JP2009142136A - Protective relay with inverse-time element and protecting method of electric power system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a protective relay and a protecting method in which time-limit cooperation does not collapse even if a back power supply at the transmission side is changed in an electric power system in which an overcurrent relay is used for the protection of the receiving side. <P>SOLUTION: The protective relay, which is provided at the transmission side of the electric power system having the overcurrent relay that has inverse-time characteristics at the receiving side, includes a distance relay means and an overcurrent relay means, which has roughly the same inverse-time characteristics as those of the overcurrent relay at the receiving side. Furthermore, a first step protection range, in which the setting of the distance relay means is instantaneously shut off, is set to approximately 80% to 85% of a line impedance value of transmission and distribution lines connecting the transmission side and the receiving side. When an output of the second step is used, the protection range, in which shutoff is output after a certain period of time, is set to approximately 120% of the line impedance value. The setting of the protection range of the overvoltage relay means is made to cooperate with the shutoff time limit of the overcurrent relay means at the receiving side inside the premise of receiving end. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a power system protection technique, and in particular, a protection relay with an anti-time limit element that can appropriately protect by maintaining time coordination even if the impedance on the power receiving side changes due to a change in the power source on the power transmission side, and The present invention relates to a power system protection method.

  Conventionally, as shown in FIG. 6, the short circuit protection of the lower system of about 22 kV is based on the distance relay (hereinafter abbreviated as DZ) 1 or the overcurrent relay with instantaneous element (hereinafter abbreviated as OC) 2 on the power transmission side 10 by a line. In the lower system end (power receiving side) 20 that is receiving a lot of power from high-end customers, both the primary and Tr secondary load lines of the transformer (Tr) 5 are overcurrent relays (OC) as power receiving relays. 3) and 4 are generally used.

  Since DZ1 or OC2 which is a protective relay on the power transmission side 10 (hereinafter referred to as a power transmission side relay) and a protection relay on the power receiving side (hereinafter referred to as a power reception side relay) OC3, OC4 need to be timed, In the case of DZ1, the three-way impedance distance of time characteristic G1d shown in FIG. 7 (a) is coordinated with the time limit, while in the case of OC2, the cooperation based on the inverse time limit characteristic shown in FIG. 8 (a) is taken.

  However, if the capacity of the rear power supply 7 decreases due to a change in the power transmission system on the power supply side, the power supply side power supply viewed from the point B on the consumer side also decreases relatively. In that case, the current at the time of an accident flowing from the power transmission side is reduced by the equivalent circuit shown in FIG. 4, so that the impedance of the power receiving point calculated by the value obtained by dividing the transmission voltage by the accident current is relatively large. Change. For this reason, when the power transmission side relay is DZ1, as shown in FIG. 7B, the operation time characteristic G1d of DZ1 moves proportionally to the power receiving point side. On the other hand, in the instantaneous operation C1 of the timing characteristic G2 of the OC3 of the power receiving side relay, the power receiving point impedance moves rightward in the figure, but the instantaneous operation limit impedance does not change, so the instantaneous operation range decreases. That is, since the instantaneous operation limit impedance does not change, the inverse time limit portion C2 of OC3 does not move (the protection range extends to the primary side). For this reason, if an accident occurs between the operation time limit Z3 of the third stage of the transmission side DZ1 between the OC3 of the power receiving relay and the secondary OC4 below it, there is a possibility that the transmission side DZ1 operates unnecessarily.

  Similarly, when the power transmission side relay is OC2, even if the back power supply decreases, the instantaneous operating impedance parts Z1 and C1 of both the power transmission side relay and the power reception side relay OC2, 3 are shown in FIG. 8B. It moves in the middle right direction, and the infinite time zones Z2 and C2 do not overlap, but there is a gap C in both instantaneous operation parts Z1 and C1 of the power transmission relay and power reception relay, and if there is an accident between them, it can operate instantaneously Therefore, problems such as fusing on power line protection occur. However, if the instantaneous element in the normal state is a value that does not cause a problem, it becomes impossible to cooperate with the customer side.

  As a technique for improving the drawbacks of this type of distance relay method, for example, in Patent Document 1, when a near-end accident near a transmission line substation occurs, the impedance is almost zero, so There is a problem that the inside and outside cannot be distinguished, and in order to solve this problem, a technique has been proposed in which the circuit breaker of the transmission line is tripped under an AND condition of an undervoltage relay, an overcurrent relay, and a direction relay.

System operation with a change in the back power supply needs to be carried out promptly in the event of an accident, and the setting changes at the site are not in time. For this reason, it becomes a problem how to take the timed coordination of each protection relay. However, since the technique of Patent Document 1 is not a technique for improving the protection coordination following the change of the power supply behind the transmission line, The problem cannot be solved.
JP-A-8-23626

  The present invention has been made in view of the above-described circumstances, and is a power transmission line or distribution line (hereinafter referred to as a transmission / distribution line) in which the back power supply is changed in an extra high-volume consumer who uses an overcurrent relay to protect the power receiving side. It is an object of the present invention to provide a protective relay with an anti-time element and a method for protecting an electric power system that can protect the transmission and distribution lines without failing in time cooperation.

  In order to achieve the above object, a protective relay with an anti-time element according to the present invention is an electric power system having an overcurrent relay having an anti-time characteristic on a power receiving side (customer receiving point). A protective relay provided in a power transmission side substation connected via a distance relay means, and an overcurrent relay means having approximately the same inverse time characteristics as the distance relay means and the overcurrent relay on the power receiving side It is provided with.

  In the present invention, the line from the power transmission end to the power reception end is protected by the distance relay means, and after the second DZ stage on the power receiving side, the distance relay and the overcurrent relay means having an inverse time characteristic are selected and protected. Therefore, even when the power supply behind the system changes, it is possible to coordinate with the overcurrent relay used as protection on the power receiving side.

  The distance relay means of the protective relay with an anti-time element according to the present invention has at least a first stage, a second stage, and a third stage protection range from the power transmission side, and is in a normal state (rear power supply capacity is The second stage protection range includes a power receiving point on the power receiving side, and the third stage protection range is set behind the power receiving point (load side) at the time of no change). Second trip determination is performed based on first trip determination means for executing trip determination based on an accident detection signal, an accident detection signal in the protection range of the second stage, and a non-use condition of the overcurrent relay means. Trip judging means, a third trip judging means for making a trip judgment using the accident detection signal of the protection range of the third stage, the on-site accident condition on the power receiving side, and the use condition of the overcurrent relay means And.

  In the present invention, for the third stage protection range that will shift to the customer premises (secondary side) due to the change in the capacity of the power source on the back side of the power transmission side, Timed coordination is maintained by outputting a trip signal based on the conditions and the usage conditions of the overcurrent relay means.

  Preferably, the on-site accident condition on the power receiving side is established when the distance relay means detects that the accident point is not within the second stage protection range and is within the third stage protection range. , It is possible to easily switch to the overcurrent relay means and maintain the timed coordination of the problematic location. Note that a condition that there is a change in the rear power supply capacity on the power transmission side may be added to this condition.

  Further, the distance relay means of the protective relay with an anti-time element according to the present invention can be set as at least the first stage, the second stage, and the third stage from the power transmission side as a distance protection range, In a normal state, the protection range of the second stage includes a power reception point on the power receiving side, the protection range of the third stage is set behind the power reception point, and the output of the overcurrent relay unit and the distance relay unit A trip signal is output based on the switching means for switching the output of the third stage, the output of the first stage of the distance relay means, the output of the second stage, and the output of the switching means. Features.

  In the present invention, the protection range of the third stage can be switched between the distance relaying means and the overcurrent relaying means having the same characteristics as the power receiving side, thereby changing the system configuration by changing the system configuration. Even when the capacity changes, it is possible to maintain time cooperation and continue appropriate protection operation.

  The protection circuit or the protection relay according to the present invention is capable of setting the distance protection range of the distance relay means in three stages, and the first and the second outputs are the first, A second timer is inserted, a third timer is inserted into the output of the overcurrent relay means, and the output, the on-site accident condition on the power receiving side, and the use condition of the overcurrent relay means are ANDed. 1 AND circuit, and second and third AND circuits that AND the output of the first and second timers and the output of the NOT circuit that negates the output of the third AND circuit, and the distance It is characterized by comprising an output of the first stage of the relay means and an OR circuit that ORs the outputs of the first, second and third AND circuits.

  In the present invention, the configuration is more specific, and the distance setting step of the distance relay means is used, and the first and second timers inserted in the output of the distance relay means and the overcurrent relay means The timer of 3 can easily set the timed coordination with the overcurrent relay on the power receiving side.

  The protection circuit or the protection relay according to the present invention includes an AND circuit of the output of the overcurrent relay means, the on-site accident condition on the power receiving side, and the use condition of the overcurrent relay means, and the AND output and the distance relay. It is characterized by comprising an OR circuit with the output of the first stage of the means.

  In the present invention, by using only the output of the first stage of the distance relay, it is possible to facilitate protection coordination with the circuit, settling, and the power receiving side.

  In the protection circuit or the protection relay according to the present invention, the first and second timers are respectively inserted into the outputs of the second stage and the third stage of the distance relay means, and the output of the overcurrent relay means and the distance There is provided a circuit of switching means composed of an AND circuit and a NOT circuit for switching between the second timer output of the third output of the relay means, and the output of the first stage of the distance relay means, It is characterized by comprising an OR circuit of the output second timer output and the output of the switching means.

  In the present invention, when the rear power supply capacity is reduced due to a system change or the like, the distance relay performs the time coordination by switching to the overcurrent relay only at a distance where the time relay cannot be coordinated with the power receiving side overcurrent relay. Can be maintained.

  A power system protection method according to the present invention is a method of protecting a line using the protection circuit or the protection relay described above, wherein the first stage protection range for instantaneously interrupting the setting of the distance relay means is a line impedance. When the output of the second stage is used from 80% to 85% of the value, the protection range that shuts off the output after a certain period of time is set to about 120% of the line impedance value in order to reliably include the transmission and distribution lines near the power receiving end. The protection range of the overcurrent relay means is set to a cutoff time coordinated with the cutoff time of the overcurrent relay means on the power receiving side within the power receiving end.

  Also, several types of inverse time characteristics of the overcurrent relay means at the power transmission end are set, and the characteristics are considered to be the same as the inverse time characteristics of the overcurrent relay means on the power receiving side, or within the range where there is no problem in terms of protection. By selecting the inverse time characteristic and using the protective relay means for setting the time cooperation time as the same setting as the power receiving side, it is possible to simplify the setting and increase the certainty of the time cooperation.

  According to the present invention, in the overcurrent relay where the protection on the power receiving side is used, the reverse end time characteristic of the overcurrent relaying means is overlapped with the distance relaying means, so that the receiving end impedance is changed due to the change in the power supply side rear power capacity. Even if it changes, it becomes possible to maintain appropriate timed cooperation.

Embodiments of the present invention will be described below.
FIG. 1 is a protection circuit on the power transmission side 10 according to the first embodiment.

  In this figure, the distance relay (DZ) 1 has three stages of outputs S1, S2, and S3 for changing the operation time according to the distance (impedance), and is the same as the overcurrent relays with instantaneous elements 3 and 4 on the power receiving side. Time coordination is achieved by an overcurrent relay (OC) 2a having a time limit characteristic and timers T1, T2 and T3.

  A signal through the timer T2 is input to the AND logic A3 as the third-stage output S3. The output of the OC2a is also input to the AND logic A1 through the timer T3 together with the counterpart end-site accident determination signal J and the signal U for use of this OC function. Further, a signal U for use of this OC function is connected as a gate input of the AND logic A3 through NOT logic N1. The output of the AND logic A3, the output S1 of the DZ1, the output of the timer T1, and the output of the AND logic A1 are respectively input to the OR logic R1, and this output is used as a trip signal for the power transmission circuit breaker.

  However, the other party premises accident judgment signal J is a signal obtained by passing the S2 signal of the DZ1 through the NOT logic N2 (determining a position 120% or more away from the line impedance to the counterpart terminal due to S2 non-operation) and the S3 of the DZ1. The signal (the backup protection settling range of the partner premises to be viewed by the power supply relay) and the signal input to the AND logic A2 are used to reliably determine the partner premises.

The operation will be described with reference to FIG. 1 and the time characteristic graph of FIG.
First, the operating point (distance) of the second stage Z2 is set slightly before the power receiving end B according to the impedance when the power transmitting side power supply 7 whose characteristics of the DZ1 are shown in FIG. Is coordinated with the OC3 instantaneous element and set to about 0.3 seconds. Then, the counter time characteristic part Zc of the OC2a is set to the same value as the counter time characteristic part C2 of the OC3 of the power receiving relay, and the timer T3 is set to about 0.3 seconds as the cooperation time with the OC3 time limit element. As a result, since the operation of the power transmission side OC2a is always delayed by the T3 settling time in an accident at the inverse time characteristic portion in the customer premises, it is possible to achieve a reliable time cooperation and settling with the same settling value as the power receiving end OC. There is an advantage that judgment is easy in the value determination work and the analysis work in the event of an accident.

  Next, a change in the time characteristic when the capacity of the rear power supply 7 on the power transmission side 10 is normal and when it decreases will be described. The dotted line portion in FIG. 2 is the time characteristic G1d of the normal power transmission relay DZ1, and moves as indicated by the solid line when the rear power supply capacity decreases. However, the inverse time characteristic part Zc of the function of the OC2a does not move because it is caused only by the fault current, and does not overlap with the time characteristic of the power receiving relays OC3 and OC4.

  Explaining the operation at the time of an accident, for example, an accident in the impedance range indicated by Z1 is tripped and output via the OR logic R1 of immediate output by the first stage output S1 of DZ1 in FIG. Further, in the range of Z2, the second stage output S2 of DZ1 outputs the same after the time limit of the timer T1 via the OR logic R1. Further, in the case of a local accident on the power receiving side 20, the circuit breaker on the power receiving side is opened according to the time characteristic G2 of the OC3 of the power receiving relay. However, when this operation is defective, when the second stage Z2 of DZ1 or the counterpart end premises accident determination signal J is set, the opening control is performed by the inverse time characteristic Zc portion of the OC2a.

  According to the present embodiment, even if the capacity of the rear power supply changes due to a change in system configuration or the like, the accident detection signal S3 in the third stage protection range, the on-site accident condition on the power receiving side, and substantially the same as the power receiving side Since the trip signal is output by selecting the calculation based on the use condition of the overcurrent relay means having the above characteristics, it is possible to achieve timed coordination.

Next, a second embodiment will be described with reference to FIG.
This embodiment is simplified by providing switching means 43-51 for manually switching the output S3 of the third stage of DZ1 in the first embodiment and the output of the OC2a. The signal AND of the signal 43U from the switching means 43-51 is ANDed to the OC2a by the AND logic A5, and the output is input to the OR logic R1. On the other hand, the output of the third stage output S3 of DZ1 through the timer T2 and the output inverted through the NOT logic N1 of 43U are input to the AND logic A4 to perform an AND operation, and the output is the OR logic. Input to R1.

  In the above configuration, when the switching means 43U is kept in a normal state, it operates with only the same DZ as before without signal output, and when 43U is switched to OC use, there is a signal output, instead of the third stage output S3 of the DZ1. And operate with the output of OC2a.

  As described above, according to the present embodiment, even if the capacity of the power source on the power transmission side changes, protection coordination between the power transmission side and the power reception side is taken, and the circuit breaker on the power transmission side is opened at the same appropriate time as normal. It becomes possible to control.

  The present invention can be used for protection of transmission lines in a power system.

1 is a circuit diagram of a protection relay on a transmission side according to a first embodiment of the present invention. It is an operation time characteristic figure in a 1st embodiment of the present invention. FIG. 2 is a system configuration diagram of a power system in which the circuit of FIG. 1 is used. FIG. 4 is an equivalent circuit diagram of the system in FIG. 3. It is a circuit diagram of the protection relay of the transmission side by the 2nd Embodiment of this invention. It is an installation figure of the protection relay in the conventional electric power system. FIG. 7A is a diagram illustrating an operation time characteristic of a conventional DZ system, in which FIG. 7A shows a time characteristic at a normal time, and FIG. FIG. 8A is an operation time characteristic diagram of a conventional OC system, and FIG. 8A shows a time characteristic at normal time, and FIG. 8B shows a time characteristic when a rear power supply capacity decreases.

Explanation of symbols

1 Distance relay (DZ, distance relay means)
2, 2a, 3, 4 Overcurrent relay (OC, overcurrent relay means)
5 Transformer 6 Receiving side power supply 7 Transmitting side power supply 10 Power transmission side substation equipment 20 Power receiving side substation equipment A1 to A5 AND logic R1 OR logic N1, N2 NOT logic T1 to T3 Timer

Claims (5)

A protective relay provided on the power transmission side of an electric power system having an overcurrent relay having an inverse time characteristic on the power receiving side,
The protective relay includes a distance relay means and an overcurrent relay means having an inverse time characteristic substantially the same as that of the power-receiving-side overcurrent relay. The distance relay means has at least a first stage, a second stage, and a third stage protection range from the power transmission side, and the normal protection range of the second stage is a power reception point on the power reception side. The third stage protection range is set behind the power receiving point,
First trip determination means for performing trip determination according to an accident detection signal in the protection range of the first stage;
Second trip determination means for performing a trip determination based on an accident detection signal of the protection range of the second stage and a non-use condition of the overcurrent relay means;
A third trip determining means for performing a trip determination using the accident detection signal of the third stage protection range, the on-site accident condition on the power receiving side, and the use condition of the overcurrent relay means;
The protective relay with an anti-time element according to claim 1.   The on-site accident condition on the power receiving side is satisfied when the distance relay means detects that the accident point is not in the second stage protection range and is in the third stage protection range. The protective relay with an anti-time limit element according to claim 2. The distance relay means can set at least three stages from the power transmission side as the distance protection range, ie, the first stage, the second stage, and the third stage. The third-stage protection range is set behind the power receiving point.
Switching means for switching between the output of the overcurrent relay means and the third stage output of the distance relay means, the first stage output of the distance relay means, the second stage output, and the switching 2. The protective relay with an anti-time-limit element according to claim 1, wherein a trip signal is output based on the output of the means. A method for protecting a power system using the protective relay according to any one of claims 1 to 4,
The first stage protection range that instantaneously cuts off as the distance relay means is set to about 80% to 85% of the line impedance value of the transmission and distribution line connecting the power transmission side and the power reception side,
When using the output of the second stage, set the protection range to cut off output after a certain time to about 120% of the line impedance value,
A method for protecting a power system, characterized in that setting of a protection range of the overcurrent relay means is coordinated with a cutoff time of the overcurrent relay on a power receiving side within a power receiving end premises.

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