JPS5939894B2 - Tap switching device under load - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an on-load tap switching device, and for example, to an improvement in a device equipped with a protection device against a short circuit between taps when a vacuum switch is used.

It is well known that when a vacuum switch is used as a switching switch for an on-load tap changer, there are advantages in many aspects such as reducing dirt inside the switching switch and the number of switching operations. However, if the vacuum switch fails to cut off the current for some reason (e.g. vacuum leak) during switching operation, a short circuit between the taps may occur, causing excessive damage not only to the on-load tap switching device but also to the transformer itself. Because of this, a method of inserting a fuse into the circuit to minimize the damage is being considered. FIG. 1 shows an embodiment of the wiring configuration of such a switching device.

In FIG. 1, T is a tap winding of a transformer having a plurality of taps, and 51 and 52 are tap selectors belonging to odd-numbered taps and even-numbered taps, respectively.

Cl is the odd number side input terminal of the switching switch connected to 51, C
2 is the even number side input terminal, O is the switching switch output terminal, SWI
is a switch that is switched to the preselected tap side prior to the opening/closing operation of other switches, Cs is an engagement portion between the SWI and the odd-numbered side lead, C4 is an engagement portion between the SWI and the even-numbered side lead, V1
, V2, and V3 are vacuum switches, and R is a current limiting resistor. F
Fuses 1 and F2 are inserted in the odd leads between Cl and Cs and in the even leads between C2 and C4, respectively. Next, the conventional switching operation will be explained with reference to FIG. In the opening/closing state of FIG. 1, the vacuum switch V1 is closed and the V
.

and V3 are open, the switch SWI is connected to the odd-numbered lead, and the odd-numbered tap is energized. To switch this to an even-numbered tap, first switch the switch SW.
4 is switched from the odd number side to the even number side. Subsequently, the vacuum switch V3 is closed, Vl is opened, V2 is closed, and finally V3 is opened. In the operation of the switch SW shown in FIG. 4, solid arrows indicate the sequence of switching from odd-numbered taps to even-numbered taps, and dashed-line arrows indicate switching sequences from even-numbered taps to odd-numbered taps. By the way, if the vacuum switch V1 fails to cut off the current during the above switching operation process, the next closing of V2 (indicated by I in Figure 2) causes a short circuit between the taps and an overcurrent flows. It turns out.

Also, if the vacuum switch 2 fails to disconnect during the switching operation process of switching from the even-numbered side tap to the odd-numbered side tap, a short circuit will occur between the taps due to the closing of 1 (as shown in Figure 2). . When such a tap-to-tap short circuit is formed, the fuses F1 and F2 inserted in the circuit are blown to break the tap-to-tap short circuit and remove the fault current. Figure 3 also shows fuses F1 and F.
A conventional circuit is shown in which the insertion points of 2 are moved between C3 and O and between C4 and O, respectively, but the other components and switching operation process are the same as the system shown in FIG. This conventional wiring configuration has the following drawbacks. First, in the wiring configuration shown in Figure 1, if only the fuse on the destination (preselection tap) side that switches taps blows due to a short circuit between taps, then the load will be Electric current will flow and there is a risk of an accident spreading.

Furthermore, if both the first and second fuses are blown, the circuit through which the load current flows will be temporarily cut off, and there is a risk that dielectric breakdown will occur at the point where the withstand voltage is the weakest due to the applied voltage of the transformer. Next, in the wiring configuration shown in Fig. 3, if only the fuse on the preselected tap side blows due to a short circuit between the taps, the current will be energized in the electrical path that passes through the vacuum switch where the fuse failed, as explained above. There is a risk that the accident will escalate.
In addition, if the first and second fuses are blown due to a short circuit between the taps, the load current will flow through the current limiting resistor R and the vacuum switch V3, and there is a possibility that this may even lead to dielectric breakdown. If the transformer was not stopped immediately, there was a risk that the accident would spread to the transformer itself. As mentioned above, depending on the location of the fuse blowout when a short circuit occurs between the taps during the tap operation, there is a risk that the insertion of the fuse may even cause a problem. In addition, the above explanation has shown the drawbacks that occur during switching operation of the conventional method, but even during normal operation, if a short circuit occurs between the taps due to external lightning, etc., and the fuse on the current-carrying side blows, the electrical circuit will be disconnected. There was fear that the damage would not only extend to the on-load tap switching device but also to the transformer itself.

The present invention has been made in order to eliminate the above-mentioned drawbacks of the conventional system. By providing the conventional switching device with a fuse shorting function, even if a short circuit occurs between the taps, it will be fatal to the tap switching device under load. The object of the present invention is to provide a highly reliable on-load tap switching device that can quickly remove fault current without causing any physical damage.

An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 4, SW2 is a switch that is connected to the current limiting resistor R and connects the leads to the odd or even side while simultaneously shorting the fuses on the odd or even side. Other components are the same as those in FIG. This fourth
The switching operation process of the circuit shown in the figure is exactly the same as the operation sequence shown in Figure 2, and the function of the switch is to short-circuit the fuse on the preselection tap side when the switch SW2 switches to the preselection tap side. The only difference is that Therefore, only the protection operation will be explained here. For example, if the first vacuum switch V1 fails to disconnect during the switching operation from the odd-numbered side tap to the even-numbered side tap, the S
1-C1-F1-1-V2-SW2-C2-S2-T short circuit is formed. The short circuit current at this time blows the fuse F1 and disconnects the short circuit, thereby removing the fault current, and thereafter the load current is reduced to S2-C2-S.
Through the circuit W2V2-6- the flow switching is completed by the opening of 3. Therefore, there is no fatal damage to the on-load tap switching device, and even after an accident, if the tap switching is locked, the transformer can continue operating, which is the characteristic of the fuse insertion. Furthermore, it can be easily understood from the operation sequence that the same effect can be obtained when switching from the state where the tap is operated on the even number side to the odd number side tap. Further, by characterizing the switching device SW2 as described above, protection can be provided not only during switching but also during normal operation. That is, during normal operation, the fuse on the energized side is short-circuited by the switch SW2, so if a short-circuit between taps occurs due to external lightning or the like during operation, a short-circuit current flows through the circuit. Therefore, the fault current is quickly removed by blowing the other fuse, and since the electrical path for the load current on the operating side is secured, there is no risk of fatal damage to the on-load tap switching device. Furthermore, since the fuse on the driving side is short-circuited, there is no need for the fuse to have continuous current carrying ability. In the above description, a vacuum switch is used, but it goes without saying that the present invention is not limited to this and can be applied to other switches.

As described above, according to the present invention, the switching device that switches before any switch at the time of switching has the function of shorting the fuse on the side that the switching device closes. Since short-circuit accidents between taps that occur during operation can be quickly and reliably eliminated, damage to the tap switching device under load can be kept to a minor level, and even after a failure, subsequent tap switching operations can be locked. This allows the transformer to continue operating.

The current carrying capacity of 2 fuses can be reduced.

This effect can be expected, and a highly reliable tap switching device under load can be obtained.

[Brief explanation of drawings]

1 to 3 are diagrams illustrating a conventional tap switching device under load, in which FIGS. 1 and 3 are circuit diagrams, and FIG. 2 is an operation sequence diagram. FIG. 4 is a circuit diagram of an on-load tap switching device according to an embodiment of the present invention. In the figure, Vl, V2, V3 are vacuum switches, Fl, F2 are fuses, and SW2 is a switching element.

Claims (1)

[Claims] 1 The first and second switches are inserted in series between the odd-numbered taps and the output terminals of the transformer windings, and between the even-numbered taps and the output terminals, and the second switches are inserted in series between each of the upper and lower switches. 1 and a second fuse, and a switching circuit that temporarily forms a power supply circuit to the load during tap switching by the first and second switches, wherein the switching element of the switching circuit is on the odd number side. When making a switching connection, the first fuse on the odd number side is short-circuited by the switching element, and when making a switching connection on the even number side, the switching element short-circuits the second fuse on the even number side. Tap changer on load.