SU113116A1 - Device for the protection of three-phase electrical installations - Google Patents

Description

To protect three-phase electrical installations from short circuits and overloads, devices are known based on the use of three transformer relays, whose cores are magnetised by current from a voltage circuit.

The proposed device differs from the known ones in that the secondary winding of each relay consists of two in series and according to the connected windings. One of these windings has two sections wound on each of the two cores, and the other is common to both cores.

This embodiment of the secondary winding of a transformer relay allows the use of this device at the same time to protect electrical installations from breaks in current circuits.

FIG. 1 is a schematic diagram of the proposed device; in fig. 2 shows the layout of the windings in a transformer relay.

In the proposed device protection

a three-phase installation / overload is carried out by a thermal relay 2 included in one of the phases of the installation to be protected. To protect against short circuits and open circuits, three transformer relays 5 are used, based on the principle of magnetizing transformer cores with voltage from voltage circuits.

Each transformer relay has two magnetic conductors 4 t 5 with a current winding 6, a voltage winding 7 and a secondary winding S. The voltage winding 7 is wound on each core and connected in series with the additional resistance 9. The secondary winding 8 consists of two in series and according to windings, one of which is wound on each core, and the second is common to both cores.

The parameters of the transformer relays are chosen in such a way that, in the absence of emergency modes in the feeder of the protected electrical installation, the relay cores with the help of voltage windings 7 and current windings 6 are magnetised and the voltage in the secondary windings 8 is small.

When a wire breaks in the feeder of the protected installation, the corresponding trans (}) of the ormator relay is demagnetized and the voltage applied to the winding 1: April 7 increases. At the same time, the capacitance of the secondary winding 8 increases, resulting in a single from the intermediate relay 10, which gives impulses to the switch // na disconnection of the electrical installation from the network.

A wire break before the protection does not cause the electrical installation to be disconnected, since in this case the winding 7 will not be attached to the wiring.

When there are short circuits in the electrical circuit, the voltage on the windings 7 is appropriate, the transformer relay sharply hits, which leads to the triggering of the corresponding weave relays 10. Short circuits in the line before the protection do not turn off the electrical installation, as in this case the current

The loads and voltages on winding 7 will be small.

When three-phase electrical installation overload thermal relay 2 breaks the circuit of the winding 7, which causes demagnetization of the core of the transformer relay. This triggers the intermediate relay 10 and the electrical installation is disconnected from the network.

Subject invention

A device for protection of three-phase electrical installations against overloads and short circuits, containing three transformer relays, the cores of which are magnetised by current from a voltage circuit, so that, in order to use the device, also to protect against breaks in the circuits current, the secondary winding of each transformer relay consists of / two in series and according to the included windings, one of which has two sections located on each of the two cores, and the other is common to both cores.

Network

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Network

FIG. 2