US 5,295,035 AGranted

Power distribution line protection system

AssigneeHitachi, Ltd.

InventorsKazuo Nishijima, Terunobu Miyazaki, Mitsuru Nakamura

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Abstract

A plurality of switches are arranged in a distributive manner on a distribution line connected to a power distribution substation, and the switches are connected respectively to fault detection relays. Each of the fault detection relays includes a memory circuit for holding a voltage resulting from a ground fault on the distribution line, and the time constants of the memory circuits are set to become greater in an ascending order from the power outlet of the distribution line. Owing to difference in the time constants, there are differences in the holding voltage of the memory circuits resulting from intermittent ground faults which precede a full ground fault. By utilizing the differences of holding voltage, the switch closest to the full ground fault as viewed from the power outlet of the distribution line is the first to open the circuit.

Claims5

Dependent claims

A power distribution line protection system comprising:

a distribution line connected to a power distribution substation;
a plurality of switches arranged distributively on said distribution line;
and
a plurality of protection equipments including a plurality of fault detection relays, respectively, each of said fault detection relays being connected to each of said plurality of switches, for on/off control thereof,
wherein each of said fault detection relays includes memory means for holding a voltage resulting from a ground fault on said distribution line;
wherein time constants of said memory means are set to become greater in an ascending order from the power outlet of said distribution line;
and
wherein according to different holding voltages at the memory means resulting from intermittent ground faults prior to a full ground fault, a switch is opened which is closest to the full ground fault as viewed from said power outlet.

5 more elements

Dependencies are inferred from the claim text.