GROUND FAULT PROTECTION RELAY SYSTEM AND GROUND FAULT PROTECTION METHOD

摘要

PROBLEM TO BE SOLVED: To improve reliability of ground fault protection for a parallel two-circuit power-transmission line of a high-resistance grounding system.

SOLUTION: In a ground fault protection relay system that protects a parallel two-circuit power-transmission line made up of first and second power-transmission lines, which are connected between a power transmission terminal bus line of a high-resistance grounding system and a power receiving terminal bus line grounded via a compensation reactor, from ground fault accident, the system includes: a main protection relay system that is used as main protection for protecting the parallel two-circuit power-transmission line from ground fault accident; first and second ground fault direction relay systems which are respectively installed to the first and second power-transmission lines and used as back-up protection of the main protection relay system; and first and second zero-phase current transformers which respectively detect first zero-phase current flowing through the first power-transmission line and second zero-phase current flowing through the second power-transmission line. The main protection relay system outputs a lock signal for stopping the operation of the first and second ground fault direction relay systems when the first zero-phase current and the second zero-phase current are approximately equal.

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