JP2009290005A - On-load tap changer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an on-load tap changer capable of surely preventing occurrence of shutoff mistake even when a direct current is carried to a main valve, and exhibiting excellent insulation performance and stable shutoff capability. <P>SOLUTION: This on-load tap changer is structured such that the main valve H is opened in a state where a valve W1 for resistance on the side of a tap 2 carrying a current before a change operation is opened and a valve W2 for resistance on the side of a tap 3 not carrying a current before the change operation is opened; the valve W2 for resistance on the tap 3 side is opened in a state where the main valve H is opened, the valve W1 for resistance on the tap 2 side which is carrying a current before the change operation is closed, and the valve W2 for resistance on the tap 3 side not carrying a current before the change operation is opened; and thereafter, a moving contact SC of a changing-over switch S starts operation to open electrical connection to a fixed contact SA in contact with it before the change operation. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a two-resistance, three-valve type on-load tap switching device, and more particularly to an on-load tap switching device capable of exhibiting stable shut-off capability even when a direct current is applied to a main valve.

  In general, a transformer connected to a power transmission / distribution system is provided with an on-load tap switching device including a switching switch and a tap selector. A switching switch usually uses a vacuum valve in which a pair of electrodes that can be brought into contact with and separated from each other are arranged in a vacuum vessel as a shut-off element. As a load tap changer, two current limiting resistors per phase are used. A two-resistor three-valve system having three vacuum valves is widely known. Such an on-load tap switching device is an essential component for adjusting and stabilizing the voltage of the power transmission and distribution system, and various techniques have been proposed (for example, Patent Document 1).

  Here, the on-load tap switching device of the 2-resistance 3-valve method described in Patent Document 1 will be specifically described with reference to FIGS. 4 and 5. FIG. 4 is a switching circuit and its operation diagram in a conventional on-load tap switching device. 4, TW is a tap winding of a transformer or the like, 2, 3 is a tap of the tap winding TW, N is a neutral point, and US is a step voltage between taps.

  5 (1) and 5 (2) show a switching sequence in the on-load tap switching device. In the main valve H, the resistance valves W1 and W2, and the fixed contacts SA and SB of the changeover switch S, The open / closed state is shown, with the upper stage being closed (ON) and the lower stage being non-contact (OFF). 5A to 5G correspond to the switching process indicated by (A) to (G) in FIG.

  As shown in FIG. 4, the on-load tap changer is provided with a tap selector having two movable contacts M1 and M2 and a changeover switch S for switching the energization state. The changeover switch S includes two fixed contacts SA and SB, and a movable contact SC that can be selectively contacted and separated from any one of the fixed contacts SA and SB.

  Between the taps 2 and 3 of the tap winding TW and the neutral point N, a current limiting resistor R1 and a resistance valve W1 are connected in series with the movable contact M1, and a current limiting with respect to the movable contact M2. A resistor R2 and a resistor valve W2 are connected in series. A fixed contact SA of the changeover switch S is provided at an intermediate portion between the movable contact M1 and the current limiting resistor R1, and a fixed contact SB of the changeover switch S is provided at an intermediate portion between the movable contact M2 and the current limiting resistor R2. Yes. A movable contact SC is installed in the vicinity of the fixed contacts SA and SB, and a main valve H is connected between the movable contact SC of the changeover switch S and the neutral point N. The main valve H and the resistance valves W1 and W2 are all vacuum valves.

Each process of the switching sequence of the on-load tap switching device having the above-described configuration will be described step by step.
(A) Operating state ((A) of FIGS. 4 and 5)
4A and 5B, the main valve H and the resistance valve W1 are closed, the movable contact SC of the changeover switch S is connected to the fixed contact SA, and the movable contact M1 of the tap selector is tapped. The driving | running state connected to the tap 2 of the line TW is shown. At this time, the load current IL flows from the neutral point N to a circuit of the main valve H, the movable contact SC of the changeover switch S, the fixed contact SA, the movable contact M1, the tap 2, and the tap winding TW as indicated by a dotted line. .

(B) Opening of the main valve H ((B) in FIGS. 4 and 5)
When the switching operation starts from the state (A), the main valve H is first opened. As a result, the load current IL flows through a circuit including the resistance valve W1, the current limiting resistor R1, and the tap winding TW as indicated by a dotted line.

(C) Start of operation of selector switch S ((C) of FIGS. 4 and 5)
Next, the movable contact SC of the changeover switch S starts moving from the fixed contact SA to the fixed contact SB side.

(D) Closing of the resistance valve W2 on the non-energizing tap 3 side ((D) in FIGS. 4 and 5)
Subsequently, the resistance valve W2 on the side of the tap 2 that is not energized before the switching operation is closed, and a short circuit is connected via the current limiting resistor R2, the resistance valve W2, the resistance valve W1, and the current limiting resistor R1. The circulating current IC flows therethrough.

  Further, the load current IL is changed from the neutral point N to the circuit composed of the resistance valve W1 and the current limiting resistor R1, and the circuit composed of the resistance valve W2 and the current limiting resistor R2, with the resistance ratio of the current limiting resistors R1 and R2. Divide it accordingly. Here, R1 = R2. That is, the load current IL flows in half by the circuit of the resistance valve W1 and the current limiting resistor R1 and the circuit of the resistance valve W2 and the current limiting resistor R2.

(E) Opening of the resistance valve W1 on the energization tap side ((E) in FIGS. 4 and 5)
Further, the resistance valve W1 on the side of the tap 2 that is energized before the switching operation is opened to interrupt the circulating current IC. At this time, the load current IL flows through a circuit including a resistance valve W2, a current limiting resistor R2, and a tap winding TW as indicated by a dotted line.

(F) Operation completion of selector switch S ((F) of FIGS. 4 and 5)
The movable contact SC of the changeover switch S completes the movement from the fixed contact SA to the fixed contact SB side.

(G) Closing of main valve H ((G) in FIGS. 4 and 5)
Finally, the main valve H is closed, and the load current IL is transferred from the neutral point N to the main valve H, the movable contact SC of the changeover switch S, the fixed contact SB, and the tap winding TW. Thus, the switching operation is completed and the operation is continued in the state shown in the drawing. Further, the switching operation to the next tap is performed in the order from (G) to (A) shown in (2) of FIG.
Japanese Patent Application No. 2007-15633

  By the way, when a surge current enters the tap switching device at the time of loading from the system, it is superimposed on the load current and becomes a direct current that does not transiently reach the zero point. Therefore, in the on-load tap switching device described in Patent Document 1, a direct current may flow during the switching operation, and the main valve, which is a vacuum valve, needs to cut off the direct current. However, since the vacuum valve normally cuts off the current at the zero point of the alternating current, it is very difficult to cut off the direct current, which has been a problem in the conventional on-load tap switching device.

  The above “cut-off of direct current” will be described in detail with reference to FIG. The state before the switching operation is shown in FIG. 6A, and when the switching operation is started, the main valve H is opened in FIG. 6B, and the superimposed current (DC) ID is cut off. However, since the main valve H, which is a vacuum valve, is difficult to cut off the direct current, it may not be cut off.

  Subsequently, the movable contact SC of the changeover switch S moves away from the fixed contact SA, but if the superimposed current (DC) ID cannot be interrupted by the main valve H, the changeover switch S as shown in FIG. a will be cut. As a result, although there is a merit such as reliable current interruption by the changeover switch S, it cannot be denied that the movable contact SC, the fixed contact SA, SB of the changeover switch S and the insulating medium in the apparatus are deteriorated by the arc a.

  In addition, if the interruption of the arc a by the changeover switch S is repeated, not only the insulation performance is lowered, but also the interruption performance of the arc a at the changeover switch S is lowered. In the worst case, FIG. As shown, the arc a reaches the fixed contact SB from the fixed contact SA, which may lead to a short circuit accident between the taps 2 and 3. As described above, in the conventional on-load tap switching device, when a direct current is applied to the main valve H, it is difficult to shut off by the main valve H, and a shut-off error may occur.

  The present invention has been proposed in order to solve the above-mentioned problems, and its purpose is to reliably avoid the occurrence of a disconnection error even when a direct current is applied to the main valve. An object of the present invention is to provide an on-load tap changer capable of exhibiting the interrupting ability.

  In order to achieve the above object, the present invention includes a tap selector that selects a tap of a tap winding between a tap of the tap winding and a neutral point, and a changeover switch that switches an energized state. The tap selector is provided with two movable contacts, the changeover switch has a plurality of fixed contacts, and a movable contact that can be selectively contacted and separated from one of the plurality of fixed contacts. A current limiting resistor and a resistance valve are connected in series between each movable contact of the tap selector and the neutral point, and between the current limiting resistor and the movable contact of the tap selector. Is a two-resistor three-valve type tap switching device under load in which a plurality of fixed contacts of the changeover switch are provided, and a main valve is connected between the movable contact of the changeover switch and a neutral point. The resistance valve connected to the energizing tap side energizing the Is closed, when the resistance valve connected to the non-energized tap that is not energized before the switching operation is in the open state, the main valve is opened first, after the main valve is opened, In a load tap switching device configured such that the resistance valve on the non-energizing tap side is closed, the resistance valve on the energizing tap side is subsequently opened, and then the main valve is closed. After the resistance valve on the non-energizing tap side that is not energized before the operation is closed, the movable contact of the changeover switch releases the electrical connection with the fixed contact that was in contact before the changeover operation. It is characterized by being configured as described above.

  In the present invention, the resistance valve on the energizing tap side that is energized before the switching operation is closed, and the resistance valve on the non-energizing tap side that is not energized before the switching operation is opened, Since the resistance valve is closed, a short circuit is formed, so that a circulating current flows. At this time, if a direct current flows through the main valve due to the surge current, the circulating current is an AC power supply. Therefore, the direct current and the circulating current are superimposed, resulting in an AC zero point in the passing current of the main valve. . In other words, even if a direct current flows at the start of the opening operation of the main valve and it is difficult to cut off, the circulating current and the direct current generated by the closing of the resistance valve on the non-energizing tap side are superimposed. Thus, the zero point can be reached, and the current can be surely interrupted at this point.

  Furthermore, in the present invention, since the resistance valve on the non-energizing tap side is closed, the movable contact and the fixed contact of the change-over switch are opened, so when this opening operation is performed, the main valve The current is cut off by. That is, there is no possibility of interrupting the arc with the changeover switch. Therefore, the changeover switch can maintain excellent insulation performance and interruption performance, and there is no fear of a short circuit accident between taps.

  According to the on-load tap switching device of the present invention, even if a direct current flows through the main valve, which is a vacuum valve, during the switching operation, the resistance valve on the non-energizing tap side is closed so that the AC power supply is provided. The circulating current can be superimposed on the DC current to generate an AC zero point, and no interruption error occurs and arc interruption by the changeover switch can be avoided, thus stabilizing the interruption capability and improving insulation reliability. We were able to plan.

  Hereinafter, typical embodiments according to the present invention will be described in detail with reference to FIGS. 1 and 3 show a switching circuit diagram and an operation diagram of an embodiment according to the present invention. The same parts as those in the prior art shown in FIG. FIG. 2 shows a switching sequence of the embodiment according to the present invention corresponding to FIG.

(1) Configuration A representative embodiment according to the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 shows a switching circuit and operation diagram of the on-load tap switching device according to the first embodiment, and FIG. 2 shows the switching sequence.

  The present embodiment has structural features in the following points. That is, after the non-energizing tap-side resistance valve W1 or W2 that is not energized before the switching operation is closed, the movable contact SC of the changeover switch S is in contact with the fixed contact SA or SB that was in contact before the switching operation. The electrical connection with is disconnected.

  First, the case where the energization is performed on the tap 2 side and the movable contact SC and the fixed contact SA are electrically connected in the changeover switch S will be described as an example. The main valve H is opened while the tap-side resistance valve W1 energized before the switching operation is closed, and the tap-side resistance valve W2 not energized before the switching operation is open. . Then, after the main valve H is opened, the resistance valve W1 on the tap 2 side that is energized before the switching operation remains closed, and the resistance valve on the tap 3 side that is not energized before the switching operation. W2 is closed. Thereafter, the movable contact SC of the changeover switch S starts to operate, and the electrical connection with the fixed contact SA that was in contact before the changeover operation is released.

  On the other hand, when the switch 3 is energized and the switch S is electrically connected to the movable contact SC and the fixed contact SA, the resistance valve W2 on the tap 3 side that is energized before the switching operation is provided. The resistance valve W1 on the tap 2 side that is not energized before the closing and switching operation is in an open state, and the main valve H is opened from this state. Then, after the main valve H is opened, the tap-side resistance valve W2 that is energized before the switching operation is kept closed, and the tap-side resistance valve W1 that is not energized before the switching operation. Is closed. Thereafter, the movable contact SC of the changeover switch S starts to operate, and the electrical connection with the fixed contact SB that has been in contact before the changeover operation is released.

  In the present embodiment, the time from when the resistance valve W1 or W2 is closed to when the movable contact SC of the changeover switch S is disconnected from the fixed contact SA or SB is determined as an alternating current that is energized. It is set to 1/2 cycle or more of the power supply (for example, 10 ms or more in the case of 50 Hz).

(2) Switching Sequence The switching sequence of the present embodiment having the above configuration will be described step by step according to the switching process shown in (A) to (G) of FIG. FIGS. 1A to 1G show the switching process shown in FIGS. 2A to 2F by (A) to (F). In addition, the switching sequence of this embodiment replaces (C) and (D) in the switching sequence of the on-load tap switching device described in Patent Document 1 above, and is otherwise the same.

(A) Operating state ((A) in FIGS. 1 and 2)
The main valve H and the resistance valve W1 are closed, the movable contact SC of the changeover switch S is connected to the fixed contact SA, and the movable contact M1 of the tap selector is connected to the tap 2 of the tap winding TW. Indicates. At this time, the load current IL flows from the neutral point N to a circuit of the main valve H, the movable contact SC of the changeover switch S, the fixed contact SA, the movable contact M1, the tap 2, and the tap winding TW as indicated by a dotted line. .

(B) Opening of the main valve H ((B) in FIGS. 1 and 2)
When the switching operation starts from the state (A), the main valve H is first opened. As a result, the load current IL flows through a circuit including the resistance valve W1, the current limiting resistor R1, and the tap winding TW as indicated by a dotted line.

(C) Closing of the resistance valve W2 on the non-energizing tap 3 side ((C) in FIGS. 1 and 2)
Subsequently, the resistance valve W2 on the side of the tap 2 that is not energized before the switching operation is closed, and a short circuit is connected via the current limiting resistor R2, the resistance valve W2, the resistance valve W1, and the current limiting resistor R1. The circulating current IC flows therethrough.

  Further, the load current IL is changed from the neutral point N to the circuit composed of the resistance valve W1 and the current limiting resistor R1, and the circuit composed of the resistance valve W2 and the current limiting resistor R2, with the resistance ratio of the current limiting resistors R1 and R2. Divide it accordingly. Here, R1 = R2. That is, the load current IL flows in half by the circuit of the resistance valve W1 and the current limiting resistor R1 and the circuit of the resistance valve W2 and the current limiting resistor R2.

(D) Start of operation of changeover switch S ((D) in FIGS. 1 and 2)
Next, the movable contact SC of the changeover switch S starts moving from the fixed contact SA to the fixed contact SB side. As already described, the switching sequence of (C) and (D) is a feature of this embodiment.

(E) Opening of the resistance valve W1 on the energizing tap side ((E) in FIGS. 1 and 2)
Further, the resistance valve W1 on the side of the tap 2 that is energized before the switching operation is opened to interrupt the circulating current IC. At this time, the load current IL flows through a circuit including a resistance valve W2, a current limiting resistor R2, and a tap winding TW as indicated by a dotted line.

(F) Operation completion of changeover switch S ((F) of FIGS. 1 and 2)
The movable contact SC of the changeover switch S completes the movement from the fixed contact SA to the fixed contact SB side.

(G) Closing of main valve H ((G) in FIGS. 1 and 2)
Finally, the main valve H is closed, and the load current IL is transferred from the neutral point N to the main valve H, the movable contact SC of the changeover switch S, the fixed contact SB, and the tap winding TW. Thus, the switching operation is completed and the operation is continued in the state shown in the drawing. Further, the switching operation to the next tap is performed in the order from (G) to (A) shown in (2) of FIG.

(3) Operational Effects In the present embodiment having the switching sequence as described above, the following operational effects can be exhibited when the superimposed current ID becomes a direct current due to the penetration of a surge into the system. Here, the state before the switching operation is shown in FIG. That is, the main valve H and the resistance valve W1 are closed, the movable contact SC of the changeover switch S is connected to the fixed contact SA, and the movable contact M1 of the tap selector is connected to the tap 2 of the tap winding TW. Yes. When the switching operation is started from this state, the main valve H is opened in FIG. 3B, and the superposed current (DC) ID is cut off. However, since the main valve H is a vacuum valve, it cannot be shut off.

  Next, the resistance valve W2 is closed, and a short circuit is formed through the current limiting resistor R2, the resistance valve W2, and the main valve H, so that a circulating current IC flows (FIG. 3C). At this time, since the circulating current IC is an AC power supply, a zero point can be generated in the passing current of the main valve H by superimposing the DC current ID and the circulating current IC. Therefore, the main valve H can reliably block the passing current.

  In FIG. 3D, the movable contact SC of the changeover switch S moves away from the fixed contact SA. However, since the current in the main valve H is cut off at this time, the changeover switch S does not turn off the arc a. In the present embodiment, since the resistance valve W2 is closed and the movable contact SC of the changeover switch S is disconnected from the fixed contact SA, the AC power supply to be energized is set to 1/2 cycle or more. The zero point of the current in which the circulating current IC and the direct current ID are superimposed can be surely reached. Even when the movable contact SC of the changeover switch S is connected to the fixed contact SB and the movable contact M2 of the tap selector is connected to the tap 3 of the tap winding TW, the state before the switching operation is present. Needless to say, similar effects can be obtained.

As described above, according to the present embodiment, even when the main valve H is energized during the switching operation, the zero point of the energized power supply can be reliably reached at the opened contact, so that a disconnection error can occur. The main valve can ensure a stable shut-off capability without generating
Further, when the movable contact SC of the changeover switch S is separated from the fixed contact SA or SB, the current is already cut off by the main valve H, so that the arc need not be cut off by the changeover switch S. Therefore, it is possible to prevent a decrease in insulation performance and interruption performance due to arc-a interruption, and there is no fear of a short circuit accident between taps.

(4) Other Embodiments The present invention is not limited to the above-described embodiment, and the configuration and shape of each part, the arrangement location, the number of arrangements, and the like can be appropriately changed. For example, the current limiting resistance and the resistance It also includes a load tap changer with higher safety by inserting an overvoltage protector such as a discharge gap or a non-linear resistor between the valve for use.

The switching circuit and operation | movement figure of typical embodiment which concern on this invention. The switching sequence diagram of this embodiment shown in FIG. The operation | movement figure when a direct current passes along the main valve in typical embodiment. The switching circuit and operation | movement figure in the conventional tap switching apparatus at the time of a load. FIG. 5 is a switching sequence diagram in the on-load tap switching device of FIG. 4. FIG. 5 is an operation diagram when a direct current passes through the main valve in the on-load tap switching device of FIG. 4.

Explanation of symbols

2, 3 ... Tap H of tap winding ... Main valve W1, W2 ... Resistor valve IC ... Circulating current ID ... Superimposed current (DC)
IL ... Load current M1, M2 ... Moving contact N of tap selector ... Neutral point R1, R2 ... Current limiting resistor S ... Changeover switch SA, SB ... Change switch fixed contact SC ... Changeover switch movable contact TW ... Tap Winding US ... Step voltage between taps

Claims (2)

Between the tap of the tap winding and the neutral point, a tap selector for selecting the tap of the tap winding and a changeover switch for switching the energization state are installed, and the tap selector has two movable elements. A contact is provided, and the changeover switch is provided with a plurality of fixed contacts, and a movable contact that can be selectively contacted with and separated from one of the plurality of fixed contacts. A current limiting resistor and a resistance valve are connected in series between the active point and a plurality of fixed contacts of the changeover switch are provided between the current limiting resistor and the movable contact of the tap selector, A two-resistor three-valve type tap switching device with a main valve connected between a movable contact and a neutral point of a change-over switch, which is connected to the energizing tap side that is energized before the switching operation. Resistor valve is closed, not energized before switching When the resistance valve connected to the non-energizing tap side is in an open state, the main valve is opened first, and after opening the main valve, the resistance valve on the non-energizing tap side is closed. Then, in the load tap switching device configured to open the resistance valve on the energizing tap side, and then close the main valve,
After the resistance valve on the non-energizing tap side that is not energized before the switching operation is closed, the movable contact of the changeover switch releases the electrical connection with the fixed contact that was in contact before the switching operation. An on-load tap changer characterized by being configured to do so.   After the resistance valve on the non-energizing tap side that is not energized before the switching operation is closed, the movable contact of the switching switch is disconnected from the fixed contact that was in contact before the switching operation. The on-load tap switching device according to claim 1, wherein the time until is set to ½ cycle or more of the AC power supply to be energized.

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