SU982134A1 - Device for relay protection of low-voltage bus-bars of unitized transformer substation - Google Patents

Description

(5) DEVICE FOR RELAY TIRES OF LOW VOLTAGE COMPLETE TRANSFORMER SUBSTATIONS

The invention relates to electrical engineering, in particular, to relay protection of complete low voltage distribution substations.

A device is known in which a maximum overcurrent protection with a time delay of 1 is installed in addition to the differential current protection kits to selectively disable faults on the tires.

This protection has complexity and lack of reliability.

The closest in technical essence to this device is a device for relay protection of a low voltage busbar section of a complete transformer substation and lines running from it, consisting of current differential protection (DTD) bus section and maximum current protection (MTZ) of each lines containing current sensors of each connection, one polar

the output voltage of which is proportional to the ratio of the connection current to its rated current, the relay body of the CTD, made unipolar in input voltage, and the relay bodies of the overcurrent relay in which the outputs of the current line sensors are connected to the inputs of the relay bodies of the overcurrent relay, the outputs of the current sensors of all connections

, Q are connected in series with each other and with the input of the DTZ relay body, the outputs of the current line sensors are interconnected according to each other, the input current sensor output is opposite, and you, 5 moves of the DTZ and MTZ relay bodies are connected to the tripping breaker blocks. The unipolar output voltage of the current sensors can be smoothed by KS filters 21,

20

In this device, in case of violation of the circuit connecting the current sensors of all connections in series, the signal to the input of the DTZ relay relay

3 9

does not arrive, and the input protection in this case is not provided, although the likelihood of such violations is quite large, since the sensors can be removed from each other for considerable distances. Failure to protect the input protection in violation of the circuit connecting the current sensors is a disadvantage this device. In emergency mode, on one of the lines, a shutdown command is sent from the output - the relay body MTZ to the disconnecting unit of this line. If for some reason the switch does not open, with a certain delay in time, the input protection must be activated as a backup, and the open switch must be given a command to disconnect. In the known device this is not provided, so the relay body of the CTD is inhibited by the voltage from the line current sensor. The lack of protection redundancy of outgoing lines, input protection is also a disadvantage of the device.

The purpose of the invention is to eliminate the failure of input protection in the event of a break in the circuit connecting the current sensors of all connections in series, and to ensure that protection of outgoing lines is protected by input protection.

The goal is achieved by the fact that a device for relay protection of low voltage buses of a complete transformer substation and lines extending from it contains a differential current protection unit (DTD) input and maximum current protection units (MTZ) of each line, including respectively input current sensors and current sensors of each line, a relay body of the DTZ input and relay bodies of the overcurrent protection lines in which the outputs of the current line sensors are connected to the inputs of the relay bodies of the overcurrent lines, the outputs of the input current sensors and each line in series with each other, and the outputs of the relay bodies of the DTZ input and MTZ lines are connected to the disconnecting bodies of the switches, a differentiating link is additionally introduced, the relay body of the DTZ input is made with two inputs, the input of the differentiating link is connected in series with the line current sensors,

)four

the output of the differentiating link is connected to the first input of the relay body DTZ input, and the second input of the relay body DTZ input is connected

to the input current sensor output,

The diagram of the proposed protection device is shown in Fig. 1, - in Fig „2 the differential brake signal form at the input of the differentiating link

(a) and its output (b).

The device contains circuit breakers 1, 2 and 3 of the input 1 connected to the secondary winding of the power transformer 4 and linear 2 and 3 at all connections of the low voltage busbars, through which the loads 5 and 6 are fed. The lines are protected by maximum current protection including se sensors

7 and 8 current lines, the outputs of which are connected to the inputs of the relay bodies 9 and 10, and the outputs of the relay bodies are connected to the tripping blocks of the switches 2 and 3. Bus section

low voltage, located between the switches, 2 and 3, is protected by a CTD, consisting of an input current sensor 11, the output of which is connected in series with the input of the differentiating link 12 and the outputs of the line current sensors 7 and 8, and the outputs of the line current sensors 7 and 8 interconnected according to each other in series, and with respect to the output of the input current sensor 11 - counter output. The output of the differentiating element is connected to the first input of the relay body 13 DTZ, the second input of which is connected to the output of the input current sensor 11, and the output of the relay body 13 is connected to disconnecting unit switch 1 input.

In the particular case, the relay body 13 of the CTD may consist of a two-transistor trigger with a normally-closed input on the transistors and 15, and resistors 16, 17 and 18, a normally open one-transistor switch on the transistor 19 and a resistor 20. The first input of the relay body 13 is the base-emitter junction of the transistor 19, and the second are connected in series by the base-emitter junction of the transistor Il and the collector-emitter junction of the transistor 19.

Claims (2)

1.Baptidanov L.N. and Tarasov VI, Electrical equipment of power stations and substations. SEI, 1959, with. 236, fig. 13-31. 2. USSR author's certificate №, cl. H P2 H 3/28, 1980. V5 sV .one FIG. 2