Transcript Improving Relay Performance By Off-line and On

Improving Relay Performance By Offline and On-line Evaluation
Mladen Kezunovic
Jinfeng Ren, Chengzong Pang
Texas A&M University, USA
CIGRE 2009
September 7 – 10, Moscow, Russia
©2009 Mladen Kezunovic.
Outline
 Introduction
 Off-line Performance Evaluation
 On-line Performance Evaluation
 Automated Post-mortem Analysis
 Case Studies
 Conclusion
©2009 Mladen Kezunovic.
Introduction
 Protective relays are designed to meet dependability and security
expectations. Occasionally, some complex condition may cause
relays to perform unintended or incorrect operation.
 Techniques and tools for performance evaluation can detect
problems with relay settings, applications or design defects.
 Two broad categories:
 On-line: Use records from relays or DFRs and innovative techniques,
such as wavelet transform, synchrophasor, expert system, to monitor,
characterize or improve operation performance.
 Off-line: Use modeling and simulation approaches or field records to
generate files for relay testing.
©2009 Mladen Kezunovic.
Introduction Cont’d
 Three sets of tools and associated methodologies were
developed over 15 year time-span:
 Relay testing
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Simulator replays of simulated or recorded waveforms
Applied for design and application tests
Test cases library was developed
 Real-time field evaluation
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Use accurate fault location techniques and fault decision-tree model
Unintended operation due to line overloading
Misoperation due to hidden failure
 Automated post-mortem analysis
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Use expert system to analyze field records
Relay operation and related fault clearing sequences
Cause-effect analysis in relay operation, communication channels and circuit breakers
©2009 Mladen Kezunovic.
Outline
 Introduction
 Off-line Performance Evaluation
 On-line Performance Evaluation
 Automated Post-mortem Analysis
 Case Studies
 Conclusion
©2009 Mladen Kezunovic.
Performance Test Methodology
 Conformance Test
• Evaluate relay design functionality and operating characteristic
• Verify relay settings
• Test cases include variety of disturbances from simulation or field records
• Statistical performance for operating characteristic and trip time
 Compliance Test
• Verify whether relay can operate as expected under peculiar
circumstances in power system particularly during abnormal operating
conditions, such as power swing, load encroachment, etc.
• Vulnerable scenarios that may cause unintended operation are applied
• Trip/no trip response and operating time are concerned
Transient signals are applied for both types of tests.
©2009 Mladen Kezunovic.
Performance Test Methodology Cont’d
 Two power networks are used to generate various disturbance
scenarios for performing conformance test and compliance test
 Reference model by IEEE PSRC
 IEEE 14-bus system
 One line diagram and ATP model for PSRC system
©2009 Mladen Kezunovic.
Test Implementation
• Developed programs and commercial software running on a PC to automate
test procedures including creating test cases, configuring relays, replaying
waveforms and retrieving event reports.
• Digital simulator generates “real” voltage and current signals to relay.
 Test implementation framework and laboratory setup
©2009 Mladen Kezunovic.
Test Case Library
Library includes:
• Test cases for conformance and compliance tests
• Scenarios for abnormal operating conditions and vulnerable cases
• Waveforms from field records and blackout events
It can be used widely as a reference of test cases for relay performance
evaluation and trouble shooting.
 Diagram of test case library
©2009 Mladen Kezunovic.
Outline
 Introduction
 Off-line Performance Evaluation
 On-line Performance Evaluation
 Automated Post-mortem Analysis
 Case Studies
 Conclusion
©2009 Mladen Kezunovic.
On-line Performance Evaluation
 Neural Network Based Fault Detection and Classification
(NNFDC) Algorithm for fault classification
• Utilizes artificial intelligence technique
• Using the time-domain voltage and current signals directly as patterns
instead of calculating phasors
• Training and testing
 Fuzzy ART neural network algorithm
©2009 Mladen Kezunovic.
On-line Performance Evaluation Cont’d
 Synchronized Sampling Based Fault Location (SSFL) Algorithm
• Very high accuracy in fault detection, classification, and location
• Using raw samples of voltage and current data synchronously taken from
two ends of the transmission line
• Immune from power swing, overload, fault resistance and switching
situation
 Event Tree Analysis
• Allowing Event/response modeling
• Identifying the consequences following an occurrence of an initial event
• Providing an efficient way for real time observation of relay operations
©2009 Mladen Kezunovic.
Outline
 Introduction
 Off-line Performance Evaluation
 On-line Performance Evaluation
 Automated Post-mortem Analysis
 Case Studies
 Conclusion
©2009 Mladen Kezunovic.
Automated Post-mortem Analysis
 Relay operation analysis is based on the comparison of expected and actual
protection operation and corresponding timing of relay logic operands.
 Expert system based application
• Forward chaining reasoning: to predict expected protection operation.
• Backward chaining reasoning: to validate and diagnose actual operation.
 Block diagram for conceptual strategy of post-mortem analysis
©2009 Mladen Kezunovic.
Outline
 Introduction
 Off-line Performance Evaluation
 On-line Performance Evaluation
 Automated Post-mortem Analysis
 Case Studies
 Conclusion
©2009 Mladen Kezunovic.
Case Studies
 Off-line relay testing
Three different distance relays are studied. Different cases were simulated with
different type of faults, locations and inception angles. Each test is repeated 30 times
and operating time is computed statistically.
• Different operating time for the same zone
• Deviation of operating time for the same fault
 An example of statistical test results
©2009 Mladen Kezunovic.
Case Studies Cont’d
 Off-line relay testing
• Relays are set to operate in zone 1
coving 80% of the line.
• Comparative analysis of trip time vs.
fault location for three distance
relays.
• The trip time for some relays were
much longer than expected.
 An example of comparative test results
Tests indicate:
• Some relays operated as unintended by either over-reaching or under-reaching in
some conditions.
• Zone 3 relays operated incorrectly by tripping unfaulted lines during some
abnormal operating conditions, particularly under power swing and heavy
loading conditions.
©2009 Mladen Kezunovic.
Case Studies Cont’d
©2009 Mladen Kezunovic.
Case Studies Cont’d
©2009 Mladen Kezunovic.
Case Studies Cont’d
©2009 Mladen Kezunovic.
Outline
 Introduction
 Off-line Performance Evaluation
 On-line Performance Evaluation
 Automated Post-mortem Analysis
 Case Studies
 Conclusion
©2009 Mladen Kezunovic.
Conclusion
 Three methodologies and tools for relay performance evaluation
are developed
 The proposed relay testing may help validate the design of the
relay logic, characterize the relay operation behavior, verify
selection of relay settings and identify vulnerable conditions apt
to causing unintended operations
 The on-line advanced fault analysis helps in improving the
accuracy of fault analysis under cascading events
 The expert system based post-mortem analysis helps to identify
incorrect settings and trace component malfunctions
©2009 Mladen Kezunovic.
©2009 Mladen Kezunovic.