Electricity: electrical systems and devices – Safety and protection of systems and devices – With specific quantity comparison means
Patent
1997-05-30
1998-09-15
Gaffin, Jeffrey A.
Electricity: electrical systems and devices
Safety and protection of systems and devices
With specific quantity comparison means
361 63, 361 82, 361 94, H02H 318
Patent
active
058088458
ABSTRACT:
Negative sequence, positive sequence and zero sequence quantities are determined from voltage and current values for a power signal on a radial distribution feeder line. Negative sequence quantities are evaluated against selected threshold standards; the negative sequence impedance is also determined, which is then evaluated to determine fault direction (if a fault is indicated). If a reverse fault is declared, the trip output of overcurrent elements in the protective relay for the feeder is blocked for a selected period of time. The same evaluation process is carried out for zero sequence quantities. A selection process determines whether the negative sequence or the zero sequence element is to be enabled. Further, voltages and currents of all three phases of the power signal are evaluated to determine relative change over a period of one cycle. If within the one cycle there is a decrease of both voltage and current in all three phases of approximately 10%, the overcurrent elements are also blocked.
REFERENCES:
patent: 4293886 (1981-10-01), Church et al.
patent: 4825323 (1989-04-01), Wilkinson
patent: 4825327 (1989-04-01), Alexander et al.
Owen, Solutions to Sympathetic Tripping of Distribution Feed ers, May 2, 1977, Conference Presentation, Colorado Springs, CO.
Jackson, Synpathetic Tripping on Distribution Feeders, Apr. 12, 1993 (Conference Presentation, Texas A&M University).
Williams, Schmus and Hanson, Transmission Voltage Recovery Delayed by Stalled Air Conditioner Suppressors, IEEE Transactions on Power Systems, vol. 7, No. 3, Aug. 1992.
Gaffin Jeffrey A.
Schweitzer Engineering Laboratories Inc.
Sherry Michael J.
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