GB2048116A - Coatings for electrical insulators - Google Patents

Abstract

A high voltage electrical insulator formed of porcelain, for example a surge arrester housing, has a thin film of a silicone oil applied to the external surface of the porcelain. When applied to new, glazed porcelain insulators the silicone oil considerably reduces the surface leakage current of the insulator, and, in contrast to the standard practice of heavily greasing such insulators, the silicone oil film does not trap airborne contaminants when significant levels of atmospheric pollutions are present.

Description

SPECIFICATION High voltage insulators This invention relates to high voltage insulators which generally comprise porcelain.

It is international practice to heavily grease all high voltage insulators, for exampie surge arrester housings, when significant levels of atmospheric pollution are present. This process is time consuming and messy and requires the operative to wear protective clothing.

This invention provides a high voltage insulator to which is applied a film of a silicone oil.

Preferably the silicone oil is of low viscosity and the film is only a few microns thick, thus barely visible to the eye or detectable by touch. We have found that if the silicone oil film is applied to a new, glazed insulator, the surface leakage current is considerably reduced.

The invention envisages the application of the thin film of silicone oil to the insulator at the factory and prior to despatch. Any necessary reapplication would be made from time-to-time on the installed insulator.

In contrast to heavily greased insulators, wherein the grease tends to trap conducting airborne contaminants until the grease itself has to be renewed before an external flashover occurs, the film of silicone oil does not tend to trap airborne contaminants and natural washing by rain occurs with advantage.

The silicone oil is applied in a manner effectively covering the complete surface area, thus filling any irregularities and minute fissures in the glazed surface.

1. A high voltage electrical insulator comprising a porcelain body having a film of a silicone oil applied to the surface thereof.

2. A surge arrester comprising a glazed porcelain housing having a film of a silicone oil applied to the glazed external surface thereof.

3. A method of reducing the surface leakage current of a high voltage electrical insulator comprising a porcelain body, which method comprises the application of a film of a silicone oil to the surface of the porcelain body.

4. A method of reducing the surface leakage current of a surge arrester comprising a glazed porcelain housing, which method comprises the application of a film of a silicone oil to the surface of the porcelain housing.

5. A method as claimed in claim 3 or 4 wherein the silicone oil is applied prior to installation of the insulator/surge arrester respectively and reapplication is made from time to time on the installed insulator/surge arrester respectively.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (5)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION High voltage insulators This invention relates to high voltage insulators which generally comprise porcelain. It is international practice to heavily grease all high voltage insulators, for exampie surge arrester housings, when significant levels of atmospheric pollution are present. This process is time consuming and messy and requires the operative to wear protective clothing. This invention provides a high voltage insulator to which is applied a film of a silicone oil. Preferably the silicone oil is of low viscosity and the film is only a few microns thick, thus barely visible to the eye or detectable by touch. We have found that if the silicone oil film is applied to a new, glazed insulator, the surface leakage current is considerably reduced. The invention envisages the application of the thin film of silicone oil to the insulator at the factory and prior to despatch. Any necessary reapplication would be made from time-to-time on the installed insulator. In contrast to heavily greased insulators, wherein the grease tends to trap conducting airborne contaminants until the grease itself has to be renewed before an external flashover occurs, the film of silicone oil does not tend to trap airborne contaminants and natural washing by rain occurs with advantage. The silicone oil is applied in a manner effectively covering the complete surface area, thus filling any irregularities and minute fissures in the glazed surface. CLAIMS

1. A high voltage electrical insulator comprising a porcelain body having a film of a silicone oil applied to the surface thereof.

2. A surge arrester comprising a glazed porcelain housing having a film of a silicone oil applied to the glazed external surface thereof.

3. A method of reducing the surface leakage current of a high voltage electrical insulator comprising a porcelain body, which method comprises the application of a film of a silicone oil to the surface of the porcelain body.

4. A method of reducing the surface leakage current of a surge arrester comprising a glazed porcelain housing, which method comprises the application of a film of a silicone oil to the surface of the porcelain housing.

5. A method as claimed in claim 3 or 4 wherein the silicone oil is applied prior to installation of the insulator/surge arrester respectively and reapplication is made from time to time on the installed insulator/surge arrester respectively.