JPS58161309A - Gas insulated transformer - Google Patents

Abstract

PURPOSE:To shorten an end insulated distance by a method wherein an insulating ring plate is provided on the whole periphery on the outside of a clamp ring in the axial direction and the ring plate is supported by a cylindrical insulating support having a smaller outside diameter to form a space filled with gas. CONSTITUTION:An insulating ring plate 9 is arranged on the whole periphery on the outside of a clamp ring 6 in the axial direction and an insulating cylinder 4 and a linear spacer 5 are mounted thereon. Moreover, a cylindrical insulating support 10 is arranged between the whole periphery on the outside of the ring plate 9 in the axial direction and a winding supporting metal fixture 8. At this time, the insulating support 10 is so arranged that the support is located outside the wedge-shaped gas gap a formed on the ring plate 9 within the ring 6 in the diametral direction. In so doing, because a space filled with gas is formed between the insulating cylinder 4 and the cylindrical insulating support 10, equal potential lines P are concentrated in this portion and the electric field of the gas gap 1 is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a gas insulated transformer, and particularly to an improvement in the winding end insulation structure of a gas insulated transformer.

Generally, the windings of a gas insulated transformer are as shown in Fig. 1.A low-voltage winding 2 and a high-voltage winding 3 are connected from the inside to an iron core 1 housed in a tank (not shown) filled with insulating gas. It is formed into a roll. An insulating cylinder 4 is inserted between the low-voltage winding 2 and the high-voltage winding 3 to maintain insulation and form a cooling duct, and linear spacers 5 are installed at several points I and F around the entire circumference of the insulating cylinder 4. It is inserted so as to form a Zandermanch-like shape.

On the other hand, at the ends of the low-voltage @ wire 2 and the high-voltage winding 3, a shield ring and a clamp ring 6 for mitigating the electric field are provided, respectively. On the outside in the axial direction of this clamp ring 6, in order to support the low and high voltage windings 2.3 and the clamp ring 6, and to maintain an insulating distance between these and the winding support fitting 8, there are several locations around the entire circumference. An insulating pedestal 7 is provided, and the low and high voltage windings 2.3, the clamp ring 6, and the insulating pedestal 7 are integrally fixed by a winding support fitting 8. in this case,
The insulating frame 7 is designed to handle the electromagnetic mechanical force, that is, the compressive force in the axial direction, that occurs when a short circuit accident occurs on the load side of the transformer and a large short circuit current flows through the low and high voltage windings 2 and 3. To ensure durability, it is usually constructed of a prismatic prism with a square radial cross section equal to the winding width of the low and high voltage windings 2.3.

In such a winding end structure, as shown in FIG. 2, which shows the details of the part ■ at the lower end of the high voltage winding 3 surrounded by the broken line in FIG. Wedge-shaped gas gaps a and b are formed between the spacer 7 and the linear spacer 5, and a wedge-shaped gas gap C is formed between the linear spacer 5 and the linear spacer 5, respectively. Incidentally, the insulating frame 7 and the linear spacer 5 are generally made of insulating paper or plastic insulating material. These solid insulating materials have a dielectric constant more than three times greater than the dielectric constant of the insulating gas sealed in the transformer tank, so the wedge-shaped gas l!
In the Ji'alblC part, the spacing between the equipotential lines is very narrow. That is, these parts have a higher electric field than the other surfaces of the clamp ring 6. On the other hand, since the dielectric strength of the insulating gas sealed in the transformer is smaller than that of the solid insulating material described above, dielectric breakdown starts from the insulating gas. Therefore, in the wedge-shaped gas gaps a, b, and c, where the electric field is higher on the first surface of the clamp ring 6 than on the other surfaces, damage is likely to occur in several parts, and this partial discharge progresses along the surface of the insulating frame 70, causing the clamp There is a risk of dielectric breakdown between the ring 6 and the winding support fitting 8. Therefore, the above-mentioned wedge-shaped gas gap a
, b, c so that the electric field does not exceed the partial discharge start value.
The axial and radial insulation distances of the clamp ring 6 are determined.

By the way, the wedge-shaped gas gap a formed on the insulating stand 7,
The electric field b is affected by the insulation distance in the axial direction, that is, the end insulation distance between the spring ring 6 and the winding support fitting 8, but the electric field between the high voltage winding 3 and the low voltage winding 2 The insulation distance is generally shorter than the insulation distance between the high-voltage winding 3 and a tank wall (not shown) located outside the high-voltage winding 3, so the wedge-shaped gas gap a located radially inside the clamp ring 6 is
The electric field becomes higher in the wedge-shaped gas gap located on the outside. For this reason, conventionally, the end insulation distance is determined by the electric field in the wedge-shaped gap a located on the radially inner side of the clamp ring 6. Therefore, in order to reduce the size of transformers in the future and to completely shorten the end insulation distance that determines the winding height, it is necessary to reduce the electric field in the wedge-shaped gas gap a located radially inside the clamp ring 6. It is an essential issue to do so.

An object of the present invention is to provide a gas insulated transformer in which the end insulation distance is shortened without reducing the partial discharge magnetic pressure at the end of the winding.

The present invention includes a winding wound around an iron core in a tank filled with insulating gas, an insulating tube arranged coaxially inside the winding, and a clamp arranged on a 141-plane portion between the windings. The upper 6 self-winding M & A winding support fitting fixed in the axial direction is provided to provide a winding end insulating structure, the insulating ring plate has an inner diameter dimension that contacts the insulating cylinder, and the cylindrical insulating pedestal is arranged radially inside the clamp ring. The above object is achieved by arranging the wedge-shaped gas gap formed on the insulating ring plate on the outside.

An embodiment of the gas insulated transformer of the present invention will be described below with reference to FIG. 3, using the same reference numerals for the same parts as those of the conventional example.

FIG. 3 is a sectional view showing a main part of an embodiment of the gas insulated transformer of the present invention, and corresponds to FIG. 2 of the conventional example. An insulating ring plate 9 is disposed around the entire circumference of the second ring 6 in the axial direction. This insulating ring plate 9 has an inner diameter dimension that makes contact with the insulating cylinder 4, and the end portion of the @ line spacer 5 is placed on this insulating ring plate 9. Further, a cylindrical insulating frame 10 is disposed between the entire axially outer circumference of the insulating ring plate 9 and the winding support fitting 8. In addition, this cylindrical insulating frame 10 is disposed on the inside of the clamp ring 6 in the radial direction and at a position outside the wedge-shaped gas gap a formed on the insulating ring plate 9.

According to this embodiment, the end insulating structure of the high voltage winding 3 includes the insulating cylinder 4 on the axially outer side of the insulating ring plate 9 and the cylindrical insulating frame 1.
0, an equipotential line P is formed in this part. Conventionally, the equipotential line P near the radially inner corner of the clamp ring 6 is directed in the direction of the arrow in the figure. It becomes a shape that is pushed out. Therefore, since the gradient of the wedge-shaped gas gap a is reduced compared to the conventional example, the voltage between the clamp ring 6 and the winding support fitting 8 can be increased without reducing the partial discharge voltage at the end of the high-voltage winding 3. This has the effect of shortening the end insulation distance, and the device fk can be made smaller.

In addition, since the cylindrical insulating frame 10 is placed in contact with the circumferential metal plate of the insulating ring plate 9, in the unlikely event that a short-circuit YL flow occurs in the high voltage winding 3, compressive force will act in the winding axial direction. However, the compressive stress per unit area of the cylindrical insulating frame 10 can be reduced to the same level or less than that of a conventional insulating frame in which multiple insulating frames are arranged around the entire circumference. It does not reduce the mechanical strength of the material.

As described above, according to the present invention, the number of portions at the end of the winding −
It is possible to provide a gas insulated transformer in which the end insulation distance is shortened without reducing the Itt pressure.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of the main part of the winding structure of a conventional gas insulated transformer, Fig. 2 is a detailed view of the section ■ in Fig. 1, and Fig. 3 is a main part of an embodiment of the gas insulated transformer of the present invention. FIG. 1... Iron core, 2... Low voltage winding, 3... High voltage winding,
4... Insulating cylinder, 6... Clamp ring, 8... Winding support metal fitting, 1 piece 2 piece 30

Claims (1)

[Claims] 1. A winding wound around an iron core in a tank filled with insulating gas, an insulating cylinder coaxially arranged with the winding between the iron core and the winding, and both end surfaces of the winding. 4, and a winding support for fixing the previous winding in the axial direction via an insulating stand disposed on the axially outer side of the shield ring, wherein the insulating strip A cylindrical shape disposed around the entire axially outer circumference of the entire insulating ring plate, and the cylindrical shape ('-7/insulating strip base metal, formed on the insulating ring plate on the radially inner side of the shield ring. An insulating ring plate is disposed at a position radially outward from the position where the wedge-shaped gas gap exists, and further has an insulating ring plate having an inner diameter that is recessed into the insulating cylinder between the cylindrical insulating frame and the shield ring. A gas insulated transformer characterized by forming a space surrounded by an inner surface of a winding support fitting, an outer circumferential surface of an insulating cylinder, an insulating ring plate direction, and an inner surface of a cylindrical insulating frame;