RU2319245C1 - Silicone bushing insulator - Google Patents

Abstract

FIELD: electrical engineering.

SUBSTANCE: proposed high-voltage bushing insulator designed for use in overhead power transmission lines, cable lines, and switchgear installations, primarily those rated at 6-110 kV, has current-conductive stick, insulation, and supporting bushing made of electricity conductive and nonmagnetic material; insulating body is made of silicone rubber and press-fitted between conductive stick and metal supporting bushing. The latter is made ion the form of cylinder or cone with orogenic rounded-off ends functioning as shields to reduce electric field strength, fastenings (flanges) being disposed in center of bushing for attachment to wall of external structure or to that of building; insulation may go onto supporting bushing and can be provided with external radial ribs.

EFFECT: enhanced electrical and mechanical characteristics, thermal and thermal-impact stability, operating reliability in all climates, reduced material input.

5 cl, 4 dwg

Description

Technical field

The invention relates to electrical engineering, in particular to high-voltage bushings (bushings) overhead power lines, cable lines, switchgears for voltage mainly 6-110 kV.

State of the art

Traditionally, bushing insulators are made of ceramic materials and are designed to introduce electric current into devices or indoors. Bushing insulators connect the external and internal sides of such installations, perform a fixing support role for the current-carrying system and at the same time its isolation from the walls of the room or the walls of the device. The bushing insulators must also be mechanically strong and sealed to withstand the stresses of the wires under wind and short circuits.

With the development of new polymeric materials, it became possible to manufacture bushings made of non-ceramic materials. Known bushing insulator GB 2289803, 11.29.1995, consisting of a central conductive rod, insulation made of a polymer material or rubber, a support sleeve made of fiberglass, through which the insulator is attached to the wall of external equipment or the wall. The disadvantage of this device is the low bending strength, since the support sleeve of fiberglass has a length along the conductive rod, much less than the length of the rod. As a result, when a force is applied to the end of the conductive rod perpendicular to the direction of the rod, the force will act several times greater in accordance with the lever rule. Given that this force is transmitted through a layer of polymer or elastic rubber to a fiberglass support sleeve, even at low values of force, the end of the conductive rod deviates from the initial value by large angles that are not acceptable for normal operation. In the figure accompanying this patent, the length of the support sleeve is not more than one fifth of the length of the conductive rod. The calculation shows that with a normal force of 12.5 kN applied to the end of the rod, the force on the fiberglass sleeve will be five times greater, about 60 kN. A fiberglass sleeve may not be able to withstand such a load. Also, this design at high voltages and currents has significant drawbacks, due to the unevenness of the electric field. The unevenness of the field is due to the fact that the support sleeve in contact with the usually grounded wall of external equipment or the wall of the building is made of fiberglass dielectric material. This creates a concentration of the electric field at the attachment point of the insulator to the grounded structure and leads to its rapid destruction during operation.

This last drawback is eliminated in the design, which is the closest analogue, - RU 2195032. In this bushing (input) for the purpose of aligning the electric field created by the central conductive rod, a tubular element of conductive rubber with a specific volumetric electrical resistance of 10-40 Ohms is introduced * cm, electrically in contact with the support sleeve and through it with an external grounded structure. The disadvantage of this insulator is also its low mechanical strength due to the small size of the support sleeve.

OBJECTS OF THE INVENTION

The objective of the invention is to create a bushing high voltage insulator with improved electrical and mechanical characteristics, reduced material consumption, high heat resistance and resistance to thermal shocks, increased reliability in all climatic conditions.

Description and implementation example

The technical result is achieved in that the high-voltage bushing contains a conductive rod, silicone rubber insulation and a support sleeve of electrically conductive and non-magnetic material, coaxially covering the insulation. The support sleeve is made in the form of a cylinder or cone with mountainous rounding of the ends, acting as screens to reduce the electric field strength, and fastening (flange) in the middle of the sleeve for mounting to the wall of the external structure or the wall of the building, and the insulation can go on the support sleeve and have radial outer ribs. The use of metal for the support sleeve increases the strength of the entire insulator and makes it technically easy to attach to external structures. The load from the conductive rod is transferred to the supporting metal sleeve through silicone rubber. Since the sleeve has a larger diameter than the conductive rod, it is the main power element of the insulator. The material of the conductive rod can be any metal having a small coefficient of electrical resistance, with any mechanical strength. In most metals, having a low coefficient of electrical resistance, have low mechanical strength and high cost, for example aluminum, copper, silver. In the proposed design, the conductive rod does not bear mechanical load, therefore, it can be quite thin and made of expensive metal. The material of the support sleeve is a sufficiently strong non-magnetic metal, such as stainless steel. The use of non-magnetic material can reduce the loss of electricity due to magnetization reversal, which occurs in closed circuits of magnetic materials when they are introduced into the field of alternating electric current, and as a result, heating by circular Foucault currents. The use of metal for the support sleeve allows you to reduce the cost, in comparison with fiberglass, simplify the manufacture, increase the reliability of the insulator as a whole. Also, the use of metal makes it possible to use traditional widespread processing methods, such as pressing, bending, welding, or use commercially available metal pipes in the manufacture of insulators. Reducing the details of the insulator to three and using only two types of materials in the insulator (metal and silicone rubber) increases the reliability and life of the insulator. Since organosilicon rubber has a guaranteed life of more than 30 years, when using non-corrosive aluminum as a material for the core and the support sleeve, a guaranteed life of the entire insulator should be expected to be more than 30 years. In addition, for the above reasons, the insulator is very resistant to thermal influences, including sharp changes in temperature up to 350 degrees, which is an order of magnitude greater than that of known insulators. The thermal resistance of the insulator is limited only by the temperature resistance of silicone rubber (about 350 degrees Celsius) or the melting temperature of the metal. The resistance to differences is determined by the fact that the insulator does not have solid parts in contact with each other, made of different materials having different coefficients of thermal expansion. Between the two metal parts there is an elastic insulation made of rubber, which compensates for all thermal expansion. Organosilicon rubber as an insulation material allows the production of internal insulation and external ribs as a whole. This is possible as a result of the unique properties of silicone rubber: high breakdown voltage for internal insulation, high tracking resistance and hydrophobicity for external insulation. The ability of organosilicon rubber to repel contaminants in comparison with traditional porcelain and glass allows the operation of insulators in open switchgears with a large amount of atmospheric pollution without overlapping an electric arc on the surface of the insulator.

The elastic properties of the insulator and the absence of brittle parts make it possible to transport insulators without a fight. The absence of a porcelain part eliminates brittle breakdown of the insulator and the possibility of a wire falling. Even if bending loads are exceeded, the metal of the support sleeve and the rod is deformed more than the normalized ones, the insulator will bend, but the rod will be isolated from the sleeve, and the insulator will continue to work. Reducing the weight of the insulator saves on transportation costs.

The manufacturing process of the proposed bushing is reduced to one operation: casting rubber insulation in the form with pre-placed there, in the form of embedded parts, a conductive rod and a support sleeve, followed by vulcanization of rubber. The mold may include forming outer ribs over the support sleeve. In the case of using direct or conversion compression technology of solid non-cast silicone rubber, the manufacturing process is reduced to three operations: pressing on the insulation core with ribs and subsequent vulcanization of rubber, putting on the insulation of the support sleeve, fixing the support sleeve on the insulator by uniformly compressing the sleeve near the edges, not touching rounded screens.

Compared with the manufacturing technology of porcelain insulators, the manufacturing time of the proposed insulator is reduced by at least 7-8 times, and not less than 1.5 times in comparison with the prototype. Given the reduction in material consumption in comparison with porcelain, the cost of manufacturing an insulator is lower than porcelain. At the same time, this solution made it possible to increase the reliability, electrical and mechanical strength of the insulator.

The invention is illustrated by drawings.

Figure 1 shows the design of a bushing containing an electrically conductive rod (1), insulation (2), a support sleeve (3) made by direct compression and vulcanization of organosilicon rubber, dressing the support sleeve with elements for attaching the insulator to the wall, radially compressing the support sleeve near the edges.

Figure 2 shows the design of the bushing made as in figure 1, while the supporting sleeve has rounding ends in the form of screens.

Figure 3 shows the design of a bushing made by casting liquid rubber into a mold, and part of the insulation (2) extends to the outside of the support sleeve (3) to increase the length of the creepage path from the electrically conductive rod to the support grounded sleeve (3) insulating surface made of tracking resistant silicone rubber.

Figure 4 shows the design of the bushing made by molding rubber into a mold, while the supporting metal sleeve (3) has toroidal curves, and the insulation (2) extends onto the outside of the supporting sleeve (3) and forms concentric ribs (4).

The implementation of the invention

At the applicant enterprise, prototypes of the proposed insulators for 10 kV voltage, 630 A currents and a minimum breaking load of 7.5 kN were designed and manufactured. In the manufacture of polymer bushing insulators for sufficiently small voltages and currents, the main problem is the significant rise in price of the insulator in comparison with the porcelain analogue. Therefore, for the prototypes, these parameters of the bushing were chosen. Due to the high strength of silicone rubber for breakdown, the insulators had small dimensions. The outer diameter of the insulator was 4 times smaller than the diameter of the porcelain bushing insulator by the same voltage. Unlike the prototype, the insulator withstood temperature differences of more than 340 degrees (from -70 ° C to + 270 ° C), this was due to the lack of fiberglass and other polymers in the design except for silicone. The insulators have withstood short-circuit current tests, lightning impulse voltage tests, and breakdown tests. In addition, the insulators confirmed the high tightness of the electric power input, which is especially important for the needs of the nuclear power industry.

Claims (5)

1. A bushing insulator comprising a conductive metal rod, an insulating body, a support sleeve coaxially covering the insulating body, characterized in that the insulating body is made of organosilicon rubber and is pressed between the conductive metal rod and the support sleeve of a non-magnetic metal. 2. The bushing according to claim 1, characterized in that the support sleeve at the ends has curvatures outward, in the form of a toroid segment, as screens to reduce the electric field strength at the ends of the support sleeve. 3. The bushing according to claim 1 or 2, characterized in that the silicone rubber insulation not only insulates the conductive core and the support sleeve, but also extends onto the outside of the support sleeve. 4. The bushing according to claim 3, characterized in that the silicone rubber insulation extending onto the outside of the support sleeve is made in the form of concentric ribs. 5. The bushing according to claim 4, characterized in that the concentric ribs are manufactured separately and glued to the insulation during manufacture to form an integral part without gaps.

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