Electricity: conductors and insulators – Insulators – Combined
Reexamination Certificate
1996-08-12
2001-07-24
Paladini, Albert W. (Department: 2841)
Electricity: conductors and insulators
Insulators
Combined
C174S1400CR, C174S176000, C174S1400CR, C174S14100R
Reexamination Certificate
active
06265669
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention pertains to high voltage insulators, of the type use on high voltage power transmission lines, and more specifically to devices intended to be used on ends of such insulators, to reduce or eliminate corrosion and erosion effects associated with current leakage and corona discharge effects.
It is well known in the high voltage insulator art that insulator end fittings are prone to erosion and corrosion effects associated directly or indirectly with high voltage current effects, particularly in the case of insulators having non-ceramic bodies. Such effects are typically caused by ultraviolet radiation created by corona discharges from surfaces under high electric field stress; and also by leakage currents flowing across the insulator surface and terminating on end fittings.
These corrosion and erosion effects eventually can cause increasing weakness of the insulator strength member, and can eventfully result in a mechanical and/or electrical failure of the insulator, thus materially shortening the useful insulator life, as compared with the life it would have absent such effects.
There is thus a need for a device which can effectively prevent such corona discharges so as to eliminate the ultraviolet radiation, and also terminate the surface leakage currents in a manner which eliminates insulator corrosion and erosion.
As detailed below, the present invention accomplishes these objectives by an insulator terminator having the combination of a semiconductor element, of the form of a disk with rounded edges, and a surface conductive element, covering about half of the semiconductor element, which elements together shield the portion of the insulator near the insulator end fitting from high electric field stress, and also eliminate surface leakage current from the part of the insulator near the insulator end fitting, by shunting such current flow through the semiconductor element and surface conductor element of the present invention device, directly to the end fitting of the insulator, which end fitting connects to the power cable, at the lower end of the insulator, and to the tower or pole structure at the upper end from whence it is connected electrically to ground potential.
SUMMARY OF THE INVENTION
The present invention is an insulator terminator device, for attachment to the conventional lower end fitting of a conventional high voltage insulator, for the purpose of extending insulator life by eliminating corrosion and erosion normally produced near the end fittings by high surface leakage currents, and ultraviolet radiation caused by corona discharges. The device, which attaches to the lower end fitting with the top of the device abutting the lower surface of the bottom rain shed of the insulator, has two split half elements formed of semiconductor material, together forming a generally tapered disk shaped structure having a rounded, smooth outer edge having no portion with a radius of curvature less than about an inch. The bottom, outer edge and outer portion of the top of each semiconductor split half has on its surface a highly conductive strength member, typically a metal such as aluminum. The entire device is attached by adhesive and clamping bolts to both sides of the insulator end fitting. High surface leakage currents and corona discharges are eliminated by the combined effect of the semiconductor and surface conductor elements of the device, as a result of the volume current which flows directly from the lowest rain shed through the semiconductor element to the surface conductive element of the device and thence directly to the end fitting, and because the lack of any sharp points on the surface conductive element prevents corona discharges. The net effect of the device is thus to shield the region near the end fitting from large electrical fields that can cause corrosion and erosion effects, even when the insulator is wet from rain. As detailed below, a device of substantially the same form may also be attached to the upper end of the high voltage insulator, at the upper end fitting.
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Cuneo Kamand
Harris Robert W.
Paladini Albert W.
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