JP2581361B2 - Thyristor switch - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thyristor switch used for the purpose of, for example, stabilizing a sectional switch in a distribution system.

[0002]

2. Description of the Related Art FIG. 3 shows, for example, a magazine OHM (July 1990).
FIG. 4 is a circuit configuration diagram showing a conventional thyristor switch of this type described in Jpn. 1 is a switch body, 2 is a thyristor switch, which comprises two thyristor elements 3 connected in anti-parallel to each other and a zinc oxide lightning arrester 4 for protecting them from surge voltage.
Reference numeral 5 denotes a vacuum electromagnetic contactor as a mechanical switch connected in parallel with the thyristor switch 2, and reference numeral 6 denotes an overcurrent detection variable for detecting an overcurrent flowing in a circuit to which the thyristor switch 2 and the vacuum electromagnetic contactor 5 are connected. A current switch 7 is a load switch as a mechanical switch for switching leakage current.

[0003] Thyristor switch 2 and vacuum electromagnetic contactor 5
Are connected in parallel, and an overcurrent detection current transformer 6 and a load switch 7 are connected in series, and are connected between the power supply terminal 8 and the load terminal 9 for each of the three phases. Switch body 1 is inserted into a three-phase circuit.
A control device 10 controls the thyristor switch 2 and the vacuum electromagnetic contactor 5 from a low voltage level, and receives a signal from the overcurrent detection current transformer 6.

Next, the operation will be described. The control device 10 has an electrical interlock between the thyristor switch 2 and the vacuum electromagnetic contactor 5, so that the vacuum electromagnetic contactor 5 can be opened only when the thyristor switch 2 is closed. Since the thyristor switch 2 has the thyristor switch 2 to shut off the steady current and the fault current of the load, the vacuum electromagnetic contactor 5 only needs to have the continuity withstand current of the steady current. In order to quickly shut off the fault current, the vacuum electromagnetic contactor 5 is opened and the thyristor switch 2 is energized in normal operation, and the fault current is immediately shut off by the thyristor switch 2 when a fault occurs.

[0005]

Since the conventional thyristor switch is configured as described above, there is a problem that a problem occurs when the load current becomes small.
That is, current transformers are designed to detect overcurrent for the purpose of providing overcurrent protection, and it is difficult to accurately measure a wide range from large current to small current with one current transformer. Therefore, it is difficult to accurately detect, for example, a current of about several thousandths of the rated current. In addition, there is a minimum current required to keep the thyristor switch in a conducting state, and this is called a holding current. When the load impedance is large (the load current is small) and becomes smaller than the holding current of the thyristor switch, A closing command should be issued from the control device to the mechanical switch provided in parallel, but this switching command is not output because the accuracy of the current transformer in the small current range is poor, and therefore the thyristor switch is In some cases, the circuit is in an open state, and for example, the operation of the distribution system is hindered.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and can perform the above-described abnormal opening operation even when the load current is small and the current drops below the holding current of the thyristor switch. Aim to obtain no thyristor switchgear.

[0007]

A thyristor switch according to the present invention comprises an overcurrent detection current transformer for detecting an overcurrent of a circuit, and a holding current detection transformer for measuring a current near a holding current of a thyristor switch. A current transformer is composed of the current transformer and the mechanical switch is controlled by a signal from the current transformer for holding current detection.

[0008]

The thyristor switch according to the present invention detects the load current below the holding current of the thyristor switch with a current transformer for holding current detection with high accuracy, and issues a command to turn on the mechanical switch. And opening a mechanical switch to prevent an open circuit condition.

[0009]

1 is a circuit diagram showing a thyristor switch according to an embodiment of the present invention. In FIG. 1, 1 to 10 are the same as those in FIG. 11 is a current transformer for detecting a current of the circuit, 12 is an overcurrent detection current transformer for detecting an overcurrent flowing in the circuit, and 13 is a current transformer for holding current detection, which is near the holding current of the thyristor switch 2. What can measure the small current of a magnitude | size accurately is used.
With a large current, the iron core may be saturated. The current transformer 11 is constituted by the current transformer 12 for overcurrent detection and the current transformer 13 for holding current detection, and an output signal is sent to the control device 10.

Next, the operation will be described. Now, it is assumed that the operation is performed with the thyristor switch 2 closed and the vacuum electromagnetic contactor 5 opened. When the load current decreases and drops below the holding current of the thyristor switch 2, this is detected from the magnitude of the output signal of the current transformer 13 for holding current detection, and the control device 10 issues a command to turn on the vacuum electromagnetic contactor 5. And output
The vacuum electromagnetic contactor 5 is turned on. Therefore, the thyristor switch does not open. If the load current returns to the holding current or more from this state, the control device 10 outputs a command to open the vacuum electromagnetic contactor 5 to open the vacuum electromagnetic contactor 5 and supply the load current to the thyristor switch 2 again. To control. The reference current value for issuing the closing command and the opening command is preferably set to be slightly larger than the holding current in view of the margin. Note that the overcurrent detection current transformer 12 operates in the same manner as in the related art.

As the structure of the current transformer 11, the overcurrent detection current transformer 12 and the holding current detection current transformer 13 may be formed separately or may be formed integrally. FIG. 2 shows the current transformer 11 of FIG.
14 is a primary conductor of the current transformer 11, around which a current transformer 12 for overcurrent detection and a current transformer 13 for holding current detection are integrated.

In the above embodiment, the vacuum electromagnetic contactor 5
Is output based on the magnitude of the output signal of the holding current detection current transformer 13, but the holding current detection current transformer 13 outputs a current that is slightly larger than the holding current of the thyristor switch 2. Is determined from the distortion of the output waveform of the current transformer 13 for holding current detection, the vacuum electromagnetic contactor 5 is controlled to be turned on when it is not saturated, and to be opened when it is saturated. Is also good.

[0013]

As described above, according to the present invention, a holding current detecting current transformer for measuring a current near a holding current of a thyristor switch is provided, and a mechanical switch is controlled by an output signal of the current transformer. Therefore, even when the load current becomes small, it can be detected accurately, and when the current becomes smaller than the holding current, the thyristor switch is opened by turning on the mechanical switch. Can be prevented. Therefore, for example, smooth operation in the distribution system is ensured.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a thyristor switch according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a current transformer of the thyristor switch of FIG. 1;

FIG. 3 is a circuit configuration diagram showing a conventional thyristor switch.

[Explanation of symbols]

 2 Thyristor switch 5 Vacuum electromagnetic contactor 10 Controller 11 Current transformer 12 Current transformer for overcurrent detection 13 Current transformer for holding current detection

Claims (2)

(57) [Claims] 1. A thyristor switch and a mechanical switch are connected in parallel to each other and inserted into a circuit to open and close the circuit and to receive a signal from a current transformer for detecting a current of the circuit. In a thyristor switch controlling a thyristor switch and a mechanical switch by a control device, the current transformer is a current transformer for detecting an overcurrent flowing in the circuit, and a holding current of the thyristor switch. A thyristor comprising: a holding current detection current transformer for measuring a current having a magnitude in the vicinity; and controlling the mechanical switch by a signal from the holding current detection current transformer. Switch. 2. The thyristor switch according to claim 1, wherein the holding current detecting current transformer is saturated with a current slightly larger than the holding current of the thyristor switch.