JPS595608A - Cooler for transformer - Google Patents

Abstract

PURPOSE:To prevent the temperature of winding from exceeding a given temperature by an apparatus wherein the oil of lower temperature is mixed with an oil which flows circulating through a transformer under a heavy load to lower the oil temperature temporarily. CONSTITUTION:When a heavy load is applied during the time a cooler 6 is operated with cooling fans 7 and feeding pumps 8 in the reduced number under a light load, a judging section 12 judges that the load current of a winding 2 has increased beyond a given value. A signal from a control section 13 then causes a solenoid valve 18 to be opened. On the other hand, the outlet part of a nozzle 19 provided in a lower piping 5 has an oil passage with the reduced sectional area, so that the flow speed of oil becomes larger and the static pressure is lowered at the nozzle part. Thus, upon opening of the solenoid valve 18, the oil of lower temperature within an oil chamber 15 is attracted into the lower piping 5 through a bypass pipe 17 to be mixed with oil circulating through a tank 3 of the transformer and then sent to the winding 2 for cooling the same.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cooling device suitable for use in a transformer that controls the cooling device in accordance with load current.

FIG. 1 shows an example of the configuration of a conventional transformer cooling device that changes the cooling power of the cooling device depending on the load current. The main body of the transformer mainly consists of a winding 2 wound around the outer periphery of an iron core 1, which is housed in a tank 3. Further, a cooler 6 is connected to the tank 3 through upper and lower pipes 4 and 5, forming a cooling system. This cooler 6 is provided with a cooling fan 7, and furthermore, an oil pump 8 is inserted in the middle of the pipe 5 described below.

A load current detector 1 is installed around the bushing 9 of the transformer body.
0 is disposed, and an oil temperature detector 11 and the like are disposed above the tank 3. These horizontal signals from the load current detector 10 and the oil temperature detector 11 are input to a determining section 12 that determines whether these signals have predetermined values. The output of the determination unit 12 is input to the control unit 13, and the control unit 13 outputs a control signal based on the determination result to the cooling fan 7 and oil pump 8, and controls the number of operating cooling fans 7 and oil pumps 8. Control 1.

The cooling oil (hereinafter simply referred to as oil) in the tank 3 flows as shown by the solid arrow and circulates while being cooled by the cooler 6. Therefore, when the load current of the transformer is large (hereinafter referred to as heavy load), all oil pumps 8 and cooling fans 7 are operated. However, if the load current is small (hereinafter referred to as light load) and the determination unit 12 determines that the temperature of the winding 2 is significantly lower than a predetermined value, the cooling fan 7 and the oil pump 8 are operated. The number of transformers was reduced, the amount of power consumed by auxiliary equipment was reduced, and transformers were operated in an energy-saving manner.

However, when operating as described above, if the load current suddenly increases during light loads, the temperature of winding 2 will occasionally exceed the predetermined value, even though it is below the predetermined value in steady state. There was a tendency. FIG. 2 shows the temperature characteristics of this winding, wire 2, and oil. Until time 1, the temperature # when operating with a light load and with the cooling fan 7 and oil feed pump 8 reduced.
It shows the characteristics. Time 1. When a heavy load is applied, all the oil pumps ≠ 8 and cooling fans 7 are operated immediately, but the time constant of the oil temperature is generally long, on the order of several hours, and the time constant of the temperature change of the winding 2 is on the order of several hours. Because the winding temperature θW is short, on the order of minutes, even though the winding temperature θW becomes less than the predetermined value θC after a certain period of time (t>tg), the winding temperature θW is temporarily (1,
, 1) tended to exceed the predetermined value θC. In order to avoid this, a method can be considered to lower the oil temperature θ0 by an amount Δθ exceeding a predetermined value θC, that is, to lower the oil temperature during light load from θo1 to θo2. However, such operation has the disadvantage that the energy saving effect of the auxiliary equipment is reduced.

An object of the present invention is to provide a cooling device for a transformer that eliminates the above-mentioned drawbacks and prevents the temperature of the transformer windings from exceeding a predetermined value during heavy loads without impairing the energy saving effect. It is in.

The present invention focuses on the fact that the time constant of the oil temperature is much larger than that of the windings, making it difficult to coordinate the temperature drop between the two, and this invention aims to improve the oil flow circulating through the transformer during heavy loads. , the oil temperature is temporarily lowered by mixing low-temperature oil to prevent the winding temperature from exceeding a predetermined value.

An embodiment of the present invention will be described below with reference to FIGS. 3 and 4, using the same reference numerals for the same parts as those of the conventional example.

FIG. 3 is an explanatory diagram showing the structure of Example A of the transformer cooling device of the present invention. Iron core 1 around which winding 2 is wound
An oil chamber 15 is formed using a heat insulating member 14 in the tank 3 that houses the oil chamber 15. Inside this oil chamber 15 is a tank 3.
A heat pipe 16 is inserted from the outside, and the heat pipe 16 keeps the temperature of the oil in the oil chamber 15 lower than the temperature of the oil circulating in other tanks. The lower part of the oil chamber 15 is connected to the lower pipe 5 through a bypass pipe 17, and the bypass pipe 17 is connected to a solenoid valve capable of 1fflJ@1 from the outside to which the output signal of the control section 13 is input. 18 is installed. In addition, a nozzle 1 is installed on the following Itg side near the joint between the lower pipe 5 and the bypass pipe 17.
9 is provided. The other configurations are the same as those of the conventional example, so explanations will be omitted.

Next, the operation of this embodiment will be explained.

In the above configuration, when the load on the transformer is light, the number of operating cooling fans 7 and oil pumps 8 is reduced,
When a heavy load is applied during operation, the determination unit 12 determines that the amount of increase in the load current of the winding 2 has increased to a predetermined value or more, and the solenoid valve 18 is activated by a signal from the control unit 13. is in an open state. On the other hand, at the outlet of the nozzle 19 provided in the lower pipe 5, the nozzle 19 reduces the cross-sectional area of the oil flow path, so the flow rate of the oil increases and the static pressure decreases. Therefore, when the solenoid valve 18 is opened, the low temperature oil in the oil chamber 15 is sucked into the lower pipe 5 through the bypass pipe 17, mixed with the oil circulating in the transformer tank 3, and the oil is mixed with the oil circulating in the transformer tank 3. line 2 to cool it.

The fourth □□□ is a diagram showing the temperature characteristics of the winding and oil of this example. In this case, time 1. Even if a heavy load is applied to the winding 2, the oil temperature θ0 is temporarily lowered, so the temperature θW of the winding 2 can be kept below the predetermined value θC.

According to this embodiment, when a heavy load is applied to the winding 2, the solenoid valve 1
8 opens, the cold oil in the oil chamber 15 flows into the lower pipe 5, and the temperature of the oil circulating in the tank 3 is temporarily lowered. This has the effect of suppressing the temperature of the winding 2 to a predetermined value θC or less during heavy loads without increasing the number of operating units. Furthermore, even when operating at a higher oil temperature during light loads than in the conventional structure, the temperature of the winding 2 can be kept below θC, so the number of operating oil pumps 8 and cooling fans 7 during light loads can be reduced. It can be significantly reduced and has the effect of improving the energy saving effect.

As described above, according to the transformer cooling device of the present invention,
The temperature of the transformer winding under heavy load can be prevented from exceeding a predetermined value without impairing the energy saving effect.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the configuration of a conventional transformer cooling device;
Figure 2 is a temperature characteristic diagram of the windings and cooling oil of a conventional transformer.
FIG. 3 is an explanatory diagram showing the configuration of one embodiment of the transformer cooling device of the present invention, and FIG. 4 is a temperature characteristic diagram of the transformer winding and cooling oil of the present embodiment. ■...Iron core, 2...Winding, 3...Tank, 4...
- Lower piping, 5... Lower piping, 6... Cooler, 10.
...Load current detector, 12... Judgment section, 13... Control section, 15... Oil chamber, 16... Heat pipe, 17
...Bypass piping, 18...Continued from page 1 ■Applicant Hitachi, Ltd. 5-1 Marunouchi-chome, Chiyoda-ku, Tokyo

Claims (1)

[Claims] 1. Cooling oil in a tank housing a transformer upper unit such as an iron core around which windings are wound is circulated through piping to a cooler installed outside. In devices that control the operating output of a cooler according to the load current of the cooler, there is an oil chamber that is partitioned into a part of the tank, and the temperature of the cooling oil in this oil chamber is maintained lower than that of the cooling oil in other tanks. a cooling means, a bypass pipe that communicates the oil chamber with the pipe connecting the tank and the cooler, a valve that opens and closes the bypass pipe, and a static pressure of cooling oil near the joint between the bypass pipe and the pipe. and a flow condenser inserted into the pipe,
A cooling device for a transformer, characterized in that when the load current of the transformer reaches a predetermined value or higher, the valve is opened to introduce the cooling oil in the oil chamber into the piping and flow into the tank. 2. As the cooling means, a heat pipe is inserted into the oil chamber with one end left outside the tank, and as the valve, a solenoid valve that opens and closes according to the load current of the transformer is inserted in the bypass piping. A cooling device for a transformer according to claim 1, characterized in that: