SU1101953A1 - Device for providing earth fault protection in isolated neutral system - Google Patents

Abstract

A DEVICE FOR EARTH-ENCLOSED PROTECTION IN A NETWORK WITH INSULATED NEUTRAL, containing a zero-sequence current relay, whose input is connected to a zero-sequence current sensor. a - to the first input of the coincidence unit, consisting of the first and second transistors, a high-frequency matching unit, whose input is connected to a zero-sequence voltage sensor, and a output to the second input of the specified coincidence unit, the output of which is connected to the unit power supply with a switch disconnecting switch, distinguished {{{{}} with the fact that, in order to exclude the on-off switch, 1 gt of damage to the connection with unresolved single-phase closures on the ground, an additional time relay introduced into it ennym normally closed auxiliary contact vyk.L1Ochatel. at the same time, the emitter-collector junction of the second transistor of the coincidence unit is shunted by the breaker contact: t () m of the relay relay.

Description

The invention relates to electrical engineering and is intended to provide protection against single-phase earth faults in networks with insulated neutral.

A device RTZ-50 containing a zero-sequence current filter, a DC amplifier, an executive relay and a power supply unit 1 is known.

However, the known device has a low reliability of operation after the elimination of single-phase short circuits on adjacent connections with damage, since this results in a long (up to 1 s) transitional phase voltage symmetry recovery mode, which leads to false alarms of this device.

It is also known a device for ground-fault protection in an insulated neutral network containing a zero-sequence current relay and a high-frequency matching channel and a matching unit on element I. This protection device has a higher reliability of operation in a transient mode of restoring the symmetry of phase voltages after the single-phase closing is eliminated on the ground 2.

However, the known device, in case the single-phase short circuit remains undetected and unrepaired, allows the actuator to be switched on a damaged connection, and when the single-phase short circuit is turned on, there are no high-frequency industrial frequency harmonics that occur at the moment of a single-phase ground fault, which is dangerous especially when working on mobile electrical installations.

The purpose of the invention is to exclude the inclusion of a switch of a damaged connection when the 1P-1X single-phase ground fault is not removed.

The goal is achieved by the fact that a device for protection against earth fault in a network with an insulated neutral, contains a zero-sequence current relay whose input is connected to a zero-sequence current sensor and the output to the first input of the coincidence unit consisting of the first and second transistors, a high-frequency matching unit whose input is connected to a zero-sequence voltage sensor, and an output to a second input of a specified matching unit, the output of which is connected to a power supply with disconnection guide coil switch, time switch additionally introduced, let the newly inputted NC contact of the switch block, the emitter-collector junction of the second transistor is shunted block matcher time relay break contact.

The drawing shows a diagram of the device.

The device consists of a zero-sequence current relay 1 consisting of

filter 2, tuned to the main industrial frequency harmonic, electronic relay trigger 3 on transistors of different structure of high frequency matching unit 4, consists of filter 5 tuned to high frequency (HF) harmonics, appearing at the time of single-phase ground fault, to eliminate spurious operation in the recovery mode of the symmetry of the phase voltages, the electronic relay-trigger 6, the drop-down unit 7, consisting of the first and second transistors 8 and 9, the time relay 10 with the opening contact 11 shunting in Ora transistor 9 coincidence unit 7, the power unit 12 with the tripping coil (QA) of the switch, a contactless relay

0 and one-shot, disconnecting the block-pin 13 switch.

The collector-emitter circuit of the input transistors of the electronic relay-triggers 3 and 6 includes RS-filters of parallel 5 type to increase noise immunity and narrow the frequency band to which the filters 2 and 5 are tuned.

In the initial state, the switch is turned off. The opening blocking contact 13 of the switch is closed, while the opening circuit 11 of the electronic time relay 10 is also closed and bypasses the transistor 9 of the coincidence unit 7.

When the switch is turned on, the auxiliary contact 13 opens, after 1.5-2 seconds the electronic time relay 10 is activated, the contact 11 is opened.

At the time of the occurrence of a single-phase closure, the inputs of the filters 2 and 5 of the zero-sequence current relay 1 and the high-frequency matching unit 5 receive 0 signals from the current sensors and zero-sequence voltage.

Filter 2 identifies the fundamental harmonic of the industrial frequency, and filter 5 identifies the high frequency harmonics of the industrial frequency, the frequencies of which are determined specifically for each connection. The selected signals from filters 2 and 5, respectively, arrive at the inputs of electronic relays-triggers 3 and 6. At the outputs of electronic relays-triggers 3 and 6, sequences of direct coal pulses are generated, which arrive at the bases of transistors 8 and 9 of block 7, which determines the time coincidence of their positive values, which determines the selectivity of the protection device. At the output of block 7, right-angle pulses are received at the control electrode of a low-power one-shot TRistor that produces pulses at the control electrode of a high-power trinistor contactless relay, which supplies current to the disconnecting switch coil.

When the switch is turned on again, if the single-phase earth fault is not eliminated, the switch is immediately turned off, as the second transistor 9 of the coincidence unit is bounded by the contact 11 of the electronic time relay 10 and the device operates as a simple current relay.

Thus, the device for protection against earth fault in networks with insulated neutral prevents the inclusion of a damaged connection in case of an unresolved earth fault and at the same time prevents false alarms on an intact connection in a transitional state of restoration of the symmetry of phase voltages, which ultimately increase safety and reduce the amount of electrical outages.

Claims (1)

A DEVICE FOR PROTECTING AGAINST CIRCUIT ON THE GROUND IN A NETWORK WITH INSULATED NEUTRAL, containing a zero-sequence current relay, the input of which is connected to a zero-sequence current sensor, and the output is to the first input of the matching unit, consisting of the first and second transistors, a high-frequency matching unit, the input of which connected to the zero-voltage voltage sensor, and the output to the second input of the specified coincidence unit, the output of which is connected to the power supply with a tripping circuit breaker coil, characterized it. that, in order to prevent the breaker of the damaged connection from being turned on during unrepaired single-phase earth faults, a time relay is additionally introduced into it, which is triggered by the newly introduced disconnecting block contact of the switch, while the emitter-collector junction of the second transistor of the coincidence block is bridged by the disconnecting contact of the time relay. §