JPH05234778A - On-load tap changer - Google Patents

Abstract

PURPOSE:To reduce an installation space by improving the cooling effect of a current limiter or miniaturization in an on-load tap changer for a gas-insulated transformer, CONSTITUTION:Only the long, narrow strip piece of resistor 6 for a current limiter is installed together with pure water into a sealed container 8, and a radiation fin is provided in the sealed container 8 and at the same time a pipe arrangement 12, a pump 13, a filter 14 and the like are provided to circulate pure water for external cooling as occasion demands and the current limiter is cooled with the pure water 7.

Description

Detailed Description of the Invention

 [Object of the Invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a load tap changer suitable for a gas-insulated transformer, and more particularly to a load tap changer which is an improvement of a current limiting resistor for suppressing a cross current at the time of tap change.

[0002]

2. Description of the Related Art In recent years, as a result of an extreme increase in power demand,
The trend toward non-combustible equipment is increasing due to the increase in the capacity of all electric power equipment and the overcrowding of cities. For this reason, in power equipment such as large transformers, there is an increasing demand for gas-insulated equipment that uses insulating gas such as SF ₆ gas as an insulator instead of conventional insulating oil.

By the way, in the resistance type load tap changer used for such a transformer, a problem when dealing with such a requirement of the non-combustible direction is a low cooling efficiency of the insulating gas. is there. In other words, the cooling efficiency of insulating gas is as low as about 1/10 of the cooling efficiency of insulating oil. Therefore, a simple calculation shows that the device using insulating gas is comparable to the conventional device using insulating oil. In order to cool the resistance and maintain nonflammability, a large resistance having 10 times the capacity of the conventional one must be used.

FIG. 5 is a switching circuit diagram of a conventional load tap changer. As shown in the figure, a plurality of taps 2a, 2b are drawn out from the transformer winding 1, and switching switches 3a, 3b and 3c, 3d are connected in series to each of them. Current limiting resistors 4a, 4 in parallel with the switching switches 3a, 3b
b is connected. In the state of FIG. 5, a current flows from the tap 2a through the switching switches 3b and 3a. Here, when switching from the tap 2a to the tap 2b, 1. First, the switching switch 3a is opened and a current is passed through the current limiting resistor 4a. 2. 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. 3. Open the switching switch 3b and let the current flow only through the current limiting resistor 4b. 4. The switching switch 3d is closed, current flows from the tap 2b to the switching switch 3d, and tap switching is completed.

Although the above operation is performed in an extremely short time, the taps 2a and 2b are short-circuited in the state of 2. Therefore, the current limiting resistors 4a and 4b are indispensable for suppressing the cross current. is there.

6 and 7 are views showing a conventional current limiting resistor used in a gas-insulated load tap changer. Since a large cooling area is required for cooling, the strip-shaped resistor 5 is formed in a meandering shape to form individual resistors 6 as shown in FIG. As described above, the current limiting resistor 4 is configured.

[0007]

When the current limiting resistor 4 having the above-mentioned structure is used in the gas-insulated load tap changer, the heated insulating gas moves upward, so that the resistance of the upper portion is increased. The container 6 is overheated, and the temperature of the container 6 rises locally.

In order to prevent such a local temperature rise due to gas convection, the resistors 6 may be appropriately divided and horizontally arranged instead of being vertically stacked.
When arranging the current limiting resistor 4 in the limited space in the transformer tank, the resistors 6 must be vertically stacked.

Further, as described above, since the cooling efficiency of the insulating gas is about 1/10 of the cooling efficiency of the insulating oil, a large resistance having 10 times the capacity is required, but the limited space is limited. In consideration of the above, an increase in the number of stacked layers in the vertical direction cannot be avoided.

On the other hand, as a method for cooling the resistance in the insulating gas, there are already many known techniques. For example, a method for circulating and cooling the gas by providing a gas delivery fan
57-50834), a method of injecting a liquefied refrigerant into a resistance (see JP-B-63-923 and JP-B-63-924), and the like. However, the former is as low as about one fifth of the cooling efficiency of insulating oil, and requires a large resistance having a capacity about 5 times that of insulating oil,
Furthermore, auxiliary equipment such as a fan is also required. In the latter case, the refrigerant must have uniform resistance and resistance, which is problematic in terms of uniformity and reliability. Further, it is wasteful to operate both of them at all times, and a detector, a sensor and the like are newly required to operate only when the taps are switched. In any case, the conventional method has a drawback that the structure of the tap changer under load becomes complicated.

In order to solve such a drawback, it is conceivable to seal the strip-shaped resistor 5 in a liquid refrigerant such as Fluorinert, but there is a problem that the refrigerant is decomposed due to the temperature rise of the current limiting resistor. was there.

Therefore, the present invention was proposed in order to solve the above-mentioned drawbacks of the prior art, and its purpose is to prevent local temperature rise and to greatly improve cooling efficiency. An object of the present invention is to provide a load tap changer including a current limiting resistor that can be arranged in a limited space in a transformer tank. [Constitution of Invention]

[0013]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention stores a current limiting resistor and a switching switch, which suppress a cross current at the time of load tap switching, in a gas-insulated transformer tank. In the load tap changer for the gas insulated transformer described above, the current limiting resistor is housed together with pure water in a sealed container and is cooled by the pure water.

[0014]

According to the load tap changer of the present invention configured as described above, since the current limiting resistor is in contact with pure water, the cooling efficiency is equivalent to that of the insulating oil. It will have a value about 10 times that of cooling. That is, compared with the conventional gas-insulated type, a current limiting resistor having a capacity of about 1/10 is sufficient, so that it can be arranged in a limited space in the transformer tank. Further, since pure water is a substance that is difficult to decompose, a tap changer under load with stable characteristics can be obtained.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG.

FIG. 1 shows an example in which a resistor 6 is enclosed together with water 7 in a sealed container 8 made of an insulating material. As the water 7, pure water (hereinafter simply referred to as water) from which gas such as electrolyte ions and oxygen has been removed before filling is used. The resistor 6 and the like should also be free of foreign matter. Pure water has a high insulating property, but if foreign molecules such as metals are mixed in, the insulating property will deteriorate. However, no voltage is applied to the current limiting resistor at all times, and there is no problem because it is a small value of about several tens of volts even when applied. Heat is generated when the resistor 6 is energized. The generated heat is cooled by the water 7. Water 7 begins natural convection,
Heat transfer is further promoted by the generated flow. Water 7
The heat carried by is transmitted through the hermetically sealed container 8 and the radiating fins 9 and is discarded. If heat is suddenly generated in the resistor 6, water 7
Has about 10 times the heat capacity of gas, the generated heat is
It can also be stored in a short time.

As described above, according to this embodiment, the current limiting resistor can be reduced to about 1/10 of the conventional one. Also,
Although the hermetically sealed container 8 is completely hermetically sealed, the hermetically sealed container can be manufactured easily because the container is compact. FIG. 2 shows another embodiment of the present invention.

In this embodiment, an inert gas 10 such as N ₂ or He is partially contained in the sealed container 8. This gas layer can prevent an increase in pressure when the temperature of the water 7 rises. Further, when the resistor 6 is heated, the water 7 is boiled and higher cooling efficiency is obtained. FIG. 3 also shows another embodiment of the present invention. In this embodiment, the bellows 11 of the sealed container 8 can absorb the increase in the pressure generated inside the sealed container 8. FIG. 4 is also another embodiment of the present invention.

In this embodiment, water 7 is circulated through a pipe 12 attached to a hermetically sealed container 8. The water 7 sent by the pump 13 passes through the filter 14 and is cooled by the radiator 15. The filter 14 functions to remove foreign matters and ions contained in the water 7 and turn the water 7 into pure water. In this embodiment, since the water 7 is forcedly circulated, high cooling efficiency can be obtained,
It becomes possible to make it more compact.

[0020]

As described above, according to the present invention, the current limiting resistor is housed together with pure water in the sealed container and is cooled by this pure water, so that the cooling efficiency is greatly improved and It can be installed in about one tenth the size of a current limiting resistor. Furthermore, by using pure water, which is a very stable liquid, it is possible to perform stable cooling without the generation of decomposition products of the refrigerant as in the case of using a refrigerant such as Freon. Therefore, according to the present invention, it is possible to provide a load tap changer including a small-sized and highly reliable current limiting resistor.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a sectional view showing a second embodiment of the present invention.

FIG. 3 is a sectional view showing a third embodiment of the present invention.

FIG. 4 is a sectional view showing a fourth embodiment of the present invention.

FIG. 5 is a switching circuit diagram of a load tap switching device.

FIG. 6 is a front view showing a strip resistance of a conventional current limiting resistor.

FIG. 7 is a front view showing a conventional current limiting resistor.

[Explanation of symbols]

1 ... Transformer winding 2a, 2b ... Tap 3a, 3b ... Switching switch 4, 4a, 4b ...
Current limiting resistor 5 ... Strip resistor 6 ... Resistor 7 ... Pure water 8 ... Sealed container 9 ... Radiating fin 10 ... Gas 11 ... Bellows 12 ... Piping 13 ... Pump 14 ... Filter 15 ... Radiator

Claims (1)

[Claims] 1. A load-time tap changer for a gas-insulated transformer in which a current limiting resistor and a switching switch for suppressing cross current at the time of load tap change are housed in a gas-insulated transformer tank. A load tap changer characterized in that a flow resistor is housed together with pure water in a sealed container and is cooled by this pure water.