US1858611A - High tension insulator - Google Patents

Description

May 17,- 1932. s. BARFOED HIGH TENSION INSULATOR Filed Feb. 11, 1931 INVENTOR.

4 W Y W ATTORNEYS.

Patented May 17, 1932 UNITED- STATES PATENT OFFICE SVEND BARFOED. OF SAN FRANCISCO, GALIFORNIA.

HIGH TEN$ION INSULATOR Application filed February ll, 1931. Serial No. 514,977.

This invention relates to high tension inunits are made equally able to withstand this sulators and especially to improvements maximum stress. I thereon whereby the formation of corona In actual practice l have observed that if streamers and incipient sparking between the shape of the insulators and the contami- S the flanges of an insulator or between adjanating layer deposited thereon is such that 50 cent insulators when mounted in a string is the air becomes overstressed, corona and inmaterially reduced and in many instances encipient sparking will occur. This takes tirely eliminated. place at sharply rounded edges and tends to The improvement is particularly intended premature sparkover between flanges and befor application to the structure shown in my tween unit and unit. 55 issued Patent No. 1,742,628, entitled High The phenomena of corona and incipient tension insulator, issued January 7th, 1930, sparking of insulators in foggy weather is but the improvement is also applicable to frequently referred to as frying and often inother types of insulators as will hereinafter creases to undesirable noises and causing appear. severe interference with radio reception. 1 m

The insulator described in the above menhave observed that the corona streamers and tioned patent is designed for use in districts incipient sparking heat up the surface of the with a contaminated atmosphere containing insulating body and the contaminating layer dust, dirt and salts, etc., in combination with in a multiple of streaks and spots whereby fog, dew, mist and light rains. These conafter some time the contaminating layer be- $5 ditions cause a deposit to be formed on the comes burned or baked on the surface of the surface of the insulators which will be parinsulating body and when this takes place it tially conducting to an extent which will pen is very difficult and costly to remove eventumit considerable leakage current to flow. ally also injuring the glaze, which again will This partially conducting layer will be of the make dirt adhere more easily; the final result an same shape as the surface of the insulators being that the insulator becomes unsuitable and presents an extension of comparatively for its purpose due to thedestroyed surface high resistance of the metal electrodes and it insulation. will assume a potential corresponding t the AS t s t of pns derable r s arch and voltage drop along this. If the condition eXPeI1menl5a1WWkhaVe Q l that comma 3% of the contaminating deposit is uniform and lnclplent p w s: can be p throughout a string of insulators the flow of presse by sllltably P p g the leakage current will cause a uniform potent OI mundmg curvature on any P of tial gradient to be established along the flanges? Skmts? @rrugatlons and e(lges of string and the electrical stress with respect is %g i g f th t m to the air will be a maximum at the line end lee 0 e pnlsen mven Ion 1s m of the strin and a minimum at the round general y lmpmve and-slmphfy end. Should on the other hand the condihon and operaimon of hlgh t-enslon mSulatO-rs;

f th d b f th th to provlde an lnsulator having a body portion Jon e eposl e nonmm en 9 andaplurality of projecting annular flanges" potential drop along the surface Wlll be nonto provide an insulator which is adapted to llnlforlln and n lay even. from Unit to unit used or in string formation and Parmaxlmum Value and @l Stresses 9 ticularly to round or curve the outer edges of 1mum value on any unit 1n any pos1t1on 1n the flanges and the ends of the insulators 45 the string. It is therefore essential that all to such a degree as to-establish a field between adjacent flanges and units which will not be overstressed or break down the insulating value of the surrounding air thereby preventing the formation of corona streamers and incipient sparking between adjacent flanges and units.

The invention is shown by Way of illustration in the accompanying drawings, in which- Fig. 1 is an enlarged central, vertical section through one form of the insulator.

Fig. 2 shows a string or assembly of insulators and a conductor suspended therefrom.

Fig. 3 shows a standard form of insulator modified or improved according to the present invention.

Referring to the drawings in detail and particularly Figs. 1 and 2. A indicates the cross-arm of a transmission line tower orv pole-of suitable construction; B the conductor carrying the high tension current and C a string of insulators from which the conductor is suspended. The type of insulator employed is that illustrated in Fig. 1. It consists of a head portion 2 and a Petticoat or skirt portion 3. This skirt portion is slightly flared or bell-shaped and its exterior surface is provided with a suitable number of superposed interspaced annular flan es or petticoats 4. These petticoats are of substantially equal diameter and an exterior corrugated cylindrical surface is the apparent result. 1

The head member 2 is hollow to receive an anchor bolt 5 which is secured by a cementitious material as indicated at 6. The anchor bolt carries a link 7 and this is, in turn, connected with a metallic h iad member 2a which encloses the head 2 of the insulator and is secured thereto by a cementitious material 8, or the like. The connections bet-ween the head members 2a and the anchor bolts 5 are preferably pivotal, as indicated at 9, and a flexible string of insulators is obtained.

The method of anchoring the bolts 5, the head members 2a and the manner of attaching the link 7 is of no importance and may be changed to suit varying conditions.

The manner of forming or shaping the annular flanges and the lower or outer edges of the insulators is of great importance and forms the subject matter of the present aplication. As previously stated the invention 1S based on the discovery that the formation of corona and incipient sparking between flanges and units may be materially reduced and in many instances entirely eliminated when the outer contour of the flanges and edges are pro erly formed.

To clearly illustrate and describe this feature reference will be made to Fig. 1. In this figure it will be noted that the lower end of the insulator and the annular flanges 4 are decidedly enlarged and rounded as indicated at 10 to provide an exterior curved Voltage to at die-a... line end of vamre string Inches 127, 000 0. 50 116, 000 0. 45 101, 000 0. 40 86, 500 0. 32 63, 500 0. B

When an insulator was constructed on this basis it was discovered that the resulting wellrounded bulb-shaped flanges and skirts were under adverse conditions able to effect a great improvement in the electrostatic field surrounding and penetrating any part of the insulating bodies on the string as a whole, avoiding undesirable concentration of the electrostatic tubes of force and thereby reducing refraction where they pass from one medium into another. This result is of great benefit when a transmission line is exposed to lightning. storms.

The usual disc-shaped suspension insulator shown in Fig. 3 and used almost universally on high-voltage lines has on its underside several thin concentric corrugations or skirts with sharply rounded edges as indi' cated by dotted lines at 11 and 12 which during lightning storms project into the high-intensity electrostatic field between line conductor and ground, causing severe refraction of the electrostatic lines of force at the sharply rounded edges. This intensifies the formation of corona-streamers at comparatively low voltage surges and causes premature sparkover between the insulators. On the other hand when the outer edge 13 and the corrugations 14 are enlarged and rounded as indicated in full lines in Fig. 3 a great improvement will be found.

In the insulator of the present invention it becomes possible to produce large units each absorbing a greater proportion of the total voltage. This results in fewer units in a string for a given voltage whereby the voltage distribution between the units will be improved. The large unit can be produced on account of the improved electrostatic field made possible by the grading action in each unit of the well rounded bulb-shaped flanges arranged in the main electrostatic field. This action of the bulb-shaped flanges is similar to the action of shields or rings or other forms of antennae placed at the line end of a string of insulators in accordance with usual practice.

In insulators designed in accordance with the resent invention, the desired result is obtained by the rounded bulb-shaped flanges preyenting premature breakdown of the air in contact with the surface of the insulating body during voltage sur es.

It is to be understoo that the radius of curvature selected for each kind of benefit secured may be the dominating one depending upon the exposure of the transmission line to atmospheric influences of various degrees of'severity.

By these means corona. and incipient sparkin can be controlled and suppressed and a aking and burning on of the contaminating layer on the surface of the insulators prevented. Undesirable noises and radio interference will be revented, and finally the insulating value 0 the insulators can be maintained in an eflicient state by the cleansing action of the natural rain, as the insulating surface will not be destroyed.

While certain features of the present invention are more or less s 'ifically described, I wish it understoo that various changes may be resorted to within the sco of the appended claims. Similarly that this materials and finish of the several parts emloyed may be such as the manufacturer may ecide, or varying conditions or uses may demand.

Having thus described my invention, what I claim and desire to secure by Letters Patent is 1. An insulator having a bod portion, a plurality of projecting annu ar flanges ormed thereon, the outer edge of said flanges being enlar ed and rounded to such a degree as to estab 'sh a field between adjacent flanges which will not be overstressed to break down the insulating value of the surrounding air when subject to high potential surges.

2. An insulator having a bell-shaped body portion, a plurality of interspaced annular flanges formed on the exterior surface of the body portion and extending from end to end thereof, the outer ed enlarged and rounde to such a degree as to establish a field between adjacent flanges which will not be overstressed to break down of said flanges being I when sub'ect to high voltages, the lowermost of said anges being enlarged to present a largerdegree of curvature than the other flanges.

4. An insulator having a bell-shaped body portion, a plurality of mterspaced annular anges formed on the exterior surface of the body portion and extending from end to end thereof, the outer edge of said flanges being enlar ed and rounded to such a degree as to estab ish a field between adjacent flanges which will not be overstressed to break down the insulating value of the surrounding air when subject to high voltages, the top and lowermost of said anges being enlarged to present a larger degree of curvature than the intermediate flan s.

s END BARFOED.

the insulating value of theosurrounding air when subject to high voltages.

3. An insulator having a bell-sha d body portion, a plurality of interspaced innular flanges formed on the exterior surface of the body portion and extending from end to end thereof, the outer ed of said flanges being enlarged and rounde to such a degree as to establish a field between adjacent flanges which will not be overstressed to break down the insulating value of the surrounding air

Images