SU1690060A1 - Device for protecting three-phase power network of alternating current - Google Patents

Abstract

The invention relates to the field of electrical engineering, in particular, to relay protection of electrical installations. The purpose of the invention is to increase the reliability of work. The goal is achieved by the addition of a three-phase transformer current sensor, three resistors, a power source, control and matching units to the device. Each matching unit contains a transistor and a voltage divider. Each control unit contains an optocoupler rectifier, a zener diode, an RC circuit, a transistor, and two voltage dividers. 1 il.

Description

This invention relates to electrical engineering, in particular, to relay protection of electrical installations.

The purpose of the invention is to increase the reliability of work.

The drawing shows a diagram of the device.

The device contains a three-phase power transformer 1, a rectifying unit 2, the primary windings of a three-phase transformer 1 are connected in series with the rectifying unit 2, and the secondary windings are connected to one of the outputs together, the switching element 3, the display unit 4, a three-phase transformer current sensor 5, three resistors 6, power supply 7, three control blocks 8, three matching blocks 9, each of which contains a voltage divider 10, one of the terminals of which is connected to the positive bus of the power supply 7, the other to minus The bus is connected to the collector of transistor 11. Each control unit 8 contains a rectifier 12, an optocoupler 13, a zener diode 14, an RC circuit on a resistor 15 and a capacitor 16, a resistor 17, a transistor 18, the first 19 and the second 20 dividers eg wives The drawing shows the load 21.

The device works as follows.

The supply voltage in normal operation from the input of the device through the primary windings of the transformer 1, the rectifying unit 2, the switching element 3 opened to saturation, the transistor using a voltage supplied from the power source 7 through the resistors 6 and the voltage divider 20, the secondary windings transformer 1 and current sensor 5 is supplied to load 21. The protection device in normal mode does not affect the operation.

In the case of a current overload in at least one of the phases, the voltage drop from the transformer sensor 5 of the current of this phase increases. Increases the voltage at the output of the rectifier 12 block 8 control (L

WITH

oh oh oh oh oh

neither this phase. The Zener diode 14 of this control block 3 is punched. The light emitter of the optocoupler 13 receives power. The photodetector of the optocoupler 13 operates. In this case, an unlocking voltage is applied to the base of the transistor 18 through the upper resistor of the voltage divider 19. The transistor 18 is also unlocked from the negative busbar of the power supply 7 through a resistor. 17, the collector-emitter of the transistor 18 open to saturation and the resistor 6 of this phase arrive at the base of the transistor of the switching element 3, locking it. When locked, the transistor of the switching element 3 breaks the common current path. In this case, the flow of current through the primary windings of transformer 1 is stopped simultaneously in all three phases due to the breaking of the circuit formed by the rectifying unit 2. At the same time, the operation mode of the three-phase transformer 1 from the two phases of the three-phase network is completely excluded. At the same time, the unlocking voltage removed from the voltage divider 19 of the control unit 8 is supplied to the base of the transistor 11 of the matching unit 9. Transistor 11 opens and outputs a signal to display unit 4.

In this device, monitoring of the phase loss helps to accelerate finding the cause of the current overload, which leads to an increase in the reliability of the protection device as a whole.

Claims (1)

A device for protecting a three-phase AC network containing a three-phase power transformer, to the primary windings of which are connected the inputs of the rectifier unit, parallel to the output of which is connected the output of the switching element, the control unit and the display unit, characterized in that additionally introduced three-phase transformer current sensor, two units control blocks and resistors according to the number of phases, the power source, while the secondary windings of the three-phase power transformer are connected in series with the primary windings of the three-phase transformer current sensor, which are intended to be connected to the load terminals, parallel to the secondary windings of the specified current sensor the inputs of the corresponding control units, each of which is designed as a rectifier, are connected in series to a parallel RC circuit, a Zener diode, an optocoupler, two voltage dividers, a transistor and a resistor, while the rectifier input is the input of the control unit, the output of the rectifier is connected the second output of the parallel RC circuit and the anode of the light emitter of the optocoupler, the photodetector of which is. This is connected in series with the first voltage divider, to the midpoint of which the base of the transistor is connected, the collector of which is connected to the middle point of the second voltage delimiter and through the corresponding additional resistor to the input of the switching element, the first output of the second voltage divider, the cathode of the photoreceiver optocoupler and connected to the positive of the power source, the second output of the first voltage divider, the first output of a resistor connected to the emitter circuit of the transistor, and the second output of the second divider voltage Wives are united and connected to minus power supply, each matching unit is designed as a voltage divider and a transistor, while a voltage divider is connected to the terminals of the power supply, to the midpoint of which the collector of the transistor, the base of which is connected to the midpoint of the first voltage divider of the control unit, and the emitter - to the corresponding input of the display unit.