JPS6149891B2 - - Google Patents

Description

Detailed Description of the Invention The present invention provides a switching switch consisting of a thyristor connected in anti-parallel, a current-carrying main contact, a current-limiting reactor or a current-limiting resistor, and a tap of a transformer tap winding in a no-load state. The present invention relates to an on-load tap switching device comprising a tap selector that selects in sequence.

Unlike mechanical oil-submerged contacts, thyristors can turn the current ON and OFF without arcing, so they do not contaminate the insulating oil or wear out the contacts, and they do not require frequent switching. It is very advantageous to use it as a load shedding means for an on-load tap changer. However, if the thyristor does not operate normally due to an abnormality in the operation command circuit of the thyristor or a defect in the thyristor itself, the main contact for current-carrying may be disconnected from the load.

If the main contacts are loaded and disconnected, an arc will occur between the contacts, which can cause deterioration of the insulating oil in the case of oil-immersed switches, and because the main purpose is to conduct current, arc resistance It is obvious that the main contacts which the main contacts do not have are subject to wear and tear, which may lead to melting and damage, thereby impairing the above-mentioned advantages.

The purpose of the present invention is to monitor the status of the thyristor main body and operation command circuit of a tap changer when on load, and if there is an abnormality, detect it instantly and protect the main circuit, thereby increasing reliability. An object of the present invention is to provide a tap switching device.

That is, in the present invention, an optical fiber is arranged near the energizing main contact of the tap selector to detect the presence or absence of an arc in the energizing main contact that occurs when an abnormality occurs in the thyristor body or the operation command circuit. This is what I did.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a circuit diagram of an embodiment of an on-load tap switching device using a reactor as a current limiting element.

Pull-out taps 2a, 2b, 2c of tap winding 1
Movable contacts 4 and 5 of a tap selector are connected to one of the taps 2b. These movable contacts 4, 5
Current-limiting reactors 6, 7 and current-carrying main contacts 9, 10 are connected in series, respectively, and both circuits are connected at their ends to form a lead 11 for drawing out the load. Further, both circuits are connected by a thyristor 8 for current cutoff, which is connected in antiparallel between the current limiting reactors 6, 7 and the main contacts 9, 10. On the other hand, the drive system of the tap changer operates the movable contacts 4, 5 and main contacts 9, 10 of the tap selector and turns on the thyristor 8 according to a predetermined sequence in which the driving force of the drive device 12 is transmitted via the mechanical system 13. -The OFF command is controlled via the operation command device 22. Optical fibers 1 are installed near the main contacts 9 and 10 for energization, respectively.
5 and 17 are provided, and these optical fibers 15 and 17 detect the arc generated at the current-carrying main contacts 9 and 10 and transmit it to the current converter 18. This current converter 18 is connected to an alarm circuit or a circuit breaker (not shown).

FIG. 2 shows the operation sequence of the tap changer, and the changeover process will be explained using this sequence.

In the steady energized state, the movable contact 4 of the tap selector
5 is applied to each tap 2b, and two minutes of load current flows in both circuits. First, at time t1 in FIG. 2, the thyristor 8 is fired and becomes ready for energization. Next, at time t2, the main contact 10 opens and at the same time tap 2b
The load current flows through two circuits: movable contact 4 -> main contact 9 and movable contact 5 -> thyristor 8 -> main contact 9 to reach load extraction lead 11 . At this time, main contact 10
Since the load current flows through the thyristor 8, the load current is not cut off, so no arc occurs. Next, at time t3, when the thyristor 8 is stopped from conducting, the load current begins to flow through only one circuit from the movable contact 4 to the main contact 9. Thereafter, at time t4 to t5, the movable contact 5, which has become unloaded, moves to the adjacent tap 2C.
When the thyristor 8 is restarted at the next time t6, the load current flows through two circuits: tap 2b → movable contact 4 → main contact 9 and tap 2c → movable contact 5 → thyristor 8 → main contact 9. At this time, a circulating current flows between the taps 2b and 2c, but since the current is limited by the current limiting reactors 6 and 7, a short circuit between the taps does not occur. After that, at t7, main contact 10
is turned on again, and the load current is divided into two circuits. Finally, at t8, the thyristor 8 is prevented from conducting, which completes the half-cycle switching, and then the movable contact 4 is tapped 2 in a similar cycle.
Switching to c completes the switching of all cycles.

Next, another embodiment of the present invention in which a resistor is used as the current limiting element will be described with reference to FIG.

Multiple drawer taps 2b, 2 of tap winding 1
Movable contacts 4 and 5 of a tap selector are connected to taps 2b and 2c of taps c and 2d, respectively.
Main contacts 9 and 10 are connected in series to each movable contact 4 and 5, and thyristors 8 and 10 are connected in antiparallel to each other.
8' are connected in parallel and their ends are connected by a load extraction lead 11. On the other hand, an auxiliary contact 19 is located between each movable contact 4, 5 and the main contact 9, 10.
is connected. This auxiliary contact 19 has a structure that can be switched to either the movable contact 4 side or the movable contact 5 side, and its common side is connected to the current limiting resistor 1.
6 to the load extraction lead 11.
Movable contacts 4, 5, auxiliary contact 19 and main contact 9,
10 is opened and closed at predetermined timings by a drive device 12 via a mechanical system 13.

Next, the operating sequence of this resistive load tap changer is changed from the energized state at tap 2b to tap 2c, as shown in Figure 3, until the movable contact 4 moves to the next tap 2d. Explain the process.

In the normally energized state, the main contact 9 is closed, the main contact 10 is open, the auxiliary contact 19 is closed to the movable contact 4 side, and both the thyristors 8 and 8' are prevented from conducting. Load current is from tap 2b → movable contact 4 →
→ Main contact 9 → Flows through load extraction lead 11. In the first step of the switching process, the mechanical command from the mechanical system 13 is converted into an electrical command by the operation command device 22, and the thyristor 8 is ignited to enable it to be energized. Next, the main contact 9 on the side to be switched opens, but at this time the load current passes through the thyristor 8 to tap 2.
b → Since the flow flows to the load extraction lead 11, no arc occurs at the main contact 9. Subsequently, the auxiliary contact 19 is switched from the tap 2b side to the tap 2c side, so that the load circuit is connected to the tap 2c side in addition to the above.
There are two circuits: → movable contact 5 → auxiliary contact 19 → current limiting resistor 16 → load extraction lead 11. At this time, the taps 2b and 2c are short-circuited by the two circuits described above, but the current is limited by the current-limiting resistor 16 located in the middle of the circuit, so that short-circuiting between the taps does not occur. In this state, conduction of the thyristor 8 is blocked and the load current flows only through the circuit from the tap 2c to the movable contact 5 to the auxiliary contact 19 to the current limiting resistor 16 to the load lead-out lead 11. Next, when thyristor 8' is fired, the load current changes from tap 2c→
It flows through the movable contact 5 → thyristor 8′ → load extraction lead 11. Finally, the main contact 10 is closed and conduction of the thyristor 8' is blocked, so that the load circuit changes from the tap 2c to the movable contact 5 to the main contact 10 to the load lead-out lead 11, and electrical switching is completed. After the main contact 9 is opened and the auxiliary contact 19 is switched, the tap 2b side becomes unloaded, so the movable contact 4 can switch from tap 2b to tap 2d without generating an arc. This completes the one-tap switch and the preparation for the next switch.

The above explanation is based on the case where the tap switching device under load operates normally.
If a failure occurs in the 8' main body or the operation command devices 22, 22', the load current will flow to the circuit passing through the thyristor 8 when the main contact 9 on the side to be switched is closed, which corresponds to time t2 in Fig. 2. Since no current flows, the load current is cut off at the main contact 9 and an arc is generated.

Therefore, the arc is detected by optical fibers 15 and 17 installed near the main contacts 9 and 10, and this arc is converted into a current by the current converter 18 and transmitted as an alarm or a circuit break command. Protect the main circuit.

Since the optical fibers 15 and 17 themselves are insulating materials, there are no problems with ground insulation when pulling them out of the load tap switching device, and they can also be routed in a curved manner. To,
It can be installed in any complicated position.

In this way, in the event of a failure of the thyristor body or operation command device, the present invention detects the abnormal phenomenon by the presence or absence of arcing at the main contact, so that abnormalities in the thyristor itself can be indirectly monitored, which was previously impossible. Anomalies can be detected. Moreover, since it is only necessary to compare the presence or absence of light due to the arc generated at the main contact by the optical fiber, there is no need for complex control parts, which improves operational reliability and detection accuracy. Furthermore, since the optical fiber is not placed near the load switch where arcing occurs constantly, the detection function itself will not deteriorate due to deterioration of the fiber due to the arc or a decrease in transparency due to oil contamination due to the arc, resulting in a long reliable life. is long enough. In addition, the thyristor, which is a semiconductor element that generally cannot detect an abnormality unless it is de-energized, is constantly monitored and abnormalities can be detected even when the thyristor is energized, that is, when the load tap switching device is in operation. Therefore, in this sense as well, the device according to the present invention can be said to be the most suitable protection means for a thyristor-type tap switching device under load.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing one embodiment of the on-load tap changer according to the present invention, FIG. 2 is a sequence diagram showing one embodiment of the operation of the on-load tap changer shown in FIG. 1, and FIG. FIG. 6 is a circuit diagram of an on-load tap changer according to another embodiment of the present invention. 1...Tap winding, 2a to 2d...Tap, 4,
5... Movable contact, 6, 7... Current limiting reactor, 8... Thyristor, 9, 10... Main contact, 12... Drive device, 13... Mechanical system, 15, 17... Optical fiber,
18...Current conversion device, 22...Operation command device, 16
...Current limiting resistor, 19...Auxiliary contact.

Claims (1)

[Claims] 1 At least a main contact for energization is connected to a pair of movable contacts of a tap selector that sequentially selects the taps of the transformer tap winding under no-load conditions, and a main contact for energization and a current switch connected in anti-parallel are connected to each other. controlling the thyristor for
In the device in which the pair of movable contacts are switched, an optical fiber is disposed near the current-carrying main contact to detect the presence or absence of an arc occurring at the current-carrying main contact, thereby preventing at least a malfunction of the thyristor main body. A tap switching device under load, characterized in that it detects.