Ground relay system in a multiplex direct grounding system

A ground relay system in a multiplex direct grounding system comprising:

• a plurality of first current transformers located in the respective phases of a sending end of a high-voltage distribution provided from a distribution substation;
• a ground over-current relay connected to the plurality of first current transformers;
• a plurality of distribution transformers located in the respective phases in the respective sections of the high-voltage distribution;
• a plurality of second current transformers connected to neutral points at the secondary sides of the plurality of distribution transformers;
• a plurality of current converters connected to the plurality of second current transformers, respectively;
• and
• a current comparator that introduces a zero-phase current of the sending end of the high-voltage distribution from the ground over-current relay to obtain a first zero-phase current, introduces the zero-phase current of a load end of the high-voltage distribution line from the plurality of current converters and sums vector to obtain a second zero-phase current, compares the levels of the first and second zero-phase currents with each other, and operates a ground protection relay that opens a circuit breaker inserted at the sending end of the high-voltage distribution if the level of the first zero-phase current is larger.

A ground relay system in a multiplex direct grounding system comprising:

• a plurality of first current transformers located in the respective phases of a sending end of a high-voltage distribution provided from a distribution substation;
• a ground over-current relay connected to the plurality of first current transformers;
• a plurality of distribution transformers located in the respective phases in the respective sections of the high-voltage distribution;
• a plurality of second current transformers connected to neutral points at the primary sides of the plurality of distribution transformers;
• a plurality of current converters connected to the plurality of second current transformers, respectively;
• and
• a current comparator that introduces a zero-phase current of the sending end of the high-voltage distribution from the ground over-current relay to obtain a first zero-phase current, introduces the zero-phase current of a load end of the high-voltage distribution from the plurality of current converters and sums vector to obtain a second zero-phase current, compares the levels of the first and second zero-phase currents with each other, and operates a ground protection relay that opens a circuit breaker inserted at the sending end of the high-voltage distribution if the level of the first zero-phase current is larger.