JPH09232152A - Gas insulated transformer - Google Patents

Abstract

(57) 【Abstract】 PROBLEM TO BE SOLVED: To provide a solid insulator between a high voltage winding and a low voltage winding, and to equip the high voltage winding with an electrostatic ring, the solid insulator and the electrostatic ring of a gas insulation transformer. The electric field concentration generated between and is relaxed. SOLUTION: An electrostatic ring 3 is provided on upper and lower end surfaces of a high voltage winding 1,
4 is fixed, and the solid insulator in the portion facing the inner peripheral surface of the electrostatic ring is cut out to form a continuous void in the circumferential direction to relax the electric field concentration.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas insulated transformer, and more particularly to a winding structure equipped with an electrostatic ring.

[0002]

2. Description of the Related Art As shown in FIG. 3, a conventional gas-insulated transformer comprises a low-voltage winding 2 wound concentrically on an iron core 7 and a high-voltage winding 1 wound outside the low-voltage winding 2. An electrostatic ring 4 made of a conductive material is attached to the upper and lower ends of the high voltage winding 1 to reduce the electric field at the end of the winding.
These electrostatic rings 4 are formed to have the same dimensions as the outer diameter and inner diameter of the winding. Further, in order to secure a vertical insulation distance between the high-voltage winding 1 and the low-voltage winding 2 and the iron core 7 and a gas passage, a duct piece made of an insulating material having the same width as the radial winding width of the low-voltage winding 2. The coils 16 are radially arranged on the upper and lower end faces of the low voltage winding 2 at several places, and duct pieces 17 of insulating material having the same width as the radial winding width of the high voltage coil 1 are electrostatically attached to the upper and lower end faces of the high voltage coil 1. Radially arranged at several places via the ring 4. The high voltage winding 1 and the low voltage winding 2 are provided above and below the duct pieces 16 and 17, respectively.
At the same time, a ring 18 made of an insulating material having a radial width sufficient to fix the above in the vertical direction is arranged to fix the high voltage winding 1 and the low voltage winding 2 in the vertical direction. Also, the iron core 7 and the low voltage winding 2
Insulating tube 19 and duct piece 20 of insulating material are provided in the gas passage between them, and duct piece 9 and insulating tube 10 of insulating material are provided in the radial direction in the gas passage between high voltage winding 1 and low voltage winding 2. The layers are stacked to secure the insulation distance.

[0003]

However, in the conventional gas-insulated transformer, the inner peripheral portion of the electrostatic ring 4 comes into contact with the duct piece 9, so that a small gas gap as shown in FIG. 11 was occurring. By the way, the electric field strength on the insulating gas side is expressed by the following equation at the portion where the insulating gas and the solid insulator such as the duct piece 9 and the insulating cylinder 10 are in contact with each other. E ₁ = V / {D−t (1-ε ₁ / ε ₂ )} [kV / mm] V: Potential difference between windings [kV] D: Distance between windings [mm] t: Solid insulator Thickness [mm] ε ₁ : relative permittivity of insulating gas ε ₂ : relative permittivity of solid insulator In addition, there is no solid insulator between windings, and the relative permittivity is 1.0.
The electric field strength in the case of only the insulating gas is expressed by the following equation. E ₀ = V / D Therefore, by arranging the solid insulator having the thickness t between the windings, the electric field strength shared by the insulating gas is E ₁ / E ₀
Double. For example, the ratio by placing a solid insulator of dielectric constant 3.3, and becomes _{E 1 / E 0 = D /} {D-t (1-1 / 3.3)} = D / (D-0.7t) . Here, the high-voltage winding 1 and the low-voltage winding 2 are connected to each other by a solid insulator such as the duct piece 9 and the insulating cylinder 10 (t≈D), and the duct piece 9 and the electrostatic ring. If there is a minute gas gap 11 that can be neglected in terms of dimensions between 4 and 4, in this minute gas gap portion, E ₁ / E ₀ ≈D / (D-0.7D) = D / 0.3D = 3 .3, and the electric field strength at the portion of the minute gas gap 11 is double the relative permittivity of the solid insulator, and a much larger electric field is applied than the electric field strength of the insulating gas at the portion without the duct piece 9. As described above, the dielectric strength is remarkably reduced in a portion to which a large electric field is applied, and the inner peripheral portion of the electrostatic ring 4 is a portion in which the electric field is most concentrated, so that it is the weakest point in insulation.

Therefore, an object of the present invention is to reduce the electric field concentration caused by using an electrostatic ring and a duct piece in a winding in a gas-insulated transformer, and improve the dielectric strength so that a highly reliable gas can be obtained. It is to provide an isolation transformer.

[0005]

In order to achieve the above object, the present invention provides a low-voltage winding wound around an iron core, a high-voltage winding wound outside the low-voltage winding, and a high-voltage winding above the high-voltage winding. The upper electrostatic ring arranged on the end face and the lower electrostatic ring arranged on the lower end face are arranged between the low-voltage winding and the high-voltage winding to maintain the insulation distance between both windings and to keep the gas passage A gas-insulated transformer, comprising: a solid insulator to be formed; and a void continuous in the circumferential direction between the inner peripheral surfaces of the upper electrostatic ring and the lower electrostatic ring and the solid insulator. Provide a vessel.

In the gas-insulated transformer of the present invention configured as described above, since the innermost portion of the electrostatic ring where the electric field is most concentrated is formed with a sufficient distance from the solid insulator, electric field concentration is achieved. Is alleviated.

[0007]

1 shows an embodiment of a gas insulation transformer of the present invention. In FIG. 1, the length of the duct piece 6 made of an insulating material inscribed in the high-voltage winding 1 is made equal to the axial length of the high-voltage winding 1, and the upper portion of the electrostatic ring 4 at the upper end of the high-voltage winding 1 is , A section T-shaped duct piece 5 of insulating material is arranged under the electrostatic ring 3 at the lower end of the high-voltage winding, and the electrostatic ring 3,
The outer peripheral side is fixed by the convex portion of the T-shaped duct piece 5 so that 4 is not displaced in the radial direction. In order to prevent the duct piece 6 inscribed in the high-voltage winding 1 from falling down, the electrostatic ring 3 at the lower end of the high-voltage winding 1 has an inner diameter smaller than that of the high-voltage winding 1 so that A duct piece 6 is projected from the pressure winding 1 to the inner diameter side and inscribed in the high voltage winding 1 on the upper surface of this protrusion.
To receive. This duct piece 6 has a notch 14 obliquely formed so that a minute gas gap is not formed between the duct piece 6 and the curved portion of the inner diameter surface of the electrostatic ring 3. With such a configuration, the space 12 facing the low-voltage winding 2 where the electric field is most concentrated of the electrostatic rings 3 and 4 is formed with the solid insulator in a circumferentially continuous space 12. Therefore, a minute gas gap does not occur and electric field concentration is relieved.

FIG. 2 shows another embodiment of the present invention. In FIG. 2, the upper part of the electrostatic ring 4 at the upper end of the high-voltage winding 1,
A T-shaped duct piece 5 is arranged below the electrostatic ring 4 at the lower end of the high-voltage winding 1, and the outer periphery is formed by a convex portion of the T-shaped duct piece 5 so that the electrostatic ring 4 is not displaced in the radial direction. Fix it. The duct piece 8 made of an insulating material inscribed in the high-voltage winding 1 has the same axial height as the height of the upper end of the high-voltage winding 1, and the duct piece 8 extends from the lower end of the high-voltage winding 1 in the inner diameter direction. Insert the notch 15 so that it becomes L-shaped. With such a configuration, a space 13 that is continuous in the circumferential direction is formed between the solid ring and the portion of the electrostatic ring 4 facing the low voltage winding 2 where the electric field is most concentrated. Therefore, a minute gas gap does not occur and electric field concentration is relieved.

[0009]

According to the present invention, since a minute gas gap does not occur in the portion of the electrostatic ring facing the low voltage winding where the electric field is most concentrated, the electric field concentration is relieved, and the dielectric strength is improved.
It is possible to provide a gas-insulated transformer with high insulation reliability.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a winding portion showing an embodiment of a gas insulation transformer of the present invention.

FIG. 2 is a sectional view of a winding portion showing another embodiment of the gas insulated transformer of the present invention.

FIG. 3 is a cross-sectional view of a winding portion of a conventional gas insulated transformer.

FIG. 4 is an enlarged view of a winding end portion of FIG.

[Explanation of symbols]

 1 High-voltage winding 2 Low-voltage winding 3, 4 Electrostatic ring 5 T-type duct piece 6 Duct piece 7 Iron core 8, 9 Duct piece 10 Insulation cylinder 11 Micro gas gap 12, 13 Vacancy 14, 15 Notch 16 , 17 Duct piece 18 Ring 19 Insulation cylinder 20 Duct piece

Claims (1)

[Claims] 1. A low-voltage winding wound around an iron core, a high-voltage winding wound outside the low-voltage winding, an upper electrostatic ring disposed on an upper end surface of the high-voltage winding, and a lower-end surface disposed on the upper end surface of the high-voltage winding. And a solid insulator disposed between the low-voltage winding and the high-voltage winding to maintain an insulation distance between the windings and to form a gas passage. A gas-insulated transformer, characterized in that a void is formed in the circumferential direction between the inner peripheral surfaces of the electric ring and the lower electrostatic ring and the solid insulator.