SU792434A1 - Device for earthing protection in mains with insulated neutral wire - Google Patents

Description

one

The invention relates to devices for protection against earth faults of ac networks operating with an insulated neutral.

Known devices for protection against earth faults

The closest in technical essence to the invention is a device that contains zero-sequence current transformers (TNCU) connected via rectifiers, amplifiers to reacting organs and to the highest voltage indicator (IBN), the outputs of the latter are connected to the inputs of the coincidence elements, where the output of the starting organ is also included in the zero sequence sequence, the outputs of the coincidence elements are connected to executive bodies 2 |.

However, the known device has insufficient reliability.

The aim of the invention is to improve the reliability of the device.

The goal is achieved by the fact that in a known device for protection against a ground fault, containing, according to the number of protected connections, zero-sequence current transformers

which are connected in series corresponding rectifiers, amplifiers, main regg: main organs and the highest voltage indicator, as well as a zero sequence voltage trigger, the output of which is connected to the first inputs of the elements, coincidence, the outputs of the latter are connected to

10 corresponding actuators, introduced additional reacting organs, connected between the outputs of the corresponding amplifiers and inputs of the highest voltage indicator performed on the thyristors, the control electrodes of which are connected to the outputs of the main reacting organs, while the outputs of the additional actuators:

20 organs are connected to the second inputs of the corresponding match elements.

The block diagram of the device shown in the drawing. It is composed for two

25 connections, the total number of which can be, any.

- It contains the launching authority 1 of the zero sequence sequence; transformer 2 for example

30 sequences; main reacting organs 3, 4; amplifiers 5, b input resistors 7-, 8; rectifiers 9, 10; transformers 11, 12 of zero-sequence current, protected connection 13, 14; additional responsive organs 15, 16; the highest voltage indicator 17 (IBN); match items 18, 19; executive bodies 20, 21 thyristors 22, 23; resistors 24-26.

The device works as follows.

In normal network mode, i.e. in the absence of a single-phase ground closure, the triggering organ 1, the reacting organs 3, 4, 15, 16 and the executive organs 20, 21 are in the initial position, the thyristors 22, 23 are closed.

When a single-phase short circuit to earth, for example, at connection 13, the total current of the single-phase ground fault starts flowing through it and, accordingly, the current transformer 11, and its own capacitive current through the current transformer 12. If the current through the current transformer 11 (the signal at the output of the amplifier 5) turns out to be greater than the response threshold of the reacting organ 3, the latter triggers and sends a signal to the control electrode of the thyristor 22, which opens and connects an additional reacting organ 15, made current, to the amplifier 5. Responsive unit 15 triggers and sends a signal to one of the inputs of the matching elements 18. Under the condition of triggering the triggering device 1, a signal appears at the output of this matching element and the operation occurs executive body 20 acting on the breaker disconnection of the damaged connection 13

If simultaneously with reacting authority 3, reacting authority 4 from a surge of its own capacitive coupling voltage 14 (when this current exceeds the response setting of reacting organ 4) does not selectively (3 disconnection of line 14 does not occur, because the additional reacting authority 16, which is made current, will be in the initial state due to the fact that it is in the channel with a lower voltage and therefore the thyristor 23 will be closed by the difference of the voltages: the greatest, released on the resistor and acting from the side of the cathodes of the thyristors, and the names of the first, acting from the side of the anodes. At the expense of resistors 1, 8 and 25, 26 the amplifier

5 operates as a normal operational amplifier, and amplifier b is in deep overcompensation mode. This mode of amplifiers provides increased accuracy of the indicator. The highest signal 17. Similarly, the device operates when a closure occurs — to earth at connection 14.

Introduction to the device to protect additional responsive organs connected via an indicator

The largest signal to the amplifiers of the main reacting organs allows to significantly increase both the selectivity of the protection operation against earth faults and its sensitivity, since it is possible to set the response of the response organs not to avoid their own capacitive currents.

This contributes to the increased reliability of power supply systems and the safety of their maintenance.

Claims (2)

1. Industrial energy, № 3, 1968, p. 4-6. 2. Bukhtorov V.F. New devices for protection against short circuits on the earth. - Overview TSNIEIugol, M., 0 1976, p. 9-11.