Insulator

Details Insulator Insulator

1994-01-18

1995-08-29

Picard, Leo P.

Electricity: conductors and insulators

Insulators

Combined

174137R, 174211, H01B 1742

Patent

active

054462428

DESCRIPTION:

BRIEF SUMMARY
This invention relates to high voltage electrical insulators, and particular to porcelain shedded insulators. By high voltage is meant a voltage in excess of about 1 kV, and particularly but not exclusively voltages in excess of about 8 kV.
Such insulators are elongate and comprise a generally cylindrical core and a plurality of sheds integral therewith and extending radially therefrom so as to enhance the creepage path length end-to-end between the conductive terminals of the insulator and to deflect, or shed, water and other liquid contaminants therefrom.
It is known to mount additional insulating components on the insulator for various purposes. EP-A-0 328 365 (Raychem Limited) for example discloses the mounting of a wraparound polymeric component on the porcelain sheds so as to extend beyond the periphery thereof in order to extend the creepage path length. This additional component is of incomplete annular configuration and may or may not employ a closure member. In order to function as a creepage extender however the component must be bonded to the surface of the porcelain shed. A polymeric wraparound device is described in UK Patent No. 1542 845 that enhances the performance of a porcelain insulator, but in a totally different manner and for a totally different purpose from that of the creepage extender. This device, known as a booster shed and available from Raychem, is wrapped around an insulator in the region of one of its porcelain sheds and overlaps itself at its free ends which are then interengaged by a pop-stud fastening arrangement. It is a specific feature of the functioning of the booster shed that in order to improve the performance of the insulator under heavy wetting conditions, it be spaced away from the surface of the porcelain shed. The booster shed reduces the damaging effect that any electrical discharges that occur on the surface of the porcelain may have. In order to achieve this increased performance it is not necessary to mount a booster shed on each of the porcelain sheds of the insulator. It is also known merely to provide mechanical protection of the vulnerable porcelain material of insulators by mounting additional components of polymeric material on the sheds thereof. For example missiles such as stones, bricks or air rifle pellets can shatter porcelain on impact therewith. For this reason, it is advantageous to enclose the porcelain, or at least the laterally extending sheds thereof, within polymeric material for protection, and so-called vandal shields are available for this purpose. In general configuration, such protective shields can be for example as disclosed in GB-B-1542 845, but for this application they are preferably mounted on all the porcelain sheds for maximum benefit.
It is one object of the present invention to provide an insulating member for mounting on a porcelain insulator having improved properties, in particular providing improved mechanical protection.
In accordance with the present invention, there is provided an electrically insulating and substantially non-tracking generally planar member suitable for mounting on a shedded elongate porcelain high-voltage insulator, the member being of annular configuration and being arranged for mounting around and spaced apart from a core of the insulator and for mounting over and spaced apart from a shed of the insulator, wherein an upper surface of the member has channels formed therein that project from a lower surface of the member, the channels intersecting to provide a plurality of projections from the lower surface thereof.
Advantageously the channels are provided by at least one channel, and preferably at least two channels, extending generally circumferentially of the annular member and at least one channel, and preferably at least two channels, extending generally radially thereof.
Preferably the intersections of the channels are deeper than the other portions of the channels, such that the projections extend substantially in only one dimension.
Although the channels of the planar member are preferably

REFERENCES:
patent: 3192312 (1965-06-01), Sauer
patent: 4053707 (1977-10-01), Ely et al.

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