To prevent the unnecessary power interruption of the entire distribution system by an earth accident by making the directions of the earth circuit and an earth detecting directional relay the same, and cutting off a breaker of a timer which has the fastest performance when the earth current enters a breaker for a feeder from a point of the earth accident through a distribution loop circuit.
A line 2 for receiving power is connected to a special high voltage line 1 connected to a power transforming station, then an earth switch 3, a disconnector 4, a breaker 5, and a transformer 6 are connected to step down special high voltage to high to voltage, and then a distribution loop circuit which is a high voltage bus is connected. A grounded transformer for measurement or capacitive voltage detector for grounding 8 is connected to a distribution loop 7, and feeders 10, 11 are also connected to the distribution loop 7. Each of the feeders 10, 11 is provided with a disconnector 12, 13 for a feeder, an earth current detector 14, 15, the grounded transformer for measurement or capacitive earth voltage detector 8, and an earth detecting directional relay 16, 17 which is used in combination with the earth current detector 14, 15. Due to this structure, the reliability of supplying power can be increased.
KURITA KAZUO
KANO KAZUO
WATANABE KENICHIRO
OHBAYASHI CORP