System for detection of transients from a coupling capacitor voltage transformer used in a protective relay
AssigneeSchweitzer Engineering Laboratories, Inc.
InventorsJeffrey B. Roberts, Daqing Hou
Life of this patent
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Abstract
The voltage and current conditions on a power transmission line are monitored to determine the coincidence of a low voltage condition and a lack of a high current condition. The coincidence of those two conditions is indicative of a CCVT transient, and the tripping action from zone 1 distance elements is delayed for a period of 1.375 cycles. The tripping delay is supervised by a fault impedance determination, which, if a threshold is exceeded, the remaining portion of the time delay is eliminated, so that a trip is allowed if the time delay period has not expired.
Claims12
A system for detecting and compensating for a transient signal from a coupling capacitor voltage transformer used in a protective relay for a power system, comprising:
- means for detecting a low voltage condition on the power transmission line which would otherwise result in a trip signal to a circuit breaker for the system;
- means for detecting a high current condition on the power transmission line;
- means for time delaying the trip signal if a high current condition is not present when the low voltage condition is detected;
- and
- means for by-passing a remaining portion of the time delay, such that a trip signal is sent to the circuit breaker prior to expiration of the time delay, if a fault impedance determination achieves a selected characteristic prior to completion of time delay.
Dependencies are inferred from the claim text.