JP2005312180A - Digital protective relay system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a digital protective relay system which is equipped with a means for quickly and surely protecting a power transmission system by making other normal differential current relays exhibit their essential rapidity even if at least one differential current relay falls in operation failure. <P>SOLUTION: In a digital protective relay system, where a power substation 1 and load electric places 6(A-E) are connected annularly and a breaker 2 and a current transformer 3 are installed each in a transmission line to each load electric place 6 and a current differential relay 5, which intercepts the breaker 2, based on the difference of the current from the current transformer 3, is installed to correspond to each load electric place 6 and an operation means (not shown in Figure), which judges the existence of an accident, based on the current from each current differential relay 5 and the information about a switch, is installed in the power substation 1, the operation means in the power substation 1 includes a signal generating means which intercepts the breaker 2 corresponding to the faulty current differential relay 5(B), based on the difference of the current between the currents from both neighboring normal current differential relays 5(A) and 5(C) that are the nearest to the faulty current differential relay 5(B). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a digital protection relay system, and in particular, a plurality of load electric stations each provided with a current differential relay and a calculation means for determining the presence or absence of an accident based on information from each of the current differential relays. The present invention relates to a means for quickly and surely protecting a power transmission system even when at least one current differential relay becomes defective in a ring system (loop system) configured by connecting power supply substations in a ring shape.

  Conventionally, the current data from the current differential relay in which the malfunction has occurred is set to zero so that the protection function is not lost even if one current differential relay malfunctions. Instead of the current relay, an overcurrent relay that operates for a limited time was made to function.

  Therefore, in the overcurrent relay, the trip operation takes time, and an incorrect control condition is transmitted to the other current differential relay, which may cause an unnecessary malfunction of the other current differential relay. It was.

In view of this, a digital protection relay has been proposed in which control conditions immediately before an operation failure is transmitted to each other so that unnecessary operation of other current differential relays is not caused (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 9-205723 (page 2, page 4, FIG. 4, FIG. 1)

  However, since the control conditions immediately before the operation failure are transmitted and the protection operation is determined based on the control conditions, the real-time control is not true. That is, there is a problem that other normal differential current relays cannot reliably exhibit the original high speed for an event that occurs after a certain differential current protection relay malfunctions.

  An object of the present invention is to provide a means for quickly and reliably protecting a power transmission system by causing other normal differential current relays to exhibit their original high speed even when at least one differential current relay becomes defective. A digital protection relay system comprising:

  In order to achieve the above object, the present invention connects a power source substation and a plurality of load electric stations in a ring, and installs a circuit breaker and a current transformer on a transmission line to each load electric station, respectively. Calculating means for determining whether or not there is an accident based on at least current from each current differential relay and switch information; In a digital protection relay system configured to be installed in a power substation, the calculation means of the power substation has a current from a normal current differential relay nearest to both sides of the current differential relay that has malfunctioned. A digital protection relay system including means for generating a signal for interrupting a circuit breaker corresponding to a current differential relay that has malfunctioned based on the difference between the two is proposed.

  As a backup protection function for the current differential relay as the main protection function, a circuit breaker is provided between the power supply substation connected in a ring and the adjacent load electric station, and each of the load electric station and the circuit breaker An overcurrent protection relay that operates for a limited time is provided.

  In the present invention, even if the current differential relay becomes inoperable, the calculation means of the power supply substation locks the operation of the current differential relay that has become inoperable, and the nearest normal current differential on both sides thereof. Based on the difference in current from the relay, it generates a signal that shuts off the circuit breaker corresponding to the current differential relay that has malfunctioned. Can be protected.

  In addition, it has a back-up protection function with an overcurrent protection relay, ensuring redundancy to cope with the case where the current differential relay protection is not differential.

  Next, an embodiment of a digital protection relay system according to the present invention will be described with reference to FIG. FIG. 1 is a block diagram showing a system configuration of an embodiment of a digital protection relay system according to the present invention.

  The digital protection relay system according to the present embodiment determines the presence or absence of an accident based on information from a plurality of load electrical stations 6 (A to E) each having a current differential relay 5 and a current differential relay 5. An annular system (loop system) is configured by connecting the power source substation 1 (not shown) with a calculation means in an annular shape.

  Breakers 2 and current transformers 3 are installed in pairs on the upstream and downstream transmission lines to each load electric station 6 (A to E). Each current differential relay 5 interrupts the corresponding circuit breaker 2 when the difference between the inflow / outflow currents of the pair of current transformers 3 reaches a predetermined value.

  Circuit breakers 2 are respectively installed between the power substation 1 and the load power station 6 (A) and between the load power station 6 (E) and the power source substation 1. Between the circuit breaker 2 and the load electric station 6 (A) and between the load electric station 6 (E) and the circuit breaker 2, an overcurrent relay 4 that operates in a time-dependent manner according to its current. Are provided.

  The overcurrent relay 4 is a so-called backup protection function when the current differential relay 5 as the main protection function is not differential, and the circuit breaker to which the current differential relay 5 corresponds even if an abnormal current occurs and a predetermined time elapses. When 2 is not cut off, each circuit breaker 2 between the power supply substation 1 is cut off to protect the ring system.

  The computing means of the power supply substation 1 collects at least current and switch information and determines whether there is an accident or the like.

  In the power transmission system, it is assumed that the current differential relay 5 itself may malfunction in addition to the occurrence of an accident in the power transmission line and the load electrical station 6 (AE) due to lightning strikes, ground faults, etc. It is necessary to take measures.

  In FIG. 1, when the current differential relay 5 of the load electrical station 6 (B) becomes malfunctioning, conventionally, the current of the load electrical station 6 (B) where the malfunction occurred is generated so as not to lose the protection function. The current data from the differential relay 5 is set to zero, and instead of the differential current relay 5 that originally operates at high speed, the overcurrent relay 4 that operates for a limited time is functioned.

  In the overcurrent relay 4, the trip operation for breaking the circuit breaker 2 takes time, and an erroneous control condition is transmitted to the other current differential relay 5, so that the other current differential relay 5 is originally unnecessary. In some cases, this could cause malfunctions.

  On the other hand, in the method in which the control conditions immediately before the malfunction is transmitted to each other and the unnecessary operation of the other current differential relay 5 is not caused, the control conditions just before the malfunction is transmitted to each other. Since the protection operation is determined based on the control condition, it is not a real-time control in the true sense, but for an event that occurs after the current differential relay 5 of the load electrical station 6 (B) becomes defective. There is a problem that the normal differential current relays 5 of the other load electrical stations 6 (A, C, D, E) cannot reliably exhibit their original high speed.

  In the combination of each load electrical station 6 (A to E) and the current differential relay 5, only the load electrical station 6 malfunctions, only the current differential relay 5 malfunctions, the load electrical station 6 and the current differential relay Three failure modes of malfunction of the relay 5 are conceivable. Among these, when only the load electric station 6 is malfunctioning, the normal current differential relay 5 exhibits a protective function.

  On the other hand, when only the current differential relay 5 is malfunctioning and the load electrical station 6 and the current differential relay 5 are malfunctioning, another protection function that operates quickly and reliably is required.

  In a ring system (loop system) in which a plurality of load electric stations 6 (A to E) and the power source substation 1 are connected in an annular shape, if the load electric station 6 (B) malfunctions, at least the load electric stations on both sides The phenomenon of being captured as a change in current also occurs in the current transformer 3 of 6 (A) and 6 (C).

  Therefore, in the present invention, the operation of the current differential relay 5 in which the load electric station 6 (B) has failed is locked regardless of whether or not the load electric station 6 (B) is malfunctioning. The current values of the current transformers 6 (A) and 6 (C) are taken from the respective current differential relays 5 into the calculation means of the power supply substation 1 to determine whether the load electric station 6 (B) is malfunctioning. Then, the operation of the circuit breaker 3 is controlled.

  When only the current differential relay 5 is malfunctioning, the circuit breaker 3 of the load electrical station 6 (B) is not interrupted and monitoring is continued.

  If the load electrical station 6 and the current differential relay 5 are malfunctioning, the load electrical station 6 (A) and the load electrical station 6 (C) are loaded based on the detected current from the normal current differential relay 5. In order to protect the power transmission line between the electric station A and the electric station C including the station 6 (B), a high-speed trip signal is output to interrupt the circuit breaker 2 at the target site.

  If the current differential relay 5 of the load electrical station 6 (A) closest to the power substation 1 is malfunctioning, the current values of the load electrical stations 6 (E) and 6 (B) are set to the current differentials. It takes in from the relay 5 to the calculation means of the power substation 1. In addition, when the current differential relay 5 of the load electrical station 6 (E) closest to the power substation 1 is malfunctioning, the current values of the load electrical stations 6 (D) and 6 (A) are set to the respective current differentials. It takes in from the relay 5 to the calculation means of the power substation 1.

  Further, when the plurality of current differential relays 5 are malfunctioning, the current values of the load electrical stations 6 on both sides are taken from the normal current differential relays 5 into the calculation means of the power substation 1. For example, when the current differential relays 5 of the load electrical station 6 (B) and the load electrical station 6 (C) are malfunctioning, the current values of the load electrical stations 6 (A) and 6 (D) on both sides are respectively set. The normal current differential relay 5 takes in the calculation means of the power supply substation 1. When the current differential relay 5 of the load electrical station 6 (B) and the load electrical station 6 (D) is malfunctioning, the current values of the load electrical stations 6 (A), 6 (C), 6 (E) on both sides Are taken from the respective normal current differential relays 5 into the calculation means of the power supply substation 1.

It is a block diagram which shows the system | strain structure of one Embodiment of the digital protection relay system by this invention.

Explanation of symbols

1 Power substation 2 Circuit breaker (CB)
3 Current transformer (CT)
4 Overcurrent relay (51Ry)
5 Current differential relay (87Ry)
6 Load electric power stations (A to E)

Claims (2)

A power source substation and a plurality of load electric stations are connected in a ring, and a circuit breaker and a current transformer are installed in a transmission line to each load electric station, and the circuit breaker is installed based on a difference in current from the current transformer. A current differential relay to be cut off is installed corresponding to each load electrical station, and calculation means for determining the presence or absence of an accident based on at least current from each current differential relay and switch information is installed in the power supply substation. In a digital protection relay system configured as follows:
The calculation means of the power supply substation corresponds to the current differential relay that has malfunctioned based on the difference in current from the normal current differential relay nearest to both sides of the current differential relay that has malfunctioned. A digital protection relay system comprising means for generating a signal for interrupting a circuit breaker. The digital protection relay system according to claim 1,
A circuit breaker is provided between each of the power substations connected in a ring and the adjacent load electric stations,
A digital protection relay system comprising an overcurrent protection relay that operates for a limited time between each of the load electric station and the circuit breaker.

Images