PURPOSE: To realize a non-grounded type protective relay device also applicable to an especially high voltage system.
CONSTITUTION: Overcurrent relays 51H and 51L are connected on the secondary side of a three-phase current detector CTa. The relay 51H is set at a value, where the relay 51H is operated by short-circuit currents but is not operated by ground fault currents, and the relay 51L is set at a value, where the relay 51L is worked when the power flow of a system is brought close to the rated current value of the three-phase current detector CTa. The overcurrent relay 51H is set at a value larger than the setting of the overcurrent relay 51L. A directional ground relay 67a has high sensitivity, and is connected on the secondary side of the current detector CTa. A switch (normally closed) 510L is operated by the overcurrent relay 51L, a switch (normally opened) 670 is worked by the relay 67a, and a switch (normally opened) 510H is worked by the overcurrent relay 51H. The switch 510L is connected in series with 670, and the switch 510H is connected in parallel with the switches 510L and 670.
TAKEUCHI NOBUHIKO
OKAMURA ISAO
TAKI SHINYA
IIDA HAJIME
CHUBU HITACHI DENKI
| JPS5889025A | 1983-05-27 | |||
| JPS59122318A | 1984-07-14 | |||
| JPH0438118A | 1992-02-07 | |||
| JPS5138045A | 1976-03-30 |