JPH03112112A - Tap switch during load for gas insulating transformer - Google Patents

Abstract

PURPOSE:To prevent partial temperature rise so as to elevate cooling efficiency and arrange it inside a transformer tank by bringing a current limiting resistor into contact with a liquid cooling medium. CONSTITUTION:Current limiting resistors 4a and 4b are constituted using respectively one resistor 6 consisting of band-shaped resistor 5 arranged in zigzag. And, the resistors 4a and 4b are stored together with a liquid cooling medium such as fluorionert, etc., inside a metallic or insulating sealed container which has a bellows 7 expansible by the pressure of the resistors 4a and 4b, and are connected to a changeover switch by lead wires 10 piercing the container 8. Accordingly the resistors 4a and 4b are in contact with the cooling medium 9 which has the cooling efficiency equivalent to that of insulating oil, so the cooling efficiency ten times as high as the case of cooling it with insulating gas can be obtained.

Description

[Detailed description of the invention] [Object of the invention] (Industrial application field) The present invention relates to an on-load tap changer for a power transformer,
In particular, it relates to a current limiting resistor that suppresses cross current during tap switching.

(Prior Art) In recent years, as a result of the extreme increase in demand for electric power, the overall capacity of electric power equipment has increased, and cities have become overcrowded, there has been an increasing trend towards non-combustible devices. For this reason, in power equipment, there is an increasing demand for gas insulated equipment that uses an insulating gas such as SF or gas instead of conventional insulating oil as an insulating medium.

By the way, when dealing with such demands for non-combustibility in a resistive on-load tap changer, the problem is the low cooling efficiency of the insulating gas. In other words, the cooling efficiency of insulating gas is approximately one-tenth that of insulating oil.
Therefore, simple calculation shows that equipment using insulating gas requires 10 times more energy to cool the resistance and maintain nonflammability to the same extent as conventional equipment using insulating oil. A large resistor with capacitance would have to be used.

FIG. 4 is a switching circuit diagram using a conventional on-load tap changer. As shown in the figure, tap 2a from transformer winding l
, 2b are pulled out, and a switching switch 3a,
3b, 3c, and 3d are connected in series. Current limiting resistors 4a, 4b are connected in parallel with the switching switches 3a, 3d. In the state shown in FIG. 4, current is flowing from the tap 2a through the switching switch 3a. When switching from the tap 2a to the tap 2b, (1) First, the switching switch 3a opens and current flows through the current limiting resistor 4a.

■ Close the switching switch 3c. At this time, a cross current is generated in the current limiting resistors 4a and 4b due to the voltage difference between the taps 2a and 2b.

■ Open the switching switch 3b and allow current to flow only through the current limiting resistor 4b.

- The switching switch 3d is closed, current flows from the tap 2b to the switching switch 3d, and tap switching is completed.

The above operation is carried out in an extremely short time, but in the state (2) above, the taps are short-circuited, so the current limiting resistors 4a and 4b are essential to suppress cross current.

FIGS. 5h) and 5(b) are diagrams showing a current limiting resistor used in a conventional insulating gas type on-load tap changer. Since a large cooling area is required for cooling, the strip resistor 5 is formed into a serpentine shape to form individual resistors 6, and a plurality of resistors 6 are connected in series or in parallel, as shown in FIG. A current limiting resistor 4 is constructed as shown in FIG.

When the current limiting resistor 4 having the above configuration is used in an insulating gas-type on-load tap changer, the heated insulating gas moves upward, so the upper resistor 6 is heated excessively.
This results in the disadvantage that the temperature locally increases.

In order to prevent a local temperature rise due to such gas convection, instead of stacking the resistors 6 vertically, it is possible to divide them as appropriate and arrange them horizontally. When placing the current limiting resistor 4 in a space, the resistors 6 must be stacked vertically.

Also, as mentioned earlier, the cooling efficiency of insulating gas is approximately one-tenth that of insulating oil, so a large resistor with 10 times the capacity is required, but considering the limited space. , it is unavoidable that the number of stacked layers in the vertical direction increases.

On the other hand, many known techniques already exist as methods for cooling a resistor in an insulating gas. For example, a method of circulating and cooling gas by installing a gas fan (Utility Model Application No. 57-508)
34) and a method of injecting liquefied refrigerant into a resistance (Japanese Patent Publication No. 63-923 and Japanese Patent Publication No. 63-924). However, the former has a low cooling efficiency of approximately one-fifth of the cooling efficiency of insulating oil, requires a large resistor with a capacity approximately five times that of insulating oil, and also requires auxiliary equipment such as a fan. The latter requires that the refrigerant be applied evenly to the resistance, which poses problems in uniformity and reliability.

Furthermore, it is wasteful to operate both of them all the time, and a new detector, sensor, etc. is required to operate them only when the tap is switched. In any case, the conventional method has the disadvantage that the configuration of the on-load tap changer becomes complicated.

(Problems to be Solved by the Invention) As mentioned above, in the conventional insulating gas type on-load tap changer, the cooling performance of the current limiting resistor is very poor compared to the insulating oil type current limiting resistor. Ten times the capacity was required.

Therefore, the present invention was proposed in order to solve the drawbacks of the conventional technology, and its purpose is to prevent local temperature rises and greatly improve cooling efficiency, while also reducing the need for transformer tanks. To provide an on-load tap changer equipped with a current-limiting resistor that can be placed in a limited space inside the vehicle.

[Structure of the Invention (Means for Solving the Problems)] In order to achieve the above object, the present invention provides a gas-insulated transformer for a current limiting resistor and a switching switch for suppressing cross current during load tap switching. In a load tap changer for a gas insulated transformer housed in a transformer tank, only the current limiting resistor is housed in a sealed container filled with liquid refrigerant, and the current limiting resistor is connected to the current limiting resistor by a lead wire penetrating the sealed container. The present invention is characterized in that a current resistor and the switching switch are connected.

(Function) According to the on-load tap changer of the present invention configured as described above, since the current limiting resistor is in contact with the liquid refrigerant, the cooling efficiency is equivalent to that of insulating oil. This value is 10 times that of cooling with gas. That is, compared to the conventional insulating gas type, a current limiting resistor having one-tenth the capacity is required, so it can be placed in a limited space within the transformer tank.

(Example) Hereinafter, an example of the present invention will be described based on FIGS. 1 to 3. Note that the same parts as those of the on-load tap changer shown in FIGS. 4 and 5 are given the same reference numerals.

FIGS. 1(1) and 1(b) are a plan view of a strip resistor and a side sectional view of a current limiting resistor for an on-load tap changer, respectively, according to an embodiment of the present invention.

In this embodiment, the current limiting resistors 4a and 4b each consist of one resistor 6, which is made up of a strip resistor 5 formed in a meandering shape, as in the conventional case, as shown in FIG. and,
The current limiting resistors 4a and 4b are housed together with a liquid refrigerant 9 such as Fluorinert in a metal or insulating airtight container 8 having a bellows 7 that expands and contracts with pressure. Connected to the switching switch.

Since the present embodiment is configured as described above, the current limiting resistors 4a and 4b are in contact with the liquid refrigerant 9 which has the same cooling efficiency as insulating oil, so compared to the case of cooling with insulating gas. It will have 10 times the cooling efficiency. In other words, a current limiting resistor having one-tenth the capacity of the conventional one is sufficient, so the space becomes extremely small. In addition, since the container 8 has the bellows 7 that expand and contract under pressure, the internal and external pressures are always equal, ensuring sufficient strength and reliability.

Therefore, the current limiting resistors 4a, 4b can be arranged even in a limited space, and are small and highly reliable.

Although this embodiment is an example in which the current limiting resistors 4a and 4b are housed in one sealed container, one current limiting resistor may be housed in one sealed container, or the current limiting resistors 4a and 4b may be stored in one sealed container. A total of six current limiting resistors for three phases may be accommodated.

FIGS. 2(a) and 2(b) are a plan view and a side sectional view, respectively, of a current limiting resistor for an on-load tap changer according to another embodiment of the present invention.

As shown in the figure, in this example, two resistors 6 are connected in series to constitute one current limiting resistor 4, three phases are stacked vertically, and housed in a rectangular parallelepiped-shaped container 8a. here,
A radiator 11 is installed to cool the liquid refrigerant 9 in the container 8a, and serves to dissipate heat generated from the current limiting resistor 4 into the transformer tank. Further, by installing a conservator 13 provided with a diaphragm portion 12, it is possible to absorb the volumetric expansion caused by the temperature of the liquid refrigerant and to always equalize the pressure inside and outside the container.

FIGS. 3(b) and 3(b) are a plan view and a side sectional view, respectively, of a current limiting resistor for an on-load tap changer according to still another embodiment of the present invention.

As shown in the figure, this embodiment is an example in which a total of six current limiting resistors 4 for three phases are arranged radially within a cylindrical container 8b. Here, the liquid refrigerant 9 in the container 8b is circulated by the pump 15 installed outside the transformer tank 14, and the heat generated in the current limiting resistor 4 is released to the outside of the transformer tank by the heat exchanger 16. ing. Further, an expansion chamber 17 having a bellows part is installed in the container 8b, and is configured to keep the pressure constant.

In addition, it is not necessary to completely fill the container 8b with the liquid refrigerant 9, but it is enough to immerse the current limiting resistor 4, and by providing an insulating gas space above, the expansion of the liquid refrigerant can be absorbed by the insulating gas. It may also be configured to allow In this case, container 8b
The internal pressure will change slightly.

Furthermore, the resistor 6 is not limited to a band-shaped resistor, and the shape and arrangement of the current limiting resistor and the container can be selected as appropriate.

[Effects of the Invention] As explained above, according to the present invention, only the current limiting resistor is housed in a closed container filled with a liquid refrigerant and having a bellows or the like whose volume changes depending on pressure, and the container is Since the current limiting resistor and the switching switch are connected with a penetrating lead wire, cooling efficiency is greatly improved, and it can be used in a limited space with one-tenth the capacity compared to the conventional insulating gas type. It is possible to provide an on-load tap changer equipped with a compact and highly reliable current limiting resistor that can be placed anywhere.

[Brief explanation of drawings]

FIGS. 1(1) and (b) are a plan view of a strip resistor and a side sectional view of a current limiting resistor for an on-load tap changer according to an embodiment of the present invention, and FIGS. 2(a) and (b) are respectively 3(1) and 3(b) are respectively a plan view and a side sectional view of a current limiting resistor for a tap changer when loaded according to another embodiment of the present invention, and FIGS. A plan view and a side sectional view of a current limiting resistor for a tap changer, Fig. 4 is a switching circuit diagram of a conventional tap changer on load, and Fig. 5 (al and (
b) is a plan view of a conventional strip resistor and a side view of a current limiting resistor for an on-load tap changer, respectively. 1... Transformer winding 2 a + 2 b... Taps 3a to 3b... Switching switch 4*4 a, 4 b... Current limiting resistor 5...
Strip resistor 6...Resistor 7...Bellows 8.8a, 8b...Container 9...Liquid refrigerant 10...Lead wire 11...Radiator 12...Diaphragm portion 13... Conservator 14...Transformer tank 15...Pump 16...Heat exchanger 17...Expansion chamber (8733) Agent Patent attorney Yoshiaki Inomata (and others)
1 person) (a) (b) Figure Figure 3 Figure Figure 3

Claims (1)

[Claims] (1) In a load tap changer for a gas-insulated transformer in which a current-limiting resistor and a switching switch are housed in a gas-insulated transformer tank, the current-limiting resistor and a switching switch are housed in a gas-insulated transformer tank. A load tap for a gas insulated transformer, characterized in that the current limiting resistor and the switching switch are connected to each other by a lead wire that penetrates the closed container and is housed in a closed container filled with liquid refrigerant. Switch.