JPS54114739A - Overcurrent relay - Google Patents

Abstract

PURPOSE:To simplify the constitution of relay by omitting reactor by the method in which auxiliary relay is energized by the impedance drop voltage of relay coil. CONSTITUTION:The overcurrent relay consists of the relay coil 54 to drive the contact 55, the auxiliary relay coil 57 to drive the contacts 58 and 59, and the tripping coil 2 into which the secondary current of current transformer is introduced on energization of the coil 57. When a short-circuit fault occurred, the current transformer secondary side current I2, corresponding to short-circuit current, flows in the coil 54 and the contact 59 and the contact 55 is closed. At this time, the impedance drop voltage VCO due to I2 is produced at the both ends of the coil 54, and the VCO is then applied to the coil 57 and the contact 58 is closed. Then, I2 dividedly into the coils 54 and 57. In this case, since the auxiliary realy is not fed back even if the VCO is lowered, the contact 58 is closed and the contact 59 is opened. Accordingly, the I2 flows in the relay coil 54 and the tripping coil 2 and the breaker 1 is operated.