JPS6038854B2 - Tap switching device under load - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an on-load tap switching device that allows easy inspection of a resistor inserted to prevent a floating phenomenon in a tap winding.

Generally, on-load tap changer (hereinafter referred to as LT) with built-in transformer
Abbreviated as C.

), the entire LTC is attached to the transformer cover 2 by a mounting flange, as shown in FIG. This LTC has a structure in which a tap selector 5 is suspended below a tap changer head 3 via a switch oil tank 4. Inside the switching switch oil tank 4, there is housed a shear cutter 6 for shearing and cutting off the load, an ocular flow resistor 8, and a drive insulating tube 9. Also, the insulating oil is not contaminated by arcing when the tap is disconnected. Therefore, it is isolated from the transformer body oil. On the other hand, it is desirable that the tap selector 5 can be easily connected to the transformer tap winding, and since its contacts do not open or close the load, they are housed in the same insulating oil as the transformer. A sub-switcher 7 (a polarity switch or a shift switch) is provided on the side of the tap selector 5 in order to increase the number of taps to be adjusted. By the way, in such an LTO, the sub-switcher 7
When the tap winding operates, a situation occurs in which the tap winding temporarily floats electrically. This float phenomenon will be explained with reference to FIG. In the circuit diagram shown in Figure 2A,
11 is a main winding, 12 is a tap winding, and these are connected via a polarity switch 13. In this embodiment, a case is shown in which a polarity switch is used as the sub-switching pupil. The tap winding 12 is provided with taps TI to T9, which are selected by contacts S1 and S2 of the tap selector. The switching switch 14 consists of main contacts M1, M2, resistance contacts R1, R2 and a current limiting resistor 15, one of which is connected to the contacts S1, S2 of the tap selector and the other to the neutral point N. Next, referring to the operation sequence diagram shown at the beginning of Figure 2,
The switching order at the tap where the polarity switch 13 operates will be explained. Now, as shown in the circuit diagram in A, the polarity switch 13 is connected to the PI
The movable contacts SI (odd number side) and S2 (even number side) of the tap selector select the T9 and TO contacts, respectively, and the main contact of the switching switch 14 is M2, which is the even number side, is closed. Assume that the TO tap is pulled out to the neutral point N'.

When a tap switching signal is received and the voltage is further lowered, first the SI contact connected to the main contact MI is switched to T.
Stay away from 9. Then, the contacts of the polarity switch 13 are also separated from the PI. If the connection between PO and PI is lost, the connection between the main winding 11 and the tap winding 12 is lost, causing the tap winding 12 to float electrically, which adversely affects the reliability of the transformer. Therefore, in order to prevent this float phenomenon, a method is generally used in which a nonlinear resistor 16 is inserted between the tap winding 12 and the main winding 11. Returning to the explanation of the switching order, the polarity switch 13 is set to P2.
After entering the contact, the SI contact of the tap selector enters the TI contact, and then the switching switch 14 is switched, and the M
I is closed, M2 is opened, and the TI tap is connected to the neutral point, completing the cutting process. However, in the above-described structure, the nonlinear resistor 16 for preventing electrical floating of the tap winding 12 is naturally housed together with the transformer body apart from the LTC, so it cannot be easily inspected. , which can sometimes cause accidents and cause serious damage to the transformer. The present invention takes the above-mentioned points into consideration, and aims to provide a load tap switching device that makes it possible to accommodate a nonlinear resistance inside the sliding door switch oil tank by changing the switching order when the sub-switching device operates. That is.

The present invention will be explained below with reference to FIGS.

In the circuit diagram shown in Figure 3A, the connection configuration of the main winding 11, tap winding 12, polarity switch 13, current limiting resistor 15, and switching switch 14 is the same as the secondary structure shown in Figure 2A. Similarly, in the on-load tap changer according to the present invention, the nonlinear resistance 26 is connected to the even-numbered side M2, R2 of the switching switch 14.
and the odd-numbered side M1 and RI.

If the nonlinear resistor 26 is connected in this manner, the electrical foot phenomenon of the tap winding 12 can be prevented by the switching order shown in FIG. That is, in the operation sequence diagram shown at the beginning of FIG. 3, first, the contact of the polarity switch 13 separates from the PI. At this time, the movable contact SI of the tap selector
(odd number side) is still connected to the T9 contact, so the tap winding 12 is connected to the main winding 11 through the nonlinear resistor 26. Therefore, the tap winding 12 does not cause a floating phenomenon. Next, the contact of the polarity switch 13 is connected to P2.

Thereafter, the contact SI of the tap selector and the contacts M1 and M2 of the sliding door switch operate, so that the tap winding 12 does not float at this time either. According to the present invention, since the polarity switch 13 is operated before the SI contact of the tap selector, the nonlinear resistor 26 is connected between the even and odd sides of the switch 14. It is now possible to place. Therefore, the nonlinear resistor 26 can be housed in the oil tank of the switching switch 14, which is isolated from the main body oil of the transformer. The inside of the switching switch oil tank can be easily inspected, and dirty oil is usually replaced and the switching switch is inspected at least once every five years. Therefore, the characteristics of the nonlinear resistor housed in the oil tank can be checked every time it is inspected, and preventive measures such as replacing the nonlinear resistor 26 can be taken if necessary. Although the explanation so far has been made with reference to the case where a polarity switch is used as the sub-switch, the present invention can be implemented in the same way when a transposed switch is used. In addition, although a nonlinear resistor is used, it is generally effective to use a nonlinear resistor, so it is also possible to use a simple high resistor. As explained above, according to the present invention, a resistor is connected between the closed contact side and the open contact side of the switching switch, and the opening/closing operation of the contacts of the sub switching switch is completed. Since the tap selector is later opened and closed, the electrical float phenomenon of the tap winding is prevented, and the resistor is housed in the switching switch oil tank, making it easier to inspect the resistor during load. A tap cutting device can be provided.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram showing a general on-load tap switching device with a built-in transformer, Fig. 2 (A) is a circuit diagram of a conventional on-load tap switching device and an operation sequence diagram showing the switching order.
Figures A and B are a circuit diagram and an operation sequence diagram showing the switching order of the on-load tap switching device according to the present invention. 11... Main winding, 12... Tap winding, 1
3... Sub-sliding switch, 14... Switching switch, 2
6...Resistor, S1, S2...Tap selector contacts. Many 1b*2 evil*・3 skin

Claims (1)

[Claims] 1. A sub-switcher is provided between the main winding and the tap winding, and a tap selector is provided to select the tap of the tap winding, and the current flowing through the tap selected by the tap selector is switched off. A resistor is connected between the open contact side and the closed contact side of the changeover switch, and the switch has a plurality of switching contacts. 1. A tap switching device under load, characterized in that the tap selector is opened and closed after the contacts of the switching device have finished opening and closing.