A ground relay system is provided which includes: first current transformers
located
in the respective phases of a sending end of a high-voltage distribution provided
from a distribution substation; over-current relays connected to the first transformers;
distribution transformers located in the respective phases in the respective sections
of the distribution; second current transformers connected to secondary sides of
the distribution transformers; current converters connected to the second transformers;
and a current comparator that introduces the currents of the respective phases
of the sending end of the distribution from the relays to produce a first zero-phase
current, introduces the currents of the respective phases of a load end of the
high-voltage distribution from the current converters to produce a second zero-phase
current, 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 current
is larger.
