JPS5925326B2 - Butching cooling system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION According to the present invention, a bushing having a hollow tubular center conductor is attached to the inside of the center conductor by penetrating the tank wall of an electrical equipment in which an insulating cooling medium is enclosed and circulated. The present invention relates to a bushing cooling device that cools an electrical device by introducing an insulating cooling medium therein.

As is well known, in bushings, especially low voltage, high current bushings used in large capacity transformers, the heat loss generated in the center conductor is large, and the temperature rise in the center of the conductor may become excessive.

Conventionally, in order to keep such temperature rise in bushings within predetermined limits, the cross-sectional area of the conductor is increased to reduce the current density. However, an increase in the cross-sectional area of the conductor leads to an increase in the size of the entire bushing, which not only increases the cost of the conductor material, but also requires the insulator tube to be one rank or larger in size, which also increases the cost. Become. Therefore, a forced cooling type as shown in FIG. 1 has also been proposed. In Fig. 1, 1 is a tank for electrical equipment, for example, a transformer.Although not shown in the figure, the contents of the equipment consisting of iron cores, windings, etc. are stored and arranged, and oil is sealed as an insulating cooling medium. It is assumed that there is Tank 1 has bushing 2 that penetrates its ceiling wall.
is installed. The bushing 2 includes a hollow cylindrical center conductor 3, an insulator tube 4 concentrically surrounding the center conductor 3 at a slight interval, and terminals 5 and 6 arranged at both upper and lower ends of the center conductor 3 and acting as closing caps. It is constructed as a main component. Oil 7 is sealed in the bushing 2 as an insulating cooling medium of the same type as in the tank 1 to such an extent that the center conductor 3 is immersed therein. The tubular space between the center conductor 3 and the insulator tube 4 has small holes 8 formed at the upper and lower ends of the center conductor 3.
It is communicated with the inner hollow part of the center conductor 3 via 9.
Conduits 10 and 11 are connected from the bushing 2 to the upper and lower ends of the annular space between the center conductor 3 and the insulator pipe 4.
The latter conduit 11 further passes through the side wall of the tank 1 and is led out together. Both conduits 10, 11 are connected externally via a radiator 12 and a pump 13. In the device shown in FIG. 1, the insulating cooling medium in the bushing 2,
That is, the oil is forced to circulate through the conduit 10, the radiator 12, the pump 13, and the conduit 11 by the pump 13, and the heat of the oil is dissipated by the radiator 12 during the circulation process.

As a result, the oil absorbs the heat of the center conductor 3 within the bushing 2 and continues to radiate heat within the radiator 12 to cool the center conductor 3. The second cooling method is certainly effective in terms of cooling performance, but on the other hand, the radiator 12 and pump 13
The bushing itself requires a separate auxiliary device, and the structure around the air terminal part of the bushing itself is complicated, which not only makes it extremely expensive, but also requires additional maintenance of the auxiliary device. There are drawbacks. The object of the present invention is to eliminate this drawback and provide a bushing cooling device that is small, inexpensive, does not require additional maintenance, and can effectively cool the center conductor. . To achieve this object, the present invention provides a bushing cooling device of the type in which the center conductor of the bushing is cooled by an insulating cooling medium in an electrical device, in which the insulating cooling medium flows into the center conductor at the lower terminal of the center conductor. A cylinder is formed inside the center conductor and has both ends opened in the axial direction. One opening communicates with the second communication port of the lower terminal, and the other opening is placed in the insulating cooling medium in the center conductor so that the insulating cooling medium outside the cylinder can move into the inside of the cylinder. A second communication port of the lower terminal is formed by opening the lower end of the tube, which is partially or entirely made of an insulating material and which is entirely disposed inside the tank of the electrical equipment, into the side surface of the lower terminal of the center conductor. and the other end of the tube is opened to a constricted portion of the insulating cooling medium flowing through the electrical equipment, so that the relatively high flow rate of the insulating cooling medium flowing around this opening creates a negative energy in the tube. By using the negative pressure inside the tube to draw out the insulating cooling medium inside the tube, the insulating cooling medium inside the electrical equipment can be connected to the first communication terminal of the lower terminal of the center conductor. This device is characterized in that it passes through the outside and inside of the tube sequentially from the mouth and circulates through the second communication port of the lower terminal of the center conductor, and will be described in detail below with reference to the drawings. FIG. 2 shows an embodiment of the present invention, in which a bushing 20 is attached to an electrical device 15, such as a transformer.

The contents of the electrical equipment 15, ie, the iron core and windings, are housed in a tank 16, but illustration thereof is omitted. Oil is sealed in the tank 16 as an insulating cooling medium. This oil is led to a cooler (not shown) via a conduit 17 attached to the upper part of the side wall of the tank 16, and is reintroduced into the tank 16 from the lower part of the side wall of the tank 16. The bushing 20 is basically the same as that shown in FIG. 1, and includes a hollow cylindrical center conductor 21, an insulator tube 22 concentrically surrounding the center conductor 21 at a predetermined interval, and attached to both upper and lower ends of the center conductor 21. terminal 23
, 24. The bushing 20 is oil-tightly attached to the tank 16 by penetrating the ceiling wall of the tank 16 by means of a mounting flange 25 joined to the insulator pipe 22. The upper ends of the central conductor 21 and the insulator tube 22 are sealed oil-tight by a removable force half plate 26 and a terminal 23. The lower end of the insulator tube 22 is also oil-tightly sealed to the center conductor 21 via a seal member 27. A lower terminal 24 provided at the lower end of the center conductor 21 has a communication port 19a for allowing oil in the tank 16 to flow into the center conductor 21, and an insulated cooling port inside the center conductor 21 is provided inside the communication port 19a. A communication port 19b is formed to allow the medium to flow out of the center conductor 21, and the inside of the center conductor 21 communicates with the inside of the tank 16, so that oil reaches near the upper end of the center conductor 21, as shown by an oil level 28. be satisfied. Further, inside the center conductor 21, a cylinder 18 made of metal or an insulator is disposed, and both ends in the axial direction are partially open. One end of this tube 18 is connected to the lower terminal 2
It is oil-tightly attached to the lower terminal 24 so as to communicate with the second communication port 19b formed in the center conductor 21, and the other end is submerged in oil slightly below the oil level 28 in the center conductor 21. The opening is opened so that oil outside the cylinder 18 in the center conductor 21 can move to the inside of the cylinder 18. A support member that maintains a predetermined distance between the tube 18 and the center conductor 21 is arranged, but its illustration is omitted. 2
9 is partly or entirely made of insulating material, and all of it is electrical equipment 1.
5, the opening 29b at one end is oil-tightly attached to the side surface of the lower terminal 24 inside the tank 16, and is connected to the second communication port 1 of the lower terminal 24.
It communicates with 9b.

Further, an opening 29a at the other end of the tube 29 is held by a support member 30 in a portion where the oil flow is restricted, such as within the conduit 17, so that the oil flows around the opening 29a. In the apparatus shown in FIG. 2, while the electrical equipment 15 is in operation, a cooler (not shown) is also operated, and the oil in the tank 16 is circulated as shown by the chain arrow.

In that case, an oil flow 31a with a considerably high flow rate V is present in the conduit 17, which has a significantly smaller cross-sectional area than the tank 16.
occurs. Therefore, there is a gap between the opening 29a of the tube 29 disposed in the conduit 17 and the opening 29b of the tube disposed on the side surface of the lower terminal 24, according to Bernoulli's theorem, which is well known per se. is opening 2
A pressure difference such as a negative pressure is generated with respect to the cylinder 9b, and an oil flow 31b as shown by the solid line arrow is generated in the cylinder 18. In addition, the oil in the tank 16 flows from the communication port 19a of the lower terminal 24 between the inner wall surface of the center conductor 21 and the outer wall surface of the cylinder 18, creating an oil flow 31c, and as a whole, the oil in the tank 16 is As shown by the solid arrow, it flows in from the communication port 19a of the lower terminal 24, passes through the outside and inside of the tube 18 in order, and circulates so as to flow out through the communication port 19b of the lower terminal 24 and the tube 29. Note that the oil flow 3 between the cylinder 18 and the center conductor 21
The flow velocity V of the oil flow 1c can be determined as a function of the flow velocity V of the oil flow 31a in the conduit 17 from the cross-sectional areas and fluid resistance of the tube 29, cylinder 18, center conductor 21, and conduit 17. It will look like the figure. As described above, in the bushing cooling device according to the present invention, the tank 16 of the electrical equipment 15 is placed inside the center conductor 21 of the bushing 20.
Cooling can be achieved by circulating an insulating cooling medium, such as oil, filled inside.

In this case, the oil is inside the cylinder 18 in the center conductor 21.
Since the fluid circulates by rising on the outside and then descending on the inside, the cross section of the flow path in the center conductor 21 becomes small and the flow speed increases. Furthermore, the presence of the cylinder 18 forms a continuous flow path within the central conductor 21, so that the oil flows smoothly without stagnation. Therefore, the center conductor 21 can be efficiently cooled, and the current density of the center conductor 21 can be increased. In addition, the oil circulation in the bushing 20 is controlled such that one opening 29a is arranged in a part where the oil flow is restricted in the tank 16 of the electrical equipment 15, and the other opening 29b is arranged in a part where the lower terminal 24 of the center conductor 21 is attached. Since this is done by the negative pressure of the tube 29, there is no need for separate auxiliary equipment dedicated to cooling the bushings, such as a separate radiator or pump for electrical equipment, making the entire bushing smaller and lighter, making it an inexpensive bushing. A cooling device can be provided. Moreover, the entire tube 29 is placed inside the electrical equipment 15,
Since no special oil-tight structure is required, there is little need for maintenance and maintenance costs are low. Tube again? Since the lower terminal 24 of the center conductor 21 is attached to the side surface of the lower terminal 24 of the center conductor 21, the internal connection between the lower terminal 24 of the center conductor 21 and the contents of the electric device can be easily performed. Moreover, the center conductor 21
Since the lower terminal 24 of is cooled by contacting with the insulating cooling medium flowing through the communication ports 19a and 19b, there is an effect that the lower terminal 24 can be made smaller. Note that the number of tubes provided according to the present invention is not limited to one; for example, as shown in FIG. The other end of one tube 35 is opened into the first conduit 17 as in FIG.
The other end of the cooling circuit 6 can be opened into a cooling circuit conduit 37, which is arranged on the opposite side of the conduit 17, for example.

According to this configuration, even if the oil flow in one of the cooling circuits is stopped due to a failure of the oil pump or the like, the bushing 20 can be continued to be cooled by the oil flow in other healthy cooling circuits. In this case, if backflow prevention devices 38 and 39 such as stop valves are provided at the tip openings of the tubes 35 and 36 in the conduits 17 and 37, cooling can be continued even more reliably. As described above, according to the present invention, it is possible to provide a bushing cooling device that is small, inexpensive, does not require additional maintenance, and can cool the center conductor and lower terminal well.

[Brief explanation of drawings]

Fig. 1 is a partially sectional front view showing a conventional bushing cooling device, Fig. 2 is a partially sectional front view showing an embodiment of the bushing cooling device according to the present invention, and Fig. 3 is an equipment related to an insulating cooling medium. A characteristic diagram showing an example of the relationship between the flow velocity in the cooling conduit and the flow velocity in the bushing in the main body, and FIG. 4 is a partially sectional front view showing another embodiment of the present invention. 15...Electrical equipment, 16...Tank, 17,37.
...Cooling conduit, 18...Cylinder, 20...Bushing,
21... Center conductor, 22... Insulator tube, 23, 24, 4
0...Terminal, 29, 35, 36...Tube, 38
, 39... Backflow prevention device.

Claims (1)

[Claims] 1. A bushing having a hollow tubular center conductor is attached to the tank wall of an electrical device in which an insulated cooling medium is sealed and circulated, so as to penetrate the tank wall. The center conductor is cooled by introducing a medium into the center conductor, wherein a first communication port is provided at a lower terminal of the center conductor for the insulating cooling medium to flow into the center conductor, and the insulating cooling medium is connected to the center conductor. A cylinder is provided inside the center conductor with openings at both ends in the axial direction, and one opening is connected to the second communication port of the lower terminal. The other opening is arranged in the insulating cooling medium in the central conductor so that the insulating cooling medium on the outside of the cylinder can move into the inside of the cylinder, and the other opening is configured to communicate with the opening and the other opening is arranged in the insulating cooling medium in the center conductor so that the insulating cooling medium on the outside of the cylinder can move into the inside of the cylinder, and the other opening is made of an insulating material. one end of a tube disposed in the tank of the electrical equipment is opened on the side surface of the lower terminal of the central conductor and communicates with the second communication port of the lower terminal, and the other end of the tube is configured to open into a constricted portion of the insulating cooling medium flow flowing through the electrical equipment so that a negative pressure is generated in the tube due to a relatively high flow rate of the insulating cooling medium flowing around the opening, By drawing out the insulating cooling medium inside the tube using the negative pressure inside the tube, the insulating cooling medium in the electrical equipment is transferred from the first communication port of the lower terminal of the center conductor to the tube. A cooling device for a bushing, characterized in that the cooling device circulates through the outer side and the inner side in order and through the second communication opening of the lower terminal of the center conductor.