SU432629A1 - DEVICE FOR PROTECTION AGAINST LEAKAGE CURRENTS - Google Patents

Description

one

The invention relates to devices for protection against leakage currents.

A device for protecting against leakage currents in three-phase networks with insulated neutral is known, which contains interlocking leakage relays, three-phase and hitch chokes, a relay amplifier, a source of operational voltage and a U-shaped quadrupole.

When using known devices, there may be cases where the resistance and isolation of intact lines, perceived as a leakage, turn out to be lower than the disconnecting value of a single-phase leakage to which the network-wide one is set up (a relay. Re-enabling intact lines will be impossible under such conditions due to uninterrupted switching on and switching off of switching devices.

In order to increase the reliability of the device by reducing the settings of the blocking relays and eliminate its false triggering when re-supplying voltage to the unwired lines in the proposed device parallel to the output capacitor of the U-shaped quadrupole, the closing contact of the executive relay is added.

Pa drawing shows the proposed device.

A common network leakage relay 3 and three contactor 4, 5 6 are connected to the busbar / switchgear, connected to the power supply through the circuit breaker 2, and connectors of the feeders A, B and C, on which the blocking relays 7, 8 are installed. and 9 leaks.

The network-wide leakage relay contains a filter for connecting the operational circuit IK of the controlled network, consisting of three-phase 10 and zero 11 and 12 chokes, as well as a capacitor 13; a rectifier bridge 14 for feeding the operational circuit; relay amplifier running in relay mode / 5 s

an output to the executive relay 16, as well as a U-shaped quadrupole 17, composed of capacitors 18 and 19 connected by a resistor 20. Enter capacitor 2 into the circuit of the general network leakage relay to create a time delay when the relay 16 drops out. , 5 and 5, the feederosis of the relay 6 has rgz, wedged contacts 22, 23 and 24 in the coils of these contactors. Capacitor 19 at the output of four.

/ 7 is shunted by the closing contact 25 of the executive relay 16.

The blocking relays 8 and 9 leaks contain a filter attachment operational, made in three-phase throttle 26,

a rectifying bridge 27 for operating circuit 1 and a sensitive relay 28. A contact 29 of the relay 25 is inserted into the coil circuit 30 of the contactor 4. The latter has an interlock contact 3} B of the operational circuit of the interlocking leakage relay.

The device works as follows.

When a leakage current occurs after the clocks of the feeder contactor (for example, 4), the amplifier 15, changes its state in a jump-like manner, connects a coil, a relay 16 with a parallel co-capacitor 21 parallel to it to the power source of the amplifier 15. The capacitance of the capacitor 21 has almost no effect on the timing of the relay 16, since the resistance of the amplifier 15 is low and the charge of the capacitor 21 therefore occurs almost instantaneously. Relay 16 is triggered and opens its contacts 22, 23 and 24 in the coil circuits coit.ktorov 4, 5 and b. As a result, the feeders A, B and C are de-energized.

At the same time, the blocking contacts of the contactors, 4, 5 and 6, in the protective voltage circuit of their blocking leakage relays are closed. From this point on, the isolation control of waste transferors A, B and C is separately carried out.

As long as the leak, which caused the operation of the network-wide protection device, was separated from it by the contacts and contactor 4, the amplifier / 5 would abruptly return to its original state. However, the relay 16 does not immediately disappear, and for some time remains on due to the discharge of the co-detector 21. The delay time must be sufficient to activate the relay 28 and open its contact, 29 in the circuit of the coil 30 of the contactor 4. Turning off this contactor will become possible L, search after increasing the insulation resistance of the feeder A to a level at which the relay 28 disappears. The feed of the feeder with contactor 4 when the ethanol is restored automatically.

When the voltage is lowered during the discharge of the capacitor 21 to the value at which the relay .16 returns to the initial state, the power supply to the intact feeders B and C is automatically restored. The power of the .4 feeder can be restored automatically. resistance of its insulation to a certain level.

The relay 16 is activated. When the insulation resistance on feeders (for example, B and C) is slowly reduced to a critical level. By opening its contacts, cts 22, 23, 24, the relay: 16 de-energizes the outgoing feeders, and by closing the contact 25 discharges the capacitor

19. Since a slow reduction in the insulation resistance of a transient process does not occur in the operational circuit, the device triggers a resistance level much lower than the atomic discontinuity of the insulation. Since the setpoint of the interlocking relays by leaks of contactors 4, 5 and 6 is greater than the critical level of the general network relay 3 in a number of times equal to the number of fnders, the feeders B and C will always be blocked. This will prevent, despite the small value of the setting of the blocking relays, uninterrupted switching on - switching off the switching devices. When the voltage decreases during the discharge of the capacitor 21 to the value at which relay 16 returns to its initial state, the feeder A automatically restores power. Simultaneously opening contact 25 of this relay, the capacitor 19 is disconnected from the capacitor 19. Therefore, the output at the U-shaped is disconnected. the quadrupole 17 at the moment the feeder A is turned on is zero. As a result of this current surge, causing unjustified repeated disconnection of lines, does not occur. The current in operational value due to the charge of the output capacitor 19 of the quadrupole 17 through the resistor 20 increases smoothly to an established value determined by the isolation level of the feeder A. This prevents proper operation of the general network leakage relay if the isolation feeder turns out to be less than the setting sewn up for sudden leakage.

Item and Fancy

Device for protection against current c.

three-phase electric networks with insulated neutral, containing leakage relays connected to buses, substations, T | three-phase and zero chokes, a relay amplifier whose output includes an actuating relay, and a source of operating voltage, to a rectifier bridge which is connected to a U-shaped quadrupole consisting of two capacitors connected by a resistor, characterized in that

in order to increase the reliability of operation by reducing the settings of the interlocking relays and eliminating its false triggering when re-supplying voltage to non-damaged lines parallel to the output condenser of the U-shaped four terminal, the closing contact of the executive relay is turned on.