1. ©2009 Mladen Kezunovic. Improving Relay Performance By Off-line and On-line Evaluation Mladen Kezunovic Jinfeng Ren, Chengzong Pang Texas A&M University, USA CIGRE 2009 September 7 – 10, Moscow, Russia

2. ©2009 Mladen Kezunovic. Outline  Introduction  Off-line Performance Evaluation  On-line Performance Evaluation  Automated Post-mortem Analysis  Case Studies  Conclusion

3. ©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.

4. ©2009 Mladen Kezunovic. Introduction Cont’d  Three sets of tools and associated methodologies were developed over 15 year time-span:  Relay testing Simulator replays of simulated or recorded waveforms Applied for design and application tests Test cases library was developed  Real-time field evaluation 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 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

5. ©2009 Mladen Kezunovic. Outline  Introduction  Off-line Performance Evaluation  On-line Performance Evaluation  Automated Post-mortem Analysis  Case Studies  Conclusion

6. ©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.

7. ©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

8. ©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

9. ©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

10. ©2009 Mladen Kezunovic. Outline  Introduction  Off-line Performance Evaluation  On-line Performance Evaluation  Automated Post-mortem Analysis  Case Studies  Conclusion

11. ©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

12. ©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

13. ©2009 Mladen Kezunovic. Outline  Introduction  Off-line Performance Evaluation  On-line Performance Evaluation  Automated Post-mortem Analysis  Case Studies  Conclusion

14. ©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

15. ©2009 Mladen Kezunovic. Outline  Introduction  Off-line Performance Evaluation  On-line Performance Evaluation  Automated Post-mortem Analysis  Case Studies  Conclusion

16. ©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

17. ©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.

18. ©2009 Mladen Kezunovic. Case Studies Cont’d

19. ©2009 Mladen Kezunovic. Case Studies Cont’d

20. ©2009 Mladen Kezunovic. Case Studies Cont’d

21. ©2009 Mladen Kezunovic. Outline  Introduction  Off-line Performance Evaluation  On-line Performance Evaluation  Automated Post-mortem Analysis  Case Studies  Conclusion

22. ©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

23. ©2009 Mladen Kezunovic.