#ternal feeder fault

Caused !y "rong angle setting

Alternate method not used

0o load a/aila!le at time of %onstru%tionfor in-ser/i%e %he%9s

Using the alternate method mightha/e pre/ented the trip

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*n%orre%t :peration #ample

Wa/eform Capture

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Con%lusion,

 Traditional +-phase testing method %an!e %hallenging

 Traditional (-phase testing methoddoes not simulate real-"orld loading

Alternate (-phase testing methodsimulates real-"orld and tests the

settings against the installation

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 Than9 Eou

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