JPS6227614B2 - - Google Patents

Description

[Detailed Description of the Invention] While conventional directional ground fault relays operate only in one direction, the present invention operates in both directions for ground faults, protects ground faults, and improves the ground fault location. This relates to a bidirectional ground fault relay that can be clearly displayed.

Ground faults are the most common occurrence in the power distribution business, and in some cases can even be life-threatening, and are a troublesome accident whose location is difficult to confirm. Therefore, each power distribution line is equipped with a ground fault relay. We are required to prevent disasters.

Some ground fault relays have directionality, while others do not, and each has its own features. Non-directional devices have advantages such as being simple, inexpensive, and easy to handle, but depending on where they are used, there is a risk of malfunction or unnecessary operation.

In Figure 1, assuming that power is being transmitted only from the power source 1-A, when a ground fault 5 occurs in the distribution line 2, the ground fault relay 4- is closer to the power source 1-A than the ground fault point 5.
a, 4-b, and 4-c operate to open the breaker 3 or warn of a ground fault to prevent disasters caused by a ground fault. At this time, there is relatively no problem if the capacity or length of the distribution line 2 is small, but if the capacity of the distribution line is large, the ground fault relay 4 located on the opposite side of the power supply 1-A from 5 to
-d, 4-e, etc. also operate, requiring time and effort to find the ground fault point, prolonging the power outage time.

At this time, if the ground fault relay 4 is directional, even if the distribution line has a large capacity, the ground fault current Io1
Since the direction of IO2 is different, directional ground fault relay 4-a,
4-b and 4-c operate, 4-d and 4-e do not operate, indicating that the ground fault point is 5.

If the distribution line 2 can transmit power from two power sources 1-A and 1-B, if the direction of the ground fault relay 4 is set to match the power source 1-A, it will not operate when power is transmitted from the 1-B side, and the reverse will occur. If the direction is set to 1-B, it will not work when 1-A is used as the power source, so it is necessary to install two sets of directional ground fault relays with different directions as shown in Figure 2. When a ground fault 5 occurs in the distribution line due to this, 1
-If you are using A power supply, 4-a, 4-b, 4-
c operates to prevent disasters due to ground faults, 4-d, 4
-e does not work, so we know that the ground fault point is 5, and if 1-B is used as the power source, 4-
d' and 4-e' operate to achieve the purpose of ground fault protection and ground fault point display, which is extremely effective for accident prevention and recovery. The only drawback of this method is that
The required number of ground fault relays 4 is doubled, resulting in an increase in cost, space, labor, etc.

The present invention aims to provide an inexpensive and reliable ground fault relay that operates in two directions using one directional ground fault relay and displays the direction. Figure 3 is a block diagram of the most commonly used directional ground fault relay at present.Relay 4 receives ground fault current Io from zero-phase current transformer 6 and ground capacitor 7 inserted into distribution line 2.
and the ground fault voltage Vo are supplied to the phase comparator 45 through a filter 41, an amplifier 42, a level detector 43, a waveform shaping device 44, etc. When the phase is within the operating range of the characteristic curve X, it is sent to the relay 4 via a timer 46.
7 to achieve the purpose of ground fault protection. FIG. 4 is an example of a polar diagram showing the operating characteristics of a ground fault relay, where X indicates the forward direction and Y indicates the reverse direction.

FIG. 5 is a block diagram showing an embodiment of the present invention, and as is clear from the figure, this is also a type of directional ground fault relay.

One-way detection is one in which the phase comparator 45 directly supplies the signal to the timer 46 to operate the relay 47. The difference from FIG. 3 is that the output of the phase comparison device 45 is supplied to the phase inversion device, and the output of the level detection 43 for current and voltage components is supplied to an AND device 49 (logical product device), and the output is Second timer 4
6', the second relay 47' is operated to provide necessary protection and indication against ground faults in the other direction. The curve of the polar diagram in FIG. 4 represents the characteristics in this case, where X is for the forward direction and Y is for the reverse direction.

Therefore, if this two-way ground fault relay is used, the second
The connection of the power distribution line is as shown in Figure 6, and the power supply 1-
When a ground fault 5 occurs whether power is transmitted from A or 1-B, the bidirectional ground fault relay 4 can perform protection and display in accordance with the power source and the ground fault point.

If directional ground fault relays 4-a and 4-b are temporarily installed as shown in Figure 7 to locate the ground fault point of the distribution line, if there is a ground fault at point 5 and the power supply reaches 1-A, In this case, 4-a is activated and 4-b is not activated, so we know that the ground fault point is between 4-a and 4-b, and we can narrow down the range to find the ground fault point. However, since 4-b is inactive at this time, there is a problem with the lack of positivity in the judgment. At this time, 4-
If a and 4-b were bidirectional ground fault relays, 4-a would operate in the forward direction and 4-b would operate in the reverse direction, actively announcing different signals, which would also be useful for determining the ground fault point. It is advantageous because it allows you to be proactive. Moreover, at this time, the grounding capacitor, zero-phase current transformer, etc.
It can be the same as the direction.

As mentioned above, after comparing the phases of the directional ground fault relay, which compares the phase between the zero-sequence voltage element and the zero-sequence current element and determines the direction of the ground fault, two sets of relays are used, and the phase of one direction is compared, and then the operation is performed. and the other direction is the current
From voltage level detection output and phase comparison inversion output
By using an AND device, a bidirectional ground fault relay that operates in different directions of ground faults can be obtained.
It can be used for terminal distribution lines, large capacity distribution lines, etc. to provide complete protection and reliable indication of the direction of ground faults.

[Brief explanation of the drawing]

Figures 1 and 2 are examples of distribution lines equipped with ground fault relays, Figure 3 is a block diagram of a directional ground fault relay commonly used today, and Figure 4 shows the characteristics of a directional ground fault relay. This is an example of a polar diagram.
FIG. 5 shows a sixth embodiment of the bidirectional ground fault relay of the present invention.
Figure 7 shows an example of a distribution line equipped with this. 1...Power supply, 2...Distribution line, 3...Cut breaker, 4...Ground fault relay, 5...Ground fault, 6...Zero phase current transformer, 7...Grounding capacitor, 41...Filter, 42...Amplifier, 4
3...Level detection, 44...Waveform shaping, 45...Phase comparison, 46...Timer, 47...Relay, 48...Phase inversion device, 49...AND.

Claims (1)

[Claims] 1 Detect the level of ground fault voltage and ground fault current,
When the phases of these ground fault voltage and ground fault current are compared and the phase is within a preset operating range, a relay operates with a phase comparison output, an inverted output that inverts this phase comparison output, and the voltage/current. The level detection output of is supplied to the AND device, and with that output,
A two-way ground fault relay characterized by being provided with an operating relay.