generator protection setting calculation

Generator relay protection setting calculation instruction

注：本定值计算书是基于保护装置原理以及国内外同容量机组运行的经验数据，

主要作为现场调试以及定值设定的参考，而并非最终结果。发电机保护实际运

行所需定值，应根据印方确定的定值清单或者电厂实际运行情况（继电保护人

员校验）予以修正，最终由印方确认。 Instruction: This setting calculation instruction is only for reference,

protection device running setting is confirmed by user.

XJ Electricity Co., Ltd

2010.11

Catalog

1. Generator Differential Protection（87G） .................................................................................3 2. Overall Differential（87ALL） ...................................................................................................4 3. Generator Inter-turn Fault（95G） ............................................................................................6 4.Generator Inadvertent Energize protection，Stator Earth Fault Protection of startup condition（99V） ...........................................................................................................................................7 5. Generator Over-voltage（59G） ................................................................................................7 6. Reverse Power Protection（32G）; Low Forward Power Protection（37G） .........................8 7. Generator Stator Overload（49G）............................................................................................9 8. Generator Negative-Sequence Over-current（46G） ...............................................................10 9. Generator Pole Slipping（78G）.............................................................................................. 11 10. Generator loss of excitation protection（40G） .....................................................................13 11. Generator Under & Over Frequency（81G）.........................................................................14 12. Generator Over Fluxing（24G） ............................................................................................15 13. Generator Under-voltage（27G） ..........................................................................................16 14. Stator Earth Fault 100%（64G1） .........................................................................................16 15. Stator Earth Fault 100%（64G2） .........................................................................................17 16. Stator Earth Fault 95%（64G3） ...........................................................................................17 17. Field Winding Earth Fault(（64F）........................................................................................18 18. Generator 95% Voltage Check（59GB）................................................................................18 19. Back Up Impedance（21G）...................................................................................................18 20. TV Fuse-failure（160G）........................................................................................................19

1. Generator Differential Protection（87G）

1.1 Basic parameter

CT ratio（ TAn ） 8000/5

rated primary current（ 1gnI） 7060A

rated secondary current（ 2gnI） A

nI

ITA

gngn 41.4

160070601

2 ===

1.2 Setting calculation

1）Min operation current 0op.I

Setting by the max unbalanced current under the condition of avoid the normal

generator rated load.

2220. 09.003.025.103.02 gngngnrelop IIIKI =××=××=

Suggest to select： 20. 2.0 gnop II =

2）Min brake current 0.resI

20. gnres II =

3）Ratio brake coefficient S

External three-phase short-circuit the maximum short-circuit current:

69.3216008.13308.0

1000008.133,,

)3(max.

=×××

=×××

=TAd

b

nXSI

k

AIIkres 69.32)3(

max. max.==

The max unbalanced current of differential protection when the generator is outer short circuit：

AIKKKIkccerapunb 27.369.325.01.02)3(

max. max.=×××=×××=

Therein： apK is the non-periodic branch coefficient， select 1.5～2.0； ccK is the

same type coefficient of transformer， select 0.5； erK is the error coefficient of

transformer ratio， select 0.1； Put the condition of the differential protection won’t error operate under the max

outer short circuit current，the secondary current value max.opI of correspondent max

operation current：

A9.427.35.1IKI max.unbrelmax.op =×==

Therein： relK is the reliable coefficient, select 1.3～1.5.

The ratio brake coefficient S is：

12.053.369.32

324.19.4IIII

S0.res

(3)max

0.opmax.op =−

−=

−−

=

Suggest to select：S=0.3。 4）Sensitivity check

Sensitivity check principle : Generator terminal side of two-phase metallic short-circuit occurs when generator is parallel off:

AnX

SITAd

bk 3.28

16008.13308.0100000866.0

8.133866.0

,,min. =××

×=

××××

=

AII kres 15.14

2min. ==

AIISII resresopop 51.4)53.315.14(3.0324.1)( 0.0. =−×+=−+=

227.651.43.28min. >===

op

ksen I

IK

5）Output model : Trip All CBs

2. Overall Differential（87ALL）

2. 1 Basic parameter Name M.T. HV Side Generator terminal A.T. HV Side Rated Voltage（kV） 230 13.8 13.8 Rated Current（A） 452.4 7539.6 7539.6 CT ratio 1000/1 8000/5 8000/5 Second side Current（A） 0.45 4.71 4.71 2.2 Setting Calculation

1）Min operation current 0.opI

Setting by the max unbalanced current under the condition of avoid the normal main

transformer rated load.：

bb II 24.0)05.005.006.0(5.1I)mUf(KI b)n(irel0.op =++×=∆+∆+=

Suggest to select： bbI5.0I 0.op =

Therein：

bI is the value of rated current of transformer norm side converted to the TA

secondary side.

relK is the reliable coefficient， 5.1~3.1Krel = ；

)n(if is the transformer ratio error of the current transformer under rated current.

U∆ is the error caused due to the regulation of transformer tapping (relative to the

percent of the rated voltage). m∆ is the error caused due to the incomplete matching of transformer ratios of TA and

TAA, m∆ takes 0.05 in general.

2）Min brake current 0.resI

Suggest to select： bres II =0.

3）Ratio brake coefficient S The calculation of three-phase main transformer high-voltage busbar metallic short-circuit

occurs current when generator is parallel off:

An

SXX

ITA

b

Tdk 674.1

10002303100000

07.008.01

23031

,,)3(max. =

×××

+=

×××

+=

External three-phase short-circuit the maximum short-circuit current:

(3)max.iaperstmax.unb I)mUfKK(I k∆+∆+=

A4185.0674.1)05.005.01.05.11( =×++××=

式中：

stK is the same type coefficient of TA， 0.1K st =

aperK is non-periodic coefficient of TA， 0.2~5.1Kaper = （ 5P or 10P type TA）

or0.1Kaper = （TP type TA）

Setting of ratio braking coefficient S：

31.036.0674.1

225.04185.05.1I-I

I-IKS

res.0res.max

op.0unb.maxrel =−−×

==

Suggest to select: 4.0S =

4）Sensitivity check Sensitivity check principle : Main transformer high-voltage side of two-phase

metallic short-circuit occurs when generator is parallel off:

AnXX

SITATd

bk 45.1

10002303)07.008.0(100000866.0

2303)(866.0

,,min. =×××+

×=

×××+×

=

AII kres 45.1min.min. ==

AIISII resresopop 661.0)36.045.1(4.0225.0)( 0.0. =−×+=−+=

5.119.2661.045.1min. >===

op

ksen I

IK

5）Setting of second harmonic braking coefficient Suggest to select: 15% 6）Difference current quick brake

Select: bop II 5=

7）Difference current quick brake sensitivity check Sensitivity check principle : Main transformer low-voltage side of two-phase

metallic short-circuit occurs:

AnXXX

SITATSd

bk 08.5

10002303)07.0022.0//(08.0100000866.0

2303)//(866.0

,,=

×××+×

=×××+

×=

2.126.225.208.5

>===op

ksen I

IK

8）Output model: Trip all CBs

3. Generator Inter-turn Fault（95G）

3.1 Basic parameter

Rated secondary current（ 2gnI ） AnI

ITA

gngn 41.4

160070601

2 ===

PT ratio（ TVn ） 31.0

31.0

38.13

3.2 Setting Calculation 1）Zero-sequence Voltage

Setting by the max unbalanced zero-sequence voltage under the condition of

avoid the normal generator rated load.

VUop 2=

2) Fault branch negative-sequence direction elements

AI gni 13.041.4%3%3 2 =×==ε

VU gnu 63.03/110%1%1 2 =×==ε

VAUInnP

gngnTATV

gnp 76.010041.43%1.03%1.0

%1.022 =×××=×××=

×=ε

3) Time delay： st 1.0= 4）Output model: Trip All CBs

4.Generator Inadvertent Energize protection，Stator Earth Fault Protection of startup condition（99V）

4.1 Basic parameter

Rated secondary current（ 2gnI ） A41.4

Rated secondary voltage（ 2gnU ） V110

4.2 Setting calculation 1）Low impedance element setting

( )Ω=××

×=

×= 4.38

41.43.031108.0

3.03

8.0

2

2

gn

gnset I

UZ

( )Ω=×== 6.324.3885.085.0 setset ZR

2）Over current element setting

( )AII gnop 32.141.43.03.0 2 =×==

3）Stator Earth Fault Protection of startup condition operation voltage

VUop 10=

Time delay： st 2= 4）Output model

Generator Inadvertent Energize protection: Trip 220kV CB & excitation CB

Stator Earth Fault Protection of startup condition: Trip excitation CBs。

5. Generator Over-voltage（59G）

5.1 Basic parameter

Rated secondary voltage（ 2gnU ） V110

5.2 Setting Calculation 1）Operation voltage

I: VUU gnop 5.11511005.105.1 2 =×==

II: VUU gnop 1211101.11.1 2 =×==

III: VUU gnop 1321102.12.1 2 =×==

2）Time delay Select：

I: st 30= II: st 10= III: st 5.0= 3）Output model: Trip all CBs

6. Reverse Power Protection（32G）; Low Forward Power Protection（37G）

6.1 Basic parameter

Generator rated power（ nP ） WM135

Generator rated secondary power（ 2nP ） W6.672

6.2 Setting Calculation 1）Min operation power

WK relop 8.146.672%)6.981%3(5.0) =×−+×=+= 21 PPP （

Suggest to select： Wop 10=P

Therein： relK is the reliable coefficient，select 0.5~0.8；

1P is the min loss when steam turbine is in reverse power operation，generally

select 2％~4％ of the rated power；

2P is the min loss when steam turbine is in reverse power operation，generally select

gn)P-(1 η ， gnP is the rated capacity of generator.

2）Time delay

Reverse Power Protection（32G）： )32(51 Gst =

)32(602 Gst =

Low Forward Power Protection（37G）：

3）Output model

Reverse Power Protection（32G）:

Time delay 1t : Alarm

Time delay 2t : Trip All CBs

Low Forward Power Protection（37G）: Trip All CBs

)37(1 Gst =

7. Generator Stator Overload（49G）

7.1 Basic parameter


allowed heat time constant of stator winding（K） 37.5 7.2 Setting calculation 1）Time specified overload

Stator winding time specified over-load can be set by the condition of the long term allowed loading current can reliable return.

AIKK

gnr

relop 14.541.4

9.005.1

2 =×=×=I

Therein： relK is the reliable coefficient， select 1.05；

rK is the return coefficient， select 0.9； Time specified overload time delay: st 9=

2）Reverse time specified overload Reverse time specified over-current can be set by the over-load ability allowed by

stator winding，it should be determined by the over-load ability allowed by the stator winding of the motor manufacturer. The relation of allowed duration time is :：

)1(IKt 2

* α+−=

Therein：K is the allowed heat time constant of stator winding，it should be based on the parameter provided by the motor manufacturer；

*I is the per-unit value based on stator rated current；

α is the heat radiation constant and related to the stator winding temperature rising and temperature margin，generally select 0.01~0.02. 3）Reverse time specified startup current

Reverse time specified startup current min.opI should be set by the condition of

matched with time specified over-load protection：

AK opCop 4.514.505.10min. =×== II

Therein： opI is the set value of time specified startup current； 0CK is the matching coefficient，select 1.05。

Reverse time specified delay lower limit: st 120min =

Reverse time specified delay upper limit current max.opI can be set by the condition of three phase metal short circuit at generator side：

AXI

d

gnop 7.32

135.041.4

"

2max. ===I

( )s

IKt

op

7.001.01

41.41.55

5.37)1( 22

max*.max =

+−⎟⎠⎞

⎜⎝⎛

=+−

=α

4）Output model Time specified overload: Alarm Reverse time specified overload: Programming Trip

8. Generator Negative-Sequence Over-current（46G）

8.1 Basic parameter


The per-unit value of generator long term allowed

negative-sequence current（ ∞2I ） ..08.0 UP

time constant of withstanding negative-sequence current

ability of rotor surface（A） 10

8.2 Setting calculation 1）Time specified overload The negative-sequence time specified over-load should be set on the condition of

under the generator long term allowed negative-sequence current ∞2I can reliable

return

AK

IKr

gnrelop 39.0

95.041.408.005.122 =

××== ∞II

Therein： relK is the reliable coefficient， select 1.05； rK is the return coefficient，

select 0.85～0.95；

∞2I is the per-unit value of generator long term allowed negative-sequence current；

Time specified overload time delay: st 5= 2）Reverse time specified overload

The reverse time specified negative-sequence over-load was confirmed by the allowed negative-sequence over-current ability of the generator rotor surface. The relation mode between the generator short time withstanding negative-sequence over-current multiple and allowed duration time is ：

22

2*2 ∞−

=II

At

Therein：is the per-unit value of generator negative-sequence current；

∞2I is the per-unit value of generator long term allowed negative-sequence

current； A is the time constant of withstanding negative-sequence current ability of rotor

surface。 Reverse time specified startup current

The reverse time specified startup current min.opI ， generally be set by the

operation current in correspondent with delay1000s（set value of reverse time specified delay lower limit：

AIAI gnop 56.008.01000

1041.41000

2222min. =+×=+= ∞I

Reverse time specified delay upper limit current max.opI should be set by the

condition of main transformer HV side two phase metal short circuit：

AXXX

I

tGd

gnop 38.8

125.02141.0135.041.4

22"

2max. =

×++=

++=I

sII

At 76.208.0

41.438.8

10

222

22*2

min =

−⎟⎠⎞

⎜⎝⎛

=−

=∞

3）Output model Time specified overload: Alarm Reverse time specified overload: Programming Trip

9. Generator Pole Slipping（78G）

9.1 Basic parameter Generator neutral CT ratio 8000/5=1600 Generator terminal CT ratio 13.8/0.11=125.4

9.2 Setting calculation 1）Reduced generator、transformer、system reactance etc. to the named unit (ohm)value with

the generator side voltage is 13.8kV.

Generator： ( )Ω=×

×= 267.070603

13800237.0'dX

Main transformer： ( )Ω=×=×= 132.0180

8.13125.022

n

gnkt S

UXX

System：( )

( )Ω=÷

= 031.08.13220

8.72sX

stX setting of system relation impedance：

( )Ω=+=+= 163.0031.0132.0stst XXX

2）Reduce 'dX 、 tX & stX to the secondary side value of generator side TV、TA.：

)(4.34.125

1600267.0'2

' Ω=×=×=TV

TAdd n

nXX

)(68.14.125

1600132.02 Ω=×=×=TV

TAtt n

nXX

)(08.24.125

1600163.02 Ω=×=×=TV

TAstst n

nXX

3）Setting lens principal axis obliquity

Select system impedance angle :085=Ψz

4）Setting of operation power angle setδ

)(71.08.0706015.13

138009.015.13

9.0min.1 Ω=×

×××

=×

= ϕCOSI

URn

n

0000min. 435.682180267.0163.071.054.1218054.12180 =×−=

+×

−=′+

−°= arctgXX

Rarctgdst

Lset

δ

Suggest to select 0120=setδ

5）Tripping blocking current setting This protection use generator neutral CT, CT ratio is 8000/5，Main transformer high side

circuit breaker rated breaking current is 40kA：

=××=8.13

2301600400005.0setI 208A

Suggest to select AIset 180=

6）Slipper times setting Outer zone，Slipper times setting:N =4； Inner zone, Slipper times setting:N =1（#1Generator）、2（#2 Generator）、3（#3

Generator）、4（#4 Generator）。

7）Reactance line position CZ

)(377.153.19.09.0 2 Ω=×== tC XZ

8）Startup current

)(3.541.42.12.1 2 AII nst =×==

9）Time delay Outer zone :0.5s Inner zone :0.1s 10）Output model Outer zone :Alarm Inner zone :Trip all CBs

10. Generator loss of excitation protection（40G）

10.1 Basic parameter Generator neutral CT ratio 8000/5=1600 Generator terminal CT ratio 13.8/0.11=125.4

10.2 Setting calculation Reduced generator、transformer、system reactance etc. to the named unit (ohm)value with the

generator side voltage is 13.8kV.


×= 33.270603

13800065.2dX

( )Ω=×

×= 267.070603

13800237.0'dX


8.13125.022

n

gnkt S

UXX

System： ( )

( )Ω=÷

= 031.08.13220

8.72sX

stX setting of system relation impedance：

( )Ω=+=+= 163.0031.0132.0stst XXX

As qd XX = ，Salient pole power equal 0W。

1）Set of static and stable boundary impedance

)(7.294.125

160033.21 Ω=×=×=TV

TAdB n

nXZ

)(1.24.125

1600163.01 Ω=×=×=TV

TAstA n

nXZ

2）Set of stable asynchronous impedance

)(7.294.125

160033.22 Ω=×=×=TV

TAdB n

nXZ

)(7.14.125

1600267.05.05.0 '2 Ω=××=×=

TV

TAdA n

nXZ

3）Set of generator terminal low voltage

)(881108.08.0 2 VUU nst =×==

4）Time delay Select t1=1.5S 、t2=1.5S 、t3=3S

5）Output model loss of excitation zone 1: Alarm；

loss of excitation zone 2: Trip all CBs； loss of excitation zone 3: exit；

11. Generator Under & Over Frequency（81G）

11.1 Basic parameter Generator under & over frequency capability tables provided by the equipment

manufacturing factor: Allow run-time Allow run-time

Frequency（Hz） accumulated

time (min)

Each

time(s)

Frequency（Hz） accumulated

time (min)

Each

time(s)

5.510.51 ≤< F 30 30 485.47 ≤< F 60 60

515.50 ≤< F 180 180 5.4747 ≤< F

10 20

5.505.48 ≤< F Run Continuously 475.46 ≤< F

2 5

5.4848 ≤< F 300 300

11.2 Setting calculation 1）Under frequency zone I

under-frequency zone I frequency setting： Hzf set 5.48.1 =

under-frequency zone I accumulated time： ssett 18000.1 =∑

under-frequency zone I time delay： st set 300.1 =

2）Under frequency zone II

under-frequency zone II frequency setting： Hzf set 48.2 =

under-frequency zone II accumulated time： ssett 3600.2 =∑

under-frequency zone II time delay： st set 60.2 =

3）Under frequency zone III

under-frequency zone III frequency setting： Hzf set 5.47.3 =

under-frequency zone III accumulated time： ssett 600.3 =∑

under-frequency zone III time delay： st set 20.3 =

4）Under frequency zone IV

under-frequency zone IV frequency setting： Hzf set 47.4 =

under-frequency zone IV time delay： st set 20.4 =

5）Over-frequency

over-frequency setting： Hzfset 51=

over-frequency time delay： stset 30=

6）Generator terminal low voltage setting， VUU nset 888.0 ==

7）Output model: Programming Trip

12. Generator Over Fluxing（24G）

12.1 Basic parameter Generator over excitation capability tables provided by the equipment

manufacturing factor: Stator voltage/Frequency

1.25 1.19 1.15 1.12 1.10 1.09 1.08 1.07 1.05

Time(sec) 5 7.5 10 15 20 30 45 60 ∞ 12.2 Setting calculation 1）Time specified over fluxing

Over fluxing times: 06.10 =N , time delay: st 50 =

Select rated voltage as reference voltage 110V。 2）Reverse time specified over fluxing

Over fluxing times: 07.11 =N ，time delay: st 601 =






Over fluxing times: 19.17 =N ，time delay: st 5.77 =


3）Output model: Trip all CBs

13. Generator Under-voltage（27G）

13.1 Basic parameter

Generator terminal PT ratio：311.0

311.0

38.13

13.2 Setting calculation

VUU nset 666.0 ==

Time delay: 0.5s 13.3 Output model: Alarm

14. Stator Earth Fault 100%（64G1）


Neutral earthing transformer ratio kV3.0/8.13

Neutral earthing transformer secondary resistance ( nR ) Ω3.1

Neutral earthing transformer primary resistance ( NR ) Ω8.2750

Neutral earthing transformer secondary CT ratio( 0TAn ) 1/100

Generator 3 relative capacitance ( 03C ) Fµ392.1

Generator capacitive reactance ( 0CX ) Ω6860

14.2 Setting calculation 1) earthing resistance

The setting of earthing resistance low set value should be set by the principle of one point earthing in the distance within 20% of generator neutral, the earthing fault point current 3I0 ≤ safe earthing current Is(1A). Means：

SCNg

gn IjXRR

UI ≤

−+

×=

)//(33332.0

30

0

SCNsetg

gn IjXRR

U=

−+

×

)//(33332.0

0.

1)6860//(8.275033

31380032.0

.

=−×+

××jR setg

Ω= kR setg 2.5.

Suggest to select：

Earthing resistance high value: Ω= kR sethg 10.

Earthing resistance low value: Ω= kR set 5.lg

Time delay: high value time delay:3s low value time delay:0.5s

AnKR

UITAIn

nset 5.0

1001.13.13002.0

0

2.50 =

×××

=××

×=

α

Therein α can generally be selected as 20％； IK is the reliable coefficient，

generally select 1.1. 2) Output model

high value : Alarm low value : Trip all CBs


15.1Basic parameter

Generator terminal PT ratio：31.0

31.0

38.13

Generator neutral PT ratio： 1.038.13

15.2 Setting calculation Setting value by the protection device according to measured data Time delay : 5s

15.3 Output model: Alarm


16.1 Setting calculation The fundamental wave zero-sequence voltage has two sections protection

including high value and low set value. Principle ,the low setting value zero-sequence voltage should be set by the max

unbalance fundamental wave zero-sequence voltage of neutral single phase voltage transformer when normal operation or three phase voltage transformer open triangle winding at generator side. The setting value applied in the project should avoid the max zero-sequence unbalance voltage that transmitted to the generator side when system HV side and plant transformer LV side earthing short circuit.

The setting of high set value zero-sequence voltage is 20～30V.

Suggest to select: VU Hop 20. = （high value）， VU lop 10. = （low value），According to the

measured maximum value of zero sequence voltage imbalance adjustment 。 Time delay: High value: 0.1s Low value: 0.3s 16.2 Output model

High value: Trip all CBs Low value: Trip all CBs

17. Field Winding Earth Fault(（64F）

Non-electrical，time delay is setting by the owner

18. Generator 95% Voltage Check（59GB）


rated secondary voltage（ 2gnU ） V110

18.2 Setting Calculation 1）Operation voltage

VUU gnop 10411095.095.0 2 =×==

2）output model: Alarm

19. Back Up Impedance（21G）

Based on actual engineering experience, this protection is valueless ,we suggest don’t use it. 19.1 Basic parameter

Generator neutral CT ratio 8000/5=1600 Generator terminal CT ratio 13.8/0.11=125.4

19.2 Setting calculation 1）Reduced generator、transformer to the named unit (ohm)value with the generator side

voltage is 13.8kV.


×= 25.070603

13800221.0'dX


8.13125.022

n

gnkt S

UXX

2）Reduce 'dX 、 tX to the secondary side value of generator side TV、TA.：

)(19.34.125

160025.0'2

' Ω=×=×=TV

TAdd n

nXX

)(68.14.125

1600132.02 Ω=×=×=TV

TAtt n

nXX

3） )(83.32.12'

1 Ω=×= dset XR

)(01.22.122 Ω=×= tset XR

20. TV Fuse-failure（160G）

21.1 Basic Parameter

rated secondary current（ 2gnI ） A41.4

21.2 Setting Calculation

Blocking current： )(3.541.42.12.1 2 AII gnset =×==

generator protection setting calculation

Documents