7UM62 Rotor Earth Fault Protection

7/29/2019 7UM62 Rotor Earth Fault Protection

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Rotor-Earth-Fault

Protection


2/26

Power Automation 2

Power Transmission and Distribution

Power Automation

Progress. Its that simple.

Presenter: Dr. Hans-Joachim Herrmann

PTD PA13Phone +49 911 433 8266

E-Mail: [email protected]

Generator Protection

Rotor-Earth-Fault Protection


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Power Automation 3


Power Automation


Requirement for Rotor Earth Fault Protection

in case of an earth fault, only small currents flow due to the galvanical isolation

Problem:

Double earth faults and interturn faults as a consequence of an earth fault cause:

magnetical unbalance (unbalanced forces; violent vibration)

high currents at the fault location

Task: Detection an earth fault already when it starts to build up

Destruction of the Rotor(Generator)

Earth fault in the rotor

RE CE

Rotor

Excitation

system

+

-Stator


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Power Automation 4


Power Automation


Protection Principle

Excitationsystem

+

-

VoltageSource

Earthing brush

CouplingUnit

Measuring

- Incoupling of an AC voltage (50 Hz or 60 Hz)- Measuring of the earth fault current- Measuring of the earth fault resistance

- Incoupling of low frequency square wave voltage

Principles:

HigherSensitivity


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Power Automation 5


Power Automation


Earth Current CriterionPrinciple (50 Hz/60Hz - Voltage Injection)

Coordinated

resonant circuit to fN

>40V

If disturbance influence from the excitation is to large

IE

Protection

Pick-up limit:

IE,Fault > IE,Dist...

L1 L2 L3

IE,Distr.

IE,Fault

4QF105;

0,75H

Connectionon the earthing

brush


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Power Automation 6


Power Automation


Earth Current MeasurementConnection

Also IEE2at 7UM62

is

possible

IEE

7

B

B

AA

-

A

B

3PP1336Err.

2B

Connection on the

phase to phasevoltage

7XR61

100 - 125

105;

105;

AC VoltageSourceappr. 42V or65V

Documentation for Coupling Device in the Internetwww.siprotec.com

External resistorsat excitation voltages> 150 V (circulating current >0,2A)


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Power Automation 7


Power Automation


Gain Characteristic of the R, C, L-Circuit

Z 50( ) 169.65! Z 60( ) 69.531!

0 50 100 150 200 250 3000

500

1000

1500

2000Filter er alte Ba d a

Freque z i Hz

Im

edaz

iO

m

Z f( )

f

mA27k1,5170

V45I

RZ

UI

fCouli

}

!

!

Imax approx. 300 mA


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Power Automation 8


Power Automation


Earth Current CriterionProtection Settings

Protection with two stages:Measuring circuit supervision

m23k1,5400

45I

Z

UI

f ou

li

};;

!

! ZCouplingl(50Hz) = 400;

ZCouplingl(60Hz) = 335;

Imax ca. 100 mA

(voltage source decreases a little bit )

Note: Coupling impedance only with R and C

Finally setting during commissioning


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Power Automation 9


Power Automation


Earth Current CriterionLogic


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Power Automation 10


Power Automation


Calculation of the Fault Resistance RE(50Hz/60Hz- Voltage Injection)

100V 42V u

Digital

protection(7UM62)

calculation

of RE

RE CE

RV CK

RV CK

L1 L2 L3

iL1)

1) Recommendedat static excitation

with inject harmonics

(3rd harm.; 6th harm.)


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Power Automation 11


Power Automation


Calculation Formula of the Fault Resistance RE

(1) (2)

(3)

(4)

combining (3) and (4):

Note: RV* and XK* are measured during commissioning

Model:

Zers ZMess Z

X*K R*V

XERE

_ aVE

2

E

2

E

2

EE*R-

,ZR

XR

XRR !

!

_ a _ aZZRZ j meMess I!

!

2

E

2

E

E

2

E

K2

EE

2

EE

V

--

2

rs

XR

XR*X

XR

XR*RZ

_ a Km2E

2

E

E

2

E -

,*I!

!

_ a _ a

_ aV

Ve

2

Km

2

E-e-

--,,, *RZR

*RZR

*XZRR

XR !!I


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Power Automation 12


Power Automation


Earth Fault Resistance CalculationLogic


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Power Automation 13


Power Automation


Earth Fault Resistance CalculationSettings

Measured during commissioning

Measuring circuit supervision

Measured current can be influenced by disturbancesCorrection during primary test,(in most case the alarm stage is concerned)


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Power Automation 14


Power Automation


Injection of Square Wave Voltage with Low FrequencyBasic Diagram

Excitation

+

-CE

RE

Digital

Protection

(7UM62)

UH

RV

RV

Ucontrol

Umeas.RM

7XR6004

Controlling device

(7XT71)IE

Measuringtransducer

RE Fault resistance

RV Coupling resistor

UH Auxiliary supply ( s 50V)

RM Measuring shunt resistor

CE Rotor capacitance

Typical frequency:

1 - 3 Hz


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Power Automation 15


Power Automation


Injection of Square Wave VoltageConnection Diagram (7UM62)

onnection on t ease to ase

olta e

Exc.1

15

11

25

-

27

7XR600425

27

7UM62

7 T71

TD1K14

K1

TD2

K16

K15

40k;

40k;

Control olt e

Meas ring oltage

100V

110V

120V

9

7


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Power Automation 16


Power Automation


Injection of Square Wave Voltage with LowFrequencyBasic Principle

RV

2

RECEUH

UMRM

UH

UM

UM

50V

- 50V

1,88V

- 1,88V

0,75V

- 0,75V

t

t

t

iE

50375

20k2

H

M

s!;!

;!

UR

R

EMM iRU !

g!ER

;} 5kE

R

0M}(U

E

V 2

CR }X

E

M

1

~R

U(

Equivalent circuit:


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Power Automation 17


Power Automation


Sources of Error and Error Compensation

Influence of field voltage and earth fault location

a) Earth fault location

Shifting of measuring voltage with

a positive or negative dc voltage

b) Jumps in the field voltage

a change in the field voltage takes

to jumps in the dc-voltage shifting

Udc = dc voltage shifting

Solution:

Calculation of the difference voltage

( U = |UM1 - UM2|

(U1 = |UM1 - UM2| ( U3 = |UM3 - UM4|( U2 = |UM2 - UM3|

Solution:

Block of measuring

at jumps (e.g. (U1 = (U2)

UM

UdcUdc1

UM1

UM2

UM3UM4

UM1 UM2 Udc2

UM


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Power Automation 18


Power Automation


Calculation Formulas

RECEUH

UMRM

RV

2

UMU1

U2

Algorithm

Voltage divider:

Filtering:

Amplitude-log frequency curve: fA = 800 Hz; N = 64

2-1-2 VM

M

HE

M

MEV

M

H RR

U

UR

R

RRR

U

U

!

!

!!!!

NN

uN

UuN

U1i

i2,2

1ii1,1

1;

1

2

-::

21

M

UUUU !(!

1KKII

(}( UU

(!(!

8

1kkU

8

1U

0 30 60 90 120 150 180 210240 270 300

0.001

0.01

0.1

1

f in Hz

G(f)

Continuity supervision:

Validity requirement

otherwise


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Power Automation 19


Power Automation


Logic Diagram Rotor Earth Fault Protection (1-3Hz)


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Power Automation 20


Power Automation


Rotor Earth Fault Protection (1-3Hz)Setting Values

Measuring circuit supervision

If the integrated test function is used,pick-up value of test resistor

Advanced parameteronly visible in DIGSI


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Power Automation 21


Power Automation


Connection of the Rotor Earth Fault Protection

GRW

RECE

EM

EX-TL+

RWUG

RE CE

L-

(50/60 Hz)

(1 - 3 Hz)

(50/60 Hz)

(1 - 3 Hz)

40k;

4 F

4 F

a) rotating diodes

b) separate Exciter

(static excitation)

40k;


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Power Automation 22


Power Automation


Generator with Rotating ExcitationFault Free Condition (Square Wave Principle)

Chance of charge of

rotor earth capacitance

Disturbances by the

excitation generator


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Power Automation 23


Power Automation


Generator with Rotating ExcitationTest Condition with a Fault Resistor

Fault resistor is inverse proportional to the difference voltage


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Power Automation 24


Power Automation


Parallel Operation of Rotor Earth Fault Protections

100V 42V

CK;4 F

CK;4 F

RK;105;

RK;105;RV;40k;

RV;40k;

RE

7UM62 7UM62uControl

uMeas.

iREF

uREF

7UM61

nur

iREF

or

1- 3 Hz principle 50 Hz principle


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Power Automation 25


Power Automation


Parallel Operation of Rotor Earth FaultProtectionsMeasurement with the 50/60 Hz Principle

( );20k2

RV

*K

R *K

C

ER

2ll:* VEER

RR !

;!!

g!

20k2

*

V

E

E

RR

R

;!

;!

4k*

5k

E

E

R

R

Measurement 7UM61 or 7UM62

(RV is earthed for an AC voltage)

Equivalent circuit:

seen from the 7UM6, RV alreadyis interpreted as a rotor-to-earth

resistance

Measurement:

measured as a fault resistance

Case 1:

Case 2:

alarm stage becomes less sensitive

open brushes can not be find out


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Power Automation 26


Power Automation


RV2

RERM2CK(8 F)

Umeas

(U

2

Measurement 7UM62 (1- 3 Hz)(CK is earthed for a DC voltage)

Equivalent circuit:

seen from the 7UM6:

high rotor capacitance

capacitors will not be

completely loaded

( U ~ RE-1

under no-earth-fault conditions

a fault resistance is already measured

alarm stage becomes less sensitive

(approx. 50k;)

longer measuring time

Parallel Operation of Rotor Earth Fault ProtectionsMeasurement with the Square Wave Principle

Documents

7UM62 Rotor Earth Fault Protection