JPS6040167B2 - Transformer load tap switching device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an on-load tap cutting device for a transposition switching type asymmetrical-resistance transformer without a foot tap.

Regarding the cross-current interruption of the above-described single-circuit device, the interruption phase angle of the contacts is not negligible compared to other cases during tap switching between the end of the coarse-tapped winding and the close-tapped winding. known to be of value.

The reason for this is that the actance between each step is the sum of the leakage reactance of both the coarse tap winding and the fine tap winding, and this value can be almost ignored like the IJ actance between other steps. Not the value, but a fraction of the current limiting resistance value
The reason is that it becomes a relatively large value. Because of this, it has been experienced that within the above specific steps, the arcing time of the contacts involved in cross-current interruption is unduly prolonged. In an asymmetrical-resistance on-load tap changer, the main contacts are involved in interrupting the cross current, so prolonging the arcing time carries the risk of developing a short circuit between taps, so it should be kept as short as possible. It won't happen. An object of the present invention is to provide an on-load tap switching device that satisfies the above requirements. Hereinafter, one embodiment of the present invention will be described in detail based on the drawings. FIG. 1 shows a load condition according to an embodiment of the present invention in which an asymmetrical-resistive load tap changer is provided on the secondary side of a transformer by a transposition switching method and connected to a coarse tap winding and a fine tap winding. A tap-changing transformer is shown.

In the figure, numeral 110 is a primary winding, and numeral 111 is a secondary main winding. Further, numeral 112 is a coarse tap winding;
113 is a fine tap winding, 114 is a transposition switch that selects coarse taps, 115 is an odd tap selector that selects odd dense taps, 116 is an even tap selector that selects even dense taps, and 117 is the pair of This is a switching switch that selects either one of the tap selectors and transfers the load current. Furthermore, numerals 1, 3, 5, 7, and 9 are odd number taps selected by the odd number tap selector 115, and all of them are provided on the close tap winding.

2, 4, 6, 8, and 10 are even taps selected by the even tap selector 116, 2 to 8 are provided on the fine tap winding, and only 10 is drawn from the end of the coarse tap winding. has been done.

Reference numeral 11 is a starting end of a finely tapped winding 113, which is selectively connected to coarse taps 12 and 13. A, B, and C are the odd-numbered tap main contact, resistance contact, and even-numbered tap main contact of the switching switch 117, respectively, and one end of each of these contacts is connected to each other, and the other end of the odd-numbered tap main contact A is connected to the other end of the odd-numbered tap main contact A. An odd-numbered tap selector is followed, one end of the current-limiting resistor R is connected to the other end of the limiting acid point B, and the other end of the current-limiting resistor R and the even-numbered tap are connected to the other end of the even-numbered tap main contact C. The main contacts are connected. Third
The figure is a sequence diagram showing the opening and closing order of the odd-numbered tap main contact A, the resistance contact B, and the even-numbered tap main contact C, and the opening and closing positions are reversible with respect to the switching direction.

Now, in FIG. 1, the transposition switch 114 is connected to the coarse tap 13, the odd tap selector 115 is connected to the odd tap, and the even tap selector 116 is connected to select the even tap. The switch 117 is currently in the middle of the sliding screen, and the odd-number tap main contact A and resistance contact B are closed.

On the other hand, since the coarse tap winding 112 is wound one step more than the fine tap winding 113, in the state shown in FIG. 1, the direction of the load current i is the same clockwise direction as the secondary voltage. Then, a cross current called IC flows counterclockwise. This cross current iC is usually e/R obtained by limiting the step voltage e (reference voltage) only by R, but for one specific step in FIG. The current is e/R+i (x, 10), which is limited by the impedance of the reactance jx and the reactance jx2 of the close-tapped winding 113, resulting in a delayed current. If resistor R is connected in the direction of A and B contrary to Fig. 1, then even tap 10
When B and C are closed in the process of switching from to odd-numbered tap 1, the current in C becomes iL+ic, and this must be cut off, so the recovery voltage e+
The phase lags behind the iLR, making it difficult to shut off, and in the worst case, there is a risk of a short circuit between taps. However, in this case, since the resistor R is connected between the resistance contact B and the even-numbered tap main contact C, the cross current in question occurs at the switching tap main contact A during switching from the odd-numbered tap 1 to the even-numbered tap 10. When resistance contact B is closed, the current flows in the opposite direction to the load current.

The breaking current of the switching tap main contact A is iL-ic
As shown in FIG. 4, since the absolute value becomes smaller and the phase is advanced with respect to the recovery voltage e-iLR, the interruption becomes much easier. Therefore, the risk of a prolonged arc at the A contact leading to a short circuit between taps is greatly reduced.
This has the effect of significantly reducing the cut-off conditions required to completely eliminate this.

Next, FIG. 2 shows a modification in which an on-load tap cutter is attached to the primary winding of a transformer.

In this modification, the difference from the case in FIG. 1 is that the resistor R
is connected between the odd-numbered tap main contact A and the resistance contact B, and when switching from the even-numbered tap 10 to the odd-numbered tap 1, a cross current flows to the even-numbered tap main contact C. shall be.

The other parts can be explained in exactly the same way by replacing the secondary side in FIG. 1 with the primary side in FIG. 2. In Fig. 2, the cross current flows through the even-numbered tap main contact C, because in the primary winding, the load current flows in the opposite direction to the step voltage, and the cross current flows in the same direction as the step voltage. are opposite to each other because they are on the even-numbered tap main twill point C side. In the above explanation, the main contact on the unconnected side of resistor R (in Fig. 1, A
, In Figure 2, only C) was considered as a problem, and this is due to the following reasons.

In other words, the breaking current of the main contact on the side connected to resistor R is the load current iL itself, and its recovery voltage is iL
Since the current is R and the phase is the same regardless of the power factor of the load, it is easy to shut off. In addition, the resistance contact B has a breaking current (e/R+j
(x, 1 &)), the recovery voltage becomes e, and the power factor is interrupted with a delay.However, even if the arc lasts for a long time, the current limiting resistor R is present in series, so there is no risk of current increase and there is no chance of extinguishing the arc. It can hold much more than the main contacts. Furthermore, even if the arc cannot be extinguished in the worst case, overheating of the current limiting resistor can be detected and protection can be provided before a short circuit occurs between the taps. Therefore,
By paying attention only to the breaking conditions of the main contact on the side to which the resistor is not connected, it is possible to realize a highly reliable transposition-cutting type asymmetrical-resistance-type load tap-cutting device. As described above, the present invention provides a finely tapped winding, a coarsely tapped winding having one step more windings than the finely tapped winding, a coarse tap provided on the coarsely tapped winding, and a shift cutter that selects coarse taps; odd-numbered taps and even-numbered taps provided in the finely tapped winding; an odd-numbered tap selector that selects the odd-numbered taps; and an even-numbered tap selector that selects the even-numbered taps; A switching switch that selects either the odd tap selector or the even tap selector and transfers the load current; It consists of a current limiting resistor connected to the main fixed point of the switch.

Therefore, according to the present invention, the risk of short circuit between taps due to excessive extension of the arcing time of the contacts related to cross current interruption, which was an issue of the present invention, can be sufficiently eliminated.

[Brief explanation of drawings]

FIG. 1 is an electrical connection diagram of a load tap switching device for a transformer according to an embodiment of the present invention, FIG. 2 is a modification thereof, and FIG. 3 is an opening/closing diagram of a switching device for the switching gate of each of the above examples. The sequence diagram, FIG. 4, is a vector diagram explaining the operation of each contact of the sliding door switch. 1, 3, 5, 7, 9...odd number tap, 2, 4,
6, 8, 10... Even number tap, 112...
・・Coarse tap winding, 113・・・・Dense tap winding,
114... Transposition switch, 115... Odd tap selector, 116... Even tap selector, 1
17...Switch for sliding door. Figure 3 Figure 4 Figure 1 Figure 2

Claims (1)

[Claims] 1. A fine tap winding with odd and even taps, a coarse tap with one step more windings than the fine tap winding, and a coarse tap with a final end tap on one side of the even tap at the end. In the on-load tap switching device for a transformer, the on-load tap switching device for a transformer is provided with a winding and a transposition switching device connected to a starting end of the fine tap winding and selecting the coarse tap on the primary side or secondary side of the transformer, respectively. an odd tap selector or an even tap selector that is sequentially selectively connected to one of the odd taps or even taps, and an odd tap main contact and a current limiting resistor whose one end is connected to each other and the odd tap selector is connected to the other end. a resistive contact connected to the odd tap selector when provided on the primary side, and to the even tap selector when provided on the secondary side, and an even tap main contact connected to the even tap selector via the and a switching switch that selects either the odd-numbered tap selector or the even-numbered tap selector and transfers the load current.