113894818-transformer-protection.ppt

7/21/2019 113894818-Transformer-Protection.ppt

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GRID

Technical Institute

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Transformer Protection


2/116


3/116

3 > Transformer Protection

Transformer Protection (1)

ransformer Connections

!vercurrent "rotection

#irectional "rotection of "arallel ransformers

"artial #ifferential "rotection of "arallel ransformers

$arth %aults on ransformer Windings

&nrestricted $arth %ault "rotection

'estricted $arth %ault "rotection

(iased #ifferential "rotection of 2 and 3 Winding

ransformers


4/116



Combined #ifferential and 'estricted $arth %ault

"rotection

"rotection of Auto)ransformers

*nter)urn %aults and (uchhol+ "rotection

!verfluxing "rotection

!verload "rotection

ransformer %eeder "rotection


5/116


Transformer Connections


6/116



A1

I A2

V EP


7/1167 > Transformer Protection

A1

I A2

V EP

a1

a2

ES




IS

A1

I A2

V EP

a1

a2

ES


P



A

(

C c

b

aa2a1

b1 b2(1(2

A2 A1

C2 C1 c1 c2

A

(C

C2

C1 A2

A1

(2(1

a

b

cc2

c1

a2

a1

b1 b2

Cloc- face numbers refer to

position of lo/ voltage phase )

neutral vector /ith respect to high

voltage phase ) neutral vector.

0ine connections made to highest

numbered /inding terminal available.

0ine phase designation is same as

/inding.




"hase displacement

roup 1

"hase displacement1

roup 2

0ag phase displacement3

roup 3

0ead phase displacement3

roup 4

5

#d

6d

57

#d7#+7

d1

#51

+1

d11

#511

+11

Transformer Vector Groups



Cloc- %ace numbers refer to position of lo/ voltage

phase)neutral vector /ith respect to high voltage phaseneutral vector

0ine connections made to highest numbered /inding

terminal available

0ine phase designation is same as /inding

Example 1 !" 11 Transformer

B1B2 b2b1

a2a1A1A2

C1C2 c2c1

8uestion 9 :o/ to connect /indings ;

HighVoltage

Winings

!o"Voltage

Winings

A PhaseWining

s

B PhaseWinings

C PhaseWining

s




3oltage >ectors

#$%

A

C B

a

c

b

!ine Designation

!" 11



2. #ra/ #elta Connection

a

c

b

A

BC

!" 11



3. #ra/ A "hase Windings

A

C B

a

b

a2

a1

A2

A1

c

!" 11



4. Complete Connections ?a@

A

B

a

c

b

a2

a1

A1

C1

C2

B1

B2

b2

b1

c1

c2

C

A2

!" 11



4. Complete Connections ?b@

c1

c2

b

1

b

2

a1 a2a

b

c

A

B

CC2

C1

B

2

B

1

A2

A1

!" 11
http://additional%20tx%20notes.ppt/



ransformer rating %use

->A

1

2

3

1

.2

1.

1.

27.22.

17

2

37

B

3.

3.

1.

2.3.

%ull load

current ?A@

'ated

current ?A@

!perating time at

3 x rating?s@

11#V !istri$ution TransformersT"pical Fuse %atings



Tra&itional 'mall TransformerProtection Pac#age

5

1

3.3k

V200/5 5051

1MVA

3.3/0.44kV1500/5

1500/564

N5

0N

51

N



Tra&itional e&ium TransformerProtection Pac#age

11&

V'$

'1

'(VA11)#*#&V

1$$$)'

1$$$)'

+,

'

1-

+,

#*#&



*ercurrent Protection



'euirements

%ast operation for primar5 short circuits

#iscrimination /ith do/nstream protections

!peration /ithin transformer /ithstand

=on)operation for short or long term overloads

=on)operation for magnetising inrush

Transformer *ercurrent Protection


23/116


Source:>

0>

1

set to 1.2 ) 1.3 x through fault level

+se of ,nstantaneous *ercurrent Protection


24/116


Concerns rela5 response to offset /aveforms ?#C

transient@

#efinition

I1 - I2

I2 x 100

I1 D Stead5 state

rms pic- up

current

I2 D %ull5 offset

rms

pic-up

current

I1

I2

D.C.

Transient *erreac-


25/116


HV2

'1

'1

'1

!VHV1

Ti.e !V

HV1HV2

Cu//entI0!V

1*2I0!V

I0HV

,nstantaneous .ig- 'et *ercurrent%ela" /pplie& to a Transformer


26/116


I3 I3

I3

I3

0.866

20101 !istri$ution (1)


27/116


I3.77 I3

.4 sec

0> rela5

:> rela5

20101 !istri$ution (2)


28/116


rid suppl5%eeders

1

1

7E

7E

1

1

Parallel Transformers!irectional %ela"s (1)

P ll l T f


29/116


11

1

1

(usSection

Parallel Transformers!irectional %ela"s (2)

rid suppl5%eeders

1

P ll l T f


30/116


Advantage 9 'educed number of gradingsta es

+

3

+

3 '1

'1

'1

'1

P1

P1

S1

S1

S2

S2

P2

P2

rid suppl5

Parallel TransformersPartial !ifferential 'c-eme


31/116


Eart- Fault Protection

T f E t- F lt


32/116


1 p.u. turns3 p.u. turns

x*"

"'

' *%"rotective'ela5

:3ratioturnsEffective

.3

.currentFault:atfaultaFor

.3

current!"ri#ar$%&us!valuesloa'fulltocurrentE/Fli#its(esistor

F.).2

F.).

F.).*

=

==

=

secon'ar$+.%.t&enr!transfor#eofcurrentloa'

fullon,ase'issi'e-"ri#ar$onratio+.%./f

3

circuit2

=

Transformer Eart- Faults

t % l ' iti it


33/116


I0

51

vercurrent

(ela$

I4as .ulti5le

o4 I0*!*

1*$

$*6

$*7

$*3

$*+

$*'

$*,

$*#

$*2

$*1

Sta/Sie

DeltaSie

$*1$*2 $*# $*, $*' $*+ $*3 $*7 $*6 1*$

5*u**89e/cu//ent Rela: Setting ;

I0*!*

*ercurrent %ela" 'ensiti*it"to Eart- Faults (1)

t % l ' iti it


34/116


1$

6

7

3

+

'

,

#

2 1

$*1 $*2 $*# $*, $*' $*+ $*3 $*7 $*6 1*$

5*u**

I4as .ulti5le

o4 I0*!*

Sta/Sie

DeltaSie


I0

51

vercurrent

(ela$

t % l ' iti it


35/116


I0

IP I-

1$

6

7

3 +

'

,

#

2 1

$*1$*2 $*#$*,$*'$*+ $*3 $*7$*61*$

5*u**

I-

IP

I0


I4as .ulti5le

o4 I0*!*

E t- F lt T f i &i


36/116


#ifferential 'ela5 Setting F of Star Winding "rotected1F F

2F 41F

3F 2F

4F 1EF

F EF

Eart- Fault on Transformer in&ing

I

#ifferential'ela5

Setting < IS

%or rela5 operation, IG IS

e.g. *f ISD 2F, then G 2F for operation

i.e.

G BF

hus BF of /inding is not protected

2

3ID

2

3

+nrestricte& Eart-fault Protection (1)


37/116


"rovides bac-)up protection for s5stem

ime dela5 reuired for co)ordination


'1

'1

'1

'1-



38/116


Can provide better sensitivit5

?C.. ratio not related to full load current@

?*mproved effective setting@

"rovides bac- up protection for transformer and s5stem

'1

'1

'1

'1-'1

-


'tar in&ing %EF


39/116


"rotected

6one

'$

%

'ela5 onl5 operates for earthfaults /ithin protected +one.

&ses high impedance principle.

Stabilit5 level 9 usuall5 maximum through fault level of

transformer

'tar in&ing %EF

%estricte& EF Protection


40/116


0> restricted $H%

protection trips

both :> and 0> brea-er

'ecommended setting 9 1F

rated

%estricte& EF Protectiono Voltage in&ings (1)

A ( C =

%estricte& EF Protection


41/116


A ( C =

0> restricted $H% protection trips both :> and 0> brea-er

'ecommended setting 9 1F rated

%estricte& EF Protectiono Voltage in&ings (2)

!elta in&ing %estricte& Eart- Fault


42/116


"rotected +one

'$%

Source

#elta /inding cannot suppl5 +ero seuence current tos5stem

Stabilit5 9 Consider max 0> fault level

'ecommended setting 9 less than 3F minimum earth fault

level

!elta in&ing %estricte& Eart- Fault

.ig- ,mpe&ance Principle


43/116


P/otecteCi/cuit

R

=

(

RCT

R!

=

(

RCT

R!I0

IS

RS

T

VS

R! R!

.ig- ,mpe&ance Principle

>oltage Across 'ela5 Circuit >S D I%?'CI 2'0@

Stabilising resistor 'Slimits spill current to IS?rela5 setting@

'SD ) '' /here ''D rela5 burden

C -nee point

>J"

D 2>SD 2I

%?'

CI 2'

0@

>S

IS

on0inear %esistors (etrosils)


44/116


#uring internal faults the high impedance rela5 circuit

constitutes an excessive burden to the CKs.

A ver5 high voltage develops across the rela5 circuit and

the CKs.

Causes damage to insulation of C, secondar5/inding and rela5.

Lagnitude of pea- voltage >"is given b5 an approximate

formula ?based on experimental results@

>" D 2 2>J?>%) >J@

Where >% D S/gr. %ault 'ating in amps x 6 of rela5

circuit C ratio

M setting

Letrosil reuired if >" G 3->




45/116


I8P

RST

VSV(

RR

Letrosil Characteristic

> D C *

Suitable values of C N

chosen based on 9

Lax secondar5 current under fault conditions

'ela5 setting voltage


%EF Protection Example


46/116


1(VA'>11$$$V,1'V

1+$$)1

RCTalue of stabilising

resistor reuired

3@ $ffective setting

4@ "ea- voltage

developed b5 CKs

for internal fault

%EF Protection Example

'olution (1)


47/116


$arth fault calculation 9)

&sing L>A base

Source impedance D 1 p.u.

ransformer impedance D . x D 4 p.u.

1

otal impedance D 14

p.u.

*1 D 1 D .E14 p.u. 14

(ase current D x 17

3 x 41

D 1112B7 Amps

*% D 3 x .E14 x 1112B7 D 234 Amps ?primar5@

D 14.B Amps ?secondar5@

1 ".&.1 4

I1

4

I2

4

I

Seuence #iagram

'olution (1)

'olution (2)


48/116


?1@ Setting voltage>S D I%?'CI 2'0@

Assuming earth C saturates,

'C D 4. ohms

2'0D 2 x 1 x E.41 x 1)3 D 1.42 ohms

Setting voltage D 14.B ?4. I 1.42@

D B3.7 >olts

?2@ Stabilising 'esistor ?'S@

'S D >S ) 1

IS IS2 Where *SD rela5 current setting

'S D B3.7 ) 1 D 37 ohms

.1 .12

'olution (2)

'olution (3)


49/116


1.7

1.2

.

.4

.4 .12.

AHmm?multipl5 b5 Ji to obtain total

exciting current in Amps@

WeberHm2?esla@

?multipl5b5Jv

toobtain'LS

secondar5volts@

Jv Ji

0ine N 1 .341=eutral C

$arth C 237 .2E

'olution (3)

'olution (4)


50/116


?3@ $ffective setting I" D C ratio x ?IS I ILA@

0ine N =eutral Cs

%lux densit5 at B3.7> D B3.7 D .B2 esla

1

%rom graph, mag. %orce at .B2 esla D .1 AHmm

Lag. Current D .1 x .341 D .1 Amps

O$arthK C

%lux densit5 at B3.7> D B3.7 D .3B7 esla

237

%rom graph, mag. %orce at .3B7 esla D .12 AHmm

Lag. Current D .12 x .2E D .33 Amps

hus, effective setting D 17 x ?.1 I P?4 x .1@ I .33Q@

$ffective setting D 1B Amps

ransformer full load current D 13B1 Amps

$ffective setting D 1B x 1F D 14.2F x rated

13B1

'olution (4)

'olution (5)


51/116


?4@ "ea- voltage D 22>J?>% ) >J@

>% D 14.B x >S D 14.B x B37 D 13B47 >olts

IS

%or O$arthK C, >J D 1.4 x 237 D 33 >olts ?from graph@

>"$AJ D 22 x 33 x ?13B47 ) 33@

D 7->hus, Letrosil voltage limiter /ill be reuired.

'olution (5)

Parallel Transformers


52/116


A=

1

(us Section

2

41 >olt

S/itchboard

C(




53/116


A=1

(us Section!pen

2

41 >olt

S/itchboar

d

C(

1=

1=

Parallel TransformersCT in Eart-

Parallel Transformers CT in


54/116


1

(us Section!pen

2

41 >olt

S/itchboar

d

1=

1=

A= C(

Parallel Transformers CT inEart- an& eutral


55/116

Tra&itional arge Transformer


56/116


Tra&itional arge TransformerProtection Pac#age

33J

>

1

2H

1L>A33H11J> 1= E

7H

74

7H

HA


57/116


!ifferential Protection



58/116


!verall differential protection ma5 be Rustified for

larger transformers ?generall5 G L>A@. "rovides fast operation on an5 /inding

Leasuring principle 9

(ased on the same circulating current principle as the

restricted earth fault protection

:o/ever, it emplo5s the biasing techniue, to maintain

stabilit5 for heav5 through fault current

(iasing allo/s mismatch bet/een C outputs.

*t is essential for transformers /ith tap changing

facilit5.

Another important reuirement of transformer

differential protection is immunit5 to magnetising in

rush current.

6iase& !ifferential 'c-eme


59/116


(*AS(*AS I2I1

!"$'A$

I1-

I2

#ifferential

Current

!"$'A$

'$S'A*=

Lean hroughCurrent

I1+

I2

2

I1-

I2



60/116


0>

'

:>

"'!$C$#

6!=$

Correct application of differential protection reuires C ratio

and /inding connections to match those of transformer.

C secondar5 circuit should be a replica of primar5 s5stem.

Consider 9

?1@ #ifference in current magnitude

?2@ "hase shift

?3@ 6ero seuence currents

!ifferential Connections


61/116


"1 "2 A2 A1 a1 a2 "2 "1

A ( C

+se of ,nterposing CT


62/116


''

'

"1 "2 A2 A1 a1 a2 "2 "1

S2 S1 "1 "2

*nterposing C provides 9>ector correction

'atio correction

6ero seuence compensation

S1 S2 S2 S1

p g



63/116


S2S1

"1"2A1A2 a2a1"2

1L>A

77-> H 11->1H H

"1

#51

S1S2

iven above9 =eed to consider )

?1@ Winding full load current ?2@ $ffect of tap changer ?if an5@

?3@ C.. polarities

Assuming no tap changer

%ull load currents9) 77->9 131 Amp D 4.3E Amps secondar5

11->9 EE Amp D 4.B2 Amps secondar5

:o/ever, reuire 11-> C..Ks to be connected in

hus, secondar5 current D 3 x 4.B2 D .2A

RATIO CORRECTION IS REQUIRED



64/116


''

'

"1 "2 A2 A1 a1 a2 "2 "1

S1 S2 "1 "2

4.B2A

S1 S2 S2 S1

4.3EA

?2.7@ ?@

1H H

*t is usual to connect 11-> C..Ks in and utilise a H interposing C.. ?this

method reduces lead >A burden on the line C..Ks@

Current from 77-> side D 4.3E Amphus, current reuired from /inding of int. C.. D 4.3E Amp

Current input to /inding of int. C.. D 4.B2 Amp

'euired int C.. ratio D 4.B2 H 4.3E D 4.B2 H 2.2

3

La5 also be expressed as 9 H 2.7

Effect of Tap C-anger


65/116


e.g. Assume 77-> IF, )1F

*nterposing C.. ratio should be based on mid tap position

Lid ap ?)F@ D 72.E ->

"rimar5 current ?1 L>A@ D 13 Amp

Secondar5 current D 4.7 Amp

*nterposing C.. ratio reuired D 4.B2 H 4.7

3

? H @

D 4.B2 H 2.77

La5 also be expressed as 9 H 2.E

Compared /ith H 2.7 based on nominal voltage

Connections C-ec#


66/116


/r$itrar" Current !istri$ution

'

'

'

S1 S2 S2 S1

"1 "2 A2 A1 a1 a2 "2 "1

S2 S1 "1 "2

Connections C-ec#


67/116


/&& !elta in&ing Current

'

'

'

"1 "2 A2 A1 a1 a2 "2 "1

S2 S1 "1 "2

S1 S2 S2 S1

Connections C-ec#


68/116


Complete Primar" !istri$ution

'

'

'

"1 "2 A2 A1 a1 a2 "2 "1

S2 S1 "1 "2

S1 S2 S2 S1

Connections C-ec#


69/116


Complete 'econ&ar" !istri$ution

'

'

'

"1 "2 A2 A1 a1 a2 "2 "1

S2 S1 "1 "2

S1 S2 S2 S1

,n07one Eart-ing Transformer


70/116


"2"1a2a1

A2A1 "1"2

S1S2

S1S2 12 "2"1

,n07one Eart-ing Transformer/lt ti (1)


71/116


/lternati*e (1)"2"1

a2a1A2A1 "1"2

S1S2

"2"1S1S2



72/116


3H1

/lternati*e (2)

BH1

! #*%%$'$=*A0

'$0A

$A':*=

'A=S%.



73/116


$A':*=

'A=S%.

3H1

! #*%%$'$=*A0

'$0A

1H.33

/lternati*e (3)

3H1

Com$ine& !ifferential an&% t i t & E t- F lt P t ti


74/116


o differential rela5

S2

S1

"1

"2'$%

S2

S1"1

"2

S2S1"1 "2

a2a1A1A2

%estricte& Eart- Fault Protection

Com$ine& !ifferential an&E t- F lt P t ti


75/116


&sing Summation Auxiliar5 Current ransformer

'estricted earth

fault rela5

(ias /indings

E E E#ifferential rela5

operating /indings

74

Eart- Fault Protection

*AE a

%1


76/116


A*AE ,

A*AE c

A

N7 77

EF%2

%3

%4

(,

2(,2

(,2

(o (o(o

F

VE(A)) 8FFE(EN%A)

(E)A9

%1

T-ree in&ing Transformer


77/116


2L>

A

11J>

73L>

A

132J>

17H3H

L>

A

33J>

1H

4.B

2.

1.33

2.

.1

All interp!in" C.T. r#ti$! re%ert &''n ()A *#!e 63()A,

Tra&itional +se of ,nterposing CT


78/116


#51?)3


79/116


8ifferentialele#ent

Nu#eric(ela$

Virtual inter"osin +%

Vectorialcorrection

(atio

correction


Compensation

*o;er transfor#er

Transformer agnetisingC-aracteristic


80/116


/ice=ormal

%lux

=ormal

%lux

=ormal=o 0oadCurrent

=o 0oad Currentat /ice =ormal

%lux

C-aracteristic

agnetising ,nrus- Current'tea&" 'tate


81/116


'

'

+

-

)

'I

'tea&" 'tate

agnetising ,nrus- Current'itc- on at Voltage 7ero o resi&ual flux


82/116


'

'2

)

I

'itc- on at Voltage 7ero 0 o resi&ual flux

Transformer !ifferential ProtectionEffect of agnetising Current


83/116


Effect of agnetising Current

Appears on one side of transformer onl5

Seen as fault b5 differential rela5

=ormal stead5 state magnetising current is less thanrela5 setting

ransient magnetising inrush could cause rela5 to

operate

Transformer !ifferential ProtectionEffect of agnetising ,nrus-


84/116


Effect of agnetising ,nrus-

S!0&*!= 1 9 *L$ #$0A

Allo/s magnetising current to die a/a5 before rela5 canoperate

Slo/ operation for genuine transformer faults



85/116



S!0&*!= 2 9 2=# ?and :@ :A'L!=*C '$S'A*=

La-es rela5 immune to magnetising inrush

Slo/er operation ma5 result for genuine transformer faults

if C saturation occurs

&sed in LiC!L "73x



86/116



S!0&*!= 3 9 A" L$AS&'$L$= $C:=*8&$

*nhibits rela5 operation during magnetising inrush

!perate speed for genuine transformer faults unaffected b5

significant C saturation

&sed in L(C: N J(C: rela5s

T"pical agnetising ,nrus-a*eforms


87/116


A

C

a*eforms

!etection of T"picalagnetising ,nrus- (58.9)


88/116


#ifferential

comparator

1 D ms 2 D 22ms

rip

(ias

#ifferential

hreshold

agnetising ,nrus- (58.9)

%estraint for Transformeragnetising ,nrus-


89/116


agnetising ,nrus-

#ifferential

comparator

(ias

#ifferential

hreshold

rip

1 D ms 2 D 22ms

#ifferential input

Comparator output

rip

'eset2

1

peration for Transformer Faults


90/116


#ifferential

comparator

(ias

#ifferential

hreshold

rip

1 D ms 2 D 22ms

#ifferential input

Comparator output

rip

'eset2

1

Protection of /uto0Transformer $".ig- ,mpe&ance !ifferential %ela"s


91/116


?a@ $arth %ault Scheme

A

(

C

:igh impedance

rela5E

.ig- ,mpe&ance !ifferential %ela"s

Protection of /uto0Transformer $".ig- ,mpe&ance !ifferential %ela"s


92/116


A

(

C

a

b

c

E E E

n

.ig- ,mpe&ance !ifferential %ela"s

?b@ "hase and $arth %ault Scheme


93/116


,nter0Turn Fault Protection

,nter0Turn Fault


94/116


=ominal turns ratio

%ault turns ratio

Current ratio

) 11, H 24

) 11, H 1

) 1 H 11,

'euires (uchhol+rela5

C

$

Shorted

turn

0oad

,nterturn Fault Current um$erof Turns '-ort Circuite&


95/116


1

7

4

2

1 1 2 2

1

7

4

2

%ault current in short

circuited turns

"rimar5 input current

%ault current

?multiples ofrated current@

"rimar5 current

?multiples ofrated current@

urn short)circuited ?percentage of /inding@

of Turns '-ort Circuite&

6uc--ol9 %ela" ,nstallation


96/116


x internal pipe

diameter ?minimum@

3 x internal pipe

diameter ?minimum@

ransformer

3 minimum

!il conservator

Conservator

6uc--ol9 %ela"


97/116


"etcoc-

Counter balance/eight

!il level

%rom transformer

Aperture adRuster

#eflector plate#rain plug

rip buc-et

o oilconservator

Lercur5 s/itch

Alarm buc-et


98/116


*erfluxing Protection

*erfluxing


99/116


enerator transformers

rid transformers

&suall5 onl5 a problem during run)up or shut do/n, but can be

caused b5 loss of load H load shedding etc.

%lux >

f

$ffects of overfluxing 9 *ncrease in magnetising current

*ncrease in /inding temperature

*ncrease in noise and vibration

!verheating of laminations and metal parts ?caused b5 stra5 flux@

"rotective rela5 responds to >Hf ratio Stage 1 ) lo/er A.>.'.

Stage 2 ) rip field

*erfluxing 6asic T-eor"


100/116


m2

*e

m

> D -f

CA&S$S0o/ freuenc5

:igh voltage

eomagnetic disturbances

$%%$CS

ripping of differential element ?ransient overfluxing@

#amage to transformers ?"rolonged overfluxing@

V.9 *erfluxing Protection


101/116


> f

J

rip and alarm outputs for clearing prolonged overfluxing

Alarm 9 #efinite time characteristic to initiate corrective action

rip 9 *#L or # characteristic to clear overfluxing condition

Settings

"ic-)up 1. to 3. i.e. 11> x 1. D 2.31

:+

# setting range .1 to 7 seconds

V.9 C-aracteristics


102/116


1

1

1

11 1.1 1.2 1.3 1.4 1. 1.7

L D

!perating

time ?s@

> :+

Setting

J D 73J D 4

J D 2

J D

J D 1

t D . I .1 x J

?L ) 1@2

$nables co)ordination /ith plant /ithstand characteristics

*erfluxing %ela"


103/116


'0

A>'

$x

>

/pplication of *erfluxing %ela"


104/116


#C

Circuit brea-erposition repeat rela5

>AA rela5

0o/er A>'

*nhibit A>'raise

Alarm

enerator field circuitbrea-er trip coil

'02)2Alarm

'02)1

'01)1

#C


105/116


T-ermal *erloa& Protection

Effect of *erloa& on Transformer,nsulation ife


106/116


B 1 11 12 13 14

:ot spot temp C

.1

1.

1

1

'elative

rateof using

life

With ambient of 2 C.

:ot spot rise of E C is

design normal.

A further rise of 7 C

doubles rate of

using life.

B

*er-eating Protection


107/116


* load

#setting

* loadop oil ofpo/ertransformer

:eater

hermalreplica

emperaturesensing resistor

'emote

emp. indication0ocal

!ff

!n

!ff

!n

Alarm

rip

"umpcontrol

%ancontrol

*erloa& Protection


108/116


Current

ime

!vercurrent protection designed for fault condition

hermal replica provides better protection for overload

Current based

%lexible characteristics

Single or dual time constant

'eset facilit5

=on)volatile

T-ermal *erloa&il Fille& Transformers


109/116


1

1

1

1

1 2 3 4 7

rip time ?s@

Current ?multiple of thermal setting@

Single

characteristic9

D 12 mins

#ual

characteristic

Single

characteristic9

D mins

T-ermal Trip Time


110/116


/here D heating time constantD actual current measured b5 rela5

D continuous current rating of protected plant

D previous thermal state

D trip threshold

D multiplier ?for actual temperature@K

I

%(*

(EF

KI

I

PI

I

ln%i#e%ri"

%(*

2

(EF

2

REF

=

I

*


111/116


Transformer Fee&ers

Protection of ParallelTransformer Fee&ers

i &


112/116


i&er :>CsCsCsCs

'*"

ransformer

#ifferential

"rotection

%eeder

#ifferential

"rotection

"*0!S%eeder

#ifferential

"rotection

'*"&=SA(*0*S$

'*"

Transformer Fee&ers


114/116


%$$#$

'

"*0!

S"W"

W

%or use /here no brea-er separates the transformer from thefeeder.

ransformer inrush current must be considered.

*nrush is a transient condition /hich ma5 occur at the instant of

transformer energisation.

Lag. *nrush current is not a fault condition

"rotection must remain stable.

LC: provides a bloc-ing signal in the presence of inrush

current and allo/s protection to be used on transformer feeders.

Transformer Fee&er Protection


115/116


8$11

*2*1

II

III

I

1 2

L>W

2MFA+

14

*)% M+M+

M+%M+%23

24

+

A

ii

iii

i*1*2

2 1

+

A

25

2>

26

2?

23

24

25

2>

26

2?

2>

2?

1?

1@

1>

1>

1@

1?

1@

1314

1>

1@

23

24

25

2>

26

2?

23

2425

2>

26

2?

1?

1>

1

P541 P542 0 Protectionof Transformer Fee&ers


116/116

*o;er transfor#er

*540

c&e#e


Vectorialcorrection

(atiocorrection


113894818-transformer-protection.ppt

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