relay setting chart _ crp panel_shambhu_revb

8/13/2019 Relay Setting Chart _ CRP Panel_Shambhu_REVB

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1

Differential

Protection

(Restrained)

ABB - RET

67087T>

Stage 1 (T2D1 )

2

Differential

Protection

(Unrestrained),Stage 2

ABB - RET

670 87T>>

3

Earth faultABB - RET

67064R LV

ow

RECOMMEND

SI. No. Type ofProtection

Relay Make/ No.

PROTECTION ANSICODE


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64R HV

es r c e

Earth faultABB - RET

67064R LV

g

Im edence

64R HV

4

Stand -by

Earth fault

Protection

HV Side

ABB - RET

67051s-EFR HV

( 4th-Stage- OFF)

RET-670 , TIME CO-ORDINATED SETTINGS OF Stan-by-

EFR ( HV & LV )


4/21

Stand -by Earth fault

Protection (LV Side)

ABB - RET

67051s-EFR LV

I_base

I1>

t1>

I2>

t2>

I3>

t3>

I4>

t4>

Stand -by Earth fault

Protection (HV Side)

ABB - RET

67051s-EFR HV

I_base

I1>

t1>

I2>

t2>

I3>

t3>

I4>

t4>

STAGE-3

STAGE-4

STAGE-1

STAGE-3

STAGE-4

STAGE-1

STAGE-2

STAGE-2


5/21

Parameter Description

150/1A (132KV side) Operation on

2000/1A (11 kV Side) IdMinSetting of minimum

differential operating current

%Z = 12.5% ( TAKE

FROM Name plate of

trafo. )End section 1 Cross-Over point b/w slope1

& Slope-2

Vector group = YNyn0 Slope section 2Setting of slope 2

stabilisation, (Slope 1 has

fixed stabilization)

End section 2Cross-Over point b/w slope2

& Slope-3

Slope section 3Setting of slope 3

stabilisation,

150/1A (132KV side)

2000/1A (11 kV Side) Idunre

Differential current, High set

(Unrestrained)

Cross blocking logic OpCrossBlock = on

Id2f / Id1f> (%) 2nd Harmonic restraint

Id5f/ Id1f> (%) 5th Harmonic restraint

Set the operation of

Negative sequence

differential protection

OpNegSeqDiff = = on

IMinNegSeq =

Setting of minimum negative

sequence differential currentlevel

NegSeqROA Relay operate angle

2000/1A (11 kV Side) Idmin (%)

ROA Relay operate angle

D RELAY SETTING CHART FOR 132/11.5kV, 20/25 MV

CT Ratio / PT Ratio/OTHER

Relay

Available setting range


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150/1A (132KV side) Idmin (%)

ROA Relay operate angle

2000/1A (11 kV Side) U alarm Operate voltage

t Alarm Operate time

U trip Operate voltage

t trip Operate time

Rs Series Resistor

150/1A (132KV side) U alarm Operate voltage

t Alarm Operate time

U trip Operate voltage

t trip Operate time

Rs Series Resistor

150/1A (132KV side) IN1>/ Ib Base Current Setting

Dir mode

Ibase

1st-stage t11> DT setting

NA k11> TMS

IN2>/ Ib Base Current Setting

Dir mode

2nd-stage t1 2> DT setting

NA k1 2> TMS

IN3>/ Ib Base Current Setting

Dir mode

3rd-stage t1 3> DT setting

NA k1 3> TMS

NEW SETTINGS OLD SETTINGS. Remarks


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100% 80%

80% of Ibase 80% of Ibase

0.96 sec 0.0 sec


1.2 sec 0.40 sec


1.4sec 0.80 sec


1.6sec 1.20 sec

100% 80%


1.26 sec 0.3 sec


1.46 sec 0.15 sec

off off

OFF OFF

off off

OFF OFF

t= 0.96 sec. is the Normal-

EFR ( in incomer of 11KV-

rex-521 ) Relay's time

setting. So, the same has

been maintained as trip-

time to SB-EFR-LV.

Assuming a time

descripation of 0.3 sec.

b/w 11KV & 132KV -trip

time , t1= 0.96 + 0.3sec. =

1.26 SEC.

600/1A (132KV side)

150/1A (132KV side)


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4.0 -100.0 30% Inst

60 - 90 Degrees 60

( 2 -500 ) V N / A

0 - 60 sec N / A 5.0 sec.

( 5 -900 ) V 109.5 V

----- ---- Inst

10 -20000 Ohms. 396 ohms.

( 2 -500 ) V N / A

0 - 60 sec N / A 5.0 sec.

( 5 -900 ) V 63 V

----- ---- Inst

10 -20000 Ohms. 250 ohms.

1.0 -2500.0 %

Ibase20% * Ibase

----- Non directional

0 - 60 Secs ---- 1.0 sec.

0.05 - 999 0.15 Secs NI 0.15 Secs

1.0 -2500.0 %

Ibase 15% * Ibase


0 - 60 Secs ---- 1.5 sec.

0.05 - 999 0.15 Secs NI 0.15 Secs

1.0 -2500.0 %

Ibase10% * Ibase


0 - 60 Secs ---- 2.0 sec.

0.05 - 999 0.15 Secs NI 0.15 Secs

a op e g - mpe ence

based REFR-Protection.

see ANNEXURE-01

see ANNEXURE-01

see ANNEXURE-01 ---


10/21

PACP Recomended Relay Settings

Parameter Description Available range PSMTMS/DMT

(sec)

1Differential Protection

(Restrained)

ABB - RET

67087T> 150/1A (132KV side) Operation on ---- ---- ----

Stage 1 (T2D1 ) 2000/1A (11 kV Side) IdMinSetting of minimum

differential operating

current

0.10-0.60 0.25 * Ibase. Inst

%Z = 12.5% ( TAKE

FROM Name plate of

trafo. )

End section 1Cross-Over point b/w

slope1 & Slope-20.2 - 1.5 1.25 * Ibase.

Vector group = YNyn0 Slope section 2Setting of slope 2

stabilisation, (Slope 1

has fixed stabilization)

10.0 -50.0 % 40 * Ibias

End section 2 Cross-Over point b/wslope2 & Slope-3

1.0 -10 3 * Ibase.

Slope section 3Setting of slope 3

stabilisation,30.0 -100.0 % 80 * Ibias

2Differential Protection

(Unrestrained) ,Stage 2

ABB - RET

67087T>>

150/1A (132KV side)

2000/1A (11 kV Side)Idunre

Differential current,

High set (Unrestrained)

100- 5000 % of

Ibase10 * Ibase. Inst

Cross blocking logic OpCrossBlock = on ----- -----

Id2f / Id1f> (%) 2nd Harmonic restraint 5-100 % of fn 15%

Id5f/ Id1f> (%) 5th Harmonic restraint 5-100 % of fn 25%

Set the operation of

Negative sequence

differential protection

OpNegSeqDiff = = on ----- -----

IMinNegSeq =

Setting of minimum

negative sequence

differential current level

(0.01 - 0.10 )* Iopr. 0.04 * Iopr.

NegSeqROA Relay operate angle 60 - 90 Degrees 60

3Restricted Earth fault

Protection

ABB - RET

67064R LV 2000/1A (11 kV Side) Idmin (%) 4.0 -100.0 30% Inst

( Low impedance bsed.) ROA Relay operate angle 60 - 90 Degrees 60

64R HV 150/1A (132KV side) Idmin (%) 4.0 -100.0 30% Inst

ROA Relay operate angle 60 - 90 Degrees 60

Restricted Earth fault

Protection

ABB - RET

67064R LV 2000/1A (11 kV Side) U alarm Operate voltage ( 2 -500 ) V N / A

(High Impedence based.) t Alarm Operate time 0 - 60 sec N / A 5.0 sec.U trip Operate voltage ( 5 -900 ) V 109.5 V

t trip Operate time ----- ---- Inst

Rs Series Resistor 10 -20000 Ohms. 396 ohms.

64R HV 150/1A (132KV side) U alarm Operate voltage ( 2 -500 ) V N / A

t Alarm Operate time 0 - 60 sec N / A 5.0 sec.

U trip Operate voltage ( 5 -900 ) V 63 V

t trip Operate time ----- ---- Inst

Rs Series Resistor 10 -20000 Ohms. 250 ohms.

see ANNEXURE-01

CT Ratio / PT Ratio/

OTHER

Relay Setting

This settings may not

be applicable - while

we have adopted High -

Impedence based

REFR-Protection.

see ANNEXURE-01


see ANNEXURE-01

RECOMMENDED RELAY SETTING CHART FOR 132/11.5kV, 20/25 MVA TRANSFORMER

Recommended setting RemarksSI.

No.

Type of ProtectionRelay Make /

No.

PROTECTION

ANSI CODE

Page 10 of 21


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12/21



(sec)


OTHER

Relay Setting




No.


No.

PROTECTION

ANSI CODE

5Stand -by Earth fault

Protection (LV Side)

ABB - RET

67051s-EFR LV 600/1A ( in NGR ) IN1>/ Ib Base Current Setting 1.0 -2500.0 % Ibase 15% * Ibase

( 4th-Stage-

OFF)Dir mode ----- Non directional

1st-stage t11> DT setting 0 - 60 Secs ---- 2.0 sec.

NA k11> TMS 0.05 - 999 0.15 Secs NI 0.15 Secs

IN2>/ Ib Base Current Setting 1.0 -2500.0 % Ibase 25% * Ibase

Dir mode ----- Non directional

2nd-stage t1 2> DT setting 0 - 60 Secs ---- 1.5 sec.

NA k1 2> TMS 0.05 - 999 0.15 Secs NI 0.15 Secs

IN3>/ Ib Base Current Setting 1.0 -2500.0 % Ibase 30% * Ibase

Dir mode ----- Non directional

3rd-stage t1 3> DT setting 0 - 60 Secs ---- 1.0 sec.

NA k1 3> TMS 0.05 - 999 0.15 Secs NI 0.15 Secs

6Under Frequency .

Protection.

ABB - RET

67081.U 132KV / 110 Volts. Operation mode on /Off on.

Ubase (KV) Base voltage setting 0.05 - 2000 volts. 132 KV

f < Start Freq.Freq setting / start

value.35 -75 Hz. 48.8 Hz.

Int_Bloc_Level Internal_Blocking_Level in % Of Ubase

0 -100 % Of UB 50%

Time delay operate 0 -60 sec. 0.2 sec.

Time delay Reset 0 -60 sec. 0.0 sec.

Time delay Restore 0 -60 sec. 0.0 sec.

Restore freq. 45 - 65 Hz. 50.10 Hz.

Timer Operation DT/ Voltage based DT ----

Unom 50 -150 % Ub 100 N / A

Umin 50 -150 % Ub 90 N / A

Exponent . 0.0 - 5.0 1 N / A

Tmax. 0.01 -60 sec. 1 N / A

Tmin 0.01 -60 sec. 1 N / A

6 Over Frequency . Protection.ABB - RET

67081.O 132KV / 110 Volts. Operation mode on /Off off


f > Start Freq.Freq setting / start

value.35 -75 Hz. 51.20 Hz.

Int_Bloc_LevelInternal_Blocking

_Level in % Of Ubase0 -100 % Of UB 50%

Time delay operate 0 -60 sec. 0.0 sec.


see ANNEXURE-01

see ANNEXURE-01

see ANNEXURE-01

Page 12 of 21


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(sec)


OTHER

Relay Setting




No.Type of Protection

Relay Make /

No.

PROTECTION

ANSI CODE

6Rate of change of

Frequency . Protection.

ABB - RET

670Df /dt 132KV / 110 Volts. Operation mode on /Off off


f > Start Freq. Gradient. Freq .Gradient. -10 - 10 Hz/sec.. 0.5 Hz /sec.

Int_Bloc_LevelInternal_Blocking

_Level in % Of Ubase0 -100 % Of UB 50%

Operate Time ( tTrip ) 0 -60 sec. 0.2 sec.


Time delay Restore 0 -60 sec. 0.0 sec.

Restore freq. 45 - 65 Hz. 49.90 Hz.

6Over Fluxing (Over

excitation)

ABB - RET

67099 (24) 220KV / 110 Volts. V/Hz> Voltage / Freq. 100 - 180% x U/f 110% x U/f

t alarm oprtng. Time 0-9000 sec. ---- 5sec.

T-alarm_level Alarm operate level 50 -120% 100%

V/Hz>> Voltage / Freq. 100 - 200% x U/f 140% x U/f

tmax.max. trip delay for I -

curves0 - 9000 sec. 1500 1800

tminmin. trip delay for I -

curves0 - 60 secs 4 sec 7

tr-pulse length of Pulse for trip 0 - 60 secs 0.1 0.1

X-leakageLeaakage reactance of

trafo. Winding.0.00-200 ohms. 0

t-coolingcooling time constant

for Trao.0.1 -9000 sec 1200 1200 sec.

CurveType curve selection.INVERSE/ IEEE /

TAILOR MADE.IEEE

see ANNEXURE-01

see ANNEXURE-01

Page 13 of 21


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(sec)


OTHER

Relay Setting




No.


No.

PROTECTION

ANSI CODE

7 Local Breaker Back-upABB - RET

67050 LBB

150 / 1A

(132KV side)Operating mode backup trip mode

1 out of 4/ 2 out of 4

/ 1 out of 31 out of 3

Retrip-mode re-trip -Off

IP >Operate Ph. Current in

% of Ibase5-200% 10%

IN >Operate Residual.

Current in % of Ibase2-200% 10%

t1 > time delay of re-trip 0-60sec. 0 sec. 0 sec.

8Residual -Over voltage

Voltage Protection Protn.

ABB - RET

67059N 132KV/3 / 110V/3 Operation Mode ---- 0n , STAGE-1

UB = Open-delta Voltage CurveType DT/C-A/C-B/C-C DT

U1 > START VOLTAGE 1- 200 % UB 30 % UB

t1 > Definite Time Delay 0 - 6000 sec. 5 sec. 5 sec.

t1 min >Operating Time for I -

curves0 - 60 sec. 5 sec. NA

k1 > TMS 0.05 - 1.10 0.05 NA

HystAbs1Absolute Hysteresis

in% of Ubase.0 -100 % UB 0.5 % UB

Operation Mode ---- 0n , STAGE-2

CurveType DT/C-A/C-B/C-C DT

U2 > START VOLTAGE 1- 100 % UB 45 % UB

t2 > Definite Time Delay 0 - 6000 sec. 5 sec. 5 sec.

t2 min >Operating Time for I -

curves0 - 60 sec. 5 sec. NA

k2 > TMS 0.05 - 1.10 0.05 NA

HystAbs2Absolute Hysteresis

in% of Ubase.0 -100 % UB 0.5 % UB

9

Back-up Overcurrent/ Earth

fualt protection ( Non-dir /

Dir )

REX 52151 / 50 / 51N / 67

/ 67N150/1A (132KV side) Operation Mode

Not in use / DT/ NI/VI /

c-2 ETC. ( 1 to 15 )DT =01 31>

H-02 NOC3Low (51) 31> Current setting (I/ In) 0.10 - 5.00 xIn. 0.7

Operate time ( in DT) 0.05 - 300 Secs 0.05

time Multiplier ' K '( in

IDMT -mode )0.05 - 1.00 0.05 IDMT

IEEE- time DAIL in

IDMT -mode 0.5 - 15 0.5

NOC3High ( 50 / 51 ) Operation Mode Not in use / DT / inst.. Inst. = 02 31>>

31>> Current setting (I/ In) 0.10 - 40 xIn. 2

Operate time ( in DT -

Mode)0.05 - 300 Secs 0.05

DT- 0.05

SECS.

see ANNEXURE-01

see ANNEXURE-02

Page 14 of 21


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(sec)


OTHER

Relay Setting




No.


No.

PROTECTION

ANSI CODE

REX 521 DEF2Low ( 67N / 51N ) Operation ModeNot in use / DT/ NI/VI /

c-2 ETC.DT =01 Io >->

Operation Criteria 67N,51N etc.., (1 to 05)4 = Non-directional

Io>-----

Operation direction forward / Reverse forward=0 N/A

Operation

Charecteristics.

IoSin(phi) / IoCos(phi)

( 0,1)0 N/A

Basic Angle -90 deg to 60 deg. -90 deg N/A

Io > Current setting (Io/ In) 0.01 - 5.00 xIn. 0.075

Uo> Start voltage 2.0 - 100 % of Un. 75% N/A


REX 521 DEF2High ( 67N ) Operation ModeNot in use / DT/ NI/VI /

c-2 ETC.DT =01 Io >>->

Operation Criteria 67N, etc.., (1 to 05)0 = Basic angle &

Uo-----

Operation direction forward / Reverse forward=0 ---

Operation

Charecteristics.


( 0,1)

0=Io*sin(phi) ----

Basic Angle -90 deg to 60 deg. -90 deg -----

Io > Current setting (Io/ In) 0.01 - 5.00 xIn. 0.075

Uo> Start voltage 2.0 - 100 % of Un. 5%


intermittent EFR Active / Not-active (0,1) 0 ---

REX 521 DOC6Low ( 67 ) Operation ModeNot in use / DT/ NI/VI /

c-2 ETC.DT =01 3I >_> 3I >>_>


Operation

Charecteristics.


( 0,1)0=Io*sin(phi) ---

Basic Angle 0 deg to 90 deg. 60 deg ---

Io > Current setting (Io/ In) 0.05 - 40 xIn. 0.75

time Multiplier ' K '( in

IDMT -mode )0.05 - 1.00 0.05 IDMT


see ANNEXURE-02

Page 15 of 21


16/21



(sec)


OTHER

Relay Setting




No.Type of Protection

Relay Make /

No.

PROTECTION

ANSI CODE

intermittent EFR -

protectionDisabled / Enabled(0,1) 0 ---

REX 521 DOC6High ( 67 ) Operation Mode Not in use / DT/ Inst. Inst. = 02 3I >>_> 3I >>_>


Operation

Charecteristics.


( 0,1)0=Io*sin(phi) ---

Basic Angle 0 deg to 90 deg. 60 deg ---

Io > Current setting (Io/ In) 0.05 - 40 xIn. 0.05

Non directional

Operation

when the dir. Cannot be

determined ( 0, 1 )0 ----


intermittent EFR -

protectionDisabled / Enabled(0,1) 0 ---

10 Under-Voltage Relay. RXEG 21 27 132000V/3 / 110V/3 Operation ModeDT -ALARM / trip

stageU< -

U< Alarm Under voltage setting. 40 -120 V 85 volts.

t > alarm time setting.(DT) 0 - 99 hrs. 3.0 sec.

U< Trip Under voltage setting. 40 -120 V 77 volts.

t > Trip time setting.(DT) 0 - 99 hrs. 1.0 sec.

11 Over-Voltage Relay. RXEG 21 59 132000V/3 / 110V/3 Operation Mode DT -ALARM / TRIPstage

U> -

U> Alarm Under voltage setting. 60 -160 V 115 volts.

t > alarm time setting.(DT) 0 - 99 hrs. 3.0 sec.

U> Trip Under voltage setting. 40 -120 V 121 volts.

t > Trip time setting.(DT) 0 - 99 hrs. 1.0 sec.

see ANNEXURE-01

Page 16 of 21


17/21

APPM-MDP

1)

a) Initial setting:( Idmin) ; ---This setting covers the un-balance created in the differential operating current by the

+10% to -15% , and hence the mean tap value : [ 10 +(-15) ] / 2 = - 2.5% and so, the Hv -amps @ mean tap value

2.56% variation in the HV-currents when mean value is considered. Also,in practice typically the initial minimum dif

30% - 40% . However, RET-670 is in-built with OLTC compensation factor and it is possible to set the Id(min) to m

preferred to se the Idmin = 0.25 of Ibase.

b) Endsection-1 setting: ; ---This is the most sensitive part of the charecteristic.Uncompensated OLTC currents a

so, the slope in this section is always zero.The end lit of this section is set at 1.25 after ensuring the risk of higher fa

set in the RET-670.

c) Slopesection-2 , End section-2 ,Slopesection-3 ; --- These settings are typically adopted to form the Differntia

for various applications as per the Technical -reference manual-rev-b (p-116) .Also, the basis for these settings are a

d) Unrestrain -high set ,Idunre ; ---This setting by defualt set at 10.This setting ensures the operation instantaneo

only due to internal fualts. Also, this by-passes the harmonic test in its operation and so, called unstabilised operatio

2)

It is a common known fact that ( compared to Low impedence based REFR protection) , High impedence based

high impedence based protections are current / voltage based , and hence makes use of METROSIL & STABILIZI

The settings for Metrosil and Stablising resistor are as under : CTR -HV = 150 / 1A . R nct = ( as per the field tes

RET-670 & REX-521 RELAY - DETAILED DESCRIPT

87T -TRAFO. DIFFERENTIAL PROTECTION: The charecteristic for this protection function as adopted i

64R-HV & 64R-LV -TRAFO.HIGH IMPEDENCE BASED RESTRICTED EARTH FUALT PROTECTION :

Page 17 of 21


18/21


19/21

APPM-MDP

Calculat ions for REFR -HV :

Rnct = 2.0 ohms , Rlead = 2.0 ohms. & Rct(ph) = 4.0 ohms. ( for calculations Rct(ph) sha

Nct -Ratio = 150 /1A

Uk -Nct = 150 Volts. ( as phase CT's are designed for Uk> 400volts,Hence the chances g

Excitation current for NCT < 30 mA @ Vk /2 ( considering the worst case ).

IfL -HV = 109.35A , CTR= 150

If = ( %Z ) x IfL = 12.5 x 109.35 = 1367 A ( Max. expected through fault current expected.

Uk = (required) = 2 x Us. = 2 x If / CTR [ Rct + Rlead ] = 2 x (1367 / 150) [4 +2 ] = 109.36

As Uk is >>> than 150 V as per the Trafo. Name plate data for NCT.The operation of pro

Us =Uk /2 = 54.68 volts.=55 V (approx.)

Now, since the RET-670 adopts High-Impedence scheme with voltage as operand.

Hence, the Stabilizing Resistor , Rs= 250 ohms. & Us>= 63volts.

The setting to adopted is = 115% of Us> = 1.15 x 55 = 63 (Approx.) volts.

Ip(prim) = (Sentivity current measured) = CTR { Ir + I_nlr + n x Ie }Ir = Current through the Relay @ voltage Us> = 63/250 = 252 mA .

Inlr = Current through the Non- Linear Resistor = (from the graph.) = 5 mA.

nxIe = no. of CT's and their average Excitation currents. = (0.0504+3x0.0252) = 126mA.

Ip(prim) = (Sentivity current measured) = CTR { Ir + I_nlr + n x Ie }= 150{ 252+5+126 } = 5

This is well below the value minimum fualt current, and only constitute 38.3 % of Rated C

Also,

As, per the above description , The Ir >= m x 0.5 x Io = 4 x 0.5 x ( 0.030 x 2 ) = 0.12 A

so, the setting is safe.

Hence, the Stabilizing Resistor , Rs= 250 ohms. & Us>= 63volts.

Calculat ions fo r REFR -LV :

Rnct = 4.0 ohms , Rct (ph) = 10.0 ohms. & Rlead = 2.0 ohms.( for calculations Rct(ph) sh

IfL -LV = 1255.15A , CTR= 2000/1A


Uk -Nct = >300 Volts. ( as phase CT's are also,designed for Uk> 300volts,Hence the chanExcitation current for NCT < 30 mA @ Vk / 4.

If = ( %Z ) x IfL = 12.5 x 1255.15 = 15690 A ( Max. expected through fault current expecte

Uk = (required) = 2 x Us. = 2 x If / CTR [ Rct + Rlead ] = 2 x (15690 / 2000) [ 10 +2 ] = 18

As Uk is >>> than 300 V as per the NGR. Name plate data for NCT.The operation of pro

Us =Uk /2 = 94.14 volts.=95 V (approx.)

Hence, the Stabilizing Resistor , Rs= Us/Ir. = 95 / 0.24 =395.83 = 396 Ohms (approx.)


The setting to adopted is = 115% of Us> = 1.15 x 95 = 109.5 (Approx.) volts.

Calculation of Stabilizing Resistor :As per manuals of RET ,

This can be directly selected to a value Rs=396 ohms .

Now , this value of resistor should satisfy the below eqn.

Ip(prim) = (Sentivity current measured) = CTR { Ir + I_nlr + n x Ie }

Ir = Current through the Relay @ voltage Us> = 109.5/396 = 276.5 mA .



Ip(prim) = (Sentivity current measured) = CTR { Ir + I_nlr + n x Ie }= 2000{ 276.5+5+218 }

This is well below the value minimum fualt current, and only constitute 49.95 % of Rated

Also,



Hence, the Stabilizing Resistor , Rs= 396 ohms. & Us>= 109.5 volts.

Page 19 of 21


20/21

APPM-MDP

3) 51Ns -HV & LV :

The stand by earth-fualt protection , is mainly to Protect the NGR from over heating due to

.So, the settings adopted have to be set in Definite time mode depending upon it's therma

is 600A for 30 secs. And hence , the settings should be planned such that the HV - S/b E

compeletely isolating the Transformer from the circuit. However , as discussed in the prio

in the System , then it's setting should be minimised to the value of Lower -rating NGR or

for your reference. Hence, the setting should be adopted for

HV S/B EFR :

CTR= 150 /1A ,

Io > setting= approx.( 15 % - considering the Lowest rating NGR ,rating = 100A ,Else 8

Time setting: definite time , and should be with in the Rated duty of NGR i.e 3.0 secs.

LV S/B EFR :

CTR= 600 /1A ,

Io > setting= approx.( 15 % - considering the Lowest rating NGR ,rating = 100A .)

4) 99 (24) : Over fluxing Protection.

Actual set limits for this protection should be in accordance with the data submitted by the

of as in the relay , suits for most of the applications. These default settings programmed a

applications. As pe the TRAFo. " Permissible Over-excitation Curve " ( attached with mail

Some Important Factors / Notes for Over fluxing Protection:

1) Over excitaion occurs from the excessive applied voltage, possibly in combination with b

Transformers are directly connected to the Generators.

2) Bmax is directly proportional to the Induced voltage., as E = 4.44 x f x n x Bmax . A

3) The calculation of the relative ( M ) ,is based on the V/Hz ratio..

4) As per IEC 60076-1 , All transformers shall be capable of operating continuously at 10%

the User does not know what exactly to be set , then th e standard IEC-60076 -1 section-

5) As long as the E/f or V/F did not cross the relative value (M) set of the relay, the Trafo.

Over excitaion = M - V/Hz >6) Operatin Time of the Overexcitation Protection :

The most famous Law ,so called IEEE Law approximates a square Law

over excitation capability charecteristics. They can match a well a transformer core capabil

t op = 0.18 x k [ M - V/Hz>)2 .= 0.18 x k / ( Overexcitaton ) .

Where: M -- is the , Mean value in the interval from t=0 to t=top .

V/Hz > ---- is the Max. continously allowed voltage at no -Load and rated Freque

K ----- is the time multiplier setting for the inverse time functions as usual & sele

Since , from - " Trfo. Data curves " over Excitation of beyond 110% is not allowed so, fo

Also, the Alarm setting in the relay is in-built and is 2% less than the set value , with a defin

chart. We have attached a " over -Excitation Protection basis for your reference along wit

Page 20 of 21


21/21

APPM-MDP

5) 81.O & 81.U - or df/dt Protection. : ( RET-670 )

The basis for this settings when derived from the over excitation limits ( V/Hz - ratio lim

found to be extremely high or extremely low , such as ( f > becomes 55 Hz. & f < becomes

Regulatory Rules bound to that region. We request M/s Customer to do this setting at site

6) 27 & 59 - Protection. : ( REXEG-21 )

These settings are based on the common practice adopted at most of the installations. Als

India. The values adopted are --- 110% of the 110V = 121 volts. ( PT -secondary Rated-

---- 70% of the 110V = 77 Volts ( PT -secondary Rated-val

7) 50/51, 50N/51N, 67 & 67N - Protection. : ( Rex-521)

These settings are based on the relay co-ordination study , and direction is also based on

relay cordination timings , then the Directional - OCR shall be graded fastly to look towards

time delay. Also, the current settings for these Relays are the full-load current of the Equip

TMS , needs a DETAILED STUDY.

Calculat ions for REFR -LV :

Rnct = 4.0 ohms , Rct (ph) = 10.0 ohms. & Rlead = 2.0 ohms.( for calculations Rct(ph) sh

IfL -LV = 15690 A , CTR= 2000/1 A


Uk -Nct = >300 Volts. ( as phase CT's are also,designed for Uk> 300volts,Hence the chan

Excitation current for NCT < 30 mA @ Vk / 4.

If = ( %Z ) x IfL = 12.5 x 1255.15 = 15690 A ( Max. expected through fault current expecte

Uk = (required) = 2 x Us. = 2 x If / CTR [ Rct + Rlead ] = 2 x (15690 / 2000) [ 10 +2 ] = 18

As Uk is >>> than 300 V as per the NGR. Name plate data for NCT.The operation of pro

Us =Uk /2 = 95 volts.=95 V (approx.)


The setting to adopted is = 115% of Us> = 1.15 x 101 = 117 (Approx.) volts.

Calculation of Stabilizing Resistor :As per manuals of RET ,

This can be directly selected to a value Rs=450 ohms .

Now , this value of resistor should satisfy the below eqn.

Ip(prim) = (Sentivity current measured) = CTR { Ir + I_nlr + n x Ie }

Ir = Current through the Relay @ voltage Us> = 117/450 = 260 mA .



Ip(prim) = (Sentivity current measured) = CTR { Ir + I_nlr + n x Ie }= 3000{ 260+5+218 } =

This is well below the value minimum fualt current, and only constitute 48.3 % of Rated C

Also,



Hence, the Stabilizing Resistor , Rs= 450 ohms. & Us>= 117 volts.

relay setting chart _ crp panel_shambhu_revb

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