RU2313875C1 - Device for protection of two parallel lines with separate switches - Google Patents

Abstract

FIELD: electrical engineering.

SUBSTANCE: the device has the first and second OR circuits, the first and second output relays, disconnection circuit of the switch of two parallel lines, and for two like phase lines of the current relay and the power direction relays connected to the current transformers of these phases of the first and second and circuits, switch contacts, additionally inserted are the first, second and third current relays, the third AND circuit and the third OR circuit, whose inputs are connected to the outputs of the current relays, the fourth, fifth, sixth current relays, the fourth AND circuit and the fourth OR circuit connected to the outputs of the inserted fourth, fifth and sixth current relays, the first NOR circuit, whose inputs are connected to the outputs of the first and fourth current relays, the second NOR circuit-to the outputs of the second and fifth current relays, the third NOR circuit-to the outputs of the third and sixth current relays, the fifth and sixth NOR circuits, whose inputs are connected to the outputs of the NOR circuits and the outputs of the fourth and third AND circuits respectively, the output of the third OR circuit is connected to the fourth input of the second AND circuit, the output of the fourth OR, circuit - to the fourth input of the first AND circuit, the output of the fifth and sixth OR circuits - to the fifth input of the first and second AND circuits respectively.

EFFECT: enhanced sensitivity of protection and economic efficiency.

1 dwg

Description

The invention relates to electrical engineering, in particular to relay protection technology, and can be used to protect two parallel lines with separate switches from short circuits.

A device is known for transverse differential current protection of two parallel lines, containing a current relay connected to current transformers of the same phases of both lines (Chernobrovov N.V. Relay protection. Because of Energy. 1974). But this device does not distinguish on which of the lines a short circuit (short circuit) has occurred and can falsely disable an undamaged line.

The closest to the proposed technical essence and the achieved effect is the device of two parallel lines with separate switches, containing the first OR element and the first output relay, the input connected to the output of the first OR element, and the output to the circuit breaker circuit breaker of the first of two parallel lines, the second an OR element and a second output relay connected by input to the output of the second OR element, and by an output to the circuit breaker circuit of the second line, and for two phases of the same name by current relay and relay direction power connected to the current transformers of these phases, according to the first and second element And, the first, second and third inputs connected respectively to the opposite outputs of the power direction switch, serially connected block contacts of the switches and the output of the current relay, and the output of the first element And is connected to the first input of the first OR element, and the output of the second AND element to the first input of the second OR element (EPFigurnov. Relay protection. M. Zheldorizdat. 2002. 720 p.).

However, this device has a low sensitivity due to the need to isolate itself from the load currents during spontaneous or erroneous tripping by the personnel of the circuit breaker on the opposite side of the line, as well as during phase failure with one-sided grounding.

The objective of the invention is to increase the sensitivity of protection, increase the economic effect.

This technical result is achieved by the fact that the protection device of two parallel lines with separate switches containing the first OR element and the first output relay connected to the output of the first OR element, and the output of the first of two parallel lines to the circuit breaker circuit, the second OR element and the second output relay, connected to the output of the second OR element by an input, and by an output - to the circuit breaker circuit of the second line, and for two phases of the same name by current relay and power direction relay connected to current transformers of these phases, according to the first and second AND elements, the first input connected to the opposite outputs of the power direction switch, the second to the contacts of the switches connected in series, and the third to the output of the current relay, and the output of the first AND element connected to the first input of the first OR element and the output of the second element And to the first input of the second element OR, additionally introduced the first, second and third current relays, inputs connected to the current transformers, respectively, phases A, B, C of the first line, the third element And the third e OR element, inputs connected to the outputs of the input current relays, fourth, fifth, sixth current relays connected to current transformers of phases A, B, C of the second line, fourth element AND and fourth element OR, connected to the outputs of the fourth, fifth and sixth current relay, the first OR-NOT element connected to the outputs of the first and fourth current relays, the second OR-NOT element to the outputs of the second and fifth current relays, the third OR-NOT element to the outputs of the third and sixth current relays, fifth and sixth elements OR, by inputs data to the outputs of the OR-NOT elements and to the output of the fourth and third AND elements, respectively, with the output of the third OR element connected to the fourth input of the second AND element, the output of the fourth OR element to the fourth input of the first AND element, the output of the fifth and sixth OR elements to the fifth input, respectively, of the first and second elements I.

The device contains (see drawing) current relays 1-3, connected to current transformers (CT) by the first of two parallel lines, current relays 4-6, connected to second-line current transformers by input, current relay 7 and power direction relay 8 (RNM) ) double-acting, the inputs connected to the CT of the same phases of both lines to the difference of their currents (RNM also the voltage of the other two phases, therefore, the RNM in the drawing shows two inputs), logic elements OR 9-14, elements AND 15-18, elements OR NOT 19-21, output relays 22 and 23, input connected to the output of the element OR 13 and OR 14, and the output of the circuit breakers of the first and second lines. Element 9 (10) with inputs connected to the outputs of all elements OR NOT 19, 20, 21 and to the output of element I-18 (15). The output of element 9 (10) is connected to the fifth input of element 16 (17). Element 11 (12) is connected by inputs to the outputs of current relays 1 (4), 2 (5), 3 (6), and by an output - to the fourth input of element 17 (16). The third input of the elements 16 and 17 is connected to the output of the relay 7, the second to the series-connected block contacts 24 and 25 of the switches of the first and second lines, the first to the opposite outputs of the RNM-8. The OR-NOT element 19 (20, 21) is connected to the output of relay 1 (2, 3) and relay 4 (5, 6). The OR element 13 (14) is connected to the output of the element 16 (17). Note that in the proposed device there are two elements 16 (17) and two relays 7 and 8 if the network is with an isolated neutral, or three if the network is with a grounded neutral (not shown in the drawing current relays 7 and PHM 8 are connected to the difference currents of other phases of two lines). The diagram shows only the inputs 26 (28) and 27 (29), to which the elements 16 (17) of other phases are connected, as well as the ends 30 (31) and 33 (32) connected to these elements, connected to the outputs of the elements 9 (10) ) and 12 (11).

Relays 1, 2, 3, 4, 5, 6 are detached from the open circuit current of the lines. Relay 7 detaches from the unbalance current with an external three-phase short circuit (K3).

The device operates as follows. In the load mode or external three-phase K3, the currents in the protected lines are approximately equal and relay 7 does not work. Therefore, there are no signals at the output of elements 16 and 17, and relays 22 and 23 do not come into operation.

In the event of an erroneous or spontaneous disconnection of a line, for example, the first one, from the opposite side, relays 1, 2, 3 return to their original position, ceasing to give out signals, since the line is without load (with a load, relays 1, 2, 3 are tripped). As a result, at the output of element 11, the signal disappears and element 17 also does not give a signal, although relays 7 and RNM 8 are triggered, giving a signal that the short circuit is on the second line (although it is not), since the entire load current passes through the second line. Thus, the element 11 blocks the false disconnection of the second line. If a three-phase short circuit occurs on the second line outside the RNM “dead” zone, then part of the current K3 will also flow along the first line and relays 1, 2, 3 are triggered, the OR element 11 gives a signal to the fourth input of the element 17, to the other inputs of which the signals are supplied, including from element 10, since relays 1-3 are activated under the action of a short-circuit current and a signal is output from element 15 and, as a result, from element 10, although signals do not come from the outputs of the elements OR NOT, since they are triggered relay 4, 5, 6. If three-phase K3 is in the RNM dead zone, then the relay does not work and there are no signals aye. The line in these cases is disabled by cut-off, as with traditional transverse shields.

With two-phase faults on the second line, two options are possible. The first, when there is no current in the intact phase, the second, when there is.

In the first case, the current relays connected to the CT of the intact phase do not work, let it be, for example, relay 1 and relay 4. Then, the elements 15 and 18 do not give out signals, and the element 19 gives out, like the elements 11 and 12 ( short-circuit current flows through damaged and undamaged lines). The signal from the element 19 starts the elements 9 and 10, and the element 10 supplies a signal to the fifth input of the element 17. Thus, all the inputs of the element 17 received signals, since the current relay 7 and RIM 8 are activated (the RNM sends a signal to the first input of the element 17 , since K3 is on the second line), the block contacts 24, 25 are closed (both lines are on), supplying a signal to the second input of element 17. As a result, the output relay 23 is triggered and sends a signal to turn off the second line circuit breaker, after which the block pins 24, preventing disconnection of the first line.

In the second case, if there is current in the undamaged phase of the damaged second line, then it is approximately equal to the current in the undamaged phase of the first line, since the resistances of these phases are approximately equal, and relay 1 and relay 4 are activated. All other current relays have been activated, and element 17 is activated, the second line is turned off, current relays 4, 5, 6 stop issuing signals and element 12 does not give a signal to the fourth input of element 16, preventing the protection from working to disconnect the first line.

If one phase is interrupted on the second line with one-sided grounding (on the other side of the line), for example, on the phase, to the CT of which relay 5 is connected (on the first line of relay 2). Relays 7 and RIMs 8 are triggered, the latter giving a signal to element 16, since the power is directed, as in a short circuit, on the first line, which threatens to shut it down. The shutdown is prevented due to the fact that the relay 5 stops issuing a signal, as it passes from the triggered state to de-energized, removing the signal from the element And 18, which, in turn, does not give a signal to the element 9. There are also no signals at the other inputs of the element 9, since there are no signals at the outputs of the elements OR NOT 19, 20, 21. Therefore, element 9 does not provide a signal to element 16, blocking the protection operation by disconnecting the first line. Similarly, you can trace the behavior of the device in case of damage on the first line.

Thus, the device has a higher sensitivity than others, which prevents large damage and brings economic benefits.

Claims (1)

A device for protecting two parallel lines with separate switches, containing the first OR element and the first output relay connected to the output of the first OR element, and the output to the circuit breaker circuit of the first of two parallel lines, the second OR element and the second output relay connected to the input the output of the second OR element, and the output to the circuit breaker circuit of the second line, and for the two phases of the same name by the current relay and power direction switch connected to the current transformers of these phases, by the first and second element And, the first input connected to the opposite outputs of the power direction switch, the second to the series-connected contacts of the switches, and the third to the output of the current relay, the output of the first AND element connected to the first input of the first OR element, and the output of the second AND element to the first the input of the second OR element, characterized in that the first, second and third current relays are additionally introduced into it, the inputs connected to the current transformers of the phases A, B, C of the first line, the third AND element and the third OR element, the inputs are connected to the outputs of the input current relays, the fourth, fifth, sixth current relays connected to the current transformers of phases A, B, C of the second line, the fourth element And and the fourth element OR, connected to the outputs of the input fourth, fifth and sixth current relay, the first an OR-NOT element connected to the outputs of the first and fourth current relays by inputs, a second OR-NOT element to the outputs of the second and fifth current relays, a third OR-NOT element to the outputs of the third and sixth current relays, a fifth and sixth OR element, inputs connected to the outputs comrade OR NOT and to the output of the fourth and third AND elements, respectively, with the output of the third OR element connected to the fourth input of the second AND element, the output of the fourth OR element to the fourth input of the first AND element, the output of the fifth and sixth OR elements to the fifth input, respectively the first and second elements I.