SU1429212A2 - Differential protection device - Google Patents

Abstract

The invention relates to relay protection and can be used to protect busbar power plants. busbars of power transformers, high voltage electric motors and syn. chronic compensators. The purpose of the invention is to increase the speed and sensitivity of protection in case of short circuit (CC) in the zone of action of protection. To do this, enter the channel internal mode identification channel and the output signal of this channel prohibits the passage of the deceleration signals stored in the first transient period of the short circuit in the nonlinearity unit and in the setpoint setting unit. As a result, the speed and sensitivity of the protection increase. 1 il. S

Description

The invention relates to electrical engineering, namely, relay protection, can be used to protect busbars of power plants and substations, busbars of power transformers, high-voltage electric motors and synchronous rotating machines and is an improvement of the device according to the author. No. 1272393. I The aim of the invention is to increase the speed and sensitivity of a short circuit (short circuit) in the area of protection.

; The drawing shows a block diagram of a device for differential protection.

I A device for differential short-circuit protection against short-circuit at a concentrated electric power object 1, for example, a modular busbar of a power station that has several connections with switches and current transformers, contains a block of two current sensors according to the number of connections of tires, primary windings of which are intended to be connected To the outputs of transformers, the current of the respective busbar connections, the first terminals of the secondary windings of current sensors are combined, and the second are connected to the multiplex diode half-bridge 3, the cathodes and anodes are diodes in which, respectively, are combined and connected to a doukhlechevnaya comparison circuit 4, with a midpoint, an adder 5, which forms protection circulating currents, the inverting input of which is connected to the anodes of the diodes of a multi-shoulder diode half-bridge 3, and the non-inverting input - i; cathodes, the reacting body 6 connected by the first input to the output of the comparison circuit 4 via the first rectifier 7, the starting body 8 connected by the first input in series with the differential resistance 9 of the load between the common point of the secondary (5 comparison circuit 4, which is then grounded, nonlinearity block 10, the input of which is connected to the output (adder 5, and the output - to the second inputs of the starting 8 and reacting 6 organs, the first logic element And 1 the first and second inputs of which are connected v1hodami trigger 8 and regulatory bodies 6, and the output - to the input ichodnogo body 12, two comparators 13 and 14, the second AND gate 15 whose first input is connected

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0 5 Oh, Q 5 Q

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with the output of the first comparator 13, the first expander of 16 pulses, the output of which is connected to the input of the logical element HE 17, and the output of the last, with the third input of the first logical element II, differentiation unit 18, the input of which is connected to the unearthed end of the differential resistance 9 of the load, driver 19 of the reference voltage, the output of which is connected to the inverting input of the first comparator 13, the waiting multivibrator 20, the input of which, like the input of the first pulse extender 16, is connected to the output of the second And 15, and the first and second outputs are connected respectively to the second and third inputs of the reference voltage generator 19, the setting unit 21, the first input of which, like the first input of the reference voltage driver 19 and the non-inverting input of the first comparator 13, is connected with the output of the adder 5, and the output with the inverting input of the second comparator 14, the non-inverting input of which is connected to the output of the differentiation unit 18 via the second rectifier 22, the first transistor switch 23 with a return delay, the delay unit 24, the input which is connected to the output of the first comparator 13, and the output to the first input of the third logic element 25, the second input of which is connected to the output of the element HE 17 and the output to the input of the second pulse expander 26, the output of which is connected to the input of the second transistor switch 27, output which is connected to the combined cathodes of the separation diodes 28 and 29, the anodes of the latter are connected respectively to the output of the non-linearity unit 10 and to the second input of the setting point unit 2.

The reacting authority 6 can be performed according to a scheme containing two compressors with a driving CS circuit between them, the first input of the first comparator being the first input of the reacting authority 6, the second input is connected to the midpoint of the divider. the level of which is the setpoint for the operation of the first comparator, and the output of the first comparator is connected to the input of the integrating time of the master KS circuit, the output of which is connected to the working input

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the house of the second comparator, on the controlling input of which, being the second input of the reacting authority 6, supplies - with a reference voltage controlling the duration of the blocking time of the comparator's turn, thus implementing the principle of braking in the reacting authority, and the output of the second comparator is output of the reacting authority.

The starting element 8 is made in the same way as the second comparator of the reacting body, with the implementation of the principle of braking on the second control input of the comparator, which is the second input of the starting body 8, and at its first input there is a rectifier circuit.

The nonlinearity unit 10 is made according to an operational amplifier circuit, which has a diode cells with a voltage divider connected to a power source at the summing input, at a midpoint of which a certain opening voltage of the corresponding diode cell is set.

The installation setting unit 21 is made according to a circuit comprising two resistor voltage dividers, a capacitor, a transistor and two separation diodes. The anode of the first separation diode is the first input of the setpoint setting unit and is connected to the output of the circulating current adder 5, and the cathode is connected to the ungrounded kong capacitor end and transistor base, incl. emitter follower. The first resistor voltage divider is connected to the emitter of the transistor, the midpoint of which is with the output of block 21, and through its second isolating diode its second point is connected to the second resistor voltage divider connected to the positive power source. The ungrounded end of said capacitor, which serves to store the braking signal, is the second input of block 21.

The device works as follows.

With an external short circuit, the voltage from the output of the adder 5 is fed to the input of the nonlinearity unit, which forms the deceleration characteristic of the relay, raising the trigger thresholds of the starting and response organs. The setpoint setting unit 21, receiving power from the adder 5, also generates a deceleration signal.

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about 0 5

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for the second comparator lA in the logical part of the relay. Clagodar braking characteristics improve the detuning of the send from the signals with an external short circuit.

With a short circuit in the zone of protection operation resulting from the transition of an external short circuit to the zone of protection operation, or with a short circuit in the zone and the presence of flowing load currents, or with a short circuit in the zone with a large difference in the phase of leaking tones, the braking signals from block 10 the nonlinearity and block 21 of the setpoint are blocked as the channel for identification of the internal short circuit starts, which is from blocks 24-27 and diodes 28 and 29.

At the same time, at the first input of the third logic element, And 25 saves the signal of the logical unit, and when it appears in the first period after the transition of the short circuit to the zone of the logical unit from the first comparator 13, the second pulse expander 26 is started and gives a signal to generate the second pulse a logical switch that stops the flow of deceleration signals from the output of the non-linearity unit 10 to the second control inputs of the start-up and reactive units, and also removes the deceleration signal on the second control The input of the set point unit 21. Thus, the starting and reacting organs and the comparator of the setpoint block return to the lowest response thresholds in the first period after the transition of the short circuit to the trigger zone, which ensures the required speed and sensitivity of the protection to damage in the zone, especially at low short-circuit currents.

Claims (1)

Invention Formula Device for D1; effective protection on auth.St. N 1272393, t - which is to ensure that, in order to improve speed and efficiency in the event of a short circuit in the protection zone, a non-linearity unit, two separation diodes, a series-connected delay unit, a third And element, a second pulse expander and a second switch, the input of the nonlinearity block is connected to the output of the adder, and the output to the second