g60 setting calculation reference 1

SETTING CALCULATION NUMERICAL PROTECTION SYSTEM

2 X 50 MW MALANA-II HYDRO ELECTRIC PROJECT

CLIENT :

ABIR INFRASTRUCTURE PVT. LTD.

MALANA-II HYDRO ELECTRIC PROJECT

Drawn: DD.MM.YYYY SS

Checked: DD.MM.YYYY SS

Approved: DD.MM.YYYY SKV

Rev. Modification Date Check Date Appd

PROJECT NO: C. 290PLANT: 2 X 50 MW MALANA-II HYDRO ELECTRIC PROJECT

= FU PLN

= LO

CUSTOMER No:

SETTINGCALCULATION NUMERICAL PROTECTION SYSTEM

Internal Drawing Number:

2 783001Page 1 of 29

Rev.

0

THIS DOCUMENT IS THE PROPERTY OF VA TECH HYDRO AND MUST NEITHER BE COPEID NOR USED IN ANY OTHER WAY WIHTOUT THE WRITTEN CONSENT OF VA TECH HYDRO NEITHER IT IS TO BE HANDED OVER, NOR IN OTHER WAY COMMUNICATED TO A THIRD PARTY. INFRINGMENT WILL LEAD TO PROSECUTION



MALANA-II HEP Page 2 of 29

SETTING CALCULATIONFOR DIGITAL PROTECTION SYSTEM

Table of Contents

1. GENERAL ............................................................................................................................3

2. TECHNICAL DATA ..............................................................................................................4

3. GENERATOR, TRANSFORMER AND UNIT AUXILIARY TRANSFORMER PROTECTION ...6

A) GENERATOR DIFFERENTIAL PROTECTION 87G .............................................................. 6B) GENERATOR UNDEREXCITATION PROTECTION 40G....................................................... 7C) GENERATOR NEGATIVE PHASE SEQUENCE PROTECTION 46G ........................................ 8D) GENERATOR OVERVOLTAGE PROTECTION 59................................................................ 9E) GENERATOR UNDERVOLTAGE PROTECTION 27G ......................................................... 10F) GENERATOR OVER/UNDERFREQUENCY PROTECTION 81O/U........................................ 10G) GENERATOR STATOR EARTH FAULT PROTECTION 64G1 .............................................. 11H) GENERATOR STATOR EARTH FAULT PROTECTION 64G2 .............................................. 11I) ROTOR EARTH FAULT PROTECTION 64R ..................................................................... 12J) GENERATOR REVERSE POWER PROTECTION 32G ........................................................ 13K) VOLTAGE SUPERVISION FUNCTION 60G, 60M AND 60A ............................................... 13L) GENERATOR UNDERIMPEDANCE PROTECTION 21G ..................................................... 14M) DEAD MACHINE 27/51V .............................................................................................. 15N) UNIT DIFFERENTIAL PROTECTION 87GT ..................................................................... 16O) RESTRICTED EARTH FAULT PROTECTION 64REF ......................................................... 17P) RESTRICTED EARTH FAULT PROTECTION 64REF- DISCRETE RELAY ............................. 19Q) OVERFLUXING PROTECTION 99G ................................................................................ 21R) UAT DIFFERENTIAL PROTECTION 87UAT..................................................................... 21S) UAT OVERCURRENT PROTECTION 50U/51U................................................................. 22

4. DISTANCE PROTECTION .................................................................................................23




1.GENERAL

This document provides information about the various protective schemes for the unit transformer protection, generator protection and UAT. The document lists the particular protective functions as how they overlap and complement each other for back-up and outlines the philosophy about the selection of the protection setting values.Please note that the generator and transformer characteristics and capability curves and data are contained in separate documents.Also the documentation with detailed descriptions of the various protection systems are provided in separate relay documents.

Note:The calculated relay settings are based on different data sheets available during the workout (e.g. generator data sheet, CB data, and single line diagram) of the document. In case of any equipment modification or change of various electrical characteristics this document has to be revised. Therefore all the settings have to be checked and revised during the commissioning on site.

Generally the calculation of the settings is done according to our best knowledge and conscience. So we cant accept any responsibility for errors included in the document. Further we are not liable for any incident or damage resulting from the content of this setting calculation.

Some protection settings (e.g. frequency, voltage) have to be checked and approved also from the power distribution owner.




2. TECHNICAL DATA

Generator:

GENERATOR OUTPUT= Sn 55560.00 kVARATED VOLTAGE= Un 11 kVPOWER FACTOR p.f. 0.9RATED CURRENT In 2915.9 ARATED FREQUENCY fn 50 HzSYNCRONOUS REACTANCE Xd 93.30%TRANSIENT REACTANCE (STAURATED) Xd' 26%NEGETIVE PHASE SEQUENCE WITHSTAND I2 8%UNBALANCED LOAD (I2/IN)xt 20 secFIELD CURRENT If 875 AdcSTATOR LEAKAGE REACTANCE xs 0.0952 PUSYNCRONOUS REACTANCE QUARD AXIS Xq 0.602 PU

Step up transformer

RATED VOLTAGE Un 11/132 kVRATED OUTPUTS Sn 63.9 MVASHORT CIRCUIT VOLTAGE Uk 12.5 %VECTOR GROUP YNd11

Auxiliary Transformer :

RATED VOLTAGE Un 11000/415 VRATED OUTPUTS Sn 500 KVAVECTOR GROUP Dyn11

Excitation Transformer :

RATED VOLTAGE Un 11000/364 VRATED OUTPUTS Sn 630 KVAVECTOR GROUP Dy5

Line Parameters:

POSITIVE SEQUENCE RESISTANCE R1 0.14 OHMS/KMPOSITIVE SEQUENCE REACTANCE X1 0.387 OHMS/KMZERO SEQUENCE RESISTANCE R0 0.272 OHMS/KMZERO SEQUENCE RESISTANCE X0 1.233 OHMS/KMLINE LENGTH L 70 KMLENGTH OF NEXT SHORTEST LINE L1 30 KMLENGTH OF NEXT LONGEST LINE L2 30 KM




Current Transformer Primary Secondary

GENERATOR TRANSFORMER HV SIDE 400A 1AGENERATOR TRANSFORMER NEUTRAL 400A 1AGENERATOR NEUTRAL 4000A 5AGENERATOR TERMINAL 4000A 5AAUX TRANSFORMER HV SIDE (OVERALL DIFF) 4000A 5AGENERATOR TRANSFORMER HV SIDE (DIFF) 600A 1AAUX TRANSFORMER HV SIDE (OVERCURRENT PROT) 100A 1A

Voltage transformer Primary Secondary

PROTECTION CORE 11000V 110VAVR CORE 11000V 110VNEUTRAL TRANSFORMER 11000V 110VMETERING CORE 11000V 110VLINE PT 110000V 110V




3.GENERATOR, TRANSFORMER AND UNIT AUXILIARY TRANSFORMER PROTECTION

A) GENERATOR DIFFERENTIAL PROTECTION 87G

This function protects the generator system from the neutral CTs to the generator terminal CTs. When function operates, the unit will be shut down immediately.

The differential setting value is calculated as follows:

555602916.14

3 11 3gp

Sn kVAI A

Un kV

Generator primary current

Now with a CT ratio = 4000/5 A the generator secondary current is calculated

2916.14A5 3.65

4000

gpgs

II A A

CTratio A Generator secondary current

The differential current setting is chosen to be 20% of the relay current rating, i.e.

AAI s 1520.087

This is in turn the equivalent to the generator rated current.

87 1% 100 100 27.4%

3.65

s

gs

I AI

I A

The bias slope is set to %40bias

Setting

Name of parameter

Range

Operate Value 1A Bias 40%




B) GENERATOR UNDEREXCITATION PROTECTION 40G

The under excitation MHO protection is used to detect failures in the excitation system of synchronous generators and to prevent damage to the equipment and power swings in the system.

The given direct reactances areSynchronous reactance xd 93.3%Transient reactance (saturated) xd 26%

A compensation factor F must be determined according to the equation below, in order to adjust the reactances to the CT and VT ratios:

11000 4000 110 51.5

2916.14 5 11000 100

G r

G r

V CTratio I V A V AF

I VTratio V A A V V

whereIr rated current of the relayVr rated voltage of the relay (100V internally)

So the adapted reactances are

1.5 0.933 1.399

' ' 1.5 0.255 0.382d d

d d

x F x pU pU

x F x pU pU

The relay function setting is calculated as follows.

1.40

' 0.382 1.40.891

2 2 2 2

d

d d

Diameter x pU

x x pU pUCenter pU

The relay will be set to the next possible set point:

Diameter: 1.4 pUCenter: 0.89 pU

The Time Delay Stage 1 is set to 5 sec.

The parameters Operate Value St. 2, Rotor Cur. Comp., Rotor Cur. Offset has no relevance.Stage 2 is using the following logical function:

The Time Delay Stage 2 is set to 1 sec.The Operate Value of the Function "27/50" is set to 50V.

& TripUnderexcitation Stage 1 PickupUndervoltage 27/40 Pickup

Time Delay Stage 2




C) GENERATOR NEGATIVE PHASE SEQUENCE PROTECTION 46G

The calculation of the setting values is done according to e.g. following generator data:

Rated power SG =55560 KVARated voltage VG = 11 kVNegative phase sequence current withstand 8%

Therefore the generator primary current is

555602916.14

3 11 3

ggp

gp

S kVAI A

V kV

and by using a current transformer with a CT ratio of 12000A/1A the corresponding secondary current is

2916.14A5 3.64

4000

gpgs

II A A

CTratio A

So the CT ratio compensation is

3.64 0.73

5gs

N

I ACT ratio comp

I A

A further data for the generator (manufacturer data) is the inverse time characteristic i2t, which is for example

i2t=20s

Note: This characteristic is only valid for high current values i, as shown below (calculation tripping time).

So the time constant is selected to be

2

203125 52

0.08

ss min

The tripping time can be calculated exactly

2

222

22ln

e

tripii

it

In case of a failure with n.p.s=45%, i2 results to 5xi2e, and the tripping time is




25ln 0.0408 127.5

24tript s

Compared with the manufacturer data

2 22

3.5 2098.7

0.45trips s

t si

The values for the "neg.ph.sequ.alarm" and "neg.ph.sequ.trip" are selected as a percentage of the load limit. The load limit is reached after approximately 4 time constants when running constant admissible unbalance current. Typical values are (depends on the customer wishes):

neg.ph.sequ.alarm=80%neg.ph.sequ.trip=100%

D) GENERATOR OVERVOLTAGE PROTECTION 59

The overvoltage function protects the generator and the transformer against electrical field stresses. The function is provided with 2 stages whereby stage 1 has a lower voltage setting and a larger time delay to cater for voltage regulator response time in case of full load rejections and stage 2 is provided with a higher voltage setting above loss of load conditions and minimum time delay.

The calculation of the setting value for Stage 1 is as follows

The setting is chosen to be 110% of the generator rated voltage, therefore

VV

VV

VTratio

VV

gps 0.12110.1

11000

11011000%110

and the time delay is set to t = 2.0 s

Stage 2 is selected to be 125% of the generator rated voltage, therefore

VV

VV

VTratio

VV

gps 5.13725.1

11000

11011000%125

and the time delay is set to t = 0.0 s

Setting:

Name of parameter Range UnitOperate Value Stage 1 121.0 VOperate Value Stage 2 137.5 VTime Delay Stage 1 2 SecTime Delay Stage 2 0 SecType 1 Over Voltage




E) GENERATOR UNDERVOLTAGE PROTECTION 27G

The function is enabled during the generator set being connected to the power system and is disabled (blocked) by the 220kV CB open position. It is a 1-stage function.

The function settings are selected as follows.

VVVV ns 7711070.0%7027 Time delay st 5.227 trip

Setting:

Name of parameter Range UnitOperate Value 77 [V]Time Delay 2,5 [Sec]Type 2 Under Voltage -

F) GENERATOR OVER/UNDERFREQUENCY PROTECTION 81O/U

The protective function has 4 Stages providing separate adjustable over- and under-frequency alarm and trip facilities. In addition to the mechanical overspeed and excitation system underspeed detection it provides backup protection for such conditions. All stages will initiate an alarm and trip the unit.

The function settings are selected as follows.

Stage 1 overfrequency Hzf 0.521.81 time delay st 5.01.81 TripStage 2 overfrequency Hzf 5.522.81 time delay st 0.02.81 TripStage 3 underfrequency Hzf 5.483.81 time delay st 0.203.81 TripStage 4 underfrequency Hzf 0.474.81 time delay st 0.04.81 Trip

The frequency settings need to be reviewed by the grid regulator.

Setting:

Name of parameter Range UnitMin. Volt. Setting 60 100 [V]Max. Volt. Setting 100 140 [V]Operate Value St. 1 52 [Hz] Time Delay St. 1 0.5 [s]Type St. 1 OverdetectionOperate Value St. 2 52.5 [Hz]Time Delay St. 2 0.00 [s]Type St. 2 OverdetectionOperate Value St. 3 48.5 [Hz] Time Delay St. 3 20 [s]Type St. 3 UnderdetectionOperate Value St. 4 47 [Hz]Time Delay St. 4 0.00 [s]Type St. 4 Underdetection




G) GENERATOR STATOR EARTH FAULT PROTECTION 64G1

The function should serve as an earth fault function for the complete 11kV-system and for the generator up to 90% of its winding. With an earth fault in the 11kV-system (respectively on the terminals of the generator) we receive the following voltage in the generator neutral:

VVkV

kV

ratiotransf

VV

Gen

N 5.63110/11

1

3

111

3sec

For a protection range of 90% we are able to calculate the setting value:

VVVrangeprot

V Nset 18.35.63%100

%95%100

%100

.%100sec

Selected value (according to setting range of the protection relay): 3.2V.

Time delay 1.0s

Setting:

Name of parameter Range UnitOperate Value 3.2 VTime Delay 1.0 SecType Over detection -

H) GENERATOR STATOR EARTH FAULT PROTECTION 64G2

For simplification an evenly distribution of the 3rd harmonic over neutral and terminals for the generator in healthy condition is assumed (see figure below).

This distribution of the 3rd harmonic over neutral and terminal side is taken for the evaluation of earth faults close to the generator neutral. The 3rd harmonic is measured in the generator neutral with a single-phase voltage transformer and on the generator leads with a voltage transformer in open delta




connection. In case of an earth fault, the 3rd harmonic in the neutral is shorted whereby the value on the generator terminals is increased by the same value (see figure below).

The following requirement is assumed: the relay with the measurement of the 3rd harmonic shall protect the 15% of the stator coil close to the neutral point. The other 85% are protected by a normal overvoltage relay with the measurement of the fundamental frequency. The correct settings will be determined on site during earth fault tests. For this purpose different measurements of the 3rd harmonic in the generator neutral and on the generator leads have to be done in dependence of different generator loads for the healthy condition and for an earth fault.

The 3rd harmonics are processed via the following formula:

valuesmeasuredvoltneutralgenHarmrdratiovoltalmintergenHarmrd ....3....3There should be a difference between the measured values for the healthy condition and for the case of an earth fault.

Setting:

Settings will be determined on site during earth fault tests.

I) ROTOR EARTH FAULT PROTECTION 64R

This protection function comprises an auxiliary supply, which is connected between the earth and one side of the field circuit. A direct voltage appears at the output, which is indirectly proportional to the rotor insulation value and corresponds to the resistance. If this measured resistance is smaller than the setting value, the required trip sequences for a unit shutdown are carried out.

The setting of the rotor earth fault protection is selected to

Stage 1: kR 50 with a time delay stdelay 10




Stage 1 will initiate an Alarm only.

Stage 2: 1500R with a time delay stdelay 1Stage 2 will initiate a trip.

Setting:

Name of parameter Setting UnitOperate Value, Stage1 50 [k]Time Delay, Stage1 10 [s]Operate Value, Stage2 1.5 [k]Time Delay, Stage2 1 [s]

J) GENERATOR REVERSE POWER PROTECTION 32G

When operating on reverse power this protective function will perform a unit shut down. The setting is selected due to our experience, i.e. -5.0% of the generator rating power.

The relay function setting is calculated as follows.

The relay primary power is

kWAkVIVP CTpprelp 77.5715130000.113cos3

The required -5.0% primary reverse power setting of the machine rating is

kWAkVIVP gpp 2259.04.26200.11305.0cos3%0.532

The required relay setting is Pp32/Prelp = -225/5715.77 = -3.94%

The time delay is set to st 0.532

Setting:

Name of parameter

Setting Unit

Operate Value -3.94 [% PN]Time Delay 5 [s]Power Direction Direction 1 -Phase Rotation Right -

K) VOLTAGE SUPERVISION FUNCTION 60G, 60M AND 60A

The setting for the negative phase sequence voltage for unbalanced secondary phase to phase voltages is selected to

Operate Value U=50.0 V with a time delay t=5s




The second condition of the function is the setting for the negative phase sequence current. A high negative phase sequence current indicates e.g. a failure in the network and the protection function is blocked. Normally an unbalanced voltage causes only a small n.p.s. current. So the setting is chosen to be

Operate Value I=0.2 A

The selection parameter declares the setting for the phase rotation.

Setting:

Name of parameter Range UnitOperate Value I 0.2 AOperate Value U 50 VTime Delay 5 [s]Phase Rotation 2 (Right) -

L) GENERATOR UNDERIMPEDANCE PROTECTION 21G

This protection function consists of two stages, whereby the first stage is a so called impedance protection relay with a current interlock and the second stage is a backup protection, which is designed as overcurrent protection relay.

Therefore the generator current is

AV

SI

gp

ggp 4.262

3

Generator primary current

The current and voltage transformer are designed according to the related voltage and rated current of the generator. For this purpose the VT ratio is selected to be 11000V/110V and the CT ratio of the current transformer at the neutral is selected to be 10000/1A

The HV and LV transformer currents are:

AV

SI

hvp

thvp 73.57

3

HV transformer primary current

AV

SI

Lvp

tLvp 35.577

3

LV transformer primary current

The primary short circuit impedance of the transformer is obtained by

835.0

10011

50.711

100

22

MVAVku

SVZ

k

t

TSp




Therefore the secondary transformer impedance is calculated

495.0825.0

110005

110300ps Z

VTratio

CTratioZ

In order not to overreach on external system faults an impedance of approximately 50% to 70% of the transformer is selected with a corresponding setting of

247.073.15.0%5021 sG ZZ With time delay st G 2.021

The impedance current interlock setting, i.e. the overcurrent stage is a starting element for the under impedance stage, is set to 120% of the generator rated current and calculated as follows

AratioCT

IIs LV 55.11300

535.5772.1

12.1

The time delay setting for stage 2 depends on the time grading of the remaining network.

Setting:

Name of parameter

Range Unit

Operate Value 0.25 [Ohm]Time Delay Imp. 0.2 [s]Time Delay Curr. Depends on time grading of remaining n/w [s]Current Interlock 11.55 A

M) DEAD MACHINE 27/51V

The overcurrent setting will be coordinated with all the other overcurrent functions (generator, transformer ...).

AI V 10.151/27 The typical operating range of a generator lies between 90% and 110% of the rated voltage. For generators with an isolated starpoint or with an earthed starpoint via a resistor the generator voltage drops to values of about 30% caused of a phase to phase fault. For this case the parameter "Voltage Limit" has to be chosen in that way, that the generator voltage is below the setting of this parameter. The operating value of the current setting will then be reduced to the "K-Factor". The setting is chosen to be 60% of the generator nominal voltage; this is for the secondary side:

VV V 0.66110%100

%6051/27




The k-factor is chosen to be 20% (to make sure that the current exceeds the setting value).

2.0K

Setting:

Name of parameter Range UnitOperate Value 1.1 [A]Voltage Limit 66 [V]K-Factor 0.2 -Time Delay 4 [s]

N) UNIT DIFFERENTIAL PROTECTION 87GT

The unit differential protection is protecting the system from the transformer 220kV CTs up to the 11kV generator neutral and Auxiliary Transformer busbar CTs. When operating the unit is tripped and will be shut down immediately.

AkV

kVA

V

SI

hvp

thvp 74.57

3110

11000

3

HV transformer primary current

AAA

A

CTratio

II

hvphvs 96.00.1

60

74.57 HV transformer secondary current

With a differential current setting of 0.20xIn the setting as a percentage of the transformer rated current can be calculated

%8.2010096.0

20.0%

A

A

I

II

hvs

shvs

By choosing a differential current setting of 0.20A secondary the primary setting is calculated as follows.

AAA

AIratioCTI hvshvp 7515.0

0.1

500

High set over current = 5.0 x IN =4.8

To cater for the different CT ratios on the transformer HV and LV side the CT ratio compensation factor system2/system1 and systm3/system1 is calculated according to following formulas whereby system 1 refers to the 220kV HV winding, system 2 to the generator leg and system 3 to the aux transformer LV winding.

5

5.0

11

1101/60

1/300

2

1.1

212

kV

kVA

A

system

systemratiotrCTsystem

CTsystemcompCTratio




05.0

11

1101/60

1/300

3

1.1

313

kV

kVA

A

system


CTsystemcompCTratio

Setting:

Name of parameter Range UnitOperate Value 20% -High Set OC 4,8A -CT Ratio Comp. 2-1 0.5 -CT Ratio Comp. 3-1 0.05 -2nd Harmonic 20 (to be verified during commissioning) %5th Harmonic 15 (to be verified during commissioning) %Bias 50 %Vector Group 1-2 1 -Vector Group 1-3 11 -Zero Sequ. Syst.1 On -Zero Sequ. Syst.2 Off -Zero Sequ. Syst.3 Off -

O) RESTRICTED EARTH FAULT PROTECTION 64REF

The grid transformer restricted earth fault protection 64REF is protecting the system from the transformer 220kV CTs up to the grid transformer neutral to cater for faults near the neutral point (grid transformer). High impedance scheme and high speed tripping is provided. When operating the function trips the generator unit.

CT data for the 220kV transformer feeder switchgear CTs.

CT ratio 600/1,0 ACT secondary current In = 1,0 A Estimated CT knee point voltage Vk > 300 VEstimated CT secondary resistance Rct = 5 Estimated single lead resistance to relay Rl = 0.3

CT data for the 220kV transformer neutral CT


The CT requirements for the High impedance transformer restricted earth fault protective function, is according to the following formula.

Vk > 2IF ( Rct + 2 Rl + Rext )




Whereby IF is the maximum secondary three phase through fault current considering a short circuit failure. The secondary fault current IF at the 220kV level is calculated as follows (British EATS 48-3 standard).

AAkV

kVA

CTratioV

SI

TF 24.12

0.1/6002203

17500016

316

220kV lead CTs Vk = 300 V > 2 x 12.24A (5 + 2 x 0.3 ) = 137.16 V220kV neutral CT Vk = 300 V > 2 x 12.24A (5 + 2 x 0.3 ) = 137.16 V

Therefore the selected restricted earth fault protection voltage setting is chosen to be greater than the minimum stability voltage IFx( Rct + 2 Rl + Rext )=68.58V Vs=69V and the resulting external stabilising resistor for a relay setting IS = 0.15A (33% rated current) is

45515.0

15.0

1.069

S

SS

STI

I

relayVAV

R

The minimum CT kneepoint voltage should be greater than twice the relay voltage setting

220kV: Vk = 300V > 2 x VS = 138V

Check, whether a voltage limiting device is required:

VVVVV KfKp 3000 22 VK=300V

VRRRRIV RSTlCTFf 56374553.02524.122

Thus, VVp 3579

Due to ensure a safety margin a voltage limiting resistor is connected into the circuit.

Continuous power rating of the setting resistor:

WRIP STScon 2.1045515.0 22 with a short time rating:

ondsforW

R

IRV

R

VP

ST

FSTK

ST

fsshort sec5.0 159

3.12

4

13

2




Thermal rating of the non-linear resistor:

WVAVIP KF 94.467730024.1215.3

44

AR

VI

STsetting 15.0

455

69

Settings:

Name of parameter Range UnitOperate Value 42.5 % -Drop Off Delay 0.5 s

P) RESTRICTED EARTH FAULT PROTECTION 64REF- DISCRETE RELAY

The grid transformer restricted earth fault protection 64REF is protecting the system from the transformer 220kV CTs up to the grid transformer neutral to cater for faults near the neutral point (grid transformer). High impedance scheme and high speed tripping is provided. When operating the function trips the generator unit.

CT data for the 220kV transformer feeder switchgear CTs.


CT data for the 220kV transformer neutral CT


The CT requirements for the High impedance transformer restricted earth fault protective function, is according to the following formula.

Vk > 2IF ( Rct + 2 Rl + Rext )

Whereby IF is the maximum secondary three phase through fault current considering a short circuit failure. The secondary fault current IF at the 220kV level is calculated as follows (British EATS 48-3 standard).

AAkV

kVA

CTratioV

SI

TF 24.12

0.1/6002203

17500016

316




220kV lead CTs Vk = 300 V > 2 x 12.24A (5 + 2 x 0.3 ) = 137.16 V220kV neutral CT Vk = 300 V > 2 x 12.24A (5 + 2 x 0.3 ) = 137.16 V

Therefore the selected restricted earth fault protection voltage setting is chosen to be greater than the minimum stability voltage IFx( Rct + 2 Rl + Rext )=68.58V Vs=69V and the resulting external stabilising resistor for a relay setting IS = 0.15A (33% rated current) is

22.16215.0

15.01.0

69

S

SS

STI

IrelayVA

VR

The minimum CT kneepoint voltage should be greater than twice the relay voltage setting

220kV: Vk = 300V > 2 x VS = 138V

Check, whether a voltage limiting device is required:

VVVVV KfKp 3000 22 VK=300V

28.205522.1623.02524.122 RSTlCTFf RRRRIV

Thus, VVp 48.2052

Due to ensure a safety margin a voltage limiting resistor is connected into the circuit.

Continuous power rating of the setting resistor:

WRIP STScon 65.322.16215.0 22 with a short time rating:

onds for W

R

IRV

R

VP

ST

FSTK

ST

fsshort sec5.082.2412

3.12

4

13

2

Thermal rating of the non-linear resistor:

WVAVIP KF 94.467730024.1215.3

44




AR

VI

STsetting 42.0

22.162

69

Settings:

Name of parameter Range UnitOperate Value 42.5 % -Drop Off Delay 0.5 s

Q) OVERFLUXING PROTECTION 99G

The degree of saturation (overfluxing) is calculated according to following formula.

fV

fVS

N

N

Whereby V and VN are the actual voltage and rated voltage and f and fN the actual frequency and rated frequency respectively.

The operating value of stage 1 is set to the maximum continuous overfluxing withstand of the generator, which must be specified by the manufacturer of the generator, i.e. to 105% voltage at rated frequency and the other stage is set to increasing higher levels.

Stage 1 alarm S1A=1.05 time delay t=10.0sStage 2 trip S2T=1.10 time delay t=1.0s

Setting:

Name of parameter Setting UnitOperate Value St. 1 1.05 [p.U.]Time Delay St. 1 10.00 [s]Operate Value St. 2 1.10 [p.U.]Time Delay St. 2 1.00 [s]Nominal Frequency 50.0 [Hz]Nominal Voltage 110 [V]

R) UAT DIFFERENTIAL PROTECTION 87UAT

This function protects the UAT system from the HV side CTs to the LV side CTs and operates for phase to phase and three phase faults.

The differential setting value is calculated as follows:

AkV

kVA

V

SI

np

ATAT-HVp 24.26

311

500

3

UAT (HV) primary current

Now with a CT ratio = 30/5 A the generator secondary current is calculated

AAA

A

CTratio

II

AT-HVpAT-HVs 37.45

30

24.26 UAT (HV) secondary current




AV

kVA

V

SI

np

ATAT-LVp 60.695

3415

500

3

UAT (LV) primary current

and with a CT ratio of 800/5A the corresponding secondary current is

AAA

A

CTratio

II

AT-LVpAT-LVs 87.01

800

60.695 UAT (LV) secondary current

The differential current setting is chosen to be 20% of the relay current rating, i.e.

AAI s 00.1520.087

This is in turn the equivalent to the generator rated current.

%16.3810062.2

0.1100%

A

A

I

II

AT-HVs

s

High set overcurrent = 5.0 x IN =13.1

The bias slope is set to %40bias

00.1

415.0

111/30

800

2

1.1

2

kV

kVA

system


CTsystemcompCTratio

Setting:

Name of parameter Range UnitOperate Value 38.16% -High Set OC 13.1 -CT Ratio Comp. 2-1 1.00 -2nd Harmonic 20 (to be verified during commissioning) %5th Harmonic 15 (to be verified during commissioning) %Bias 40 %Vector Group 1-2 11 -Zero Sequ. Syst.1 Off -Zero Sequ. Syst.2 Off -

S) UAT OVERCURRENT PROTECTION 50U/51U

This function protects the auxiliary transformer against substantial overloading and heavy internal and external HV side short circuits and will trip the generator unit when operating. For the overcurrent protection stage 1 an inverse time characteristic is chosen to cater for field forcing conditions and the current setting is selected to be 1.0x the transformer rated current. The overcurrent protection stage 2 setting is chosen to be about 5 x In with a small time delay




The protective function settings are obtained

AkV

kVA

V

SI

np

ATATp 24.26

311

500

3

auxiliary transformer primary current

and with a CT ratio of 50/5A the corresponding secondary current is

AAA

A

CTratio

II

ATpATs 62.25

50

24.26 auxiliary transformer secondary current

Hence the current setting for Stage 1 is selected to be 120% of the rated current

AAII ATs 15.32.162.22.151

With a Time Multiplier setting 5.0TMS normally inverse time characteristic

The Stage 2 current setting is selected to be approximately 5 x In and is obtained

AAII 75.150.515.30.55150

The time delay of Stage 2 is chosen to be st 1.050

Setting:

Name of parameter Range UnitOperating Val. St.1 3.15 ATMS St.1 0.5 -Curve normal inverse -Operating Val. St.2 15.75 ATime delay St.2 0.1 Sec

4. Distance Protection

Line Parameters:

POSITIVE SEQUENCE RESISTANCE R1 0.0659 OHMS/KMPOSITIVE SEQUENCE REACTANCE X1 0.3836 OHMS/KMZERO SEQUENCE RESISTANCE R0 0.272 OHMS/KMZERO SEQUENCE RESISTANCE X0 1.233 OHMS/KMLINE LENGTH L1 70 KMLENGTH OF NEXT SHORTEST LINE L2 30 KMLENGTH OF NEXT LONGEST LINE L3 30 KMARC RESISTANCE PH-PH Arc ph-ph 0 OHMSARC RESISTANCE PH-EARTH Arc ph-e 20 OHMS

Primary Values per Km:




R1=0.0659X1=0.3836R0=0.272X0=1.233

3892.0111 22 XRZ

2517.801

11),( 1

R

XTanPhPhLineAngle

2626.1000 22 XRZ

5598.770

00),( 1

R

XTanEPhLineAngle

Values Protected Line:

Primary Value:

R1pL1=0.0659*70=4.6130X1pL1=0.3836*70=26.8508R0pL1=0.2720*70=19.0400X0pL1=1.2330*70=86.3100

Secondary Value:

06.0PTratio

CTratio

R1sL1=4.6130*0.06=0.2767X1sL1=26.8508*0.06=1.6110R0sL1=19.0400*0.06=1.1424X0sL1=86.3100*0.06=5.1786

Earth Impedance (residual) Compensation:

Resistance Ratio:

Reactance Ratio:

Earth Compensation Factor, Ko:

04248.113

1

1

0

R

R

R

R

L

G

7381.013

1

1

0

X

X

X

X

L

G

1

3

1

1

00 Z

ZK




iK 0508.07469.00 7486.00508.07469.0)( 220 KABS

89.37469.0

0508.0tan)( 10 KARG

Next Shortest Line:

Primary Value:

R1pL2=0.0659*30= 1.9770X1pL2=0.3836*30= 11.5075R0pL2=0.2720*30= 8.1600X0pL2=1.2330*30= 36.99

Secondary Values:

R1sL2=1.9770*0.06=0.1186X1sL2=11.5075*0.06=0.6904R0sL2=8.1600*0.06=0.4896X0sL2=36.9900*0.06=2.2194

Next Longest Line:

Primary Value:

R1pL3=0.0659*30= 1.9770X1pL3=0.3836*30= 11.5075R0pL3=0.2720*30= 8.1600X0pL3=1.2330*30= 36.99

Secondary Values:

R1sL3=1.9770*0.06=0.1186X1sL3=11.5075*0.06=0.6904R0sL3=8.1600*0.06=0.4896X0sL3=36.9900*0.06=2.2194

KPCL Setting Philosophy:

Zone1 : 80% of Protected Line

Zone2 : 100% of protected line + 50% of next shortest line




Zone3 : 100% + 100% of next longest line

Zone4 : Normally 15% to 20% of Zone 1

Zone 1 Calculation:

Phase to Phase Faults:

Primary Values

69.3)8.0*11(11 pharcphpLRpZR 481.21)8.0*11(11 pLXpZX

Secondary Values

221.006.0*1111 pZRsZR 289.106.0*1111 pZXsZX

Phase to Earth Faults:

Primary Values

232.35)8.0*10(10 earcphpLRpZR 048.69)8.0*10(10 pLXpZX

Secondary Values

114.206.0*1010 pZRsZR 143.406.0*1010 pZXsZX

Zone 2 Calculation:


Primary Values

602.5)5.0*21()11(21 pharcphpLRpLRpZR 605.32)5.0*21()11(21 pLXpLXpZX

Secondary Values

336.006.0*2121 pZRsZR 956.106.0*2121 pZXsZX





Primary Values

120.43)5.0*20()10(20 earcphpLRpLRpZR 805.104)5.0*20()10(20 pLXpLXpZX

Secondary Values

587.206.0*2020 pZRsZR 288.606.0*2020 pZXsZX

Zone 3 Calculation:


Primary Values

590.6)31()11(31 pharcphpLRpLRpZR 358.38)31()11(31 pLXpLXpZX

Secondary Values

395.006.0*3131 pZRsZR 301.206.0*3131 pZXsZX


Primary Values

200.47)30()10(30 earcphpLRpLRpZR 300.123)30()10(30 pLXpLXpZX

Secondary Values

832.206.0*3030 pZRsZR 398.706.0*3030 pZXsZX

Reverse Zone 4 Calculation:


Primary Values




923.0)2.0*11(41 pharcphpLRpZR 370.5)2.0*11(41 pLXpZX

Secondary Values

055.006.0*4141 pZRsZR 322.006.0*4141 pZXsZX


Primary Values

808.23)2.0*10(40 earcphpLRpZR 262.17)2.0*10(40 pLXpZX

Secondary Values

428.106.0*4040 pZRsZR 036.106.0*4040 pZXsZX

Settings:

Name of parameter Set Value Unit

Line Angle ph-ph 80.2517 Degreesph-e 77.5598

Earth fault Compensation Factors

Re/Rl 1.042489Xe/Xl 0.738143

Zone 1(Forward)

ph-ph R 0.221

OhmsX 1.289

ph-eR 2.114X 4.143

Zone 2(Forward) ph-ph

R 0.336 OhmsX 1.956




ph-e R 2.587X 6.288

Zone 3(Forward)

ph-ph R 0.395

OhmsX 2.301

ph-e R 2.832X 7.398

Zone 4(Reverse)

ph-ph R 0.055

OhmsX 0.322

ph-eR 1.428X 1.036

Operation time

Zone 1 0

secsZone 2 0.4Zone 3 0.8Zone 4 1.2

g60 setting calculation reference 1

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