SU51480A1 - Device for increasing the power supplied to the relay by the direction of energy in earth fault protection with incomplete grounding - Google Patents

Description

The invention relates to a device for increasing the power supplied to the meter-relay in earth fault protection with incomplete grounding. The device differs from the known use of three energy direction relays, the shunt windings of which are connected to the line voltages of the protected system, and the series windings flow around the current coinciding in phase with the neutral voltage of the system relative to ground; the contacts of these relays are connected in series in pairs, and through each such pair of contacts to the shunt winding of an earthing relay, the total phase voltage of the system is brought, which coincides in phase with the neutral voltage of the system relative to ground.

The idea of the device is that when ground to ground is connected to the shunt winding of the meter relay, the normal voltage / f of the grounded phase of the system, regardless of the magnitude of the zero-sequence voltage, is applied. The series winding of a power meter relay is connected in one of the well-known ways to the zero-sequence current. As a result, when grounding in the protected zone, the power supplied to the meter-based relay turns out to be proportional to al / -f, where a is the ratio of the zero-sequence voltage to the normal phase voltage of the system. In the well-known schemes (for example, in the AEG scheme, the indicated power is proportional to A. Uff, i.e.

v less by a factor.

The described device, the electrical circuit of which is shown in the drawing, consists mainly of three energy direction relays 7, 2 and 5 with two-sided contacts. The serial windings of these relays are connected in series, and the neutral voltage of the system relative to ground is connected to them through the limiting resistance R. Interfacial voltages of the system are applied to the shunt windings; The L, B, C, and L wires from the voltage transformer (three phases and zero). Due to such switching-on, when grounding a single phase of the system, two any relays will operate, depending on which phase is grounded. In this case, one relay will get positive power, and the other negative. Through the contacts of the energy direction relay I, 2 and 5, the shunt winding of the earth-powered earth relay (not shown in the diagram) supplies the full phase voltage of the grounded phase via line 5. For example, if phase L is grounded, then relay 2 will close the right contacts (positive torque), and relay 3 will close the left contacts (negative torque), and the full voltage of the relay 7 will be connected to the shunt winding of the wattmeter ground relay. in this case does not matter.

From consideration of the switching circuit it is easy to verify that when the fuses in the shunt winding circuit of the power direction relay fail, the device will not work falsely (either it will work correctly or it will not work at all).

For the sake of economy, a single device can be installed for each system, which serves the earth protection of all feeders that are attached to this system of women.

Since the magnitude of the voltage supplied to the schuntoBY winding of an earthing meter relay is almost always the same, i.e. equal to the phase voltage of the system, there is no need to apply throttles and a special voltage relay.

The proposed device can be simultaneously used to signal the grounding.

The sensitivity of the device will obviously depend on the power of moving the power direction relays and on the resistance value R. The latter, in order to increase the sensitivity of the device, can be done, for example, two-step. In this case, one stage should normally be shunted by means of a relay for raising the neutral voltage of the system relative to the earth, which operates on contact opening.

The application of the proposed device should allow: a) either to increase the sensitivity of the watt-meter ground fault protection (the author believes that the percentage of unprotected generator turns can be reduced by 4-5 times); b) either reduce the ground fault current; c) either to increase the power of moving the watt-meter relay for protection against earth fault, which, in turn, should lead to a decrease in the suction of the switching current, since the relay can be used with a smaller impedance serial winding.

The subject matter of the invention.

A device for increasing the power supplied to the power direction relay B earth-fault protection with incomplete grounding, characterized in that three wattmeter-type relays are used, in which the shunt windings are connected to the linear voltages of the system being protected and the contacts are connected in series in pairs , and each such pair of contacts is connected to a circuit that supplies the phase voltage of the system to the shunt winding of the energy direction relay, which coincides in phase with the neutral voltage relative to ground, with the series winding the relays are connected to the neutral voltage of the system of 0 ground.

to the author's certificate of V.E. Kazansky

L 51480

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