PSRC Line Protection Subcommittee Working Group D4 Application of Overreaching Distance Relays Presented to the: 64th Annual Georgia Tech Protective Relaying Conference by Russell W. Patterson Patterson Power Engineers, LLC Atlanta, GA May 5-7, 2010

Power System Relaying Committee Scope: Standards, technical papers and guide the industry relative to the protection system, including communication between, among and within relays and relay systems. Maintenance of liaison and collaboration as required with other committees of the Power & Energy Society and associated Groups and Societies of the IEEE. Web Site: http://www.pes-psrc.org/ Upcoming Meetings: May 10-14, 2010 Madison, WI September 13-16, 2010 Berkeley, CA January 10-14, 2011 Atlanta, GA 2 of 30

Power System Relaying Committee New or Revised Standards: Guide for Power System Protection Testing (C37.233) Guide for the Protective Relay Applications to Power Systems Buses (C37.234) Synchronous Generator Tutorial Revision (95-TP-201) Reports Published: Understanding Microprocessor-Based Technology Applied to Relaying Adjustable Speed Drive Motor Protection Applications and Issues Ancillary Protective and Control Functions Common to Multiple Protective Relays   3 of 30

PSRC Subcommittees B – Advisory Committee C – Systems Protection Subcommittee D – Line Protection Subcommittee H – Relay Communications Subcommittee I – Relaying Practices Subcommittee J – Rotating Machinery Subcommittee K – Substation Protection Subcommittee 4 of 30

D4 Members Chair: Russell Patterson Vice-chair: Walter McCannon R. Beazer G. Benmouyal G. Brunello J. Burger S. Chano A. Darlington P. Elkin Walt Elmore D. Fontana R. Haas B. Kasztenny B. Kennedy C. Kim, Suwon Kyunggi-do G. Kobet R. Lavorin F. Lopez M. McDonald P. Mysore M. Nagpal C. Rogers S. Sambasivan M. Schroeder G. Sessler D. Tziouvaras E. Udren Q. Versosa T. Wiedman 5 of 30

6 of 30 Outline 1. Introduction Why we are writing this document. 2. Background . Zone Descriptions . Purpose of overreaching distance zones; step-distance and pilot . Susceptibility of overreaching distance zones to undesirable operation 3. Application Practice . Application of high-speed distance functions (forward and reverse) in pilot schemes . Permissive and blocking schemes . Phase versus ground distance . Stepped-distance and remote backup applications . Remote backup by zone two or zone three . Special considerations: . Three-terminal applications . Loadability limitations . Power swing considerations (brief discussion of the existing practice, or the lack thereof) 6 of 30

7 of 30 4. Overreaching Distance Functions and Line Loadability: . Definition of loadability and sample calculations . Zone Characteristics Impacting Loadability: . Variations in Zone Positioning a. Mho characteristic angle adjustment - maintaining a given mho circle b. Offsetting of mho characteristics 2. Variations in Zone Shape a. Lens characteristic b. Rectangular (Quadrilateral) characteristic 3. Supervision of Zone tripping a. Use of blinders b. Use of load encroachment characteristics . Means to prevent tripping on load: . Shaping the characteristics & load encroachment blocking . Using ground directional overcurrent (67N) instead of Z2 in pilot schemes . Maximum sensitivity angle (characteristic or torque angle) Considerations 7 of 30

5. Overreaching Distance Functions and Power Swings: . Power Swings and Their Impact on The Power System . Impedances Seen by Distance Relays During Power Swings . Effect of Power Swings on Distance Relays . Means to Prevent Tripping on Power Swings. . Power-Swing Blocking and Tripping Functions . Power-Swing Blocking and Tripping Principles . Additional Considerations . Distance Protection Requirements During OOS Conditions . Power Swing Protection During Single Pole Open Conditions . Three-Phase Faults Following Power Swings 8 of 30

6. Alternatives to Remote Backup Application of Overreaching Zones: A. Local Breaker failure Protection Systems B. Redundant Line Protection Systems C. Communication Applications D. Direct Transfer Tripping and other Teleprotection Applications 7. References 8. Bibliography Appendix A. Zone 3 and Load Power Appendix B. NERC Interim Requirements for Line Loadability Appendix C. Effect of Fault Resistance in Loop System Appendix D. Transmission Circuits Protection Schemes and Limitations 9 of 30

“Why we are writing this document.” Overreaching distance relays tripping under load have played a part in many major blackouts. August 14th, 2003 November 9th, 1965 November 4th, 2006 In an effort to help protection engineers avoid repeating history this document is being written to describe some of the susceptibilities of distance relaying and methods to circumvent them while adequately providing the intended protection function these relays are in place to provide. 10 of 30

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Power System Relaying Committee http://pes-psrc.org/ Upcoming Meetings: May 10-14, 2010 Madison, WI September 13-16, 2010 Berkeley, CA January 10-14, 2011 Atlanta, GA 30 of 30