US1225738A - Insulator for high-tension conductors. - Google Patents

Description

A. AICHELE.

INSULATOR FOR HIGH TENSION cououcmns.

APPLICATION FILED NOV. 25. I913.

Patenwd May 15, 1917.

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UNITED STATES PATENT OFFICE.

ALBERT AICHELE, OFBADEN, swl 'rznanann, ASSIGNOR 'ro .AKTIENGESELLSCHAFT BROWN BOVERI5& c111, or BADEN, SWITZERLAND.

iics'rma'roa ronHIoH-rENsIoN commcroas.

To all wkomiganay concern:

Be it knowh'that I, ALBERT Aiouenn, a citizen of the Swiss Republic, and residing at Wiesenstrasse 10, .Baden, Switzerland, have invented certain new and useful Im- 'provements in and Relating to Insulators as thecover of a transformer or an oil switch which is earthed. For convenience this hole in the metal wall is hereinafter referred to as a socket.

The object of the invention is to provide an improved insulator of this kind.

The invention consists in an insulator so constructed that the surface in the vicinity of the socket is so shaped that the electric field is directed almost at right angles to the insulator surface so that low discharge alon the surface is preventec l and thus the tension at which the spark passes is increased.

In the accompanying diagrammatic drawigure 1 illustrates an insulator according to one form of the present invention;

Fig. 2 shows an explanatory diagram.

In the form of the invention illustrated in Fig. 1 the high tension conductor d lies centrally within the insulating sleeve a attached to a socket f.

The lines of force due to the electric field between the conductors are represented by the lines It and the equi-potential lines by the curves n n.

The insulating sleeve (1 is so shaped that the direction of the field especially at the lower part near the socket f is almost at.

right angles to the surface of the insulator. This results in an insulator with a comparatively small height for any given diameter and a concave shape from the exterior aspect.

The explanation of this is as follows In insulating sleeves the glow appearances which start the sparking over extend substantially in the direction of the lines of force. If then this direction coincides with the surface of the insulating sleeve as in Specification of Letters Patent.

Patented May 15, 1917.

Application filed November 25, 1913. Serial No. 802,971.

considered to be the socket since the drop in potential per unit of distance between the socket and the conductor is greater at this point than at some point such as p.

In the spreading of the glow discharge over the surface, first that portion of .the surface on which the glow appears is rendered electrically conductive by the ionization of the air. The effective part of the insulator is thereby shortened. For this reason the glow discharge gradually advances until finally sparks are produced and flashing over takes place.

Now in order to raise the discharging tension for a certain length and height of insulator, so that the height of the insulator sleeve may be made as small as possible for a given discharging tension, it is necessary to avoid entirely if possible, the glow discharge.

This can be effected as described above by making the insulatin sleeve of such a shape as will cause the e ectrical field to be directed almost at right angles to the surface of the insulator especially in the vicinity of the socket, so that the glow discharge and the sparking over will -"take place through the air and not along the surface of the insulator.

InFig. 2 if the di-electric constant of the insulator were equal to that of air, then the lines of force which are produced, will have approximately the direction of the curves k, k, whereas the equipotential lines will have the path of the curves n, 11, etc.

Now for the purpose of causing the direction of the field at the socket place to be at right angles to the surface of the insulator the contour of the surface would tends to keep away from the insulator surface and therefore does not encourage sparking-over along the insulator surface.

Only in the mid le part of the insulator sleeve near the point marked P, thesurface conforms for ashort distance to the direction of the lines of force, but it is much less important there because the drop in otential is not so eat there as at the soc et. Further by suitably shaping, it is possible to limit this zone and to locate it at a place where the field strength is relativel small.

With this form of insulator there is a considerably smaller ratio, for a given sparking tension, between height and diameter in the vicinity of the socket, than in the usual cylindrical type. This gives also the very important advantage that the place which is the most decisive factor for the production of glow discharges at the socket and which is marked Q in Fig. 1, is surrounded by the insulator surface in such a manner that the field extending out from this point will enter almost at right angles into the insulator wall.

By this means, as has been shown by experiment, the formation of glow discharges along the surface is entirely obviated, and if the tension is sufficiently high,

revolution with a concave outer surface for the maximum part of its length, the maxi mum diameter being at a position slightly displaced from the socket.

In testimony whereof, I aflix my signature in presence of two witnesses.

ALBERT AICHELE. -Witnesses:

CARL GUBLER, AUGUST Riircc.

Copies of this patent may be obtained for five cents each, by addressing the "Commissioner of Patents, Washington, D. O.

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