SU1596421A1 - Arrangement for automatic shunting of phase in electric network with insulated neutral - Google Patents

Abstract

This invention relates to electrical engineering, namely, devices that increase electrical and fire safety in networks with insulated neutral. The purpose of the invention is to increase the speed of the blocking of the shunting during the double ground loops. When a decrease in insulation occurs in the second phase, or when the device triggers due to short circuits in the windings of electrical consumers, the current in the shunting circuit increases sharply. A polarized relay 13 operates, opening its contacts 16, 14 in the control circuit of the triac 11 and the supply circuit of the windings of the shunt relays 4-6. The invention makes it possible to reduce the weight and dimensions of the device. 1 il.

Description

This invention relates to electrical engineering, in particular, to devices that increase electrical and fire safety in networks with insulated neutral.

The purpose of the invention is to increase the speed of the blocking of the shunting during the double ground loops.

The drawing shows a block diagram of the device.

The proposed device contains a zero-sequence voltage sensor 1. connected to the block for selecting the faulty phase 2, the outputs of which are connected to the inputs of the amplifier 3. The windings of the shunt relays 4-6 are connected to the outputs of the amplifier 3. The relay contacts 7-9 are connected between the phases of the network and merged into a star. To the common point of contact is connected the first output of the current sensor 10. Between the second output of the current sensor 10 and

Triac 11 is connected to ground. The output of current sensor 10 through rectifier 12 is connected to the first winding of polarized relay 13. First disconnecting contact 14 of polarized relay 13 is connected between the power supply and the common connection point of the windings

relay 4-6. Second break contact 15

KD is included in the triac control circuit 11,

A return button 16 is turned on in the power supply circuit of the second winding of the polarized relay 13. In series with the contacts

Executive relays include low-impedance ballast resistors 17. Limiting the current to a double earth fault up to the level allowed by the triac and closed relay contacts.

The device works as follows.

With a single-phase human touch to one of the phases. or insulation fault, voltage sensor zero

Sequence 1 selects a signal proportional to the offset of the neutral of the network, which is fed to the damaged phase selection block 2. The phase selection block determines the phase in which the contact or insulation breaks and sends a signal to one of three outputs to amplifier 3. which amplifies signal and energizes one of the windings of the relay 4, 5 or b, the contacts of which shunt the damaged phase to earth. In this case, the control circuit of the triac 11 is connected to the control voltage and the triac is in a conducting state. The phase-to-ground current circuit closes and a shunting current begins to flow through it, the value of which in the normal mode is determined by the value of the phase capacitances relative to ground. At the same time, the voltage at the output of the current sensor 10, rectified by the rectifier 12, is less than the switching voltage of the polarized relay 13.

When a breakdown occurs in the second phase, or when the device triggers due to short circuits in the windings of electrical consumers, the current in the shunting circuit increases sharply. The voltage on the first winding 13 of the polarized relay also increases and it works, opening its contacts in the triac control circuit and the power circuit of the windings of the shunt relays. The triac is locked at the first current zero crossing, and since the return time of shunt relays 4-6 is more than 10 ms, the contacts open without current, the relays return time is increased by shunting their windings with diodes 18. Other times, if necessary, for longer times. methods for delaying the return of relays, for example, shunting windings of an RC chain.

Thus, the device controls the amount of current flowing in the shunting circuit and automatically shuts off the shunting circuit in the event of a dangerous emergency mode.

In the proposed device, the effect is achieved due to the combination of features inherent in devices for arc-free switching and the use of a polarized relay to control simisticrs and bypass relays.

The use of a polarized relay as a threshold organ simplifies the circuit by combining the current measurement functions and storing the actuated state for any time until the circuit returns manually. In addition, the operation of a polarized relay does not require smoothing of the rectified signal, due to which the protection has a limiting

speed (3-13 ms). At the same time, the final intrinsic response time of a polarized relay makes it possible to rebuild the protection against a surge of capacitive current when the phase is bridged by a relay contact.

Claims (1)

Invention Formula A device for automatically shunting a phase in an electrical network with an insulated neutral, containing a zero-sequence voltage sensor, the inputs of which are connected to the terminals for connection to the electric network and to the grounding terminal, and the outputs are connected to the input according to the zero sequence of the damaged phase selection block, the various inputs of which are connected to the terminals for connection to the network, and the outputs are connected to the inputs of the amplifier, the outputs of which connected to the first winding pins of the shunt relays, the second winding pins of these relays are combined, in a common point, the relay contacts are connected between the terminals for connecting to the mains phases and the first current output of the current sensor, power source, rectifier and threshold organ, from the e. what. in order to increase the speed of blocking the shunting at double ground loops, a triac connected between the second current output of the current sensor and the terminal for connecting to the grounding conductor was additionally introduced into the device, and the threshold organ was designed as a two-winding polarized relay with two normally open contacts, the first winding which is connected via a rectifier to the output of the current sensor, vtopa the winding is connected via the return button to the source power supply, the first normally closed contact is connected between the output of the power source and the common point of the windings of the shunt relays, and the second normally open contact is connected to the triac control circuit. . W