SU1246224A1 - Device for earth leakage protection of high-voltage isolated neutral system - Google Patents

Abstract

The invention relates to electrical engineering, namely, to relay protection of 3-10 kV networks with insulated neutral from earth faults, for example, to electrical grids of quarries, hydromechanization networks. The purpose of the invention is to increase the reliability of the protection operation by eliminating non-selectivity in case of failure of the current threshold unit. The device contains an input switch 1 and connection switches 3, zero-sequence current transformers 5 and zero-sequence voltage transformers 4. The zero-phase element 7, the second delay element II, are connected to the zero-sequence voltage transformers 4. An element N 9, an element OR 12, the second executive body 14 is connected to the zero-sequence current transformers. The elimination of non-selectivity in case of failure of the current threshold organ is achieved by introducing into the circuit each connection of the second delay element 11 and the element OR 12. 2 Il. ate .E1C 4 Cbe ke | C NCi

Description

The invention relates to electrical engineering, in particular, to relay protection of networks, and can be used to protect against single-phase earth faults in electrical networks x 3-10 kV with insulated neutral, requiring shutdown for the indicated type of damage. Examples of such networks are quarries, hydromechanization, and the like.

The purpose of the invention is to increase the reliability of the protection operation by eliminating non-selectivity in case of failure of the current threshold unit.

FIG. Figure 1 shows the high-voltage circuit protection circuit for a high-voltage network with insulated neutral; in fig. 2 - device for protection of the network in which the switches are concentrated.

The scheme contains an input switch 1, camshaft 2, a switch 3 connection, a transformer 4 zero sequence voltage, a transformer 5 zero sequence current, a cable 6 connection, the first threshold organ 7, the second threshold organ 8, element 9, the first organ 10 delay, the second delay authority 11, element OR 12, the first executive authority 13, the second executive authority 14, the distribution network 15

The second threshold organ 8 can be implemented as an overcurrent organ. The second threshold authority 8 may also be implemented as a zero-sequence maximum power directional authority. In this case, this threshold organ is connected to the current circuit and the zero-sequence voltage (in Fig. 1).

The device works as follows.

The time setting of the second delay organ 11 must be less than that of the first delay organ 10.

When a single-phase earth fault in cable 6, the first threshold organ 7 and the second threshold organ 8 of the damaged cable 6 are triggered, a signal is generated at the output of the AND 9 element without delay, which, through the OR element 12, triggers the actuator 14 of the damaged cable 6 and disconnects it switch 3 without time delay.

In the case of a single-phase closure to earth 2 or network 15, the second threshold organs 8 do not work, since the closure is outside the zone of their operation. At the same time, the first threshold organs 7 work, which through the second delay organs 11 turn off the switches of the 3 connections, and then through the first delay organs 10

if necessary, turn off the input switch 1. Thus, the lines to consumers are disconnected regardless of the health of the input switch, which causes

consumer safety.

When a single-phase circuit in cable 6 and the failure of the second threshold organ 8 element And 9 does not work and the instantaneous disconnection of the damaged cable does not occur. However, by triggering the first

the threshold authority 7 launches the second delay 11, after which the delay, which is less than that of the first delay 10, expires through the OR 12 and the second execution unit 14, the switch 3 is disconnected, and the input switch 1 does not have time to turn off goals

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Claims (1)

Invention Formula A high-voltage ground fault protection device for a high-voltage network with an insulated neutral, containing an input switch and switches according to the number of connections, zero-sequence voltage transformers mounted on the connections, i; on the input voltage thresholds are connected to their secondary windings, the first delay opraif, the input is connected to the threshold voltage element and installed at the input, the output is connected to the first usable relay connected to the disconnecting input of the input switch, transformers zero-sequence current installed in the circuit of each connection, to the secondary windings of which threshold current organs are connected, the outputs of the latter are connected to the first inputs of the I element, and the second inputs of them are connected to the outputs of g The horn bodies are connected, the executive bodies of the connections connected to the shut-off inputs of the switches of the connections characterized in that, in order to increase the reliability of the protection by eliminating non-selectivity in case of failure of the current threshold unit, the second delay element and the element are added to it. OR, the inputs of which are connected to the output element And the output of the second qprana the delay, the input of the connection voltage connected to the threshold organ, and the output of the element OR is connected to the executive body of its terminal. FIG ..