Protection through a power transformer using compensated voltages and currents
AssigneeSchweitzer Engineering Laboratories, Inc.
InventorsDale S. Finney, Bogdan Z. Kasztenny
Life of this patent
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Abstract
A distance protection element for fault coverage through a transformer that introduces a break in the zero-sequence equivalent network is disclosed herein. Voltage and current signals from a delta (low) side of the transformer are obtained and compensated using wye (high) side neutral current and nominal values. The compensated voltage and current signals are used in a distance protection element to detect faults on the wye (high) side of the transformer. The distance protection element may be implemented in a generator protection device as backup distance protection.
Claims20
A generator protection relay of an electric power delivery system, the generator protection relay comprising:
- a signal processing subsystem to obtain power system signals and to produce:
- stator current signals related to phase currents of a stator of a generator;
- stator voltage signals related to phase voltages of the stator of the generator;
- and
- transformer neutral current signals related to a current on a neutral of a second side of a transformer, wherein the transformer receives electric power from the generator;
- a protection element to:
- determine a compensating current factor using the transformer neutral current signals;
- determine transformer second side compensated currents using the stator current signals and the compensating current factor;
- determine transformer second side compensated voltages using the stator voltage signals, and the compensating current factor;
- implement a distance element to detect a fault condition within a zone of protection using the determined transformer second side compensated voltages and the determined transformer second side compensated currents;
- and,
- assert a protective action upon determination of the fault condition.
A method for fault coverage through a generator step-up (GSU) transformer of an electric power delivery system, comprising:
- an intelligent electronic device (IED) in communication with the electric power delivery system obtaining
- transformer first side current signals related to phase currents of a first side of the transformer;
- transformer first side voltage signals related to phase voltages of the first side of the transformer;
- and
- transformer neutral current signals related to a current of a neutral of a second side of the transformer;
- determining a compensating current factor using the transformer neutral current signals;
- determining transformer second side compensated currents using the transformer first side current signals and the compensating current factor;
- determining transformer second side compensated voltages using the transformer first side voltage signals, and the compensating current factor;
- exciting a distance element with the determined transformer second side compensated currents and the determined transformer second side compensated voltages to determine a fault condition within a zone of protection;
- and,
- asserting a protective action upon determination of the fault condition.
A system for protecting an electric power delivery system that includes a transformer, comprising:
- a signal processing subsystem to obtain power system signals and to produce:
- transformer first side current signals related to phase currents of a first side of the transformer;
- transformer first side voltage signals related to phase voltages of the first side of the transformer;
- and
- transformer neutral current signals related to a current of a neutral of a second side of the transformer;
- a protection element to:
- determine a compensating current factor using the transformer neutral current signals;
- determine transformer second side compensated currents using the transformer first side current signals and the compensating current factor;
- determine transformer second side compensated voltages using the transformer first side voltage signals, and the compensating current factor;
- implement a distance element to detect a fault condition within a zone of protection using the determined transformer second side compensated voltages and the determined transformer second side compensated currents;
- and,
- assert a protective action upon determination of the fault condition.
Dependencies are inferred from the claim text.