Residual current circuit breakers ground fault in electrical networks three-phase AC

摘要

The invention relates to electrical engineering, namely to the power supply system, and can be used for selective protection of single phase earth faults in underground workings and on the surface of coal and mining enterprises. Technical result of utility model is to increase the stability of the selective protection by eliminating the effect of "floating" power and reduce the load on the amplifier. A device for tripping of the earth fault, comprising TTNP, overvoltage protection circuit, the sensor 1 zero-sequence voltage, is connected to the monitored line. General sensor point via trimming resistor R3 is connected to ground, while TTNP sensor and a thyristor are connected to two amplifiers connected according to the "AND" and loaded on actuating relay K2, which contacts mounted in the switch circuit 4 and the circuit signaling 5. Scheme overvoltage protection is provided with a protective relay K1, K2 and the output relay via the relay contact K1 is connected to the second power supply line. When the closure phase on the amplifier input receives the same direction by half-wave voltage and is their opening and operates the output relay K2, whereby the network is disconnected and the circuit switched signaling. The apparatus provides stability selective protection within a predetermined range. To check the serviceability of the device close the keys Sn, wherein the current flows in both channels at the output relay K2, and it closes its contacts in the circuits. 1 z.p.f., 1 fig.