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7/23/2019 02b_SGF100_procent_ protection.pdf
1/22
The year of Profitable Growth
Global networkof innovation
100% - Stator - Ground-
Fault Protection
7/23/2019 02b_SGF100_procent_ protection.pdf
2/22
Power Automation 2
Power Transmission and Distribution
Power AutomationProgress. Itsthatsimple.
Presenter: Dr. Hans-Joachim Herrmann
PTD PA13
Phone +49 911 433 8266E-Mail: [email protected]
Generator Protection
100%-Stator-Ground-Fault
Protection
7/23/2019 02b_SGF100_procent_ protection.pdf
3/22
Power Automation 3
Power Transmission and Distribution
Power AutomationProgress. Itsthatsimple.
Basic ProblemFaults Close to the Star Point
V0Displacement voltage
At faults close to the star point V0 goes to zero. Protection criteriadisplacement voltage and ground current do not work.
Alternatives: Evaluation of 3rd harmonics in the zero sequence voltage Additional injection of low frequency voltage into the star
point (20 Hz =Siemens principle)
U0
7/23/2019 02b_SGF100_procent_ protection.pdf
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Power Automation 4
Power Transmission and Distribution
Power AutomationProgress. Itsthatsimple.
Distribution of 3rd Harmonics in a Generator
V0 3.Harm(V03H>)
V0 3.Harm(V03H
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Power Automation 5
Power Transmission and Distribution
Power AutomationProgress. Itsthatsimple.
Considered Notes at the Applicationof 3rd Harmonics
? The distribution of 3rd. harmonics can be different fromgenerator to generator - the application of this principle canbe sometimes determined only during a primary test
? The harmonics (e.g. measuring location at the star point)are detectable not before the nominal voltage is available
? The part of harmonics depends also from the operationcondition of the generators (Influence of active and reactivepower)
- Application is not always possible
- Application has a restricted operating range
7/23/2019 02b_SGF100_procent_ protection.pdf
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Power Automation 6
Power Transmission and Distribution
Power AutomationProgress. Itsthatsimple.
Measurements on a Generator
V0
G
7UM 61ILU0
VLILV0
1. Test device 7UM 61
2. Test device 7UM 61
6 MVA; Yd55,25/58,3 kV
6 MVA5250 V
400 Rpm
45 VA5P20
800/5 A
606 Ohm5250 100 100
?3 ?3 3 V5250?3
100 V60 kV
5 %+-
7/23/2019 02b_SGF100_procent_ protection.pdf
7/22
Power Automation 7
Power Transmission and Distribution
Power AutomationProgress. Itsthatsimple.
Measurements on a GeneratorInfluence of the Active and Reactive Power
Influence of theactive power isvisible
Approx. 15 V measured
without load
Release of theprotection functionat a determinedactive power is
recommended
150-Hz-Voltage at the star point as a function of
active power; Parameter reactive power
0
20
40
60
80
100
120
140
0 1 2 3 4 5 6
Active Power in MW
150-Hz-voltagein
V
150 Hz at Q = - 2 MVar 150 Hz at Q = 0 MVar
150 Hz at Q = 2 MVar 150 Hz at Q = 4 MVar
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Power Automation 8
Power Transmission and Distribution
Power AutomationProgress. Itsthatsimple.
Comparison ofMeasuring Resultsbetween Star Pointand Terminals
Reactive Power 2 MVar
-150
-100
-50
0
50
100
150
200
250
300
0 2 4 6 8 10 12
Stator (0= star point; 10= terminal)
150-Hz-
voltage
in
V
P 2 MW P 3 MW
P 4 MW P 5,6 MW
Earth fault at 2 MVar and 4 MW
During an ground fault onthe star point the dis-
placement voltage on theterminal side was lowerthan the 3rd harmonics atfull load.A higher voltage wasexpected.
7/23/2019 02b_SGF100_procent_ protection.pdf
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Power Automation 9
Power Transmission and Distribution
Power AutomationProgress. Itsthatsimple.
Fault RecordSwitching OFF of a Generators during Full Load
Generator: 25 MVA, 6,3 kV
iL3
VL3
VE
3rd harmonicsdrops
7/23/2019 02b_SGF100_procent_ protection.pdf
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Power Automation 10
Power Transmission and Distribution
Power AutomationProgress. Itsthatsimple.
0 50 100 150 200 250 300 3500
2
4
6
8
10
Zeit in ms
Spannung
inV
10
0
5.58
9.3
U03hi
knU
10 tan( )i
312.633.344
181
tai
Fault on a Transmission Line (Ph-E ?) -An increasing of3rd harmonics on a broken delta winding was observed.
Pickup generatorovercurrentprotection
Drop off overcurrentprotection
Time in ms
Calculated 3rd harmonicsfrom a fault record
Secondarydisplacementvoltage(3rdharmonics
)
3rd harmonicsunder load
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Power Automation 11
Power Transmission and Distribution
Power AutomationProgress. Itsthatsimple.
Logic Diagram
PreferredConnection:Star point(V3.H
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Power Automation 12
Power Transmission and Distribution
Power AutomationProgress. Itsthatsimple.
Injection of a 20-Hz-voltage into the Star Point
Basic idea ? With the injection of a voltage into thestar point a electromotive force isavailable in case of an ground fault
? Also during an ground fault in the starpoint a fault current flows through thefault resistance.
? This measuring principle is independentfrom the operation conditions of thegenerator. A measuring during stand stillis possible.
? Following additional devices arenecessary:
20-Hz-Generator,20-Hz-Band passCurrent CT
20 Hz
RE
max.200 V
I
7/23/2019 02b_SGF100_procent_ protection.pdf
13/22
Power Automation 13
Power Transmission and Distribution
Power AutomationProgress. Itsthatsimple.
20-Hz-Measuring Principle is the Real100%-Stator Ground Fault Protection
U0
100 % protection range includes VTsand low side of unit transformer
? Measuring principle is independent from the operationconditions of the generator
? Measuring is possible during stand still of the generator
? High sensitivity (negative influence of capacitive currentwill be eliminated)
? Different and independent measuring principle againstthe displacement measuring method
90 % protection range with displacement voltage measurement
10 % -25 % Protection range of 3rd harmonic, with additional limits(see previous slides)
7/23/2019 02b_SGF100_procent_ protection.pdf
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Power Automation 14
Power Transmission and Distribution
Power AutomationProgress. Itsthatsimple.
Basic Scheme - Unit ConnectionInjection via Grounding or Neutral Transformer
Load resistor should be> 0,5 ?
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Power Automation 15
Power Transmission and Distribution
Power AutomationProgress. Itsthatsimple.
Scheme DesignGas Turbine with Neutral Transformer
Currenttransformer:Direct orderat RitzKS60-03 Size 315VA Cl.1 FS5
UER13
R14
RL
Neutral
transformer
J7
J8
TD3
K18
K17 +
UErrExcitation
TD1K14
K13 +
IEE1
7XT33
7XT34
20-Hz-
Generator20-Hz-
Band pass
4A3
4A11B4
1A1
1A2
1A3
3A2
3A1
3A3
1B1
Wiring shielded
400A
5A
max 200 V
kl
7KG6+ 31
- 32
+ 12
- 11 (Amplifier)
max. 10 cm Wiring twisted and shielded
Shunt:10 A/ 150 mV
2A1
2A3BE
+UH-UH
UL1UL2
UL3
Deviceready
Auxi liary
voltage
DC AC
external
block
KL
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Power Automation 16
Power Transmission and Distribution
Power AutomationProgress. Itsthatsimple.
100%-Stator Ground-Fault ProtectionNumerical Design
Replica:
ises
ises Vses
20HzRE RBCE
RE = Fault resistance
CE = Ground capacitance instator circuit
Vses
ises
1) Filtering
3) Impedance replica of fault 4) Calculation of fault resistor from 2) and 3)
2) Calculation of the real part
Yers CE RE Yers =1
RE
+ j ? CE RE =V2r+ V
2i
Vr. Ir + Vi
. Ii
Re
Vr. Ir+ Vi
. Ii
V2r+ V2
i
Fourierfilter
(20Hz)
V20 = Vr+ jVi
I20 = Ir+ jIi=
???
???
20
20
V
I
7/23/2019 02b_SGF100_procent_ protection.pdf
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Power Automation 17
Power Transmission and Distribution
Power AutomationProgress. Itsthatsimple.
Filter Coefficients of the 20-Hz-FIR Filter
0 10 20 30 40 50 60 702
0
21.989
1.733
af1
bf1
630 f1
af1
cos 2 ?
32
f1 0.5( )? 1 cos 2 ? f1 0.5
64
??
bf1
sin 2 ?
32f1 0.5( )? 1 cos 2 ?
f1 0.5
64??
Filter window: 4 cycles (64 filter coefficients)
7/23/2019 02b_SGF100_procent_ protection.pdf
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Power Automation 18
Power Transmission and Distribution
Power AutomationProgress. Itsthatsimple.
Compensation of Sources of an Error
? Angle error of CT 400A/5A
(measuring currents in mA - 20 Hz current can be max. 3A )
? Primary to secondary impedance of the grounding/ neutraltransformer
? Angle errors of relay transformers
Compensation of the angle error via parameter(5309 PHI I SES Correction angle for I SGF)
Primary to secondary resistance from grounding orneutral transformer can be set (that is New)(5311 SGF Rps Resistance Rps)
Calibration is only for one point possible, e.g. Trip stage
Final settings during the primary test
7/23/2019 02b_SGF100_procent_ protection.pdf
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Power Automation 19
Power Transmission and Distribution
Power AutomationProgress. Itsthatsimple.
Fault Record during a Primary Test
At the device
inputs aresmallsecondaryvalues
The capacitivecurrent is visible.This disturbance
current will beeliminated by thealgorithm.
Phase to groundvoltage
Displacementvoltage
Ground current
7/23/2019 02b_SGF100_procent_ protection.pdf
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Power Automation 20
Power Transmission and Distribution
Power AutomationProgress. Itsthatsimple.
100 % Stator Ground Fault Protectionwith Primary Load Resistor
UER13
R14
RL
J7
J8 IEE1
7XT337XT34
20-Hz-Generator20-Hz-
Bandpass
4A3
4A11B4
1A1
1A2
1A3
3A2
3A1
3A3
1B1
2A1
2A3BI
+UH-UH
UL1UL2UL3
Device
ready
Aux.
voltage
DC AC
external
Block
1A4 1A3
UN
?3500 V
CT Ratio 1: 1
Voltagetransformer
7UM62
1A1
Voltage transformer:two pole isolated,until VN saturation freefor 20 Hz should be Rps< 1000?20s approx. 3 kVA
Current transformer:5P10 or 5P15 (or 5FS10)1A secondaryCT Ratio: 1A/1A(max. Ampere windings)
7/23/2019 02b_SGF100_procent_ protection.pdf
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Power Automation 21
Power Transmission and Distribution
Power AutomationProgress. Itsthatsimple.
Setting Sheet of the100% Stator Ground Fault Protection
Two Stages
Back-upovercurrent
Supervision
Calibration
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Power Automation 22
Power Transmission and Distribution
Power AutomationProgress. Itsthatsimple.
Logic Diagram