JPH0439766B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a main circuit configuration of an on-load tap changer.

[Conventional technology]

FIG. 6 shows a first example of a circuit of a conventional on-load tap switching device. This conventional example is co-authored by Murakami and Shima, "On-load tap changer and its circuit" (published by Denkishoin)
is shown. In the figure, a tap winding 1 has voltage taps 2, 3, 4, and 5, and a tap selector 6, which is driven by a common drive shaft (not shown).
7 selects the voltage tap. The switching switch 8' is composed of fixed contacts 9, 10, 11 and 12 and a movable contact 13. Tap selector 6 is connected to fixed contact 9, tap selector 7 is connected to fixed contact 12, and fixed contacts 10 and 11 are connected to current limiting resistors 14 and 15, respectively, which limit the bridging current between the taps. are connected to tap selectors 6 and 7, respectively. The output terminal 16 is for connecting a load (not shown) to the movable contact 13. FIG. 6(a) shows a state in which the voltage tap 4 is connected to the output terminal 16. At this time, the load current flows through the voltage tap 4, the tap selector 7, the fixed contact 12, and the movable contact 13. When switching the load from voltage tap 4 to voltage tap 5, movable contact 13 is rotated counterclockwise. When the tap switching operation begins, movable contact 13 temporarily contacts both fixed contacts 12 and 11 and is switched to fixed contact 11 as shown in FIG. 6b. At this time, an arc 17 is generated between the fixed contacts 11 and 12. Movable contact 1
3 rotates, it temporarily contacts both fixed contacts 11 and 10, as shown in FIG. 6c,
The contact is switched to a fixed contact 10 as shown in FIG. 6d. While the movable contact 13 is in contact with both the fixed contacts 10 and 11, the potential difference between the voltage taps 4 and 5 causes a bridging current between the taps to flow through the voltage tap 4, the tap selector 7, and the current limiting resistor. 15, the fixed contact 11, the movable contact 13, the fixed contact 10, the current limiting resistor 14, the tap selector 6, and the voltage tap 5. This inter-tap bridging current is caused by the current limiting resistor 14,
15, an arc 18 is generated between the movable contact 13 and the fixed contact 11 when the movable contact 13 switches to the fixed contact 10.
By a similar operation, the movable contact 13 is finally switched to the fixed contact 9 as shown in FIG. 6e. FIG. 7 shows a second conventional example. Portions designated by numbers 1 to 7 and 14 to 16 in the figures are common to the first conventional example. In this conventional example, the switching switch 8'' is replaced by switching switches 19, 20, 2.
1 and 22. FIG. 8 shows the switching sequence of the semiconductor switch during tap switching. As shown in the figure, semiconductor switches 19, 20,
21 and 22 are configured to be switched with a predetermined overlap state with each other.

[Problem that the invention seeks to solve]

In the first prior art on-load tap switching device, an arc is generated during switching, which contaminates the oil filled in the switching switch. In addition, wear and tear of the contacts is unavoidable, and the oil and contacts must be replaced periodically, resulting in the problem of requiring a great deal of effort and expense for maintenance. In addition, in the second conventional load tap switching device, the switching switch is made of semiconductor, so it does not generate arcs and has a long lifespan, and there are no maintenance problems, but it requires four expensive semiconductor switches. There were problems in that the price was high and the method for controlling the semiconductor switch was complicated and expensive.

[Means for solving problems]

The on-load tap switching device according to the present invention includes two sets of tap selectors connected to the load via a voltage limiting element having a current blocking voltage range higher than the instantaneous maximum voltage between the two taps to be switched. , and one set of tap selectors connected to a load via a semiconductor switch, and the three sets of tap selectors are configured to perform tap switching operations in a predetermined order.

[Effect]

The on-load tap switching device according to the present invention ignores bridging current between taps during switching by using a voltage limiting element having a current blocking voltage range higher than the instantaneous maximum voltage between both taps to be switched. Limit it to the value you get. On the other hand, the current is switched by a semiconductor switch, and only one set of semiconductor switches is required.

〔Example〕

FIG. 1 shows an embodiment of the invention. In the figure, a tap winding 1 is provided with voltage taps 4 and 5. Tap windings 23, 24 are connected to output terminal 16 via voltage limiting elements 26, 27, respectively. The tap selector 25 is connected to the output terminal 16 via the switching switch 8. The switching switch 8 is composed of a known semiconductor switch 28. The voltage limiting elements 26 and 27 are preferably elements containing zinc oxide as a main component and having current-voltage characteristics as shown in FIG. The value is selected to be larger than the instantaneous maximum voltage between the taps and sufficiently lower than the output voltage of the voltage tap.

Next, the operation of this embodiment will be explained. 1st
Figure a shows the state in which the tap selectors 23, 24, 25 are in contact with the voltage tap 4, and the voltage tap 4 is connected to the output terminal 16. The states of the tap selectors 23, 24, 25 and the semiconductor switch 28 are shown in the timing chart of FIG. In the figure, at time _T1 , tap selectors 23, 24,
25 are all in contact with the voltage tap 4, and the semiconductor switch 28 is closed, representing the state shown in FIG. 1a. At this time, the load current is applied to the voltage tap 4, the tap selector 25, the semiconductor switch 28, and the output terminal 16.
It is supplied to the load (not shown) through the. When the tap switching operation begins, the tap selector 24 first switches to the second tap selector 24.
It leaves the voltage tap 4 at time T ₂ shown in the figure, and at time T ₃
Then touch voltage tap 5. This state is shown in Figure 1b.
Shown below. Since the semiconductor switch 28 still remains closed, a voltage between the taps corresponding to the potential difference between voltage taps 4 and 5 is applied to the voltage limiting element 27, but the limiting voltage of the voltage limiting element 27 is Since the voltage is selected to be higher than the instantaneous maximum value of the voltage between the taps, no bridging current between the taps flows through the voltage limiting element 27. Next, at time T ₄ , semiconductor switch 2
8 becomes "open", the potential difference across the semiconductor switch 28 tries to rise to the voltage of the voltage tap 4, but since the limited voltage of the voltage limiting element 26 or 27 is sufficiently small compared to the tap voltage, the voltage limiting element 26 limit voltage will not be exceeded. At this time, the load current is divided between the voltage tap 4, the tap selector 23, the voltage limiting element 26, the output terminal 16, and the voltage tap 5.
The voltage flows through two paths: the tap selector 24, the voltage limiting element 27, and the output terminal 16. This state is shown in Figure 1c.
Shown below. At time _T5 , tap selector 25 leaves voltage tap 4, but since semiconductor switch 28 is already open, no arc occurs. Tap selector 25, which has left voltage tap 4, contacts voltage tap 5 at time _T6 . FIG. 1d shows the state at this time. Next, at time _T7 , the semiconductor switch 28 is closed, and the load current flows through the voltage tap 5, the tap selector 25, the semiconductor switch 28, and the output terminal 16. The state at this time is shown in FIG. 1e. At this time, an inter-tap voltage corresponding to the potential difference between voltage tap 4 and voltage tap 5 is applied across the voltage limiting element 26, but as described above, the voltage limiting element 26
Since the limiting voltage is higher than the instantaneous maximum value of the inter-tap voltage, no inter-tap bridging current flows through the voltage limiting element 26. Finally, at time T ₈ , the tap selector 23
leaves voltage tap 4 and returns to voltage tap 5 at time _T9 .
However, as explained above, there is no bridging current between the taps, so no arc occurs. By the above operations, switching from voltage tap 4 to voltage tap 5 is completed. The state at this time is shown in FIG. 1f.

In the above embodiment, the load current flows through the semiconductor switch 28 during normal times when no tap switching operation is being performed, but as shown in FIG.
It is also possible to connect an energizing switch 29 in parallel with the energizing switch 29, and to allow the load current to flow through the energizing switch 29 during normal times. In general, semiconductor switches produce a voltage drop of several volts when conducting, so when used in a large current area, the power consumed within the semiconductor switch becomes considerably large, and a cooling device is required to cool the semiconductor switch. However, in such a case, by using the energizing switch 29 as described above, the power loss in the semiconductor switch can be significantly reduced, and a small cooling device can also be omitted. A timing chart of the operation in this embodiment is shown in FIG. The energizing switch 29 indicates the time when the switching operation starts.
It is controlled to open at T ₁ , which is a little before T ₂ , and to close again at T ₁₀ , which is a little after the switching operation completion time T ₉ .

〔Effect of the invention〕

The on-load tap switching device of the present invention suppresses bridging current between taps through a voltage limiting element having a current blocking voltage range higher than the instantaneous maximum voltage between both taps to be switched, so arcs occur when switching taps. There is no occurrence of oil, the oil filled in the switching switch is not contaminated, and the wear of the contacts is extremely low. Furthermore, since only one switch is required, the cost of the entire device is relatively low even if an expensive semiconductor switch is used.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the switching operation of an embodiment of the load tap switching device of the present invention, FIG. 2 is a timing chart showing the operation of the embodiment shown in FIG. 1, and FIG. 3 is a diagram showing the operation of the embodiment shown in FIG. 1. FIG. 4 is a diagram showing the structure of another embodiment of the present invention. FIG. 5 is a timing chart showing the operation of the embodiment shown in FIG. 4. FIG. A diagram showing the operation of the first example of the tap switching device under load, FIG. 7 is a diagram showing the configuration of the second example of the conventional tap switching device under load, and FIG. 2 is a timing chart showing the operation of a conventional example. 4, 5: Voltage tap, 23, 24, 25: Tap selector, 26, 27: Voltage limiting element, 28: Semiconductor switch, 29: Current-carrying contact.

Claims (1)

Claims: 1. Each voltage limiting element 2 having a current blocking voltage range of a value higher than the instantaneous maximum voltage between the first voltage tap 4 and the second voltage tap 5 of the tap winding 1.
A first tap selector 24 and a second tap selector 23 are connected between the first voltage tap 4 and the output terminal 16 via terminals 6 and 27, and the first voltage tap 4 is connected via a semiconductor switch 28. and a third tap selector 25 connected between the output terminal 16 and the first voltage tap 4.
The third tap selector 25 is configured to switch from the first voltage tap 4 to the second voltage tap 5 after the first tap selector 24 switches from the first voltage tap 4 to the second voltage tap 5. 1 voltage tap 4 to 2nd
After the third tap selector 25 switches from the first voltage tap 4 to the second voltage tap 5, the second tap selector 23 switches from the first voltage tap 4 to the second voltage tap 5. Voltage tap 4 to 2nd
The semiconductor switch 28 is configured to switch to the third voltage tap 5, and the semiconductor switch 28 is configured to switch to the third voltage tap 5.
5 is configured to be closed except when it is open during switching from voltage tap 4 to voltage tap 5, thereby causing first tap selector 24 to switch from first voltage tap 4 to second voltage tap 5. After switching, open the semiconductor switch 28, switch the third tap selector 25 from the first voltage tap 4 to the second voltage tap 5, then close the semiconductor switch 28, and then switch the third tap selector 25 from the first voltage tap 4 to the second voltage tap 5. A tap switching device under load, characterized in that a tap selector 23 is switched from a first voltage tap 4 to a second voltage tap 5. 2. The on-load tap switching device according to claim 1, characterized in that a current-carrying contact is provided in parallel with the semiconductor switch.