JPS6070922A - Ultrafine ground-fault relaying system - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Technical field to which the invention pertains] The present invention provides a slight ground fault selection relay that detects ground faults in a range where generally well-known ground fault directional relays do not respond, that is, so-called slight ground faults. This invention relates to a slight ground fault relay system that uses a small ground fault relay system to protect power distribution lines.

[Prior art and its problems]

Conventionally, such a small ground fault selection relay detects only the ground fault zero-sequence voltage, and based on this, the distribution line is opened experimentally in a predetermined order by a distribution line breaker, and as a result, the zero-sequence If the voltage disappears, the circuit breaker determines that a slight ground fault exists in the open distribution line. In other words, according to this method, the order in which circuit breakers on distribution lines are opened is determined in advance, so if there is a slight ground fault in a distribution line at the end of the order, This has the drawback of cutting off and opening lines, resulting in unnecessary power outages. Further, such work is not only complicated but also requires a long time.

[Purpose of the invention]

This invention was made to eliminate such drawbacks, and it is possible to eliminate unnecessary power outages as described above, and to easily and quickly select and cut off distribution lines in which a slight ground fault exists. The purpose is to provide a slight earth fault relay system.

[Key Points of the Invention] “The key points are that not only the ground fault zero-sequence voltage but also the zero-sequence current of each distribution line is detected, and the direction of the zero-sequence current is determined in the same manner as the conventional well-known ground fault direction relay; By determining the magnitude of the zero-sequence current in each distribution line, it is possible to predict which distribution lines are experiencing slight ground faults, and then shut off each distribution line in the order of the highest probability.

The reason is that we made it open.

[Embodiments of the invention]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a block diagram showing a table for storing the operation order of circuit breakers. In Fig. 1, 1 is a bus bar, 2 (21 to 24) is a distribution line,
3 (31-34) is a breaker, 4 (41-44) is a zero-sequence current detector, 5 is a zero-sequence voltage detector, and 6 is a slight earth fault selection relay. In addition, the slight ground fault selection relay 6 used here
The computer has a built-in arithmetic processing unit, such as a microphone computer, and at least a storage table as shown in FIG. 2(a) or (b).

Therefore, similar to the conventional well-known earth fault direction relay, the slight earth fault selection relay 6 first selects each The direction of the ground fault zero-sequence current flowing through the distribution line 2 is determined, and then the magnitude relationship of each current value is examined. Now, for example, the power distribution in Figure 1! Assuming that a slight ground fault has occurred at point P of 124, in the slight ground fault selection relay 6, the direction of each current II to 4 is as shown by the arrow in the same figure, I4 is the operating direction, and
(2) Identify 3 as the non-operating direction, and give top priority to the order of shutting off the distribution lines corresponding to the current identified as the operating direction. Then,
Comparing the magnitudes of the zero-sequence currents 11 to I4, in this case I4 is the largest, and the remaining ones have different values due to differences in the grounding method of the distribution line, etc., but the relationship in magnitude is, for example, Is > If Ir>12, the distribution lines are cut off in this order. Note that even if there are multiple currents in the operating direction, that is, if a slight ground fault occurs in multiple distribution lines, the order of shutoff will be determined by the magnitude of the currents. In this way, the cutoff order of the distribution line is determined as, for example, 24e 23p 2t e 22, so the slight earth fault selection relay 6 stores it in its internal table as shown in FIG. A command is given to the circuit breakers 3 (31 to 32) to sequentially cut off predetermined distribution lines. It goes without saying that when it is determined that the zero-sequence voltage has disappeared, the subsequent shutoff is stopped. Further, FIG. 2(6) is a table showing an example of a case where the cutoff is performed as determined in advance, and by doing so, it is possible to use the same control method as the conventional example. Note that after a predetermined cutoff control is performed using such a table, the contents of the table are cleared and stored for future use.

〔Effect of the invention〕

According to this invention, since the order of distribution lines to be cut off from zero-sequence voltage and current caused by a slight ground fault is determined, it is possible not only to avoid the complicated and time-consuming work as in the past, but also to Since it becomes possible to select and cut off power more accurately, unnecessary power outages will not occur, thus bringing about the advantage of improved reliability.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a block diagram showing a table for storing the operation order of circuit breakers. Code explanation 1... Bus bar, 2 (21-24)... Distribution line, 3 (3i-34)... Breaker, 4 (4
,~44)...Zero-phase current detector, 5...
・Zero-phase voltage detector, 6...-m ground fault selection relay Patent attorney Akio Namiki Patent attorney Kiyoshi Matsuzaki 61

Claims (1)

[Claims] A zero-sequence current detector and a zero-sequence voltage detector each detect a zero-sequence current and a zero-sequence voltage generated based on a micro-ground fault in at least one location of a distribution line, and each wiring is detected from the detected current and voltage values. A slight ground fault selection relay that determines the order in which each distribution line should be cut off by determining the direction of the zero-sequence current flowing through the wires and determining whether the six current values are large or small, and based on the output of the relay. A slight earth fault relay system characterized by comprising an individual breaker that disconnects each distribution line from its bus bar.