MALFUNCTION PREVENTIVE CIRCUIT BY EXCITED RUSH CURRENT OF RATIO DIFFERENTIAL RELAY

摘要

PURPOSE:To prevent the malfunction by the excited rush current of a transformer using a ratio differential relay for which inrush current measure, etc., are not taken by closing the breaker on low voltage side after the rush current of the transformer decreases. CONSTITUTION:By making a breaker 2 on high voltage side, the auxiliary contact 2a of a breaker on high voltage side closes. At this time, the breaker 4 on low voltage side is not made yet, a trip control circuit is not formed. By making the breaker on low voltage side after the excited rush current of the transformer 3 attenuates, it comes that the auxiliary contact 40 of the breaker on low voltage side closes, that a trip circuit is formed, and that the contact 1a of a ratio differential relay 1 lives. Hereby, the contact of the ratio differential relay becomes effective after the excited rush current of the transformer attenuates, the malfunction by the excited rush current of the transformer can be prevented using a cheap ratio differential relay, for which inrush measures are not taken.