US1735560A - Insulator for withstanding fog conditions - Google Patents

Description

NOV. 12, 1929. o, us 1,735,560

INSULATOR FOR WITHSTANDING FOG CONDITIONS Filed Aug. 11. 1924 2 Sheets-Sheet l INVENTOR WW. BY K M A T T ORNE YS Nov. 12, 1929. A. o. AUSTIN 1,735,560

INSULATOR FOR WITHSTANDING FOG CONDITIONS Filed Aug. 11, 1924 2 Sheets-Sheet 2 BY Q/ A TTORNEXJ' Patented Nov. 12, 1929 UNITED STATES PATENT OFFICE ARTHUR O. AUSTIN, OF BARBERTON, OHIO, ASSIGNOR, BY MESNE ASSIGNMENTS, TO

THE OHIO BRASS COMPANY, OF MANSFIELD, OHIO, A CORPORATION OF NEW JER- SEY INSULATOR FOR WITHSTANDING FOG- CONDITIONS Application filcd August 11, 1924. Serial No. 731,506.

This invention relates to improvements in high potential insulators to enable said insulators to withstand conditions occasioned by foggy weather or similar conditions.

The invention is exemplified in the combination and arrangements of parts shown in the accompanying drawings and described in the following specification, and it is more particularly pointed out in the appended 0 claims.

In the drawing Fig. 1 is an elevation with parts in sect on showing an insulator having the present invention applied thereto.

Fig. 2 shows a modified detail.

Fig. 3 is an elevation partly in section showing the invention applied to a tubular insulator.

In the operation of transmission lines it 0 frequently happens that troubleis experienced with the ordinary insulators through fog belts and particularlywhere the insulators are coated with electrolyte or dust con-' taining electrolyte and are subjected to fog. Where an insulator is cold and a fog suddenly blows across the insulator, moisture is condensed and allsurfaces become conducting to a very considerable extent. Where the insulator is covered with 'a dust or deposit.

containing electrolyte, flash-over is likely to occur, although the insulator may operate successfully at all other times and even under a rain. During a rain the upper surfaces of the insulator flanges are usually washed off before the lower surfaces of the insulator flanges get wet or become sufliciently conducting to cause trouble. It is this clean ng of the upper surface that frequently permits the operation of an insulator under rain condi- 10 tions, although the same insulator will cause trouble under fog conditions.

In some localities the rise in temperature of the air while the insulator is still cold causes a condensation on the surface of the insulator with a resulting flash-over. This condition occurs insome localities in the early morning'or shortly after sunrise and causes considerable trouble.

In the improved type of insulator serious condensation is prevented by keeping the insulator warm, or, at least above the dew point so that condensation on the surfaces will not occur to the extent that flash-overs will develop.

To establish this condition it is necessary to dissipate energy from the line, the present invention dealing with one of these methods whereby the necessary heat is generated over the surface of the insulator.

It is generally not feasible to coat the surfaces of an insulator with resisting material unless the path is exceedingly long, as the resistances available for this usually have a large negative coefficient and it is necessary to provide suficient surface so that radiation will keep the temperature down. If this is not taken care of, the resistance will decrease with rise in temperature, permitting more current to flow untilthe insulator or resistance is damaged or flash-over occurs.

The drawing shows an application of the method to a large pin type insulator. The leakage current flows from the tie wire 10 over the surfaces until it reaches pin 11. Owing to the large negative coefficient of resist ance for the deposit and for air break-down, leakage starting from the tie wire may tend to develop into a streamer. Owing to the high voltage the air ma} be readily broken down, particularly where aggravated by low surface resistance, the combined leakage and charging current under severe conditions causin streamers to start arcs over the surface w ich may form a path so that the power are will follow. If these streamers can be controlled, the insulator will withstand far more voltage without danger of flash-over.

Owing to the change in diameter and width of the leakage path, the distribution of voltage along the surface will be uneven. This tends to concentrate the stress of leakage cur rent and aggravate the shunting effect of the streamers due to the large negative coeflicient.

In the method shown the surface gradient is improved and the resistance raised due to a drying actionmaused by dissipation of en ergy in a long resistancepath. In order to dissipate the energy, a spiral resistance path starting at the tie wire 10v shown as 17 in Fig.

1, permits the current to flow. The flow of current in this resistance path causes the resistance and the dielectric member upon which it is mounted, to warm up. The resistance in the path must be exceedingly high for the average high voltage line as the following would show. An 88,000 volt line will impress approximately 51,000 volts on a single insulator. If it is desired to dissipate 100 watts along the resistance. path, this path must have an effective resistance of approximately 25,000,000 ohms. In order to obtain a path of this resistance, it is practically necessary to use a resistance path of a refractory nature or one which may be impregnated with an electrolyte having a suitable resistance. One method of producing the resistance path is to construct the spiral coating 17 of a porous composition. This composition may be similar to the main dielectric 12 except that the composition will be such as to make it porous. Such a composition may be readily made from a body composition of from 20% to 50% of ground flint or by leaving out part of the feldspar of the regular body composition. There are many ways of varying this composition which are well known to anyone familiar with the art, the main essential being that the composition will adhere to the main body.

One method of producing this result is to lay on a small strip to form the resistance path while the insulator is being trimmed and is still soft. This will permit a bond between the soft wet composition and the insulator. Where it is desired to leave this resist,-

ance zone unglazed, the resistance zone may.

be coated with parafline when the insulator is dried so that the glaze will not adhere. In some cases, however, it is possible to glaze the surface entirely over depending upon small breaks or pin holes in the surface for the entrance of moisture or the escape of steam. Where a composition of this kind is used, it Will have an exceedingly high resistance when dry and it is usually necessary to impregnate or saturatethe composition with an electrolyte. This may be I obtained by the dust in service or by an application of calcium chloride or other material. In some cases the composition may be made of permanent resistance without the addition of electrolyte.

One method of accomplishing this is to use a carborundum mixture, the composition depending upon the resistance desired and cross-section of the resistance path. A composition of this kind may be composed of from 5% to 10% ball clay and the remainder carborundum. A slight amount of silicate of soda may be added with sufficient water to make a composition which will adhere to the surface when pressed on to same. This re- 21 sistance material may be glazed over 01' left unglazed as desired.

Another method is to apply the resistance material on the glazed insulator and retire so that it will have a good bond to the insulator and the ball clay and silicate of soda will become mixed so that they will not wash out.

Owing to the variation of diameter, the surface resistance will be very unequal at different diameters, and, although a high resistance composition may be placed over the surface, as a whole, this will generally be very inefficient owing to the unequal gradient through. the change in diameter. Where the diameter is fairly uniform, however, as in the case of a cylindrical member or a shell having fairly uniform diameter, the member may be covered with a porous or high resistance layer. Such construction is shown in the member immediately below the upper member 12. Dielectric member 13 is covered bya resistance layer 14. Owing to the very wide path, this resistance layer must be exceedingly high. A very thin layer of porous material, either under or over, the glaze will satisfy this condition. In general it is advisable'that the resistance path be continuous from tie wire to pin. With the construction shown, a very long path is provided so that the energy displaced will not be concentrated. The heat will be so distributed that the insulator will be above the dew point, hence the fog will not tend to condense and lower the surface resistance to'the danger point. It is evident that the method may be used in many different ways and will apply to insulators of various designs such as those having long tubular members. In the case of tubular insulators, the resistance may be applied to an inner member so that the resistance will be protected from weather conditions and will remain constant. It will, however heat up the outer insulating surface. If the resistance zone is started out a short distance from the electrodes, or the cement joints in the shell, the resistance will not be operated under dry conditions but a leakage current will readily bridge this space as conditions tend to become severe. Where the resistance zone is subjected to air, its resistance will be lowered under severe conditions, particularly where it contains an electrolyte which has a strong affinity for moisture.

For parts of this insulator where the surface is more nearly cylindrical and especially where such parts are somewhat protected it may be desirable to provide a continuous high resistance surface coating asshown at 14 or parallel extending paths as shown at 20. The circumferential paths on the other parts may be spirally disposed as shown on the upper flange in Fig. 1 or an equivalent result may be produced by arranging the paths in circles and providing offset connections'as shown at lFig. 2 shows an arrangement especially applicable to wood pins 22. An insulator sleeve 23 is provided having a high resistance coating 24 thereon grounded at 25 and making electrical connections at its upper end with a part 26 of the high resistance path to the conductor.

Fig. 3 shows one form of the invention adapted to a suspension or underhung insulator. The insulator is provided with an eye or attaching means 26. for attaching to the tower or cross arm and an attaching means 27 at the other end for attaching to a clamp which holds the conductor.

The insulator consists of an outer shell 28 having water sheds 29. The insulator has a safety core 30 of some material such as a fibre tube which will hold up the line in case the fragile member 28 is broken.

The insulatin member 31 is provided with a-spiral path 0 high resistance material 32. Under operating conditions, the voltage on the line forces current through the heating member 32 which warms the outer surface of 'the insulator, maintaining its insulating value under severe conditions. The space 33 may be filled with oil or compound to transfer the heat readily to the outer shell and to revent hot spots in the resistance member 32.

11 some cases the insulating oil or material ma be used to advantage in curing spots WhlCh are overly hot owing to a concentrated resistance in the member 32. This is brought about by the intense localized heating causing carbonization of the oil and a lowering of the resistance at this point. In this case, it is advisable to connect a breather 34 so as to permit the escape of pressure, either due v to expansion or contraction of the oil or liquid or due to gas produced by localized heating. It is, of course, evident that the insulator may be made up in many forms and the water sheds 29 may be metal providin there is sufficient insulation in the main bo y member.

I claim 1. The combination with an insulator for high potential transmission lines of means for heating said insulator to dispel the moisture therefrom, said heating means comprising a resistance path for current of a width less than the periphery of the insulator and consisting of orous material.

2. The com ination with an insulator for high potential transmission lines of means for heating said insulator to prevent the accumulation of moisture thereon, said heating means comprising a circuitous ath of porous vmaterial for retaining an e ectrolyte and 4. The combination with an insulator for high potential transmission lines of means for heating said insulator to prevent the accumulation of moisture thereon, said heating means comprising a porous coating uniformly distributed over a portion of the surface of said insulator.

5. The combination with an insulator for high potential transmission lines of means for heating said insulator to prevent the accumulation of moisture thereon, said heating means comprising a narrow spirally disposed path of porous material on the surface of said insulator, said material being impregnated with an electrolyte, the resistance of which decreases in the presence of moisture.

, 6. The combination with an insulator for high potential transmission lines of means for heating said insulator to prevent the ac cumulation of moisture thereon, said heating means comprising a resistance path of porous material between said transmission line and ground and disposed adjacent the surface of said insulator, said porous material having calcium chloride retained therein.

7. An insulator having a plurality of parts and a high resistance leakage path extending from over the surface of said partsfrom one terminal of said insulator to the other, the nature of said path being difierent in width and direction for the different parts.

8. An insulator having a radially projecting flange and another part in series in the leakage path of said insulator with said flange of more nearly cylindrical shape than said flange and a high resistance path over the surfaces of said parts, the path on said flange progressively assing circumferentially about the axis oi said insulator while the path on the other part has longitudinally extending portions at various circumferentially disposed positions.

- 9. In combination an insulator having petticoat flanges arranged at various angles, and a high resistance current path comprising a circumferentially disposed narrow strip on a more nearly radial flange and a high resistance continuous coating on a more nearly cylindrical flange.

10. The combination with an insulator for high potentials, of means for heating said insulator to prevent undue accumulation-of moisture thereon, said heating means automatically operating to increase the amount of heat delivered to said insulator when the cumulation of moisture thereon, said heating means comprising a circuit for conducting a heating current in roximity to said 1nsulator and from said conductor to ground, and means controlled by weather conditions for regulating the current flowing in said circuit.

13. The combination with an insulator for a high potential transmission line, of means for receiving energy from said line for heating said insulator to prevent the accumulation of moisture thereon, said heating means comprising a high resistance circuit of orous material arranged to retain an electro yte.

14. The combination with an insulator for high potential transmission lines, of means for heating said insulator to prevent the accumulation of moisture thereon, said means comprising a resistance path formed oi. material having openings therein to retain an electrol te.

15. he combination with an insulator for high potential transmission lines, of means for heating said insulator to prevent the accumulation of moisture thereon, said heatin means comprising a high resistance path 0 orous material impregnated with an electroyte, the reactance of which decreases in the presence ofmoisture.

In testimony whereof I have signed my name to this specification on this 7 t day of August A. D. 1924.

ARTHUR O. AUSTIN.

CERTIFICATE OF CORRECTION.

Patent No. 1,735,560. Granted November 12, 1929, to

ARTHUR 0. AUSTIN.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 3, line 93, claim 7, strike out the word "from" first occurrence; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 17th day of December, A. D. 1929.

M. J. Moore, (Seal) Acting Commissioner of Patents.

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