JPS6152614B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a balanced protection relay device for a power system.

First, FIG. 1 shows an example of a power system to which this type of relay device is applied. 1a is a protection system, 2 is a system through which a zero-phase circulating current flows, and the protection system forms a parallel two-circuit power transmission line. Each of the above-mentioned systems is connected to the power supply side via bus B. On the power supply side, there is a breaker 4
and is grounded via a neutral point grounding resistor 3. Further, a reactor 5 for extinguishing a fault current is connected in parallel to the breaker 4 and the neutral point grounding resistor 3.

FIG. 2 shows a conventional balanced protection relay device for protecting such a system. Moreover, FIG. 3 shows the sequence.

6a and 6b are current transformers provided in each power transmission line 1, 1, and a ground fault balance relay 7 is commonly connected to their secondary sides. 8 is a current transformer 6a,
Detect the sum of the current of each power transmission line detected in 6b,
Supplied to directional ground fault relay 9. Reference numeral 10 denotes a voltage transformer, which is connected to the bus B on its primary side and to the overvoltage relay 11 on its tertiary side. The relays 7, 9, and 11 are connected to each other.

In addition, each contact 7a, 9 of each relay 7, 9, 11
a and 11a form a trip circuit in the sequence shown in FIG.

In the arc-extinguishing reactor-based power system as described above, when a ground fault occurs, the circuit breaker 4 is opened after several Hz and only the reactor 5 is left open, waiting for the fault current to naturally extinguish. Then, when the arc ends (approximately 1 second), the shield breaker 4 is turned on again to check whether there is a failure.

In this case, it is conceivable to memorize the current before the failure as a protective relay for countermeasures against zero-phase circulating current, and then determine the difference between the memorized current and the current after the failure at the time the failure occurs.

However, when the grounding resistor 3 is turned off or on, the current changes frequently, which may cause the protection relay to make an erroneous determination. Therefore, conventionally, P
A directional ground fault relay 9 is provided on the end side and inserted into the trip circuit.

The zero-sequence circulating current is calculated from each power transmission line (No. 1, No. 2
The direction of the current in each wire is opposite because the wires circulate through the wires. Therefore, when the sum of the currents in each line is taken, the circulating current is canceled out, so the directional ground fault relay 9 does not operate with the zero-phase circulating current.

Therefore, fault currents can be clearly distinguished.

However, even if it is sufficient to install a directional ground fault relay 9 at the P end, if a directional ground fault relay 9 is installed at the Q end where there is no power supply to take the sum current, it will not operate in the event of an accident within the protection range. . Therefore, the directional ground fault relay 9 cannot be installed at the Q end. Therefore, at the Q end, the operating value must be increased so that the ground fault balance relay 7 does not operate under the zero-phase circulating current. However, if this is done, the circuit will not operate with zero-phase circulating current, and although unnecessary trips can be avoided, the sensitivity will deteriorate and the failure detection ability will deteriorate. On the other hand, in the case of an accident in which a fault current twice as large as the zero-sequence circulating current flows in the opposite direction of the zero-sequence circulating current as shown in FIG. 4, the ground fault balance relay 7 does not operate at the P terminal.

Since the conventional ground fault balance relay is constructed as described above, it has the disadvantage that it is necessary to lower the sensitivity at the non-power supply end, and there is also the possibility that the relay may not operate at the power supply end.

This invention was made in order to eliminate the above-mentioned drawbacks.In particular, by providing a protective relay circuit for zero-phase circulating current countermeasures, it provides balanced protection that can operate reliably in the event of an accident within the protection range. The purpose is to provide a relay device.

Hereinafter, one embodiment of the present invention will be described in detail with reference to FIG. In this embodiment as well, the configuration of the main circuit is the same as in the case of FIG. Therefore, the featured sequences will be described below. In this case, the ground fault balance relay 7 is a relay that takes measures against zero-phase circulating current, so the code is 16.
It will be explained as follows.

Reference numerals 12 and 15 indicate auxiliary relays, 13 and 17 indicate timer relays, and 14 indicates an immediate-action slow-release auxiliary relay, which are connected in parallel to each other. Auxiliary relay 12
The normally closed contact 15b ₁ of the auxiliary relay 15, the normally open contact 16a of the ground fault balance relay 16, and the normally open contact 11a of the overvoltage relay 11 are connected in series, and the self-holding contact of the auxiliary relay 12 is connected to the contact 16a. 1
2a are connected in parallel. timer relay 13
The normally closed contact 15b ₂ of the auxiliary relay 15 and the normally open contact 12a of the auxiliary relay 12 are connected in series. The auxiliary relay 14 is connected in parallel to the timer relay 13 and contact _15b2 . A normally open contact 13a of the timer relay 13 for generating a trip output is connected between the auxiliary relay 14 and the contact _15b2 . The auxiliary relay 15 has
Normally open contact 14a of auxiliary relay 14, auxiliary relay 1
Two normally closed contacts 12b are connected in series. A normally open contact 15a of the auxiliary relay 15 and a normally closed contact 17b of the timer relay 17 are connected in series to the timer relay 17. and between auxiliary relay 15 and contact 14a and timer relay 17 and contact 1.
5a are mutually connected. _12a3 is a normally open contact of the auxiliary relay 12 that generates an alarm output.

Since the contact 16a is a zero-phase circulating current countermeasure relay, it will not operate unnecessarily with zero-phase circulating current.

Next, the operation will be explained.

Now, when a ground fault occurs within the protection range, the overvoltage relay 11 and the ground fault balance relay 16 operate, and the contacts 11a and 16a are closed. the result,
Auxiliary relay 12 is energized. When auxiliary relay 12 is energized, it is self-held by self-holding contact 12a ₂ and timer relay 13 and auxiliary relay 14 are energized by closing contact 12a ₁ .
When timer relay 13 is energized, contact 13a closes and a trip command is generated.

In other words, it selects a failure when an accident occurs, holds itself while the accident continues, sets the time for re-applying the earthing resistor 3 using the timer relay 13, and generates a trip command when the earthing resistor 3 is applied. It is.

Once the fault disappears after the fault occurs until the earthing resistor 3 is turned on again, contact 1 of the overvoltage relay 11
1a returns and the self-holding of the auxiliary relay 12 is released. As a result, the normally closed contact 12b is closed and the auxiliary relay 15 is energized during the return time of the contact 14a. The auxiliary relay 15 is self-held by the contact 15a, and the self-holding state is released after the timer relay 17 expires. Then, the contacts 15b ₁ and 15b ₂ are used to control the "return of earthing resistance 3 + α" from the time of the accident occurrence.
(seconds), the alarm and trip signals are locked to avoid unnecessary false-judgment trips. Generally, if an accident occurs and the driver does not recover, it is safe to assume that the same accident occurred during that time.

Note that although the above embodiment has been described using an auxiliary relay circuit, the same effect can be achieved even if a transistor circuit is used.

As described above, according to this invention, when an accident is selected,
Since it is self-maintained under the condition that the accident continues and a trip command is generated when the earthing resistor is turned on, it is possible to reliably prevent erroneous selection when turning on or off the earthing resistor.

[Brief explanation of the drawing]

Figure 1 is a power system diagram of a parallel two-line transmission system.
Figure 2 is the main circuit diagram of a conventional balanced protection relay device.
FIG. 3 shows the sequence, FIG. 4 is a system diagram explaining an example of an accident, and FIG. 5 shows the sequence of a balanced protection relay device according to an embodiment of the present invention. 1a...Protection system, 3...Neutral point grounding resistance, 4
...Shiya breaker, 5... Arc extinguishing reactor, 6a, 6
b... Current transformer, 8... Auxiliary current transformer, 9... Directional ground fault relay, 11... Overvoltage relay, 12, 14,
15... Auxiliary relay, 13, 17... Timer relay. In the figures, the same reference numerals indicate the same parts.

Claims (1)

[Claims] 1. A ground fault balance relay that detects a ground fault in a parallel two-line transmission line through which a zero-phase circulating current flows, an overvoltage relay that operates by detecting overvoltage on the bus bar side when the above ground fault occurs, and the above ground fault balance relay. and a relay circuit that operates under the condition of operation of the above-mentioned overvoltage relay and self-maintains its operating state while the above-mentioned ground fault occurs; A timer circuit that generates a trip command when a grounding resistor installed on the power supply side of the power transmission line is turned on; and a timer circuit that generates a trip command when the grounding resistor installed on the power supply side of the power transmission line is turned on; A balanced protection relay device comprising a trip lock circuit that locks the relay circuit until a certain period of time has elapsed.