ppt power system fault simulation - tata power
TRANSCRIPT
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Simulation of Power System Faults for Protection Performance Analysis
-Case Studies of Tata Power By
S G Patki M V Kini P K Jain G T Jawale
Presented at:International Conference on Power System Protection,
CPRI, Bangalore
20-21st February, 2007
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Introduction
Need for Simulation Tool
Methodology Adopted for Power System Simulation
Salient features of Dynamic test kit
Setup of Dynamic test kit
Benefits of Analyzing faults using Simulation Tool
Two case studies – 1. Mal-operation of Protection
2. Non-operation of Protection
Overview
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TPC Inducted Numerical Protection Relays and Fault Disturbance Recorders (FDRs) since early 90s
Fault details can be obtained from the Software supplied by FDR Manufacturers. Some software include tools for
a) Distance to fault location
b) Impedance Locus
c) Harmonic analysis, etc
Advantage of stand-alone FDR – High Sampling Rate for event recording. Therefore, Reproduction of disturbance record captured by Standalone FDR found to be better than the events recorded byNumerical Protection Relay
Introduction
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Numerical Protection relays of different makes, types and version can exhibit different behavior during abnormal power system condition
Selection of Appropriate relays
Routine and Acceptance Testing by conventional methods may not reveal the deficiencies in the relays either due to inherentprotection algorithm or due to incorrect adopted configuration /setting
Need for Simulation Tool
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Analyzing and comparing performance of Numerical relays during dynamic power system condition.
Dynamic Simulation tool allows simulation of power system condition as well as replay of captured current and voltage signals from fault disturbance records
Computer aided system simulation tool for analysing mal-operation / non-operation of protective relays
Methodology Adopted for PS Simulation
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Can be used without PC (local mode) or with PC
Can be used for testing relays based on Voltage, Current and Frequency in local mode
However, With PC, few advanced functions such as Replaying of disturbance records, injection of Harmonic voltages / currents, Automatic Relay Testing etc.
Attaching a pre-fault waveform to the waveform recorded during fault
Selection of CTR / PTR is possible in software depending on 1 / 5 Amp for currents and PT ratio for Voltage Waveform
Truncation of waveform to find out the point on the waveform where the relay has operated
Salient features of Dynamic test kit
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Setup of Dynamic test kit
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Benefits of using Simulation Tool
The disturbance records captured by the numerical relays and fault disturbance recorders can be used to simulate the disturbance and play the same on various types of devices
Fault library can be maintained and used for evaluating / accepting new relay products
Reduction in Cycle Time for acceptance testing of new relays
Analysis of the protection performance will help in improving the power system protection and maintaining grid stability
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Case Study – I: Mal-operation of Distance Relay
220 kV220 kV
Salsette
220 kV TPCL N/W
G
Tata Trombay
220 kV
MSETCL Trombay
Kalwa
3 Lines
MSEB N/W Bkrs Tripped
220 kV Trombay – Salsette line # 1 / 2 tripped by Distance Protection for fault in reverse direction
Details of the Line: Line Length – 23.98 km; CTR – 2000/1; PTR – 240 kV / 120 VLine Impedance: Z+/- = 1.457 + j 9.428; Zo = +j30.806
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Waveform captured by Disturbance Recorder during the fault
Waveform Produced by simulation tool for replaying on the relays
Case Study – I: Mal-operation of Distance Relay
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Protection Provided on Line – Main I (Distance), Main II (Distance) and Directional O/C relays
During the disturbance Main – II relay, which is of switched Distance relay type operated and Main I relay, which is of non-switched distance relay type did not operate
The Fault Disturbance Record captured is replayed on another type of non-switched relays and the relays found to be stable
Case Study – I: Mal-operation of Distance Relay
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Case Study – II: Non-operation of Under frequency Relay
Under frequency relays at receiving & Generating stations for Load shedding and Islanding Scheme
Under frequency relay of Islanding scheme at 110 kV Salsette R/S failed to operate during one of the System Disturbances. However, the fault got isolated by the operation of distance protection
Under frequency relay settings: Stage I: 47.6 Hz, 0.15 Sec
Stage II: 47.0 Hz, 0.2 Sec
During the disturbance, frequency dropped from 50.3 to 46.7 Hz and TPC system islanded from rest of the Grid
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Frequency TrendSystem islanding on 21/09/05 at 0958 hrs.
46
46.5
47
47.5
48
48.5
49
49.5
50
50.5
51
51.5
52
52.5
-12
-10
-8.5 -7
-5.5 -4
-2.4
-0.9
0.72
2.36
3.97
5.55 7.1
8.64
10.2
11.7
13.2
14.6
16.1
17.6
19.1
20.6
22.1
23.5 25
26.5 28
29.5 31
32.5 34
35.5 37
time (s)
Freq
uenc
y (Hz)
-df/dt = 2.5 Hz/s
df/dt = 0.45 Hz/s
2.43s
frequency plot during system disturbance
(recorded by frequency trend monitor)
Case Study – II: Non-operation of Under frequency Relay
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Waveform captured by Disturbance Recorder during the fault
Waveform Produced by simulation tool for replaying on the relays
Case Study – II: Non-operation of Under frequency Relay
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Under frequency relays was of static type self powered relay (Powered by PT Supply) with built-in U/V block at voltage below 70 % of rated voltage
Relay operation was getting inhibited due to under voltage condition on 110 kV bus during system disturbance
The Waveform was replayed on Numerical Relay on which U/V blocking can be set manually. Initially Numerical relay also didnot operate with U/V setting at 70 %. However, by lowering the U/V block setting, the relay operated correctly
Case Study – II: Non-operation of Under frequency Relay
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Conclusions
Numerical Protection relays of different makes, types and version can exhibit different behavior during abnormal power system condition. Conventional testing of the relays may not reveal thedeficiencies in the relays either due to inherent protection algorithm or due to incorrect adopted configuration / setting
The disturbance records captured by the numerical relays and fault disturbance recorders can be used to simulate the disturbance and play the same on various types of devices
The typical fault records can be preserved as fault library and used for evaluating new relay products
Analysis of the protection performance will help in improving the power system protection and hence contribute to grid reliability and stability