SU1728915A1 - Device for protecting from single-phase fault to earth for mains with isolated neutral conductor - Google Patents

Abstract

Use: for relay protection of electrical installations against earth faults. SUMMARY OF THE INVENTION: Introduction of voltage converters 6-9, comparators 10-13 with inverse outputs, single-oscillators 14.15, logic elements IL AND-HE 16, NOT 17, AND 18, 19, and delay element 20 allows to increase the selectivity of protection when working in longitudinal power supply lines. 1 il.

Description

The invention relates to electrical engineering, in particular, to devices for relay protection of lines against earth faults in longitudinal electrical networks of 10-35 kV with insulated neutral, mainly for railways.

A device for directional selective protection of a zero sequence from earth faults in networks with insulated neutral, containing filters of currents and voltage of zero sequence, a current organ made in the form of an AC amplifier with an industrial frequency filter in the output circuit, a phase-sensitive organ made in as a phase-sensitive amplifier, to the output of which the executive relay is connected, provides selective disconnection of the damaged radial distributor connection single-phase short circuit to earth.

The disadvantage of this device is the non-selective operation of the protection when introducing an influencing zero-sequence voltage and a zero-sequence current pulse in a damaged adjacent line when using this device to protect longitudinal power supply lines. As a rule, these are lines of different voltage classes 110 and 35 kV, 35 and 10 kV, etc., mounted on the same supports and intended for powering industrial and agricultural consumers, as well as SCB users.

It is also known a device for protection against single-phase ground fault in a three-phase network with insulated neutral, containing a zero-sequence current transformer, a zero-sequence voltage transformer, a phase-matching element, a phase voltage sensor, a block for detecting a damaged phase, an adder and an actuator.

A zero-sequence current transformer is installed at each connection, a zero-sequence voltage transformer in the protected network.

The output of the zero sequence current transformer is connected to the first input of the phase-matching unit, the output of which is connected to the executive body.

The output of the zero-sequence voltage transformer is connected via the phase-shifting element to the second input of the phase-matching body, to the first input of the block for detecting the faulty phase and to the first input of the adder, the output of which is connected to the input of the phase-matching body.

The phase voltage sensor is connected to the three phases of the network, its outputs are connected

to the phase inputs of the block detecting the damaged phase, the output of which is connected to the second input of the adder.

The known device provides for selective disconnection of the damaged connection 0 and determination of the damaged phase in the radial network at different values of the transient resistance at the circuit point.

5 The disadvantage of this device is that when using protection in longitudinal electrical networks, despite the presence of a phase-matching element and control of phase voltages, it cannot distinguish between damage on the protected line and damage on the adjacent line. This is due to the fact that at the time of damage to the adjacent line in the protected line of the longitudinal power supply, induced zero sequence voltage and a zero sequence current pulse, which are classified by the measuring bodies of this protection as alarm parameters, are observed. Protection

0 nonselectively disables an intact protected line located on the same supports with an adjacent damaged line.

The aim of the invention is to increase the selectivity of protection when operating in longitudinal power supply lines.

To achieve this goal, a device for protection against single-phase earth faults in a network with isolated

0 neutral, containing a zero-sequence current sensor installed on each protected line, the output of which is connected to the first input of the phase-matching element, the second input of which

5 is connected to the output of the zero-sequence voltage sensor, a phase voltage sensor and an actuator, four voltage converters, four comparators with inverse outputs, two one-vibrators, OR NOT elements, NOT AND two elements and a delay element are introduced. To the first input of the first element, and the output of the phase-matching element is connected, to the second input of the first

5 And element - the output of the second element And, the first input of which is connected to the series-connected first element is NOT, the first one-oscillator, the first comparator and the first voltage converter, the input of which is connected to the output of the zero-sequence voltage sensor, the second input of the second element And is connected to connected in series by the second one-shot and the element OR-HE, whose inputs are connected via the second, third and fourth comparator, respectively, connected in series with the second m, the third and fourth voltage converter, to the corresponding outputs of the phase voltage sensor, with the output of the first element I through the delay element connected to the input of the actuator.

The drawing shows a block diagram of the proposed device.

The device installed at both ends of each section of the protected line contains a zero-sequence current sensor 1, a zero-sequence voltage sensor 2, a phase voltage sensor 3, a phase-matching unit 4, an actuator 5, four voltage converters 6-9, four a comparator with inverse outputs 10-13, two one-shot 14 and 15, logic elements OR NOT 16, NOT 17, first and second logic elements AND 18 and 19, and delay element 20.

The zero sequence current sensor 1 is a standard zero sequence current transformer, the output of the zero sequence current sensor is connected to the first input of the phase-matching unit 4, the second input of which is connected to the output of the zero sequence voltage sensor 2, which is a zero-sequence winding of the measuring transformer, the output of the phase-matching body 4 is connected to the first input of the first element I 18, to the second input of which the output of the second element is connected And 19, the first input of which is connected to the output of the element HE 17, whose input through the one-shot 14 is connected to the inverse output of the comparator 10, the input of the comparator 10 is connected to the output of the first converter 6 of the voltage, the input of which is connected to the output of the sensor 2 zero sequence. The second input of the second element AND 19 is connected via the second one-shot 15 with the output of the element OR NOT 16, whose inputs are connected respectively via the second, third and fourth comparators 11-13 to the outputs of voltage converters 7-9, the inputs of which are connected to the corresponding outputs sensor 3 phase voltage, representing the secondary windings of the phase voltage measuring transformer. The output of the first element And 18 is connected through the element 20 of the delay to the input of the Executive body 5.

The proposed device can be implemented using the following elements: standard CTPS and TNPs can be used in current and zero-voltage sensors, comparators can be implemented on a PH-53 voltage relay or on a microelectronic element base using isolating transformers and rectifiers , comparators of the K 554 CA 1, K 554 CA 3 series, AND, OR NONE, NOT elements can not be realized by the circuit of connecting the relay contacts or using the microelectronic element base on K 155 L microcircuits A 3, K 155 L N 2, K 155 L R 1, single vibrators can be implemented using standard EV-238 time relays using a microelectronic element base, single vibrators are implemented on elements 2 AND-NOT of a K 155 L A 3 chip, output element can be implemented on relay RP 23 and the like when using the microelectronic element base on the E 155 TM 2, K 155 TV 1 trigger series, the time relay and the actuating element are used standard ones adopted in this protection and automation circuit.

The device works as follows.

In the normal mode of operation of the power supply lines at the inputs of the phase-matching body 4, there are no signals on the presence of current and zero-sequence voltage, the outputs of the voltage sensor 3 contain alternating voltages corresponding to the normal phase voltages of this line, and the output signal of the voltage sensor 2 the presence of zero sequence voltage is absent, the output of the voltage converter 6 is missing a signal about the presence of zero sequence voltage, the comparator 10 is inoperative state, the first one-shot 14 is in a steady state, at the output of the element NOT 17 is a inhibitory signal, the outputs of the converter 7–9 voltages contain constant voltages proportional to the voltages of the phases of this line, the comparators 11–13 are in the actuated state, at the output of the logical element OR NOT 16 is a inhibitory signal, the single vibrator 15 is in a steady state, at the input of the element AND 19 is the enable signal, at the second input of the element AND

18 - enabling signal.

When a single-phase ground fault occurs on the protected line at the outputs of current sensors 1 and zero-sequence voltage, a zero-sequence voltage and voltage appear. The phase of the current and voltage of the zero sequence falls into the region of operation of the phase-matching body 4, the signal from its output goes to the first input of the first element I 18, the voltage of the zero sequence appears at the output of voltage sensor 2 and the output voltage of the converter 6 The voltage is a constant voltage proportional to the zero-sequence voltage of the damaged line. The comparator 10 is triggered, a signal appears at its output, which transforms the one-oscillator 14 into an unstable state, at the output of the element NOT 17 a prohibiting signal appears, which is fed to the first input of the element AND 19, the voltage at any phase line disappears, respectively, the signal disappears at the corresponding output of the sensor 3 voltage. One of the comparators 11-13 returns to the non-triggered state, a signal about this through an OR-NOT 16 logic element is fed to the input of the single selector 5, translating it into an unstable state. At its output, a prohibiting signal appears, which is fed to the second input of element And 19, since at its first input there is a permitting signal from the element NOT 17. At the output of the element And 19 the signal remains unchanged, the enabling signal from the output And

19 enters the input of AND 18, and since both inputs contain triggered alarms, a time relay is triggered on the delay element 20 and the damaged line is turned off.

When an adjacent line is damaged, the outputs of the voltage sensors 2 and zero-sequence current 1 appear, respectively, the zero-sequence voltage induced from the adjacent line, and a zero-sequence current pulse, when the phase-generating element 4 triggers an input element I 18, the signal appears In order to disconnect the line, the output of the voltage sensor 2 is an alternating voltage proportional to the zero-sequence voltage induced in the line. A constant voltage proportional to the zero-sequence voltage is present at the output of the voltage converter 6, the comparator 10 is activated, the one-oscillator 14 is switched to an unstable state, the enabling signal appears at the output of the element HE 17, and there are variable voltages at the outputs of the voltage sensor 3 proportional to the phase voltages of the line. The system of phase voltages is distorted due to the inserting influencing zero-sequence voltage of the adjacent line; at the outputs of converters 7–9 there are constant voltages proportional to the phase voltages of the protected

the lines, but none of them is less than the voltage of the setpoint of the comparators 11-13, so the latter remain in the actuated state, the signals at their outputs do not change. At the output of the OR-NOT 16 element, there is a signal prohibiting the transition of the single-selector 15 to an unstable state, and the output of the single-selector 15 is an enabling signal. The permissive signals at the inputs of the AND 19 element coincide, at its output a inhibitory signal appears, which arrives at the second input of the And 18 element, thereby blocking non-selective work and the protected line remains in operation, and the adjacent line

disconnects from its earth fault protection unit.

The effectiveness of the proposed device is determined by reducing the delay time of trains,

with the exception of interruptions in power supply of industrial and agricultural consumers and reduction of labor costs for finding and repairing damage.

Claims (1)

Invention Formula Device for protection against single-phase earth faults in the network with insulated neutral, containing a sensor installed on each protected line zero-sequence current, the output of which is connected to the first input of the phase-matching unit, the second input of which is connected to the output of the zero-sequence voltage sensor, A phase voltage sensor and an actuator, characterized in that, in order to increase the selectivity of protection when operating in the longitudinal power supply lines, it is equipped with four voltage converters, four comparators with inverse outputs, two one-vibrators, OR-NOT and NOT elements, two elements And and a delay element, while the output of the phase-matching body is connected to the first input of the first element And to the second input of the first element I is the output of the second element I, the first input of which is connected to the sequence included no first entry in the first monostable first comparator and a first voltage converter having an input connected to the output of the sensor zero-sequence voltage, a second input of the second AND gate is connected to the series connected second and One-Shot timer 0 the OR-NOT element, whose inputs are connected via the second, third and fourth comparators, connected in series with the second, third and fourth voltage converters, respectively, to the corresponding outputs of the phase voltage sensor, the output of the first And element being connected to the input executive body.