JPS6190408A - Foil-wound transformer - Google Patents

Abstract

PURPOSE:To obtain the foil-wound transformer of high-reliability in which an insulating performance of winding at the end of a cooling duct is improved by increasing an insulating performance of an insulating sheet arranged on a connection part of the end part of the cooling duct. CONSTITUTION:In the winding in which a metallic sheet and an insulating sheet 8 are wound with lamination, cooling ducts 9a, 9b... in which a cooling medium is enclosed are inserted. An insulating sheet 18 adjacent to the cooling ducts 9a, 9b... is made of the material having a dielectric constant larger than that of the insulating sheet 8 which is wound in the part where the cooling duct 9 is not interposed. Accordingly, in the cooling duct 9a and the metallic sheet 7a; and the cooling duct 9b and the metallic sheet 7b, which have a poten tial difference of one turn, an electrostatic capacity of the part where the cooling duct is interposed becomes larger in proportion to the dielectric constant and the voltage which is shared by a connection part 15 decreases in inverse proportion to the electrostatic capacity. Therefore, the voltage shared by the end parts of the cooling ducts or the gap 16 and, etc. produced in adjacency of the end part of cooling duct decreases extremely and the insulation resistance among the cooling ducts is improved distinguishedly.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a foil-wound transformer in which a cooling duct is built into a winding formed by overlappingly wound a metal sheet and an insulating sheet.

[Technical Background of the Invention] Foil-wound transformers and transformers have a good winding space factor and can be made small and lightweight, and are small-capacity transformers with relatively low voltages of several KV or several hundred KVA. It has been put into practical use. In recent years, in view of its excellent advantages, research has been conducted to expand its application to higher voltage, larger capacity transformers, such as 275 KV and 300 MVA class transformers.

In order to put such high-voltage, large-capacity transformers into practical use, it is important to consider how to improve the insulation ability of the windings, suppress potential fluctuations in the windings due to the intrusion of lightning surges, and improve the potential distribution of the windings. An important technical issue is how to improve it further. still,
Although this kind of high-voltage suspension transformer has not been put into practical use,
As shown in Figure 4, a cooling duct is built into the winding, and a refrigerant with excellent insulation properties is fed into this cooling duct, and the heat generated from the winding loss is cooled using the latent heat of evaporation of the refrigerant. A heat pipe type foil-wrapped pressure device is promising.

- That is, an iron core 2 is provided inside a tank 1 filled with insulating oil or an insulating gas such as SF6 gas as an insulating medium. An insulating cylinder 3 is provided on the outside of the main leg 2a of this iron core 2.
A low-voltage winding 4 is wound through the low-voltage winding 4, and a high-voltage winding 5 is wound around the outside of the low-voltage winding 4 through an insulating barrier 6.

These low-voltage windings 4 and high-voltage windings 5 are constituted by foil-like windings formed by overlapping and winding a metal sheet 7 made of aluminum foil or the like and an insulating sheet 8 made of resin film or the like.

A cooling duct 9 extending in the axial direction is wound around and built into the low voltage winding 4 and the high voltage winding 5. The inside of this cooling duct 9 contains Freon 113 and Fluoriner hFC.
J3 is hollow so that a refrigerant such as 75 or the like can pass therethrough.In the process of passing through the cooling duct 9, this refrigerant takes away the heat generated by the windings 4.5 as the latent heat of evaporation of the refrigerant and cools the windings a4 and 5. Then, this refrigerant is cooled and condensed by water cooling in a condenser 10 provided outside the tank 1. After the liquefied refrigerant is stored in the refrigerant tank 11, the pump 12 connects the liquid guide pipe 13 and the insulating pipe 14. It is sent out into the cooling duct 9 through the cooling duct 9.

In addition, the liquid guiding pipes 13 made of gold a are arranged at both ends of the winding 4.5, and connection ports are formed at both ends of the cooling duct 9.
The connection port between the liquid guide pipe 13 and the cooling duct 9 is an insulated pipe 14.
connected via.

[Problems with the previous day's technology] By the way, the arrangement of the cooling duct 9 built into the winding of the foil-wound transformer as described above is as shown in the sectional view of FIG. That is, the shape of the cooling duct 9 is such that the length of the arc is 18 in circumferential angle from the viewpoint of ease of attachment to the windings and manufacturing.
00, a plurality of cooling ducts 9a and 9b are arranged on the same winding, and the cooling ducts 9 arranged in this way are inserted at predetermined intervals in the radial direction of the valley line. has been done. Here, generally, the thickness of the metal sheet 7 is several hundred μm or less, and the thickness of the insulating sheet 8 is 10 μm or less.
In many cases, the thickness of the cooling duct 9 is 2 to 5 mml, so at the end of the cooling duct 9 inserted into the winding, the inside Since a so-called transition section 15 is formed where the wound metal sheet 7 and insulating sheet 8 move to the outside of the cooling duct 9, a transition section 15 is formed around the end of each cooling duct 9 as shown in FIG. A gap 16 is created. This gap 16 is cold! It has a curved triangular shape formed by the end of the duct 9, the metal sheet 7, and the insulating sheet 1-0.

However, in a foil-wound transformer, such a gap 16
If this happens, the dielectric constant of that part will drop significantly, leading to concentration of electric fields, and the insulating effect of the insulating gas placed inside the tank will be insufficient. moreover,
Due to the potential difference between the cooling ducts 9a and 9b arranged on the same winding, dielectric breakdown may occur between the ends of the attached cooling ducts 9a and 9b, and the insulation performance of the winding between the cooling ducts may deteriorate significantly. It also had the disadvantage of being degraded.

[Object of the Invention] The present invention was proposed in order to eliminate the drawbacks of the prior art as described above, and its purpose is to improve the insulation performance of the winding at the end of the cooling duct inserted into the winding. An object of the present invention is to provide an improved and highly reliable foil-wound transformer.

[Items of the Invention] The foil-wound transformer of the present invention improves the insulation performance of the insulating sheet disposed at the transition portion of the end of the cooling duct, thereby reducing the gap that occurs at the end of the cooling duct or around the end of the cooling duct. The insulation performance of the winding at the end of the cooling duct is improved by reducing the voltage distributed to the cooling duct.

[Embodiments of the invention] An embodiment of the present invention will be described below with reference to FIG.

Note that the same members as those in the conventional foil-wound transformer shown in FIGS. 4 to 6 are designated by the same reference numerals, and explanations thereof will be omitted.

In FIG. 1, cooling ducts 9a, 9b, . . . , each containing a refrigerant sealed therein, are inserted into a winding in which a metal sheet 7 and an insulating sheet 8 are wound together. The insulating sheet 18 adjacent to the cold 7Jl ducts 9a, 9b, . .

In the foil-wound transformer of this embodiment configured in this way,
Since the relative dielectric constant of the insulating sheet 18 adjacent to the cooling duct 9 is larger than the relative permittivity of the insulating sheet 8 wound around other parts, the cooling duct 9a and the metal sheet 7a and the cooling duct have a potential difference of one turn. 9b and the metal sheet 7b, the capacitance of the portion through this cooling duct increases in proportion to the dielectric constant. As the capacitance increases,
The voltage distributed across the transition portion 15 decreases in inverse proportion to the capacitance. Therefore, the voltage distributed to the ends of the cooling duct and the gap 16 generated around the duct part becomes extremely small, and the dielectric strength between the cooling ducts is dramatically improved.

Note that the present invention is not limited to the above-mentioned embodiment, and as shown in FIG. 2, a cooling duct 9a.

The number of insulating sheets 8 wound may be increased in the transition portion 15 at the end of 9b. In this case as well, by increasing the thickness of the insulating sheet at the end of the cooling duct, which is the weak point in terms of insulation, the insulation distance between turns increases, so the electrical stress applied to the cooling duct is significantly reduced and the dielectric strength increases. will be significantly improved.

Also, as shown in FIG. 3, a cooling duct 9a.

The same effect as described above can be obtained by making the thickness of the insulating sheet 28 wound around the transition portion at the end of the cooling duct 9b thicker than the thickness of the insulating sheet 8 wound around the portion not passing through the cooling duct. .

In the above-described embodiment, only the configuration of the insulating sheet disposed near the cooling duct is changed, so that the space factor of the winding is not reduced.

[Effects of the Invention] As described above, according to the present invention, the insulation sheet wound around the transition portion of the end of the cooling duct is structured so as to improve the insulation performance. This has the effect of providing a highly reliable foil-wound transformer with improved wire insulation performance.

[Brief explanation of drawings]

FIG. 1 is an enlarged sectional view of the main part showing one practical example of the foil-wound transformer of the present invention, FIGS. 2 and 3 are enlarged sectional views of the main part showing another embodiment of the invention, and FIG. 5 is a cross-sectional view showing the structure of a conventional foil-wound transformer, FIG. 5 is a cross-sectional view thereof, and FIG. 6 is an enlarged view of the main part of FIG. 5. 1...tank, 2...iron core, 2a...main landing gear, 3...
...Insulating tube, 4...Low voltage winding, 5...High voltage winding, 6
... Insulating barrier, 7... Metal sheet, 8... Insulating sheet, 9... Cooling duct, 10... Condenser, 11
...Refrigerant tank, 12...Pump, 13...Liquid guide t1.14...Insulating vibe, 15...Transition part, 1
6... Gap, 18.28... Insulating sheet. 7317 Agent Patent attorney Kensuke Norichika (1 other person) No. 1 Figure 15 7a 16 Figure 2 t83 Figure 4 fJ S Figure

Claims (4)

[Claims] (1) A foil winding formed by overlapping and winding a metal sheet and an insulating sheet is wound around the legs of the iron core, and a cooling duct curved into an arc is arranged within this winding, In a foil-wound transformer that cools a foil winding by circulating a refrigerant in the cooling duct, an insulating sheet disposed at a transition portion at the end of the cooling duct is disposed at a wound portion of another metal sheet. A foil-wound transformer characterized by having a structure such that its insulation performance is improved compared to that of an installed insulation sheet. (2) A patent claim characterized in that the dielectric constant of the insulating sheet disposed at the transition portion of the end of the cooling duct is greater than the dielectric constant of the insulating sheet disposed at the portion not passing through the cooling duct. The foil-wound transformer according to item 1. (3) The foil-wound transformer according to claim 1, characterized in that the number of insulating sheets disposed at the transition portion at the end of the cooling duct is increased. (4) The foil-wound transformer according to claim 1, characterized in that the thickness of the insulating sheet disposed at the transition portion at the end of the cooling duct is increased.