JPH0584656B2 - - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to on-load tap changers, and more particularly to an improvement of a two-resistance type using a vacuum valve.

[Technical background of the invention and its problems]

Vacuum valves have advantages such as excellent shutoff performance, long contact life, and no contamination of oil because the arc is extinguished in a vacuum container, so in recent years, tap changers have been replaced under load. Used in switches.

In the conventional on-load tap changer shown in FIG. 4, a tap winding W _T is provided in the low voltage or high voltage winding of a transformer. This tap winding W _T is provided with a plurality of taps, for example taps T ₁ and T ₂ are shown. Also, the tap changer on load has taps T ₁ and T ₂ .
It is provided with movable contact circuit parts 3 _a and 3 b on the a side and the b side, which are connected in contact with the a and b sides. In other words, the movable contact circuit section 3a on the a side has a resistance contact vacuum valve W _a (hereinafter abbreviated as valve W a) in series with the movable contact _{1 a} that is in sliding contact with the tap T ₁ between the tap T ₁ and the neutral point N. and main contact vacuum valve H _a (hereinafter abbreviated as valve H _a )
A current limiting member such as a current limiting resistor is provided between the connection point _5a between both valves W _a and H _a and the neutral point N.
Connect R _a .

An auxiliary contact K _a is connected between the connection point 5 _a and the valve H _a . The auxiliary contact _Ka is used for abnormality protection by causing the light to fire when the valve _{H a} continues firing and detecting this light with an optical fiber (not shown). Similarly to the _a side, the movable contact circuit section _3b on the b side is constructed between the tap _T2 and the neutral point N as shown in the part number and name code with the suffix b.

The operation order of the circuit configured in this way will be explained with reference to the sequence diagram of FIG. 5. Valve H _a ,
W _a is on or closed and driven to tap T ₁ . First, valve H _a is turned off or opened,
The load current flows through the valve W _a and the current limiting resistor R _a . Next, the b-side valve _Wb closes to short-circuit the taps _T1 and _T2 . The auxiliary contact K _a then opens without current, and at the same time the auxiliary contact K _b closes.
Then, the valve W _a on the a side opens, and the load current transfers to tap T ₂ . Valve H _b then closes, completing the one-tap switching operation.

If we consider a case where the shutoff performance of the vacuum valve of such a conventional on-load tap changer deteriorates and the arc cannot be extinguished, the following will occur.

(i) If the switching progresses with the arcs of valves H _a and H _b prolonged, the a side changes from closed to open according to the sequence shown in Figure 5, and the b side changes from closed to open.
The sides move from open to closed. Also, on the a side, the valve H _a ,
W _a is connected in series, and valves H _a and W _b are also connected in series on _{the b} side, so if the vacuum level of valves H _a and H _b becomes poor, the breaking performance deteriorates, and the arc is prolonged. , the current is cut off by the valves W _a and W _b .

At this time, the duty of shutting off the valves W _a and W _b is more difficult than their normal duty, but since the shutoff ability of the vacuum valve is large, the shutoff is completed and a situation such as a direct tap-to-tap short circuit does not occur.

(ii) If the interrupting performance of valves W _a and W _b deteriorates and the arc time becomes longer, in such a case, as switching progresses, valve H _a will open on side a, which is closed, according to the sequence. , followed by valve W _a
becomes open. Also, the b side that is open is a valve.
W _b is closed, and then valve W _b is closed. In this process, circulating currents determined by the step voltage and the values of the current limiting resistors R _a and R _b continue to flow through the valves W _a and W _b to the a side and the b side, respectively. Therefore, there is a risk that the current limiting resistors R _a and R _b may overheat and melt due to this circulating current. Since the circuit breaker can be tripped by detecting the pressure change in the switching switch container due to the expansion of the gas generated at that time, it is possible to prevent a short circuit between the taps.

(iii) When the shutoff performance of both valves H _a and H _b and valves W _a and W _b deteriorates. That is, valve H _a ,
If the interrupting performance of both H _b and valves W _a and W _b decreases at the same time, a short circuit will occur between the taps.

As mentioned above, in the conventional on-load tap changer shown in Fig. 4, the valves H _a , H _b and the valves W _a ,
If the breaking performance of both W _b decreases at the same time, there is a risk of short circuit between taps. Also, the valve W _a ,
When the breaking performance of W _b decreases, the current limiting resistors R _a and R _b
A circulating current flows through the current limiting resistors R _a and R _b , which generate heat.
Since the circuit breaker is tripped by detecting the increase in gas pressure caused by the melting, there is a problem that needs to be solved in that it is not possible to detect the circuit breaker in a short period of time before the trip occurs.

Auxiliary contacts Ka _{and Kb} are provided to detect this in advance. That is, as shown in the sequence diagram of FIG. 5, when the valves H _a and H _b have reduced shutoff performance due to vacuum failure, etc., and the repeated arc phenomenon continues, the auxiliary contacts K _a and K _b fire. The firing of the auxiliary contacts K _a and K _b is detected by optical fibers (not shown), and tap switching is prevented, thereby preventing a short circuit between the taps as described above.

In conventional devices configured in this way, the auxiliary contact
Since Ka _{and Kb} directly interrupt the load current, the structure of the auxiliary contacts Ka _{and Kb} must be adapted to the interrupting current value. In other words, if the vacuum valve continues to fire for several tens of cycles, the auxiliary contacts Ka _{and Kb} will fire during this period. Therefore, the heat generated by this arcing could have an effect on surrounding components, such as melting and damage, and increase in pressure in the switching switch oil tank due to gasification of the insulating oil, so it was necessary to provide this protection device. As a way to prevent the above situation, it is possible to provide the auxiliary contacts K _a and K _b with a breaking ability commensurate with the magnitude of the load current, but this solution would make the entire device larger and more expensive. I have a problem that needs to be addressed.

[Purpose of the invention]

The present invention has been made in consideration of the above points, and
The purpose of this is that the auxiliary contacts K _a and K _b can be constantly energized without any support, and the tap switch under load can fire only when the vacuum valve continues firing, and this firing can be detected. It is about providing the equipment.

[Summary of the invention]

According to the present invention, in order to achieve such an objective,
The auxiliary contacts K _a and K _b are fired only for the time necessary for detection using an optical fiber or the like, and then reclosed, thereby reducing the size of the entire device.

[Embodiments of the invention]

An embodiment of the on-load tap changer according to the present invention will be described below with reference to FIGS. 1 to 3. The drive shaft 11 is connected to a power storage device (not shown) and responds to the quick cutting operation of the power storage device. A cam groove 12a is formed in the cam 12 fixed to the drive shaft 11.
1 and performs a fast cutting operation.

A roller 13 is slidably engaged with the cam groove 12a, and opens and closes the auxiliary contact portion 15 along the cam groove 12a. This auxiliary contact portion 15 corresponds to auxiliary contacts Ka _{and Kb} . (See Fig. 4) Also, the cam groove 12b is connected to vacuum valves H _a , W _a ,
This is a groove that opens and closes W _b and H _b .

The roller 13 is slidably housed within the cam groove 12a, and reciprocates along the cam groove 12a in the left-right direction in the drawing. The roller 13 is fixed to the driving rod 16, and this driving rod 16
is secured to one end of the insulating rod 19 by pins 17,18. Further, a spring case 20 is fixed to the other end of the insulating rod 19 by pins 21 and 22. Further, a movable contact 22 that is constantly pressed by a compression spring 21 is housed in the spring case 20, and an auxiliary contact portion 15 is formed by bringing the movable contact 22 into contact with and separating from a fixed contact 23 facing the movable contact 22.

The spring case 20 is provided with two guide bars 25 which are guided by a bearing plate 26 to allow the spring case 20 having the movable contacts 22 to reciprocate. The bearing plate 26 is attached to upper and lower supports 27. A switching switch oil tank is formed by the insulating cylinder 28, and the arcing of the auxiliary contact is detected on the inner wall of the insulating cylinder 28, on the surface facing the auxiliary contact 15 corresponding to the auxiliary contacts Ka _{and Kb} . Light receiving element 2
9 is attached, and is guided from the light receiving element 29 to the outside through an optical fiber 30 through the head of the switching switch oil tank (not shown).

Next, the operation of the present invention will be explained. The drive shaft 11 is rotated by a power storage device (not shown), and the cam 12 is thereby rotated. First, the valve H _a is turned off or opened by the cam groove 12 _b , and then the valve H a is turned off or opened.
W _b is on or closed. Subsequently, when the cam 12 rotates, the auxiliary contacts K _a and K _b are simultaneously opened by the cam groove 12 _a . During this time, valve W _a opens, and finally valve H _b closes, completing the one-tap switching operation.

As described above, if the valve H _a continues to arc and the switching operation continues with the arc time extended, the auxiliary contact K _a will fire. Since this firing time may be within the time that the light receiving element can detect, the auxiliary contact _Ka closes immediately. Therefore, the breaking ability of the auxiliary contact is significantly reduced. Accordingly, the auxiliary contact has a reduced configuration.

〔Effect of the invention〕

As explained above, according to the present invention, the auxiliary contact
K _a and K _b can be energized at all times without any trouble, and only when the vacuum valve continues to fire, it is fired and then reclosed, and by detecting this firing, the breaking ability of the auxiliary contact can be greatly increased. It is possible to provide an on-load tap changer that can be used repeatedly, has reduced damage, has a reduced size auxiliary contact, and has minimal damage due to arcing.

[Brief explanation of the drawing]

FIG. 1 shows the main part of the present invention, and FIG.
2 is a cross-sectional view taken along the - line in FIG. 1; FIG. 3 is a sequence diagram showing the operation of the present invention; FIG. 4 is a circuit diagram of a conventional on-load tap changer; FIG. 5 is a sequence diagram showing the operation of FIG. 4. 11... Drive shaft, 12... Cam, 12 _a , 12 _b
...Cam groove, 13...Roller, 15...Auxiliary contact section, 16...Driving rod, 17,1
8, 21, 22...Pin, 19...Insulating rod,
20... Spring case, 21... Compression spring, 22...
...Movable contact, 23...Fixed contact, 25...Guide bar, 26...Bearing plate, 27...Support, 28
...Insulating cylinder, 29 ... Light receiving element, 30 ... Optical fiber, W _a , W _b , H _a , H _b ... Vacuum valve (valve), K _a , K _b ... Auxiliary contact, R _a , R _b ...Current limiting resistor.

Claims (1)

[Claims] 1 a tap selector having a pair of movable contacts in contact with the taps of a tap winding; first and second vacuum valves connected in series between the movable contacts and a neutral point; Connect an auxiliary contact in series between the vacuum valves to detect the continuation arc of the vacuum valve.
Furthermore, in a load tap changer formed by connecting a current limiting resistor in parallel with the second vacuum valve from between the first vacuum valve and the auxiliary contact, the cam groove is connected directly to the drive shaft. A tap changer on load, characterized in that it is configured to open after the second vacuum valve is opened and to reclose the circuit immediately after detecting a subsequent arc.