PSRC Line Protection SubcommitteeWorking Group D4

Application of Overreaching Distance Relays

Presented to the:

64th Annual Georgia TechProtective Relaying Conference

by Russell W. Patterson

Patterson Power Engineers, LLC

Atlanta, GAMay 5-7, 2010

Power System Relaying CommitteeScope:

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

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Power System Relaying CommitteeNew 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  

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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

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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

Chair: Russell Patterson Vice-chair: Walter McCannon

D4 Members

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Outline1. Introduction Why we are writing this document.

2. BackgroundA . Zone Descriptions

B . Purpose of overreaching distance zones; step-distance and pilot

C . Susceptibility of overreaching distance zones to undesirable operation

3. Application Practice A . Application of high-speed distance functions (forward and reverse) in pilot schemes

1 . Permissive and blocking schemes 2 . Phase versus ground distance

B . Stepped-distance and remote backup applications

1 . Remote backup by zone two or zone three

C . Special considerations:1 . Three-terminal applications 2 . Loadability limitations 3 . Power swing considerations (brief discussion of the existing practice, or the lack

thereof)

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4. Overreaching Distance Functions and Line Loadability:A . Definition of loadability and sample calculations

B . Zone Characteristics Impacting Loadability: 1 . 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

C . Means to prevent tripping on load:1 . Shaping the characteristics & load encroachment blocking

2 . Using ground directional overcurrent (67N) instead of Z2 in pilot schemes

3 . Maximum sensitivity angle (characteristic or torque angle) Considerations

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5. Overreaching Distance Functions and Power Swings: A . Power Swings and Their Impact on The Power System

1 . Impedances Seen by Distance Relays During Power Swings2 . Effect of Power Swings on Distance Relays3 . Means to Prevent Tripping on Power Swings.

B . Power-Swing Blocking and Tripping Functions1 . Power-Swing Blocking and Tripping Functions2 . Power-Swing Blocking and Tripping Principles3 . Additional Considerations4 . Distance Protection Requirements During OOS Conditions5 . Power Swing Protection During Single Pole Open Conditions6 . Three-Phase Faults Following Power Swings

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6. Alternatives to Remote Backup Application of Overreaching Zones: A. Local Breaker failure Protection SystemsB. Redundant Line Protection SystemsC. 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

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“Why we are writing this document.”

Overreaching distance relays tripping under load have played a partin 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.

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http://pes-psrc.org

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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

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