RU2530543C1 - Protective device for two parallel lines - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: the device comprises the first, second and third current relays coupled to secondary windings of the current transformers for the respective A, B, C phases of the first line; the fourth, fifth and sixth current relays coupled to secondary windings of the current transformers for the respective A, B, C phases of the second line, the first, second, third and fourth AND elements and each of the above elements is coupled to the respective current relay. The first OR element is connected to the first, second and third AND elements. The first multiplier and the fourth comparing element are coupled to the secondary winding of the phase A of the current transformer in the first line. The second multiplier and the fifth comparing element are coupled to the secondary winding of the phase B of the current transformer in the first line. The third multiplier and the sixth comparing element are coupled to the secondary winding of the phase C of the current transformer in the first line. The fourth multiplier and the first comparing element are coupled to the secondary winding of the phase A of the current transformer in the second line. The fifth multiplier and the second comparing element are coupled to the secondary winding of the phase B of the current transformer in the second line. The sixth multiplier and the third comparing element are coupled to the secondary winding of the phase C of the current transformer in the second line. The fifth and sixth AND elements are coupled to the second OR element.

EFFECT: device reliability improvement.

5 dwg

Description

The invention relates to electrical engineering, in particular to a relay protection technique, and can be used to protect two parallel lines.

A device for protecting two parallel lines [Andreev V.A. Relay protection and automation of power supply systems. - M .: Higher. shk., 2008. - S.328-337], containing the power direction switch connected to the line current transformers and the voltage transformer, and the current relay connected to the same current transformers. The outputs of the power direction switch and current relay are included in the circuit breaker circuit breaker.

The disadvantages of this device are the presence of a dead zone due to the use of a power direction relay, improper operation when a wire break with a one-sided short circuit, and low sensitivity due to the need to tune from the maximum load currents and currents in undamaged phases.

Closest to the proposed device is to protect two parallel lines [RU 2313875 C1, IPC H02H3 / 28, H02H7 / 26 (2006.01), publ. 12.27.2007], 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 breaker of the first of two parallel lines, the second OR element and the second output relay, connected to the output of the second OR element, and the output to the circuit breaker circuit breaker of the second line, and for two phases of the same name by 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 relay n power directions, the second to the contacts of the switches connected in series, 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 input of the second OR element. The first, second and third current relays are connected by inputs to current transformers of phases A, B, C of the first line, respectively. The third element AND and the third element OR inputs connected to the outputs of the first, second and third current relays. The fourth, fifth, sixth current relays are connected to current transformers of phases A, B, C of the second line, respectively. The fourth AND element and the fourth OR element are connected to the outputs of the fourth, fifth and sixth current relays. The first OR-NOT element is connected to the outputs of the first and fourth current relays by inputs, and the second OR-NOT element is connected to the outputs of the second and fifth current relays. The third element is OR NOT connected to the outputs of the third and sixth current relays. The fifth and sixth OR elements are connected to the outputs of the OR-NOT elements and to the output of the fourth and third elements I. The output of the third OR element is connected to the fourth input of the second element I. The output of the fourth OR element is connected to the fourth input of the first element I. The output of the fifth and of the sixth element OR is connected to the fifth input, respectively, of the first and second elements I.

The disadvantages of this device are the low reliability due to the use of voltage circuits, which are damaged more often than current circuits, and a deep decrease in voltage, which can lead to unnecessarily triggered protection, as a result, even to a major accident, for example, to a man-made accident in the USA in 1995 . [Koshcheev L.A., Semenov V.A. Systemic accidents in the Western United States Energy // Electricity. 1997. No. 10. S.24-28].

The objective of the invention is to increase the reliability of the device.

The problem is solved due to the fact that the device for protecting two parallel lines, as in the prototype, contains the first, second and third current relays connected to the secondary windings of current transformers of the corresponding phases A, B, C of the first line, fourth, fifth and a sixth current relay connected to the secondary windings of the current transformers of the corresponding phases A, B, C of the second line, the first, second, third, fourth AND elements, each of which is connected to the corresponding current relay, the first OR element is connected to the first, second and temu element and a second OR gate connected to the fourth element I.

According to the invention, the first multiplier and the fourth comparison element are connected to the secondary winding of the phase A current transformer of the first line. The first multiplier is connected to the first comparison element. The second multiplier and the fifth comparison element are connected to the secondary winding of the phase B current transformer of the first line. The second multiplier is connected to the second comparison element. The third multiplier and the sixth comparison element are connected to the secondary winding of the phase C current transformer of the first line. The third multiplier is connected to the third comparison element. The fourth multiplier and the first comparison element are connected to the secondary winding of the phase A current transformer of the second line. The fourth multiplier is connected to the fourth comparison element. The fifth multiplier and the second comparison element are connected to the secondary winding of the phase B current transformer of the second line. The fifth multiplier is connected to the fifth comparison element. The sixth multiplier and the third comparison element are connected to the secondary winding of the phase C current transformer of the second line. The sixth multiplier is connected to the sixth comparison element. The fifth and sixth current relays are respectively connected to the fifth and sixth element I. The first, second and third comparison elements are respectively connected to the first second and third elements. The fourth, fifth and sixth elements of comparison are respectively connected to the fourth, fifth and sixth elements of I. The fifth and sixth elements of AND are connected to the second element of OR. The output of the first OR element is connected to the circuit breaker circuit of the second line, and the output of the second OR element is connected to the circuit circuit of the circuit breaker of the first line.

Using this device eliminates the voltage circuit, which increases the reliability of the device.

In FIG. 1 presents the proposed device.

In FIG. 2 is a diagram of two parallel lines with short circuits between phases A and B on the first line outside the cascade zone and in it.

In FIG. 3 is a diagram of two parallel lines with double earth faults of phase A on the first line and phase C of the line extending from the buses of the opposite substation, outside the cascade zone and in it.

In FIG. 4 is a diagram of two parallel lines with short circuits of phase A ground on the first line outside the cascade zone and in it.

In FIG. 5 is a diagram of two parallel lines with phase A break on the first line.

The device for protecting two parallel lines contains the first 1 (Fig. 1), second 2, third 3 current relays, which are respectively connected to the secondary windings of the first 4, second 5, third 6 current transformers of phases A, B, C of the first line 7 (Fig. . 2). The fourth 8 (figure 1), fifth 9, sixth 10 current relays are respectively connected to the secondary windings of the fourth 11, fifth 12, sixth 13 current transformers of the corresponding phases A, B, C of the second line 14 (Fig. 2).

The inputs of the first element And 15 (I1) (Fig. 1) are connected to the outputs of the first current relay 1 and the first element of comparison 16 (C1). The inputs of the second element And 17 (I2) are connected to the outputs of the second current relay 2 and the second comparison element 18 (C2). The inputs of the third element And 19 (I3) are connected to the outputs of the third current relay 3 and the third comparison element 20 (C3). The inputs of the fourth element And 21 (And4) are connected to the outputs of the fourth current relay 8 and the fourth comparison element 22 (C4). The inputs of the fifth element And 23 (I5) are connected to the outputs of the fifth current relay 9 and the fifth comparison element 24 (C5). The inputs of the sixth element And 25 (I6) are connected to the outputs of the sixth current relay 10 and the sixth comparison element 26 (C6). The inputs of the first element OR 27 (OR 1) are connected to the outputs of the first 15 (И1), second 17 (И2) and third 19 (И3) elements I. The inputs of the second element OR 28 (OR2) are connected to the outputs of the fourth 21 (И4), fifth 23 (I5) and sixth 25 (I6) elements I. The outputs of the first 27 (OR1) and second 28 (OR2) elements OR are respectively connected to the circuit breakers 29 (Fig. 2) of line 14 and 30 of line 7. First 31 (Y1 ) (Fig. 1), second 32 (Y2), third 33 (Y3) multipliers and inputs of the fourth 22 (C4), fifth 24 (C5), sixth 26 (C6) comparison elements, respectively, are connected to the secondary windings of the first 4 , second 5, third 6 current transformers. The fourth 34 (U4), fifth 35 (U5), sixth 36 (U6) multipliers and inputs of the first 16 (C1), second 18 (C2), third 20 (C3) comparison elements are respectively connected to the secondary windings of the fourth 11, fifth 12 and Sixth 13 current transformers. The first 16 (C1), second 18 (C2), third 20 (C3), fourth 22 (C4), fifth 24 (C5), sixth 26 (C6) comparison elements are respectively connected by inputs to the outputs of the first 31 (U1), second 32 (V2), third 33 (V3), fourth 34 (V4), fifth 35 (V5) and sixth 36 (V6) multiplier.

As a current relay, relays of the RT-40 type can be used. Comparison elements, OR and AND, amplifiers can be performed on a series 51 microcontroller from amtel AT89S53.

The principle of operation of the device is to determine the damaged line by comparing the currents of the same phases of two parallel lines in absolute value and prohibiting operation to turn off the first (second) line if there is no current in any of the phases of the second (first) line when the damage is cascaded, wire break with unilateral grounding, erroneous or spontaneous disconnection of the line from the opposite side.

The selection of the damaged line is carried out by the first 16 (C1), second 18 (C2), third 20 (C3), third 20 (C3), fourth 22 (C5), fifth 24 (C5), sixth 26 (C6) elements of the condition that the current in the damaged line is greater current intact k times. When this condition is met, a signal is sent to disable the corresponding line. At the outputs of the comparison elements 16 (C1), 18 (C2), 20 (C3), signals to disable the second line appear if the following conditions are met, respectively:

I _A2 ≥ k · I _A1 (one) I _B2 ≥ k · I _B1 (2) I _C2 ≥ k · I _C1 (3)

where I _A1 , I _B1 , I _C1 and I _A2 , I _B2 , I _C2 - currents in phases A, B, C of lines 7, 14;

k is the offset coefficient.

At the outputs of the comparison elements 22 (C4), 24 (C5), 26 (C6), the signals to turn off the first line appear if the following conditions are met, respectively:

I _A1 ≥ k · I _A2 (four) I _B1 ≥ k · I _B2 (5) I _C1 ≥ k · I _C2 (6)

The value of k is determined as follows. It should be such that the protection does not work unnecessarily when there are no short circuits on the lines, and the ratio of currents in their phases of the same name is maximum. This occurs during three-phase short circuits on the buses of the opposite substation, when the error ε ₁ of the current transformers reaches its maximum value. We also take into account the errors ε ₂ , taking into account the difference in the line resistances, and ε ₃ devices. In accordance with existing assumptions, we take ε ₁ = 0.1, ε ₂ = 0.02, ε ₃ = 0.02. Then

, $$k=\frac{|\; |\; |I_{\mathrm{to}}^f|\; |\; |}{|\; |\; |I_{\mathrm{to}}^f|\; |\; |}\cdot \frac{\mathrm{one}+{\epsilon }_2}{\mathrm{one}-{\epsilon }_{\mathrm{one}}-{\epsilon }_2-{\epsilon }_3}=1.18$$

,

- ток в фазах линий при трехфазном КЗ на шинах противоположной подстанции без учета погрешностей; с запасом принимают k=1,2.Where $$|\; |\; |I_{\mathrm{to}}^f|\; |\; |$$

- current in the phases of the lines with a three-phase short circuit on the tires of the opposite substation without taking into account errors; with a margin take k = 1.2.

The operation currents of the first 1, second 2, third 3, fourth 8, fifth 9, sixth 10 current relays are detached from the open circuit currents of the lines.

The device operates as follows. In normal mode, the currents of the same phases of both lines are equal. Therefore, inequalities (1-3) in the first 16 (C1), second 18 (C2), third 20 (C3) elements of comparison and inequality (4-6) in the fourth 22 (C4), fifth 24 (C5), sixth 26 ( C6) comparison elements are not performed, there are no signals at their outputs. Therefore, one input of the first 15 (I1), second 17 (I2), third 19 (I3), fourth 21 (I4), fifth 23 (I5), sixth 25 (I6) elements And the signal is not received. And although the first 1, second 2, third 3, fourth 8, fifth 9, sixth 10 current relays are in the operating state, the signals at the outputs of the first 15 (I1), second 17 (I2), third 19 (I3), fourth 21 ( I4), the fifth 23 (I5), the sixth 25 (I6) elements And are absent. Protection does not work.

When disconnecting line 7 from the opposite side, the first 1, second 2, third 3 current relays return to their original positions and there are no signals at their outputs. Fourth 8, fifth 9, sixth 10 current relays remain in the tripped state. At the outputs of the fourth 22 (C4), fifth 24 (C5), sixth 26 (C6) there are no signal comparison elements, since the conditions for their operation are not satisfied. At the outputs of the first 16 (C1), second 18 (C2) and third 20 (C3) comparison elements - there are (currents in the phases of line 14 are greater than in line 7, and the corresponding inequalities are satisfied). At the outputs of the first 15 (I1), second 17 (I2), third 19 (I3), fourth 21 (I4), fifth 23 (I5), sixth 25 (I6) elements And there are no signals, since they received signals only one entry. Protection does not work.

In case of a three-phase short circuit on line 7 (not shown in Fig. 1), the first 1, second 2, third 3, fourth 8, fifth 9, sixth 10 current relays remain activated, the conditions for tripping of the fourth 22 (C4), fifth 24 (C5), sixth 26 (C6) comparison items and are not performed - the first 16 (C1), the second 18 (C2) and the third 20 (C3). Therefore, at the outputs of the first 15 (I1), second 17 (I2), third 19 (I3) elements And there are no signals, and the fourth 21 (I4), fifth 23 (I5), sixth 25 (I6) elements And and the second element OR 28 (OR2) - is. As a result, a signal is sent to turn off the circuit breaker 30 of line 14. In a two-phase fault, for example between phases A and B, at point 37 on line 7 (Fig. 2), if there is a current in the intact phase, the first 1, second 2, third 3 fourth, 8th, fifth 9th, sixth 10 current relays, in the absence of the first 1, second 2, fourth 8th, fifth fifth current relays, and the third 3th, sixth 10 current relays return to their original positions. The signals appear only at the outputs of the fourth 22 (C4) and fifth 24 (C5) elements of comparison, the fourth 21 (I4) and fifth 23 (I5) of the elements And and the second element OR 28 (OR2). The switch 30 is turned off. In the case of a two-phase short circuit in the cascade zone, for example between phases A and B, at point 38, on line 7 (Fig. 2), the switch 39 on the receiving side will first open (this will protect the opposite side). At the outputs of the third 20 (C3), fourth 22 (C4) and fifth 24 (C5) comparison elements, signals appear, the first 1, second 2, fourth 8, fifth 9, sixth 10 current relays remain activated, the third current relay 3 returns to the original position, at the outputs of the fourth 21 (И4), fifth 23 (И5) elements AND and the second element OR 28 (OR2), signals appear (at the outputs of the first 15 (И1), second 17 (И2), third 19 (И3), sixth 25 (AND6) elements AND and the first element OR 27 (OR1) no signals), the switch 30 is turned off.

In case of double earth faults in networks with isolated neutral, if one damage occurred, for example, in phase A of line 7, and the other in phase C of a line extending from the power substation, points 40, 41 (Fig. 3), then the first 1 , second 2, third 3, fourth 8, fifth 9, sixth 10 current relays (Fig. 1) remain activated. Since I _A1 ≥ k · I _A2 , the fourth comparison element 22 (C4) generates a signal that, through the fourth element AND 21 (AND4) and the second element OR 28 (OR2), is applied to trip the switch 30. If one damage has occurred, for example , in phase A of line 7 in the cascade zone of protection, and the other in phase C of the line extending from the power substation, points 42, 43 (Fig. 3), then the first 1, fourth 8, fifth 9, sixth 10 current relays ( Fig. 1) remain activated, the second 2, third 3 current relays return to their original positions and block the protection effect on disconnecting whether 14 ns, the signals appearing at the outputs of the fourth comparing element 22 (C4), a fourth AND gate 21 (I4) and the second OR gate 28 (or 2). The switch 30 is turned off.

In case of single-phase short circuits in a network with a grounded neutral, for example, in phase A of line 7, point 44 (Fig. 4), in the absence of current in the undamaged phases, the first 1 and fourth 8 current relays are activated, and the second 2, third 3 and fifth 9, the sixth 10 current relays return to their original positions. If there is a current in them, the first 1, second 2, third 3, fourth 8, fifth 9, sixth 10 current relays remain activated. In both cases, at the outputs of the first 16 (C1), second 18 (C2), third 20 (C3), fifth 24 (C5), sixth 26 (C6) elements of comparison, the first 15 (I1), second 17 (I2), third 19 (И3), fifth 23 (И5), sixth 25 (И6) elements AND, the first element OR 27 (OR1) there are no signals, and at the outputs of the fourth comparison element 22 (С4), the fourth element И 21 (И4) and the second element OR 28 (OR2) they are. As a result, the switch 30 is turned off. With a single-phase short circuit in the cascade zone, point 45 (Fig. 4), the first 1, fourth 8, fifth 9, sixth 10 current relays are in the activated state. The second 2, third 3 current relays return to their original positions. There are signals at the outputs of the second 18 (C2), third 20 (C3), fourth 22 (C4) comparison elements and the fourth element And 21 (I4). The switch 30 is turned off. After it is turned off, the first 1, second 2, third 3 current relays return to their original positions, currents in transformers 4 - 6 of line 7 are absent at the outputs of the first 15 (I1), second 17 (I2), third 19 (I3), fourth 21 (I4), the fifth 23 (I5), the sixth 25 (I6) elements And there are no signals. Protection is taken out of action.

When a phase wire, such as phase A (Fig. 5) is broken and its grounding is one-sided (on the opposite side), a signal appears at the output of the first comparison element 16 (C1), but the first current relay 1 returns to its original position, and therefore the outputs of the first element AND 15 (AND) and the first element OR 27 (OR) no signals. Protection does not work.

By analogy with the above, it is easy to trace the operation of the device during a short circuit on the other phases of line 7, breaks in their wires and double earth faults. The behavior of the device in case of damage on line 14 is also considered. Let, for example, a two-phase short circuit between phases B and C occur on it. If there is a current in the intact phase, the first 1, second 2, third 3, fourth 8, fifth 9, the sixth 10 current relays, in the absence - the second 2, third 3 and fifth 9, sixth 10, and the first 1 and fourth 8 current relays return to their original positions. At the outputs of the second 18 (C2), third 20 (C3) comparison elements, second 17 (I2), third 19 (I3) AND elements and the first element OR 27 (OR1), signals appear. The switch 29 is turned off.

The proposed device allows you to provide two parallel lines with sensitive and reliable protection against interphase faults.

Claims (1)

A device for protecting two parallel lines containing the first, second and third current relays connected to the secondary windings of the current transformers of the corresponding phases A, B, C of the first line, the fourth, fifth and sixth current relays connected to the secondary windings of the current transformers of the corresponding phases A, B, C of the second line, the first, second, third, fourth AND elements, each of which is connected to the corresponding current relay, the first OR element is connected to the first, second and third AND elements, and the second OR element is connected to the fourth ele And, characterized in that the first multiplier (31) and the fourth comparison element (22) are connected to the secondary winding of the phase A current transformer of the first line, the first multiplier (31) is connected to the first comparison element (16), the second multiplier (32) and the fifth comparison element (24) is connected to the secondary winding of the phase B current transformer of the first line, while the second multiplier (32) is connected to the second comparison element (18), the third multiplier (35) and the sixth comparison element (26) are connected to the secondary winding of the transformer phase current C of the first line, and tre The third multiplier (33) is connected to the third comparison element (20), the fourth multiplier (34) and the first comparison element (16) are connected to the secondary winding of the phase A current transformer of the second line, and the fourth multiplier (34) is connected to the fourth comparison element (18) ), the fifth multiplier (35) and the second comparison element (18) are connected to the secondary winding of the phase B current transformer of the second line, the fifth multiplier (35) connected to the fifth comparison element (24), the sixth multiplier (36) and the third comparison element ( 20) transformers connected to the secondary winding phase II phase C current matrices, the sixth multiplier (36) is connected to the sixth comparison element (26), the fifth (9) and sixth (10) current relays are connected to the fifth (23) and sixth (25) AND element, and the first ( 16), the second (18) and third (20) comparison elements are respectively connected to the first (15), second (17) and third (19) AND elements, the fourth (22), fifth (24) and sixth (26) comparison elements respectively connected to the fourth (21), fifth (23) and sixth (25) AND elements, the fifth (23) and sixth (25) AND elements are connected to the second OR element (28), the output of the first IL element AND (27) is connected to the circuit breaker circuit of the second line, and the output of the second OR element (28) is connected to the circuit circuit of the circuit breaker of the first line.

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