JPH0917659A - Tap change-over transformer - Google Patents

Abstract

PURPOSE: To prevent the floating potential of a tape winding, to enhance its reliability and to reduce it by connecting a second change-over contact element to a first change-over contact element through an arrester at the time of changing over the first change-over contact element. CONSTITUTION: A polarity change-over switch 5 has a positive electrode P (N) (or a negative electrode) which is connected the tap terminal 21 of the winding start (or the winding finish) of a tap winding 2, a negative electrode (or a positive electrode) terminal N (P) which is connected to the tap terminal 25 of the tap winding and two change-over contact elements 51, 52. The change- over contact element 51 is movably provided in a terminal Q which is connected to the terminal of the series winding 1 of the change-over contact element 51 to change over the connection of the positive electrode terminal P and the negative electrode terminal N. Also, the change-over contact element 52 is movably provided in a newly provided terminal L to change over the connection of the negative electrode terminal N and the positive electrode terminal P. The terminal L is connected to the terminal Q through a zinc-oxide arrester 9.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tap switching transformer used for linking high system voltages, and more particularly to a tap switching transformer provided with means for preventing potential floating when switching the polarity of a tap winding. It is about transformers.

[0002]

2. Description of the Related Art A polarity switching type tap switching autotransformer has been widely used for interconnection between ultra high voltages. 2. Description of the Related Art Conventionally, as shown in FIG. 2, the polarity switching type of an autotransformer has a series winding 1 and a tap winding 2 on an iron core leg (not shown).
And the shunt winding 3, and one end 11 of the series winding 1
Is connected to the primary terminal 4, and the other end 12 of the series winding 1 is connected to the tap winding 2 via the switching contact 501 of the polarity switching device 50.
Of the positive pole terminal P or the negative pole terminal N of the tap changer 7, the one end 31 of the shunt winding 3 is connected to the secondary terminal 6, and the tap 71 is provided by the contact 71 of the tap changer 7. It is switchably connected to one of the tap terminals of the winding 2 (the terminals 21 to 25 or the tap terminal 26 connected to the other end 12 of the series winding 1), and the other end 32 of the shunt winding 3 is neutral. While connecting to the point terminal 8,
The polarity switcher 50 is provided with a terminal Q connected to the terminal 12 of the series winding 1, and this terminal Q and a negative electrode (or a winding start (or end) terminal 21 of the tap winding 2 (or A tap switching transformer having a structure capable of switching connection between a positive electrode terminal N (P) or a positive terminal (or negative electrode) terminal P (N) connected to a winding end (or winding start) terminal 25 of the tap winding 2. .

In the tap change transformer with the connection shown in FIG. 2, when the primary voltage is the highest voltage, the terminal Q is connected to the negative terminal N by the change contact 501 of the tap changer 50, and the tap changer 7 is connected. Contact 71 of tap terminal 2
Connect to 1. As the primary voltage drops from here,
The tap terminals are switched in the order of 21, 22, 23, 24, 25.

When the primary voltage is the rated voltage, the contact 71 of the tap changer 7 is connected to the tap terminal 26 connected to the terminal 12 of the series winding 1. In the case of the rated voltage, the terminal Q is connected to the negative terminal N by the switching contact 501 of the polarity switcher 50, the contact 71 of the tap switcher 7 is connected to the tap terminal 25, and the polarity switcher 5 is used.
The terminal Q and the positive electrode terminal P are connected by the switching contact 501 of 0, and the contact 71 of the tap changer 7 is connected to the tap terminal 2
Although the same voltage can be accommodated when connected to 1, the switching contact 501 of the polarity switcher 50 must be connected to the negative terminal N when the voltage rises above the rated voltage, and when the voltage drops below the rated voltage. Is the switching contact 50 of the polarity switcher 50.
Since 1 needs to be connected to the positive terminal P, the contact 71 of the tap changer 7 is connected to the tap terminal 26 connected to the terminal 12 of the series winding 1.

When the primary voltage is the lowest voltage, the terminal Q is connected to the positive terminal P by the switching contact 501 of the tap changer 50, and the contact 71 of the tap changer 7 is connected to the tap terminal 25. As the primary voltage increases from here, the tap terminals are switched in the order of 25, 24, 23, 22, 21. In addition, when it goes up from the rated voltage,
After the terminal Q is connected to the negative terminal N by the switching contact 501 of the polarity switching device 50, the contact 7 of the tap switching device 7 is connected.
When the tap is switched by 1 and drops from the rated voltage, the terminal Q is connected to the positive terminal P by the switching contact 501 of the polarity switch 50, and then the tap is switched by the contact 71 of the tap switch 7.

FIG. 3 is a principle diagram showing the principle of the tap switching transformer, in which a core winding 10 is provided with a tap winding 2, a series winding 1 and a shunt winding 3. From the tap winding 2, tap terminals 21, 22, 23, 24 and 25 are drawn out,
A positive terminal P and a negative terminal N of the polarity switching device 50 are connected to both ends thereof, and are connected to either of them by a switching contact 501 of a terminal Q. The primary terminal 4 is drawn out from one end 11 of the series winding 1, and the other end 12 is connected to the terminal Q of the polarity switching device 50. Shunt winding 3
The secondary terminal 6 is drawn out from one end 31 of the, and the other end 32 is connected to the neutral point terminal 8. One end 31 of the shunt winding 3
Is also connected via the tap changer 7 to switch the tap terminals. Further, the terminal Q is connected to the tap terminal 26.

Although FIG. 3 shows the case where the shunt winding 3 is wound outside the series winding 1, the series winding 1 is the shunt winding 3.
It may be wound on the outside. Further, although this example is a method of switching the primary voltage, when switching the secondary voltage, a tap winding is provided on the shunt winding side.

[0008]

In the polarity switching method of the autotransformer described in the prior art, when a lightning surge enters from the high voltage line or the low voltage line terminal of the autotransformer, the transition voltage and the potential oscillation cause The ground potential of the tap winding and the potential between the tap windings increase. For this reason, there is a problem in that the size of the insulation needs to be increased and the size of the transformer becomes large.

When switching the polarity of the tap winding,
The tap winding is in a floating state, and the ground potential of the tap winding is a potential determined by the capacitance between the windings and between the ground. Therefore, an excessive potential is generated in the tap switching device,
There is a possibility of causing a dielectric breakdown accident of the tap changer,
There is also a problem.

In FIG. 3, the iron core leg 10 and the tap winding 2
Between them, there is a tap winding-to-ground capacitance C _E , and between the tap winding 2 and the series winding 1 there is a series-winding-to-tap winding capacitance C _S. When the secondary terminal 6 and the tap terminal 26 are switched in the connected state, the tap winding 2 is in a floating state during the switching operation. The tap winding ground potential V _T when the polarity switching tap is floating is expressed by the following equation (1).

[0011]

## EQU1 ## V _T = {(V ₁ −V ₂ ) / 2} · {C _S / (C _S + C _E )} ± (V _R /2)...(1) where V _T is a polarity switching tap floating ground potential, V ₁ is the primary voltage of the tap winding of time, V ₂ is the maximum voltage across the secondary voltage, V _R is tapped winding. Here, since C _S and C _E are almost the same, the shared voltage between the polarity switching (Q-N, Q-P) is

[0012]

[Number 2] _{V 2 -V T = {1/4 (} 3V 2 -V 1)} will be caused excessive potential difference of ± (V _R / 2), there is a possibility that dielectric breakdown occurs in a polar switcher .

Conventionally, in order to prevent such potential floating,
Although a linear resistance element has been used, there is a problem that a considerable amount of current flows even during normal operation and the temperature rises significantly, resulting in a problem of long-term reliability.

The present invention has been made in view of the above problems of the prior art. Even when the terminal Q of the polarity switching device when the polarity of the tap winding is switched, the tap winding is floated. The floating potential can be prevented, and it is possible to protect from abnormal overvoltage in the event of a lightning surge intrusion, which improves the reliability of the tap change transformer and provides a reduced tap changer and tap change transformer. The purpose is to

[0015]

Means for Solving the Problems In the present invention, a means for solving the above-mentioned problems is to install a series winding, a tap winding and a shunt winding on an iron core leg, and to connect one end of the series winding. As a primary terminal, and the other end of the series winding is switchably connected to a positive terminal or a negative terminal having a tap winding through a polarity switch, and one end of the shunt winding is a secondary terminal,
In the tap switching transformer, which is switchably connected to the tap terminal of the tap winding and the other end of the series winding by a tap switching device and has the other end of the shunt winding as a neutral point terminal, the polarity switching The device includes a positive terminal and a negative terminal of the tap winding, a first switching contact for switching between the positive terminal and the negative terminal and connecting to the other end of the series winding, and switching between the first switching contact. And a second switching contact which is connected to the positive electrode terminal or the negative electrode terminal to which the first switching contact is not connected, the second switching contact being connected to the first switching contact via an arrester. Connect with a child.

[0016]

With the above-described structure, when the polarity of the tap winding is switched, even if the terminal Q of the polarity switch is floating, the charging current of the zinc oxide arrester is applied to the tap winding at the positive terminal P. Alternatively, since it flows through the negative terminal N, the floating potential of the tap winding can be prevented, the potential can be suppressed to a potential lower than the dielectric strength of the polarity switcher, and the current flowing through the zinc oxide arrester in the normal operation state leaks by an extremely small resistance. The current can be suppressed, and even if a lightning surge enters, the zinc oxide arrester operates to protect the abnormal winding from overvoltage, which improves the insulation reliability of the tap switching transformer. Since the switching device can be downsized, the tap switching transformer can also be downsized.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the tap change transformer of the present invention will be described below with reference to the drawings.

FIG. 1 is a connection diagram of an embodiment of the present invention. The present invention has the same basic configuration as that of the conventional example of FIG. 2 except for the polarity switcher. Therefore, the same or corresponding portions as those in FIG. 2 are designated by the same reference numerals and the description thereof will be omitted.

The polarity switcher 5 according to the present invention comprises a positive (or negative) terminal P (N) connected to a tap terminal 21 at the beginning (or end) of the tap winding 2 and a tap terminal of the tap winding. It has a negative electrode (or positive electrode) terminal (N) connected to 25 and two switching contacts 51 and 52.
The switching contact 51 is movably provided at the terminal Q connected to the terminal 12 of the series winding 1, and switches the connection between the positive electrode terminal P and the negative electrode terminal N. Further, the switching contact 52 is movably provided on the newly provided terminal L and switches the connection between the negative electrode terminal N and the positive electrode terminal P.

Then, the terminal L is connected to the terminal Q through the zinc oxide arrester 9.

The connection relationship between the switching contacts 51 and 52 is such that when the switching contact 51 is connected to the positive terminal P, the switching contact 52 is always connected to the negative terminal N so that the switching contact 52 is always switched. The contact 51 is configured to be connected to the terminal P or N which is not connected.

That is, in the operation of the polarity switcher 5 of the present invention, the terminal L is connected to the positive terminal P when the terminal Q is floating. Here, when the terminal Q is connected to the positive electrode terminal P, the terminal L performs a connecting operation to a negative electrode terminal N different from the connection position of the terminal Q. When switching the terminal Q to the negative terminal N,
This operation is reversed, and the operation of polarity switching is interlocked so that the arrester 9 is always inserted between the tap windings.

In the zinc oxide arrester used here, as shown in FIG. 4, only a very small resistance leakage current (several tens of μA) flows at the voltage in the normal operation state, and the tap winding is in a floating state. When a charging current (about several mA) flows through the zinc oxide arrester, the terminal voltage of the zinc oxide arrester has a good characteristic that the terminal voltage is almost constant with respect to the change of the charging current.

In this way, the tap winding 2 has an arrester 9
When the polarity of the tap winding is switched, the charging current of the arrester 9 flows through the terminal P (or N) in the tap winding 2 even when the terminal Q of the polarity switch 5 is floating. Therefore, the floating potential of the tap winding can be prevented.

When a lightning surge enters, an abnormal overvoltage is suppressed by the operation of the arrester 9.

The present invention can be applied not only to the autotransformer but also to a normal tap-changing transformer in which the neutral point is formed through the polarity changer.

[0027]

Since the present invention is configured as described above, the following effects can be obtained.

When the polarity of the tap winding is switched, even if the terminal Q of the polarity switching device is floating, the charging current of the arrester flows through the terminal P or the terminal N in the tap winding. Since the potential can be prevented and the potential can be suppressed to be equal to or lower than the dielectric strength of the polarity switching device, the insulation reliability of the tap switching transformer can be improved.

Since the current flowing through the zinc oxide arrester in the normal operation state can be suppressed to an extremely small leakage current due to the resistance, the long-term reliability of the tap switching transformer can be improved.

Even if a lightning surge enters, the tap windings can be protected from abnormal overvoltage by the operation of the zinc oxide arrester, so that the insulation reliability of the tap switching transformer can be improved. Since it is possible to reduce the
The tap change transformer can also be downsized.

[Brief description of the drawings]

FIG. 1 is a connection diagram showing an embodiment of a tap switching transformer of the present invention.

FIG. 2 is a connection diagram showing a conventional tap switching transformer.

FIG. 3 is an explanatory diagram of the principle of a tap switching transformer.

FIG. 4 is a characteristic diagram showing a VI characteristic of a zinc oxide arrester.

[Explanation of symbols]

 1 ... Series winding 2 ... Tap winding 3 ... Shunt winding 4 ... Primary terminal 5 ... Polarity switch 6 ... Secondary terminal 7 ... Tap changer 8 ... Neutral point terminal 9 ... Arrestor 10 ... Iron core 51, 52 ... Switching contact P ... Positive electrode terminal of the polarity switching device N ... Negative electrode terminal of the polarity switching device Q, L ... Polarity switching device terminal

Claims (1)

[Claims] 1. An iron core is provided with a series winding, a tap winding, and a shunt winding, and one end of the series winding serves as a primary terminal,
The other end of the series winding is switchably connected to a positive terminal or a negative terminal of the tap winding through a polarity switch, and one end of the shunt winding is used as a secondary terminal, and A tap switching transformer that is switchably connected to a tap terminal of a tap winding and the other end of the series winding, and has the other end of the shunt winding as a neutral point terminal, wherein the polarity switching device is a tap winding. Of the positive electrode terminal and the negative electrode terminal, a first switching contact for switching between the positive electrode terminal and the negative electrode terminal and connecting to the other end of the series winding, and when switching the first switching contactor, The second switching contactor is connected to the positive electrode terminal or the negative electrode terminal which is not connected, and the second switching contactor is connected to the first contactor via an arrester. And tap change transformer.