SU1001286A1 - Method of protecting overhead power transmission line from break - Google Patents

Description

The invention relates to electrical engineering, in particular, to relay protection and automation of electrical networks and systems, and is intended to disconnect 110-220 kV high-voltage lines when the wire is broken before a short-circuit (k.z) occurs with a wire falling to the ground or the phase below. lines.

There is a known method of protecting a three-phase electrical installation from the interruption of one of the phases, which allows to disconnect the installation in the case of an interruption of phases t in networks with voltages up to 35 kV.

The disadvantage of this method is the inability to selectively disable the damaged section of the branched network.

Closest to the present invention is a method of protecting against a power line interruption, which generates capacitive currents, consisting in controlling the current symmetry in the phases, in violation of which they produce a signal for disconnecting the line and disconnecting the line 2.

The disadvantage of this technical solution is its low reliability due to the fact that the method of protection: does not provide selectivity quickly

active line disconnection in the event of a line break.

The purpose of the invention is to increase reliability by providing selectivity and speed.

This goal is achieved by the fact that according to the method of protection against breaks in an overhead transmission line that generates capacitive currents, which consists in monitoring current symmetry in phases, in violation of which they generate a signal to turn off the line and disconnect the line, they additionally measure the magnitude of the current in phases 15, when decreasing to the level of capacitive current and less, produces a second signal to disconnect the line, and the line is disconnected when the two mentioned signals coincide.

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The drawing shows a schematic functional diagram of the proposed device for disconnecting an overhead transmission line in extensive networks of high voltage (25-220 KB) electrical system.

The method consists in the fact that by means of current transformers 1 control the symmetry of the current in phases A, B

Claims (2)

30 and C line 2 and with the appearance of asymmetry producing a signal to disconnect the line 2. In addition, through the same current transformers 1 control the amount of current in phases Л, В and С, with decreasing it to the level. bone current and less generate a second signal for disconnecting line 2 When these two signals coincide on the logic unit AND 3, the line is disconnected by means of switch 4. From the drawing it can be seen that detachable aerial line 1 is connected to high-voltage network 5 through switch 4, in the circuit of each phase 1 current transformers are installed. The secondary windings of each of the current transformers 1 are connected to a series circuit consisting of a relay 6-8 winding, a relay protection unit 9 and a relay 10 current, included in the neutral conductor of the current transformer 1, respectively. The opening contacts of the relay 6-8 are connected to three inputs of the logical block OR 11, the output of which is connected by a series circuit consisting of a logical block 3 and a delay block 12, with one of the inputs of block 13 of the output intermediate relays, to the second input of which the output of the block is turned on 9 relay protection, and the output of the block 13 is connected to the switch 4, the closing contact of the current relay 10 is connected to the second output of the block 3. The method is carried out as follows. In known devices, when a wire is broken on the line 2 that is switched on, the current level in the damaged phase first decreases sharply and only after a certain time, during which the broken wire falls to the ground, a short circuit occurs, the current in the damaged phase sharply increases. , the relay protection unit, the output intermediate relay unit is activated, and the command is issued to turn off the switch. In the interval. The time from the moment of breaking the wire to the appearance of AD sensitive steps of protection against ground faults of the line, fixing with their current elements the presence of asymmetry of the line currents, usually do not have time to trip the circuit breaker, since their time delay is longer than the interval. Thus, the line is disconnected by known methods short circuit damage. The operation of the proposed device is based on fixing the fact of the simultaneous occurrence of a current of zero sequence and a decrease in current in one or two phases. When switch 4 is disconnected before a fault occurs. If, for example, the phase A wire on the line breaks, the relay 8 drops off and its normally closed contact closes, and the current relay 10 starts to flow around and makes its closing contact. from the relay 8 through the block 11 and from the relay 10 current to the input of the block 3 two signals are received, which causes the signal at the output of the block, and after passing it through the blocks 12 and 13, the switch 4 is turned off, the block 12 of the delay introduces on shutdown off, t 4 time delay (on the order of 0.2 s) to ensure reliable failure of the device in the event of non-simultaneous operation of the switch phases with on-line switching on and off of the linear switch 4. The presence of relay 10 makes it possible to ensure the failure of the device when the current decreases in symmetrical modes, for example, asynchronous Progress on overhead lines or when swinging x. Current relays 6-8 close their open contacts with a current equal to the capacitive current of the line and less, so that it is possible to ensure the operation of the device in the event of a wire break at the end of an overhead line. The tripping current of the relay 10 can be selected based on the requirement to ensure that the relay operates in the event of a break in the mode of the minimum load current flowing along the line. Thus, the proposed method allows to increase the reliability of the line by disconnecting the damaged part of it before the damaged wire falls to the ground and a short circuit occurs on the line. Claims for protection against breakage of an overhead transmission line that generates capacitive currents, which control the current symmetry in the phases, in violation of which they produce a signal to disconnect the line, and disconnect the line, in order to increase the reliability of the network by providing selectivity and speed, the current in the phases is additionally measured, and when it decreases to the level of capacitive current, the second signal is produced to disconnect the line, and the line is disconnected if mentioned signals. Sources of information taken into account in the examination 1. The author's certificate of the USSR 6.55013, cl. H 02 H 7/09, 1976. 2. USSR author's certificate if 50717, cl. H 02 H 7/09, 1974.