JPS62250618A - Foil-wound transformer - Google Patents

Abstract

PURPOSE:To improve reliability on insulation among a shielding for relaxing an electric field and the neck sections of cooling ducts without damaging the field relaxing effect of the end section of a winding by notching one part of the shielding for relaxing the electric field for a section oppositely faced to the neck section of the cooling duct arranged on the outermost side in the cooling ducts incorporated into the winding. CONSTITUTION:Electrostatic shieldings 15 for relaxing an electric field are each mounted at upper and lower end sections on the outermost side of a high- voltage winding 5 consisting of a foil-wound winding. Cooling ducts 6 are incorporated into the high-voltage winding 5 in conformity with the rated capacity of the winding on its midway of the winding 5, and neck sections 7 projected from the high-voltage winding 5 are formed in order to cause a refrigerant to flow. One parts 16 of the electrostatic shieldings 15 of sections oppositely faced to the neck sections 7a disposed on the outermost side in the electrostatic shieldings 15 and the neck sections 7 are notched. Accordingly, insulating distances among the neck sections 7a of the cooling ducts 6 and the electrostatic shieldings 15 are ensured, thus improving reliability on insulation among the neck sections 7a of the cooling ducts 6 and the electrostatic shieldings 15.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention uses a foil-wound wire in which a metal sheet and an insulating sheet are wrapped in layers, and furthermore, a cooling duct is built into the winding. related to foil-wound transformers.

(Prior Art) A foil-wound transformer has a good winding space factor and can be made smaller and lighter. It has already been put to practical use in small capacity transformers with relatively low voltages of several KV and several hundred KVA.

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 275KV and 300MVA, but the biggest technical problem is how to improve the cooling capacity. The two issues are whether the winding can be made to have high insulation capacity and whether it can withstand radial mechanical force of 1!1q in the event of a short circuit accident. Although such high-voltage, large-capacity transformers have not yet been put into practical use, as shown in Figure 3, a cooling duct is built into the windings, and a refrigerant with excellent insulation properties is fed into the cooling ducts, and the windings are A heat pipe-type foil-wound transformer, which uses the latent heat of evaporation of a refrigerant to cool the heat generated from loss, is a promising option.

That is, in this foil-wound transformer, a low-voltage winding 4 and a high-voltage winding 5, which are made by overlapping metal sheets 2 and insulating sheets 3, are wound around a leg 1 of an iron core. A hollow cooling duct 6 is built-in.

In the thin gap in the hollow part of the cooling duct 6, Freon R-1
A refrigerant such as 13 or Fluorinert FC75 is sealed, and the refrigerant is circulated by a pump 8 from a neck 7 that protrudes from the windings of the cooling duct 6. Heat generation in the windings is absorbed by the latent heat of evaporation of the refrigerant, and the vapor is transferred to a condenser 9. It is designed to be cooled and condensed by a cooling pipe 10 inside. A cooling system is constructed in which the liquefied refrigerant is stored in a refrigerant tank 11 and further fed into the windings by a pump 7.

The liquid guide pipe 12 constituting the cooling system is made of metal such as stainless steel, and the liquid guide pipe 12 and the cooling duct 6 are connected via an insulating tube 13 made of Teflon resin or the like. The liquid guide pipe 12 is also connected to the ground potential of the tank 14 and the like. On the other hand, since the cooling duct 6 is built into the winding, it is electrically connected to the same potential as the adjacent winding. Furthermore, insulation of each part of the winding is ensured by an insulating gas such as SF6 gas sealed in the tank 14.

Furthermore, electrostatic shields 15 are provided on the outer peripheries of the upper and lower ends of the high-voltage winding 5 to alleviate electric fields in order to prevent dielectric breakdown from the ends.

(Problem to be solved by the invention) This core-wound transformer has excellent cooling characteristics, so it can be considered to be applied to high-voltage, large-capacity transformers. It was difficult to secure sufficient insulation at the ends of the windings, resulting in the following drawbacks:

That is, an electrostatic shield 15 is usually attached to the end of the high voltage winding 5 for the purpose of alleviating the electric field in order to prevent damage from the end. The size, shape, and position of the electrostatic shield 15 are determined by the rated voltage of the high voltage winding 5, the insulation distance to a grounded object such as the tank 14, and roughly the end structure of the high voltage winding 5. In general, by increasing the size of an electrostatic shield to a certain extent after ensuring an insulation distance, the effect of alleviating the electric field at the end of the winding is increased, and the electric field on the surface of the shield is also reduced. However, this electrostatic shield 15 not only faces the tank 14 and other grounded objects, but also directly faces the neck 7 of the cooling duct 6 and the liquid guide pipe 12 connected therefrom. As a result, an insulating distance between the electrostatic shield 15 and the neck 7 and liquid guide tube 12 cannot be ensured, and the electric field becomes much more severe than in other parts. Furthermore, if there are irregularities on the surface of the neck portion 7 or the liquid guide tube 12, the electric field strength will become particularly severe, and there is a risk of dielectric breakdown.

One way to prevent this is to make the surfaces of the neck 7 and liquid guide tube 12 smooth, to devise the shapes of the neck 7 and liquid guide tube 12, and to roughly attach a shield to reduce the electric field. , which was extremely complex in terms of design and manufacturing.

The present invention has been made in view of the above points, and its purpose is to provide a foil wrapping that improves the insulation reliability between the electric field mitigation shield and the cooling duct neck without impairing the electric field mitigation effect at the end of the winding. Our goal is to provide transformers.

(Structure of the Invention) (Means and Effects for Solving the Problems) The foil-wound transformer of the present invention has a cooling duct built into the winding, and a portion facing the neck of the cooling duct disposed at the outermost side. This is a cutout of a portion of the electric field mitigation shield. This ensures an insulation distance between the neck of the cooling duct and the electrostatic shield, improving insulation.

(Example) An embodiment of the present invention will be described below with reference to FIG.

In FIG. 1, electrostatic shields 15 for mitigating the electric field are provided at the outermost upper and lower ends of a high-voltage winding 5 made of a foil-wound wire. A cooling duct 6 is built into the high-voltage winding 5 in accordance with the rated capacity of the winding, and has a neck 7 projecting from the high-voltage winding 5 to allow the coolant to flow roughly. The electrostatic shield 15 and a portion 16 of the electrostatic shield 15 facing the outermost neck portion 7a of the neck portion 7.
Cut out.

FIG. 2 does not show a plan view of the electrostatic shield 15 and the neck portion 7a seen from above. It is constructed by cutting out a portion 16 of the electrostatic shield 15 that faces the cooling duct neck portion 7a. The range of this notch is determined by the rated voltage and rated capacity of the high-voltage winding 5, etc., and is optimally determined by the position of the large knurling of the electrostatic shield 15, the cooling duct 6, and the neck 7a to ensure an insulation distance. .

The operation of this embodiment configured as described above is as follows. The neck portion 7a of the cooling duct 6 disposed closest to the outer circumference of the high voltage winding 5 is closest to the electrostatic shield 15 provided to relieve the electric field at the end of the high voltage winding 5. By cutting out a portion 16 of the electrostatic shield 15 at the closest portion, an insulation distance between the neck 7a of the cooling duct 6 and the electrostatic shield 15 is ensured.
Insulation reliability between a and the electrostatic shield 15 is improved. Further, a part 16 of the electrostatic shield 15 is cut out, but since the neck part 7a of the cooling duct is disposed close to this part, the neck part 7a of the cooling duct 6 is not connected to the end of the winding of the electrostatic shield 15. Even if the electrostatic shield 15 is cut out, there is no problem with the electric field relaxation effect at the end of the high-voltage winding. Rather, the electrostatic shield 15 is designed to ensure an insulation distance between the neck 7a of the cooling panel 6 and the electrostatic shield 15.
Increasing the inner diameter of the electrostatic shield 15 and moving it away from the high-voltage winding 5 will reduce the electric field relaxation effect. Therefore, in the present invention, the electrostatic shield 15 is moved as close to the high-voltage winding 5 as possible, and the neck 7 is moved away from the high-voltage winding 5.
By cutting out the portion of the electrostatic shield 15 adjacent to a, the electric field relaxation effect at the end of the winding can be enhanced, and the insulation reliability between the neck portion 7a and the electrostatic shield 15 can also be roughly improved.

Further, since there is no need to increase the size of the electrostatic shield 15, the winding can be made smaller. The larger the electrostatic shield 15 becomes, the heavier its ff1ffi becomes, and the support structure becomes a problem, but here, since it is placed close to the high-voltage winding 15, the support structure itself is simplified.

Note that the present invention is not limited to the positional relationship between the electrostatic shield and the winding, and in cases where the electrostatic shield is arranged to protrude more than the end of the winding, etc. The effect becomes even more pronounced by cutting out the electrostatic shield in the area where the electrostatic shield is attached.

(Effects of the Invention) As explained above, according to the present invention, by cutting out a portion of the electrostatic shield in the portion facing the neck of the cooling duct, the electric field relaxation effect of the electrostatic shield at the end of the winding can be impaired. It is possible to improve insulation reliability near the neck of the cooling duct, reduce the size and weight of the winding, and provide an economical and highly reliable foil-wound transformer.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of the foil-wound transformer of the present invention;
FIG. 2 is an enlarged plan view of essential parts of the @-wound transformer shown in FIG. 1, and FIG. 3 is a sectional view showing the structure of a conventional foil-wound transformer. 1... Legs of iron core 2... Metal sheet 3...
・Insulating sheet 1...Low voltage winding 5...High voltage winding 6...Cooling duct 7.7a...Neck
15... Electrostatic shield 12... Liquid guide pipe
13...Insulated pipe 16...Kirihiki Department agent Patent attorney Nori Chika Ken Yudo Hirofumi Mitsumata No. 1 Figure 2 Figure 3

Claims (1)

[Claims] A foil-wound transformer uses a foil-like winding made by wrapping a metal sheet and an insulating sheet in layers, and has a cooling duct built into the winding.The foil-wound transformer has a cooling duct built into the winding. A foil-wound transformer characterized in that an electrostatic shield for mitigating the electric field is provided at the outermost end of the wire, and a portion of the electrostatic shield facing the cooling duct neck protruding outside the winding is cut out.