JPS6147614A - Foil-wound transformer - Google Patents

Abstract

PURPOSE:To equalize voltage distribution of winding when a transitional excessive voltage such as surge voltage is applied and improve insulation reliability by forming a part or entire part of wedge which forms a cooling duct with nonlinear resistance element. CONSTITUTION:The cooling ducts 6 are formed with adequate intervals to a high voltage winding 9 which is formed by winding in overlap a metal sheet and an insulation sheet. The cooling duct 6 is formed by providing a plurality of wedges 12 in the radius direction of winding with adequate interval when the winding is formed. A part of entire part of this wedge 12 is formed by nonlinear resistance element. Thereby, since static capacitance between turns holding the colling duct becomes very smaller than that between other turns not holding the cooling duct when a transitional excessive voltage is applied, a voltage applied on the cooling duct becomes larger than a voltage applied between other turns but a voltage between ducts is suppressed with a limit voltage of nonlinear resistance element which forms a cooling duct.

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 foil-like winding formed by overlappingly wound a metal sheet and an insulating sheet. In particular, the present invention relates to improvements in the configuration of the cooling ducts to effectively protect the windings from transient overvoltages penetrating the windings.

[Technical Background of the Invention] A foil-wound transformer has a good winding space factor and is characterized by being small and lightweight. Transformers with relatively low voltage and thermal capacity of several KV or several hundred KVA have already 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 275KV and 300MVA class transformers, but the biggest key is how to improve cooling capacity and maintain high insulation capacity. It all depends on whether you can hold the line. In particular, in such conventional small-capacity, low-voltage transformers, as a means of protecting the windings against the intrusion of transient overvoltages such as surge voltages, it is well known that lightning arresters are installed outside the transformer. It was sufficiently effective. Furthermore, since it was used for power distribution, there was no need to consider railway transportation limits.

However, with recent technological advances, the cooling efficiency of foil-wound transformers has been greatly improved, such as 275KV, 300M
As foil-wound transformers such as VA class are being developed and researched, it is no longer possible to adequately protect the windings of the transformer as in the past. In other words, in this class of substation transformers, in order to effectively suppress transient overvoltages such as surges, it is necessary to place the lightning arrester as close to the transformer windings as possible; It is most desirable to put the number inside. By the way, in a conventional transformer using rectangular copper wire, it is relatively easy to install a lightning arrester between sections of the windings since there is sufficient space, and its application has been considered.

However, in a foil-wound transformer, the windings are tightly wound with a metal sheet and an insulating sheet, so it has been difficult to incorporate a lightning arrester between the windings. Therefore, foil-wound transformers still require an external lightning arrester, which has the disadvantage that the windings are destroyed by the penetration of transient overvoltage, reducing the reliability of the transformer.

Also, avoid like this? At Seizo, where the R equipment is installed, the equipment becomes larger, which also poses an economical problem. Furthermore, foil-wrapped transformers used for substations are transported by rail from the factory to the installation site, so it is necessary to consider the size and weight limits during transportation. The main points are:

An example of such a foil-wound transformer is shown in FIG. That is, an insulating cylinder 2 made of a synthetic resin with high mechanical strength such as FRP (glass fiber reinforced plastic) is placed around the outer periphery of the main leg 1 of the iron core.
is fitted, and the metal sheet 3 and the insulating sheet 4 are overlapped and wound around the outer periphery of the insulating cylinder 2.
is wrapped.

Here, the thickness of the metal sheet 3 used as the foil winding of the high voltage transformer as described above ranges from several hundred microfrons to 10 microfrons.
It is very thin at 0 microns.

In the low-voltage winding 5, cooling ducts 6 are formed by wedges as voids extending in the stack direction at appropriate intervals.

Furthermore, a reactance gap 7 is provided around the outer periphery of the low voltage winding 5.
An insulating tube 8 made of synthetic resin or the like is disposed coaxially with the insulating tube 2, and a metal sheath h
3 and an insulating sheet 4 are twisted together and wound to form a high-voltage winding 9. A cooling duct 6 is also formed in this high voltage winding 9. Furthermore, these windings are entirely housed in a tank 10 and filled with an insulating medium 1 such as SF6 gas or insulating oil.
1 is sealed in the tank 10.

[Problems with the Background Art] Incidentally, such foil-wound transformers generally have a relatively better potential distribution than transformers using ordinary rectangular copper wires, but in terms of cooling the foil-wound wires, When a cooling duct is provided between the turns of the winding as shown in Fig. 4, the capacitance between the turns sandwiching the cooling duct 6 is extremely large compared to the capacitance between other turns in which no cooling duct is inserted. Therefore, if a surge voltage enters, a large voltage will be shared between the turns sandwiching the cooling duct 6, as shown in FIG. 2B.

In this case, the voltage distribution not only between the turns of the duct part but also between the adjacent turns becomes poor, so the same group becomes a weak point in insulation, increasing the risk of dielectric breakdown, and the potential of the entire winding. This was a problem because it worsened the distribution.

[Purpose of the Invention] The present invention was proposed in order to eliminate the drawbacks of the prior art as described in Improve the
An object of the present invention is to provide a foil-wound transformer with improved insulation reliability.

[Summary of the Invention] The foil-wound transformer of the present invention has a non-linear resistance element that limits voltage sharing in the cooling duct portion by configuring part or all of the wedge forming the cooling duct with a non-linear resistance element. The voltage is suppressed to equalize the potential distribution of the windings when a transient overvoltage such as a surge voltage occurs.

[Embodiment of the Invention] 1 An embodiment of the present invention as described above will be specifically described with reference to FIG. In addition, the same parts as the conventional one are indicated by the same reference numerals, and the explanation thereof will be omitted.

In the figure, cooling ducts 6 are appropriately formed at appropriate intervals in a high voltage winding 9 made of a metal sheet and an insulating sheet wound one on top of the other.

This cooling duct 6 has a plurality of coil windings 12 at the same time.
It is formed by arranging the winding in the axial direction with a suitable ErrA, and part or all of this wedge 12 is constituted by a non-linear resistance element.

The operation of this embodiment having such a configuration is as follows.

That is, as mentioned above, when a transient overvoltage enters, the capacitance between turns that sandwich the cooling duct becomes extremely small compared to the capacitance between other turns that do not sandwich the cooling duct.
Although the voltage applied to the cooling duct portion is higher than the voltage applied between other turns, in this embodiment, the voltage between the ducts is suppressed by the limited voltage of the nonlinear resistance element that constitutes the cooling duct. In this way, by suppressing the voltage between J and reduct with the nonlinear resistance element, the overall potential distribution can be made almost uniform, as shown by Δ in FIG.

Furthermore, in high-voltage, large-capacity transformers with a large winding diameter and a large number of turns, the number of cooling ducts installed between the windings increases. It will be more effective if applied. FIG. 3 shows the improvement in turn-to-turn voltage within the winding when the present invention is applied to a foil-wound transformer in which multiple layers of cooling ducts are provided at appropriate intervals within the winding.

As shown in the figure, in the conventional foil-wound transformer, the turn rod voltage is high in the cooling duct portion, and as a result, the potential distribution of the entire winding is poor as shown in B. In contrast,
In the foil-wound transformer according to the present invention, by being suppressed by the limiting voltage C of the non-linear resistance element, it is possible to make the potential distribution not only in a portion of the cooling duct but also in the entire winding uniform as shown in A.

Furthermore, the present invention also has the following effects.

In other words, since the non-linear resistance element is connected inside the winding as a wedge forming a cooling duct, the non-linear resistance element is installed directly inside the winding, thereby minimizing transient overvoltage such as surge voltage. This can be suppressed as effectively as possible, and therefore the function of the nonlinear resistance element can be fully demonstrated. In addition, since the non-linear resistance element is used as a component of the cooling duct, it does not take up extra space unlike when a non-linear resistance element is installed outside the winding, and the voltage sharing between the winding units is reduced. Since it can be kept low, the space required for insulation protection can be reduced accordingly, which also has the advantage of making equipment more compact.

[Effects of the Invention] As explained above, according to the present invention, by configuring the pattern constituting the cooling duct with a non-linear resistance element, it is possible to prevent the intrusion of transient overvoltage such as surge voltage. By making the potential distribution of the wire uniform, it is possible to effectively insulate and protect the winding, further downsizing the equipment, and providing a foil-wound transformer.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view showing an embodiment of a foil-wound transformer according to the present invention, FIG. 2 is a coordinate diagram showing the potential distribution of the windings of the present invention and a conventional foil-wound transformer, and FIG. FIG. 4 is a coordinate diagram showing inter-turn voltages in the windings of the present invention and the conventional foil-wound transformer.
FIG. 2 is a cross-sectional view showing an example of a conventional foil-wound transformer. DESCRIPTION OF SYMBOLS 1... Main leg of iron core, 2... Insulating tube, 3... Metal sheet 4... Insulating sheet, 5... Low voltage winding, 6...
Cooling duct 1-12... wedge. 7317 Agent Patent attorney Close window body (1 person outside) +m J2Wi Figure 3 Figure 4 n

Claims (1)

[Claims] (1) In a foil-wound transformer in which a cooling duct consisting of an air gap is formed by inserting a wedge into a foil winding formed by overlapping and winding a metal sheet and an insulating sheet around the leg of an iron core, the cooling duct is 1. A foil-wound transformer characterized in that part or all of the wedge forming the wedge is composed of a non-linear resistance element.