JPH0313812B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a short-circuit capacity suppression device that performs power interchange between power systems.

[Conventional technology]

FIG. 6 shows a specific circuit to which the conventional short-circuit capacity suppressing device shown in FIG. 5 is applied. In the figure, 1 is the first power system, 2 is the second power system,
Reference numeral 3 denotes a short-circuit capacity suppressing device that interconnects both power systems 1 and 2, and is configured for each phase of A, B, and C.
4a, 4b, 4c and 5a, 5b, 5c are input/output terminals between each power system 1, 2 and the short-circuit capacity suppressing device 3.

Note that the A phase, B phase, and C phase are functionally equivalent. Therefore, the following explanation will be made only regarding the A phase. 6 and 7 are thyristors connected in antiparallel, and are composed of a plurality of thyristors. 8 is a series reactor that suppresses the peak value of the fault current, and its value has been selected so as not to interfere with the interconnection effect. A voltage detector 9 includes a voltage transformer that detects the voltage applied to the thyristors 6 and 7, and outputs a voltage signal 10. 11 is a current detector consisting of a current transformer that detects the interconnection current; 12 is a current value discriminator that receives the current signal 12 from the current detector 11 and determines the level of the interconnection current; When the accident detection signal 14 is generated. A gate signal generator 20 generates gate signals P ₁ and P 2 in synchronization with the voltage signal 10 when there is no accident detection signal 14, and stops the gate signals P ₁ and _{P 2 when} the accident detection signal 14 is received.

v _a1 , v _b1 and v _c1 are A and B on the first power system 1 side
and C are the voltages between each phase and ground. v _a2 , v _b2 and
v _c2 is the voltage between each phase of A, B, and C on the second power system 2 side and the ground.

In the above configuration, when both power systems 1 and 2 are in a normal interconnected state where no fault has occurred, the voltages of both power systems 1 and 2 are almost the same, and there is no large difference in phase. Furthermore, since the gate signal generator 20 always generates the gate signals P ₁ and P ₂ , the thyristor 6,
7, one of them is always conductive.

Therefore, the two power systems 1 and 2 are interconnected via the impedance of the reactor 8, and the voltage and phase difference between the two power systems 1 and 2 are not large.
The interconnection current is below the specified value.

This situation is shown in FIGS. 7a to 7d. That is, FIG. 7a shows the voltage between each terminal of the thyristors 6 and 7 and the ground.
v _a1 and v _a2 are shown. FIG. 7b shows the difference voltage. When the voltage phase applied to the thyristors 6 and 7 is approximately 90°, the gate signal _P1 to the thyristor 6 is output, and the current flows through the thyristor 6 at 180°. It flows for a period of ゜. Thyristor 7 receives gate signal _P2 with a delay of 180° from thyristor 6, and is also energized for a period of 180°. This operation is repeated one after another, and a continuous current i _a flows as shown in FIG. 7c as the interconnection current, and this value is less than the specified value.

Note that gate signals P ₃ , P ₄ , P ₅ and P ₆ for phases B and C other than phase A are also shown in FIG. 7d.

Next, consider a case where an accident such as a ground fault or short circuit of a power transmission line occurs in the second power system 2. Since the voltage of the second power system 2 drops due to the accident, a large voltage difference occurs between the two power systems 1 and 2, and the fault current flows from the first power system 1 to the second power system 2. Become. This increased the fault current (that is, increased the short circuit capacity) by interconnecting both power systems 1 and 2.
Therefore, considering the responsibility of the circuit breaker to eliminate accidents, this is not desirable. For this reason, if an accident occurs, all gate signals to the thyristors 6 and 7 of the short-circuit capacity suppressing device are immediately stopped, and the fault current flowing from the first power system 1 to the second power system 2 is immediately stopped. Can be blocked.

Therefore, although the circuit breaker for accident recovery in the second power system 2 is connected to the first power system 1 during normal times, it is connected to the first power system 1. It would be good to have a disconnection obligation that does not take into account interconnection.

[Problem that the invention seeks to solve]

Since the conventional short-circuit capacity suppressing device is configured as described above, in the event of a fault, only one wave of fault current flows, and then the thyristor is turned OFF and the fault current is completely cut off. However, if an accident occurs on another line, it may be possible to simply reduce the current without completely shutting down the power system.

For example, if a ground fault occurs at point A of another line as shown in FIG.
OFF, and both power systems 1 and 2 are completely separated, which poses a problem in that the system may become unstable.

In addition, in the conventional short-circuit current suppressing device shown in Figs. 5 and 6, the voltage across the thyristors is detected as a condition when starting and stopping the thyristors 6 and 7. Ignition voltage (for example, it varies depending on the system, but
(approximately 1KV) is required, and in the event of an accident, the system voltage (e.g., approximately 345KV, depending on the system) is required.A voltage transformer is required that can detect a very wide range. The problem was that it was difficult to detect.

This invention was made to solve the problems mentioned above, and it makes the system more stable after an accident.
The purpose is to obtain a short-circuit current suppression device that improves reliability in system operation.

[Means for solving problems]

The short-circuit capacity suppressing device according to the present invention includes a suitable reactor inserted in parallel with a thyristor in which a first power system and a second power system are connected in antiparallel, and a suitable reactor is inserted in parallel with a thyristor that connects a first power system and a second power system in antiparallel. A current detector for detecting a system current, a current value discriminator for discriminating the current value, and a gate signal generator for outputting a firing signal for the thyristor are provided.

[Effect]

The reactor connected in parallel with the thyristor in this invention connects both the first and second power systems even when the thyristor is turned off.
The system can be made more stable after an accident. In addition, since the signal as a condition for starting and stopping the thyristor is not detected from the voltage across the thyristor but from the interconnection current between the two power systems, detection accuracy is increased and reliability in system operation is improved. I can do it.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. 1, in which the same parts as in FIG. 5 are denoted by the same reference numerals. In FIG. 1, 15 is a reactor connected in parallel with the thyristors 6 and 7.

Similarly to the above, if a ground fault occurs at point A of another line, the fault current will flow and the short circuit capacity suppression device 3
operates, and thyristors 6 and 7 turn off, but reactor 15 connected in parallel with thyristors 6 and 7
Therefore, both the first and second systems 1 and 2 remain interconnected. In addition, the fault current is suppressed by the reactor 15, the shield breaker 25 becomes more likely to break, and both systems 1 and 2 remain interconnected, thereby increasing the stability of the system.

FIG. 2 shows a specific example of a circuit to which the short-circuit capacity suppressing device 3 of the present invention is applied, and the same members as in FIG.
In FIG. 2, 16 is a current value discriminator that monitors the current signal 13, and is used for both the first and second power systems 1 and 2.
When the interconnection current exceeds a specified current, a current level detection signal 17 is output as a first signal. 18 is
The AND gate inputs the inverted signal of the accident detection signal 14 as the second signal output from the current value discriminator 16 and the current level detection signal 17, and when the AND condition of both signals is satisfied, the thyristor 6 , 7 outputs the ignition permission signal 19. 21
When receiving the ignition permission signal 19, the thyristor 6,
The gate signal generator 7 alternately outputs firing signals P ₁ and P ₂ respectively, and does not output gate signals P ₁ and P ₂ when there is no firing permission signal 19. Figure 3 shows the voltages that show how the main circuits operate when the thyristors 6 and 7 change from OFF to ON.
It is a waveform diagram of a current.

On the other hand, when the interconnection currents of both power systems 1 and 2 become small and the current signal 13 from the current detector 11 that detects the interconnection current becomes less than a predetermined value, the current value discriminator 16 uses the current detection signal 22 Output. When the gate signal generator 21 receives the current detection signal 22, it turns off the thyristors 6 and 7. FIG. 4 is a voltage and current waveform diagram showing how the main circuit operates when the thyristors 6 and 7 are turned from on to off.

The current level discriminator 12 in the above embodiment is as follows:
Any known comparator can be used. It can also be constructed using software using a microcomputer.

〔Effect of the invention〕

As described above, according to the present invention, since the reactor is connected in parallel with the thyristor connected in anti-parallel between both power systems, both power systems are interconnected through the reactor even after an accident, so the system can be made more stable. In addition, by detecting the signal as a condition for starting and stopping the thyristor from the interconnection current between both power systems, there is no need to interconnect when the interconnection current is small, and the minimum current at startup can be reduced. By increasing the size, the detection accuracy can be increased, and the reliability in system operation can be improved.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram of a short-circuit capacity suppressing device according to an embodiment of the present invention, Fig. 2 is a specific circuit diagram to which the short-circuit capacity suppressing device is applied, and Fig. 3 is a circuit diagram of a thyristor.
Figure 4 is a voltage and current waveform diagram showing how the main circuit operates when the thyristor is turned on. Figure 5 is a voltage and current waveform diagram showing how the main circuit operates when the thyristor is turned off
FIG. 6 is a circuit diagram of a conventional short-circuit capacitance suppressing device, FIG. 6 is a specific circuit diagram to which the short-circuit capacitance suppressing device is applied, and FIG. 7 is a waveform diagram of voltage, current, and signal of this circuit. 1 is the first power system, 2 is the second power system,
6 and 7 are thyristors, 11 is a current detector, 12 is a current value discriminator, 15 is a reactor, and 21 is a gate signal generator. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Scope of Claims] 1. A short-circuit capacity suppression device that interconnects a first power system and a second power system using thyristors connected in antiparallel to exchange power, comprising a reactor connected in parallel with the thyristor, and a reactor connected in parallel with the thyristor. , a current detector that detects the interconnection current between the first and second power systems; and a current detector that outputs a first signal when the interconnection current is a predetermined value or more, and a current detected by the current detector. a current value discriminator that outputs a second signal when is greater than a predetermined value; and outputs a firing signal for the thyristor when an AND condition of the first signal and an inverted signal of the second signal is satisfied. A short circuit capacitance suppressing device comprising a gate signal generator. 2. When the interconnection current of both the first and second power systems is below a predetermined value, the current value discriminator outputs a signal that blocks the firing signal of the thyristor to turn off the thyristor. A short-circuit capacity suppressing device according to claim 1.