SU995190A2 - Device for protecting three-phase up to 1000v line from phase wire break - Google Patents

Description

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The invention relates to electrical engineering, and more specifically to relay protection in electrical installations, primarily to devices for protecting a three-phase line, with a voltage up to 1000 V from breakage of the phase conductors.

On the main. Avt. St. No. 884024 a device is known that contains an organ that responds to a broken phase conductor, is installed at the end of a protected line, is made in the form of a negative-sequence voltage filter and is connected to an actuator that acts on a short circuitor consisting of a diode and a current-limiting resistor, as well as a measuring body, made in the form of even-harmonic current filter, which is installed at the beginning of the protected line and connected to the protection body acting on the circuit breaker.

The device most fully satisfies the conditions of operation, especially the increased level of electrical safety when one of the wires is broken, and is one of the promising devices 1.

A disadvantage of the known device is the relatively low reliability of power supply. This is especially manifested when it is used on three-phase lines without an electromotive load 5 (three-phase electrode boilers, floor heating in the pig stock ID).

In such networks, in the event of a wire break, the line must be disconnected in accordance with the requirements of the safety regulations. However, the known device will disconnect the line not only if the wire of the air line is directly broken, but also in the case of an incomplete phase mode, caused, for example, by the blown fuse on the 10 kV side of the power supply transformer.

In this case there is no need to disconnect the line from the point of view of the technological process.

The purpose of the invention is to increase the reliability of power supply.

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The goal is achieved by the fact that in the device for protection of a three-phase line with voltage up to 1000 V from breakage of phase wires, a second voltage filter is installed at the beginning of the protected line

reverse sequence, the output of which is connected to the forbidden input of the body of protection.

The drawing shows the functional diagram of the device.

At the end of the protected three-phase line 1, a negative-sequence voltage filter FNOP 2 is connected, the output of which is connected to the actuator 3, and the output of the latter to the short circuit 4, between the phase terminals of which are connected chains consisting of diodes 5 and b and current limiting resistors 7 and 8 .

At the beginning of line 1, a block 9 is installed, which is an even-harmonic current filter and is connected to the enable input of the protection unit 10, the output of which is connected to the circuit breaker 11. At the beginning of line 1 is connected a second negative-order voltage filter 12, the output of which is connected to prohibiting the input of the protection unit 10 supply transformer 13.

The device works as follows.

When one of the phase conductors of line 1 is broken, a signal appears at the output of the filter 2 of negative-sequence voltage, which triggers the actuator 3. The latter, acting on the short circuiter 4, connects the diodes 5 and 6 to the network via current-limiting resistors 7 and 8. In this case, even harmonic currents flow in the wires of the network 1, which are fixed by the block 9. The latter acts on the protection block 10 and causes it to trip, which causes the automaton 11 to switch off.

In the event of a wire break in a transformer 13 or a sectional fuse blown in a high-voltage network, a reverse sequence voltage appears.

However, in this case, line 1 does not need to be disconnected according to the requirements of safety regulations, and, as already indicated, in a number of cases the technological load allows operation in an incomplete phase mode. Therefore, a second reverse voltage filter 12 is introduced into the device.

sequence, which by its signal prohibits the operation of block 10 protection. Thus, in the case of an incomplete phase mode caused by damage to transformer 13, a signal appears at the output of FNOP 2 and FNOP 12. Signal from FNOP 2

 acts through the actuator 4 on the short circuit 4. The short circuit 4 connects the diodes 5 and 6 to the network through current-limiting resistors 7 and 8. In this case, the wires of the line 1 have currents of even harmonics, which are fixed by the block 9. The block 9 acts on the protection unit 10, however, the latter does not work, since its prohibitory input has a signal from the FNP 12, so the automaton 11 is not turned off and line 1 remains in operation.

The use of the proposed device allows performing a sensitive and reliable protection of a three-phase line with a voltage up to 1000 V and increasing the reliability of power supply to consumers.

as it leads in a number of cases to the refusal to disconnect the line.

Claims (1)

Invention Formula A device for protection of a three-phase line with a voltage of up to 1000 V against an interruption of the phase conductors using aut. St. No. 884024, characterized in that, in order to increase the reliability of the power supply, at the beginning of the protected line a second negative-order voltage filter is installed, the output of which is connected to the prohibitory input of the protection body. Sources of information taken into account during the examination 1. USSR Author's Certificate No. 884024, cl. H 02 H 5/10, 1980. j u NS. Nj S k V