JPH0898400A - Distribution line fine grounding relay - Google Patents

Abstract

PURPOSE: To enable a fault circuit to efficiently interrupt without fetching a zero phase current of each circuit, by interrupting the circuit successively starting with a distribution line, with most frequent grounding fault in the past, based on increasing zero phase voltage of a bus in the case of generating the grounding fault in the distribution line. CONSTITUTION: In a distribution line bus, its zero phase voltage is detected by a grounding potential transformer GPT, and in a distribution line fine grounding relay, a processor 3 and an interface circuit 5 to breakers of each distribution line are provided. The processor 3 has a rank order memory 4 counting a number of times stored of generating a grounding fault in each distribution line. When zero phase voltage exceeds a setting value, based on a value of number of times of interrupting the distribution line stored in the rank order memory 4, a distribution line interrupting rank order is decided. This decision is performed based on a decreasing frequency of interruption of the distribution line. The distribution lines from the first to the n-th rank order, rearranged by this rank order, are successively interrupted by the breakers.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distribution line micro-ground fault relay applied to a high-voltage distribution system composed of a bus bar and a plurality of distribution lines connected to the bus bar.

[0002]

2. Description of the Related Art A directional ground fault relay (67G) is usually used for detecting a ground fault in a high-voltage distribution line, but a fine ground fault which cannot be detected by this is a fine ground fault relay. May be used. This micro-ground fault relay receives the zero-phase voltage of the bus bar as an input, and considers that a ground fault has occurred when the zero-phase voltage continues for a certain level over a certain level, and a relay installed in each distribution line bus bar ( 1
0G) is cut off in a predetermined order, and when the zero-phase voltage disappears, the cutoff line at that time is used as a ground fault line.

However, when using such a relay,
Since it also cuts off other healthy lines connected to the busbar, it has the disadvantage of causing unnecessary power outages. Therefore, an invention has been proposed in which a ground fault line is detected at high speed without interrupting a healthy line (see Japanese Patent Application Laid-Open No. 59-194631). That is, based on the phase relationship between the zero-phase voltage of the bus and the zero-phase current of each line, or the phase relationship between the change of the zero-phase voltage of the bus before and after the failure and the change of the zero-phase current of each line, In this invention, the line with the smallest phase difference is specified as the faulty line.

[0004]

However, in the above invention, since it is necessary to take in the zero-phase current of each line, it is necessary to install a zero-phase current transformer (ZCT) for each line. Therefore, the equipment becomes large-scale and the cost also rises. On the other hand, there are various routes through distribution lines, and among them, there are lines that are prone to ground faults.
For example, a line passing through a mountainous area is likely to come into contact with trees, and a wiring passing along a coastal area is likely to have low insulation due to salt damage.

Therefore, an object of the present invention is to consider a past failure history of a distribution line and to effectively cut off the failed line without taking in the zero-phase current of each line. Is to provide.

[0006]

According to a first aspect of the present invention, there is provided a distribution line micro-ground fault relay for achieving the above object, which comprises: a zero phase voltage detecting means for detecting a zero phase voltage of a bus connected to the bus;
Based on the increase of the zero-phase voltage of the bus when one of the distribution lines has a ground fault, an order cutting means for cutting the order of each distribution line and the occurrence of a ground fault in the past of each distribution line. The storage means stores the number of times of occurrence, and the order cutoff means cuts off in order from the distribution line in which the ground fault has occurred in the past, which is stored in the storage means.

[0007]

According to the above configuration, the distribution lines with the highest frequency of failures are cut off in order based on the past failure history. As described above, a distribution line with a large number of failures has a strong tendency for similar failures to occur, and therefore, there is a high possibility that the zero-phase voltage of the bus bar disappears by cutting off early. Therefore, it is not necessary to cut off another distribution line.

[0008]

Embodiments will be described in detail below with reference to the accompanying drawings showing embodiments. FIG. 2 is a distribution line system diagram in which a plurality of distribution lines 1F, 2F, ..., NF are connected to the busbars of A, B, and C phases, and a block of a distribution line micro-ground fault relay applied to this distribution line system. A circuit diagram is shown.

The distribution line busbar is connected to a grounding type instrument transformer GPT for detecting the zero-phase voltage V ₀ of the busbar, and the distribution line micro-ground fault relay is a sample hold (S / H) circuit, A /
A D conversion circuit 2, a processing device (CPU) 3, and an interface circuit 5 for interfacing with a breaker provided in each distribution line are provided. The processing device 3 has a rank memory 4 (comprising a RAM or a programmable ROM) that counts and stores the number of times that a ground fault has occurred in each distribution line. The distribution line interruption frequency value for each distribution line k stored in the rank memory 4 is expressed as C _k (k = 1,2,3,
..., n).

The processing procedure performed by the processing device 3 will be described below with reference to the flowchart (FIG. 1). The processor 3 first sets the distribution line interruption frequency value C _k stored in the rank memory 4 to 0 (step (1)), and sets the zero-phase voltage V _0.
Is checked to see if it exceeds the setpoint (step
(2)). In this check, timed elements are adopted,
It may be checked whether the zero-phase voltage V ₀ exceeds the set value for a certain period of time or longer.

If the zero-phase voltage V ₀ exceeds the set value, the distribution line interruption order is determined based on the distribution line interruption frequency value C _k stored in the order memory 4 (step (3)). This determination is based on the descending order of the distribution line cutoff frequency value C _k , but initially each C _k = 0, so at this time, the subscript k is determined in order. Then, the distribution lines from the first rank to the nth rank rearranged in this order are sequentially cut by a breaker.

Immediately after these interruptions, it is checked whether the zero-phase voltage V ₀ has disappeared (step (5)). If it disappears, the disappeared distribution line (this distribution line is referred to as iF) has a failure. As a result (step (6)), 1 is added to the distribution line interruption frequency value C _i and stored in the rank memory 4 (step
(7)). Then, the restoration processing of the distribution lines other than the distribution line iF is performed.

As described above, power distribution other than the faulty power distribution line is performed.
For wires, the distribution line cutoff value C_kAs it is
However, the value C of the number of cuts in the distribution line of the defective distribution line_kCounts 1
You can From the next, a similar ground fault will occur.
For example, in step (3), the distribution line interruption frequency value C _kBased on
The distribution line interruption order is determined, so the most frequent
The distribution line where the failure occurred is cut off immediately.

As described above, a distribution line having a large number of faults has a strong tendency for similar faults to occur, and therefore the zero-phase voltage V ₀ is likely to disappear by shutting off immediately. Therefore, it is not necessary to cut off the other distribution lines, and the disadvantage of unnecessary power failure is eliminated. In the above embodiment, the distribution line interruption frequency value C _k is counted based on whether or not the zero-phase voltage V ₀ disappears in step (5).

However, since this entire process is originally performed as a backup protection of the direction ground fault relay (67G), a ground fault may be detected by the direction ground fault relay. Also in this case, it is desirable to count the distribution line interruption frequency value C _k . Other various modifications can be made without changing the gist of the present invention.

[0016]

As described above, according to the distribution line micro-grounding relay of the present invention, it is highly possible that the zero-phase voltage of the bus bar disappears at an early stage by preferentially cutting off the distribution line with many failures. Therefore, it is possible to minimize the occurrence of unnecessary power failure. Therefore, it is possible to realize a distribution line fine ground fault relay useful for maintenance and operation of the distribution line system.

Further, as compared with the conventional distribution line micro-ground fault relay which measures the zero-phase current for each distribution line, the zero-phase current transformer for each distribution line is unnecessary and the phase determination calculation is also unnecessary. Become.

[Brief description of drawings]

FIG. 1 is a flowchart showing a procedure for interrupting a distribution line sequence according to the present invention.

FIG. 2 is a distribution line system diagram in which a plurality of distribution lines are connected to a bus bar,
It is a figure which shows the block circuit diagram of the distribution line fine ground fault relay applied to this distribution line system.

[Explanation of symbols]

 1 Sample and hold circuit 2 A / D conversion circuit 3 Processing device 4 Rank memory 5 Interface circuit

Claims (1)

[Claims] 1. A zero-phase voltage detecting means, which is applied to a high-voltage distribution system composed of a busbar and a plurality of distribution lines connected to the busbar, and which detects a zero-phase voltage of the busbar connected to the busbar, Based on the increase of the zero-phase voltage of the bus when the distribution line of the above has caused a ground fault, the order cutting means for performing the order cut of each distribution line and the number of times the ground fault has occurred in the past of each distribution line A storage unit that stores the stored data, wherein the order cutoff unit cuts off in order from a distribution line stored in the storage unit that has a large number of ground faults in the past. Relay relay.