SU1270830A1 - Device for compensating active earth-leakage current in electric network - Google Patents

Abstract

The invention relates to electrical engineering, in particular, to devices for compensating the active earth fault current in an electrical network. The purpose of the invention is to increase the accuracy of the device. With decreasing insulation resistance of one i fie.g

Description

from the network phases, the voltage on the neutral relative to the earth increases. This leads to the triggering of the phase-sensitive rectifier 4 of the damaged phase. The voltage from the output of the gate 4, reaching a predetermined value when comparing in the threshold element 5 with the reference voltage of the source 9, triggers the logic element AND block 6, from the output of which three signals are generated; one to open the switching element of the electronic key 7, and the other two to block the operation of the intact phases. Commutator 0 generates a signal supplied to the signaling element of the channel of the damaged phase, and also commutes the counteracting EMF from source 8 to the input of transformer 3, which outputs the output to the circuit of the zero-sequence counter-EMF network. Thus, increasing the accuracy of the device for compensating the active current of the earth fault allows more reliably detecting the damaged phase and thereby suppressing the development of damage in an accident, which increases electrical safety in electrical networks. 2 Il.

The invention relates to electrical engineering and can be used to compensate for the active ground fault current in neutral-compensated electrical networks.

The purpose of the invention is to improve the accuracy of the device.

FIG. 1 shows a block diagram of the device; in fig. 2 (a, O, b) - structural diagrams of the phase-sensitive rectifier, logic block and electronic key, respectively.

The device contains a power transformer 1 of the network, a unit 2 for compensating the capacitive current of the earth fault, two: a winding transformer 3 with a high-resistance output, which is a compensator of the active component of the current of the circuit, a phase-sensitive rectifier 4, threshold elements 5, logical blocks 6, electronic switches 7, source B against one's own EMF (a three-phase transformer with secondary windings included in the zigzag), source 9 of the reference voltage. The phase-sensitive rectifier contains a cell 10, a voltage converter 11 between the mains phase and the neutral, a matching unit 12 of the neutral voltage with the input voltage of the cell. Logic unit 6 consists of logical elements HE 13 and 14 and logical element 15. Electronic key 7 consists of

switching element 16 and the alarm element 17.

The device works as follows.

When the insulation resistance of one of the mains phases is reduced or the circuit through the resistance is equal to zero, the voltage on the neutral is relatively

of the earth increases, which leads to the triggering of the phase-sensitive rectifier (cells 10) of the phase with weakened insulation and an increase in the voltage at its output, since the voltage on the voltage converter 11 between the network phase and the neutral (voltage phase-neutral) and agree -. unit 12 (neutral earth voltage) after inverting one

180 ° of name stresses

coincide in phase (Fig. 2a). The voltage from the output of the phase-sensitive rectifier 4, having reached the specified value and comparing in the threshold element 5 with the voltage of the source of the specified reference voltage 9, leads to its operation and the operation of the logic element 15 of the logic unit. 6, from the output of which

Three signals are generated: one to open the switching element 16 of the electronic key 7, and the other two to block the operation of the phases without damaging the insulation relative to

land, preventing their false work, by acting on the elements NOT 13

and 14 (Fig. 26) logical blocks of 6 intact phases.

The switching element 1b generates a signal applied to the alarm element 17 to trigger the electronic key 7 (Fig. 2c) of the activated channel of the phase with damage, and also commutes the counteracting EMF from source 8 to the input of the transformer 3, introducing a zero-sequence into the high-impedance circuit anti-EMF networks.

The technical and economic efficiency of the device for compensating the active current of the earth fault in compensated networks consists in solving the problem of determining the phase with insulation failure, the possibility of suppressing the development of damage in an accident, and thus preventing under-power. consumers, the possibility of compensation of currents to values that ensure electrical safety in case of accidental contact with the live part.

Claims (1)

Invention Formula A device for compensating the active ground fault current in an electrical network containing phase-sensitive rectifiers whose inputs are connected to a source of phase voltages relative to the neutral of the network and a source of neutral voltage relative to earth, keys, a source of counter-electromotive force whose inputs are connected to a source of phase-to-line voltage , and the outputs through the keys - to the input of the compensator of the active component of the ground fault current, which is the fact that, in order to increase the accuracy of the device, they are entered into it The phase sequence of serially connected threshold elements and logical blocks made on the AND element and two NOT elements, while the input of the threshold element is connected to the output of the corresponding phase-sensitive rectifier, and the output to the first input of the AND element, to the other two inputs of which are NOT connected the blocking outputs of logical blocks of other phases, the direct output of the logical element AND is connected to the control input of the key, and the blocking outputs of the element AND are connected to the inputs of the elements NOT of logical blocks - two other phases.