7um62_rotor earth fault protection
TRANSCRIPT
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Rotor-Earth-Fault Protection
Power Automation 2
Power Transmission and Distribution
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simple.
Presenter:Dr. Hans-Joachim Herrmann
PTD PA13
Phone +49 911 433 8266
E-Mail: [email protected]
Generator Protection
Rotor-Earth-Fault Protection
Power Automation 3
Power Transmission and Distribution
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simple.
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
RECE
Rotor
Excitationsystem
+
-Stator
Power Automation 4
Power Transmission and Distribution
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simple.
Protection Principle
Excitationsystem
+
-
Voltage Source
„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
Power Automation 5
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Earth Current CriterionPrinciple (50 Hz/60Hz - Voltage Injection)
Coordinatedresonant 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
4F105
0,75H
Connectionon the earthingbrush
Power Automation 6
Power Transmission and Distribution
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Earth Current MeasurementConnection
Also IEE2 at 7UM62is possible
IEE1
J7
J8
1B1
1B3
1A1
1A3
+
-
4A1
4B1
3PP1336Err.
2B1
7UM6
Connection on the phase to phase voltage
7XR61
100 V - 125 V AC
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)
Power Automation 7
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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
2000Filterverhalten Bandpaß
Frequenz in Hz
Impe
danz
in
Ohm
Z f( )
f
mA27k 1,5 170
V 45 I
R Z
U I
fCoupling
Imax approx. 300 mA
Power Automation 8
Power Transmission and Distribution
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simple.
Earth Current CriterionProtection Settings
Protection with two stages:Measuring circuit supervision
mA23k 1,5 400
V 45 I
R Z
U I
fCoupling
ZCouplingl(50Hz) = 400
ZCouplingl(60Hz) = 335
Imax ca. 100 mA
(voltage source decreases a little bit )
Note: Coupling impedance only with R and CFinally setting during commissioning
Power Automation 9
Power Transmission and Distribution
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Earth Current Criterion Logic
Power Automation 10
Power Transmission and Distribution
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Calculation of the Fault Resistance RE
(50Hz/60Hz- Voltage Injection)
100V 42V u
Digitalprotection(7UM62)calculationof RE
RE CE
RV CK
RV CK
L1 L2 L3
iL1)
1) Recommendedat static excitationwith inject harmonics(3rd harm.; 6th harm.)
Power Automation 11
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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
VE2
E2
E
2EE *R -
, ZR
XR
XRR
ZZRZ j meMess I
2E
2E
E2
EK
2EE
2EE
V
- - j
2
ersXR
XR*X
XR
XR*RZ
Km2E
2E
E2
E -
, *XZ
XR
XRX I
V
Ve
2Km
2
E - e -
- - , ,
, *RZR
*RZR
*XZR
R
XR
I
Power Automation 12
Power Transmission and Distribution
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Earth Fault Resistance CalculationLogic
Power Automation 13
Power Transmission and Distribution
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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)
Power Automation 14
Power Transmission and Distribution
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Injection of Square Wave Voltage with Low Frequency Basic Diagram
Excitation
+
-CE
RE
Digital Protection (7UM62)
UH
RV
RV
Ucontrol
Umeas.RM
7XR6004
Controlling device(7XT71)IE
Measuring transducer
RE Fault resistanceRV Coupling resistorUH Auxiliary supply ( 50V)RM Measuring shunt resistorCE Rotor capacitance
Typical frequency:1 - 3 Hz
Power Automation 15
Power Transmission and Distribution
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Injection of Square Wave Voltage Connection Diagram (7UM62)
Connection on the phase to phase voltage
Exc.17
15
11
25
+
-
27
7XR600425
27
7UM62
7XT71
TD1K14
K13 +
TD2K16
K15 +
40 k
40 k
Control voltage
Measuring voltage
100 V110 V
120 V
9
7
Power Automation 16
Power Transmission and Distribution
Power AutomationProgress. It‘s that
simple.
Injection of Square Wave Voltage with Low FrequencyBasic Principle
RV
2
RECEUH
UMRM
UH
UM
UM
50V
- 50V
1,88V
- 1,88V
0,75V
- 0,75V
t
t
t
iE
50V
375
20k 2
H
M
V
U
R
R
EMM iRU
ER
5k ER
0 M UE
V 2
CR
EM
1 ~ R
U
Equivalent circuit:
Power Automation 17
Power Transmission and Distribution
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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
Udc
Udc1
UM1
UM2
UM3UM4
UM1 UM2 Udc2
UM
Power Automation 18
Power Transmission and Distribution
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Calculation Formulas
RECEUH
UMRM
RV
2
UM U1
U2
Algorithm
Voltage divider:
Filtering:
Amplitude-log frequency curve: fA = 800 Hz; N = 64
2- 1 -
2 V
MM
HE
M
MEV
M
H RR
U
UR
R
RRR
U
U
NNu
NUu
NU
1 ii2,2
1 ii1,1
1 ;
1
2
- : :
21
M
UUUU
1KK I I UU
8
1 kkU
8
1 U
0 30 60 90 120150180210240270300
0.001
0.01
0.1
1
f in Hz
G(f)
Continuity supervision:
Validity requirement
otherwise
Power Automation 19
Power Transmission and Distribution
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Logic Diagram Rotor Earth Fault Protection (1-3Hz)
Power Automation 20
Power Transmission and Distribution
Power AutomationProgress. It‘s that
simple.
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
Power Automation 21
Power Transmission and Distribution
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simple.
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
4µF
4µF
a) rotating diodes
b) separate Exciter (static excitation)
40k
Power Automation 22
Power Transmission and Distribution
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Generator with Rotating ExcitationFault Free Condition (Square Wave Principle)
Chance of charge ofrotor earth capacitance
Disturbances by the excitation generator
Power Automation 23
Power Transmission and Distribution
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Generator with Rotating ExcitationTest Condition with a Fault Resistor
Fault resistor is inverse proportional to the difference voltage
Power Automation 24
Power Transmission and Distribution
Power AutomationProgress. It‘s that
simple.
Parallel Operation of Rotor Earth Fault Protections
100V 42V
CK;4µF
CK;4µF
RK;105
RK;105RV;40k
RV;40k
RE
7UM62 7UM62uControl
uMeas.
iREF
uREF
7UM61
nuriREF
or
1- 3 Hz principle 50 Hz principle
Power Automation 25
Power Transmission and Distribution
Power AutomationProgress. It‘s that
simple.
Parallel Operation of Rotor Earth Fault ProtectionsMeasurement with the 50/60 Hz Principle
( )20k 2
RV
*KR *KC
ER
2 ll : * V
EE
RRR
20k 2
*
VE
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-earthresistance
Measurement:
measured as a fault resistance
Case 1:
Case 2:
alarm stage becomes less sensitive
open brushes can not be find out
Power Automation 26
Power Transmission and Distribution
Power AutomationProgress. It‘s that
simple.
RV
2
RERM
2CK
(8µF)
Umeas
U2
Measurement 7UM62 (1- 3 Hz)(CK is earthed for a DC voltage)
Equivalent circuit:
seen from the 7UM6:high rotor capacitance
capacitors will not becompletely 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