Electricity: electrical systems and devices – Safety and protection of systems and devices – Feeder protection in distribution networks
Patent
1991-09-03
1994-04-19
DeBoer, Todd E.
Electricity: electrical systems and devices
Safety and protection of systems and devices
Feeder protection in distribution networks
361 9, 361 58, H02H 308
Patent
active
053051742
ABSTRACT:
An electrical power system protection device includes a circuit breaker and a switch connected in series to a power line. The protection device also has a current limiting element connected in parallel to the circuit breaker. When the level of electrical current flowing in the power line, detected by a current detector, has exceeded a predetermined first set level, a first over-current detector delivers immediately a trip command to the circuit breaker. As a consequence, fault current is commutated to the current limiting element so that any drop of voltage in the power line upstream of the circuit breaker is greatly suppressed. When a state in which a predetermined second set level is exceeded by the detected current level is continued beyond a predetermined period, a second over-current detector delivers an off command to the switch, thus protecting the upstream portion of the power line against the fault in this power line. The current level is set to fall within a range which activates a momentary element of an over-current relay of a receiving end breaker of a downstream sub-system connected to the power line. In the event of a failure in the downstream power line, the receiving end breaker is tripped immediately so that the sound portion of the power line is reset to a normal state of operation.
REFERENCES:
patent: 4214289 (1980-07-01), Otsuka et al.
patent: 4351013 (1982-09-01), Matsko et al.
patent: 4791520 (1988-12-01), Stegmuller
patent: 4814932 (1989-03-01), Morelli
Arita Hiroshi
Kurosawa Yukio
Morita Masao
Ueda Toshiaki
Yamagiwa Tokio
Chubu Electric Power Co., Ltd.
Deboer Todd E.
Hitachi , Ltd.
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