US1856123A - Heater for insulators - Google Patents

Description

May 3, 1932.

A. o. AUSTIN 1,856,123

HEATER FOR INSULATORS Filed Dec. 11, 1929 2 Sheets-Sheet l Arfhur 0. Ausfm May 3, 1932- A. o. AUSTIN 1,856,123

HEATER FOR INSULATORS Filed Dec. 11, 1929 2 Sheets-Sheet 2 11v VEIY TOR Arfhur 0. AusI/n A TTORNEY Patented May 3, 1932 UNITE ARTHUR O. AUSTIN, F NEAR- BARBERTON, OHIO, ASSIG-NUR, BY IVIESNE ASSIGNIHENTS, TO THE OHIO BRASS COMPANY, OF TrZANilFEELD, GHIO, A. CORPORATION OF NEW JERSEY Application filed December 11, 1929.

particularly pointed out in the appended claims.

In the drawings:

1 is an elevation with parts in section showing one embodiment of the present invention.

Fig. 2 is a fragmentary elevation showing a modification of the invention.

Fig. an elevation looking toward the right in Fig. 2.

Fig. 4- is a view similar to Fig. 2 showing another modification.

Fig. 5 is a view similar to Fig. 1 showing a different form of the invention.

Fig. 6 is an elevation looking; toward the right in Fig. 5.

Fig. 7 is a somewhat diagrammatic vertical sectional view showing another modification of the invention.

Fig. 8 is a view similar to Fig. 7 showing a different modification.

In tr. smission lines operating at high voltage, considerable difficulty is caused by heavy leakage currents to ground or by insulators ar over where the insulators are subjected to for or to chemical or dust de-- posits. Lines operating alone; the coast or along lakes where salt or other chemical eposits become heavy, are likely to are over,

ularly when the insulators are subfo or rain. In the vicinity of railroads, cement plants, coke ovens or other locations where there are discharges into the air, conditions are likely to be very severe.

HEATER FOR INSULATORS Serial No. 413,378.

are likely to be subjected to heavy ges of steam from the locomotive greatly incr the leakage, and sometimes causes an arc to ground interrupting the service. On many lines, the discharges on the insulator, frequently cause radio disturbances.

The above considerations apply not only to transmission insulators of either the suspension, strain or pin type, but also to bushings, bus insulators and other insulating supports; both on the line and at stations. Due to the presence of spray ponds, very severe conditions frequently exist at the electrical station. In many cases, the outer ends of bushin 's projecting from station walls or roofs have to be increased in size in order to prevent arcing under the more severe condi tions existing in fog or rains.

It is well recognized that if the surface of the insulator can be maintained in a dry condition the danger of arcing is greatly reduced or eliminated. Where the surface of the insulator can be maintained in a dry con dition, heavy deposits do not cause trouble to the s me extent as where they are damp or wet. Where the surface is maintained in a dry condition, the deposits apparently do not adhere so stron rlv to the surface, consequently, wind or wind and rain tend to keep the surfaces cleaner than where the surfaces are wet for a crest portion of the time. This is probably due. in part at least, to the fact that the leakage current or charsgino; current flowin .07 over the surface of the insulator is greatly reduced where the surface is kept dry. This leakage or chore-inc; current flowing over the surface undoubtedly forms new compounds with the deposit in many cases, producing deposits which are highly conducting when damn or wet.

l l hile it is reco nired that maintaining the tempera ure of the insulator above the dew o nt will greatly improve the effective insulation of the insulator and reduce the dancer of arcino' to ground for a given electrical stress, it has been found ditficult and expensive to warm the insulator, particularly where the line voltage is high, without lowering its effective insulation for lightning or other severe conditions.

In the present invention, an arrangement is employed which makes it possible to provide an insulator of high length efliciency or arcing voltage for abnormal conditions so that high electrical integrity may be maintained for these conditions, and, at the same time, permits of heating of the insulator to raise at least an appreciable portion above the condensation point.

In the scheme used, it is possible to apply the improvement to a part or all of the insulator as desired. In many cases, a part of the insulator only need be equipped with heating means. This reduces the cost and makes it possible to use orcinary insulating elements for the remainder of the insulator. Keeping the insulator surface dry, even though it may be covered by a deposit. makes it possible to provide high effective flashover voltage for very severe conditions, such as lightnin where the surface deposits do not necessarily affect the performance of the insulator to the same degree as fog or damp surface under the normal operating voltage. This applies to suspension or dead end strings, bushing insulators, tandem insulators or other types of insulation.

In Fig. 1 is shown a suspension insulator, the upper portion of the string being composed of usual suspension members 10 or of suspension members of any suitable special type as desired. The insulators are attached to a tower support 11. A heated insulator element 12 is attached to the end of the suspension units 10. The heated insulator member 12 is provided with flanges or weather sheds 13 to provide add tional insulation and reduce the tendency to discharge over the surface. The conductor 14 is placed in a special clamp 15 which produces reactance in the conductor 14. This clamp is composed of a seat piece of suitable form which in av be provided with projections 16 to taper off the stress and dampen out vibrations. The conductor is preferably wrapped with a suitable insulation 17, and the construction of the clamp is such that a short circuit path will not be provided in the clamp for the magnetic core which acts to set up the reactance in the conductor 14. he reactance in the conductor 14, due to the clamp 15, forces current through the jumpers 18 and 19 which by-pass the portion of the conductor at the clamp. One of the umpers is preferably attached to the metal cap 20 or to a guard ring so as to provide leakage current for the insulator. This prevents a break-clown of the insulation between the con ductor and the clamp seat. Where t 1e umper 18 is bonded to the cap or guard ring, the jumper 19 is insulated from the cap or guard ring. Between the jumper 18 and 19 is placed a suitable resistance 21. This is preferably placed inside of the insulating element 12,

although it may be placed outside of the insulating element if desired. This heating element 21 will have a low resistance and will be designed in accordance with the current in the line. In Fig. 1, the space 22 is filled with an insulating oil and the insulator is provided with a. tension member 23 which is an insulator. This member 23 may carry the entire mechanical load or may be used to carry the load only if the outer insulating member should fail mechanically. Under some conditions, the load may be distributed between the two if desired.

Several forms of reinforced insulating members are shown more in detail. in my prior Patents No. 1,484,051 and No. 1,497,319.

Where an impedance is placed in the line, as shown, the current will be forced through the jumpers 18 and 19, and the heating element 21. This will heat the fluid 22 inside of the insulator which, in turn, will heat the outer surface and a considerable portion of the insulating flanges. WVhere these insulating flanges are made long, large and with considerable droop, they will tend to hold in the heat and provide a large dry surface. here they are made fairly short, however, and open, a large portion will be washed by rain. The open construction for the insulator is permissible in many cases as the insulation provided will be suliicient to prevent arcing until the rain has had an opportunity to wash ofl' dirt and thus improve greatly the insulating surfaces. It is evident that it is not necessary to place the reactance in the conductor directly at the clamp, as it may be placed at one side, if desired, and the jumpers provided on either side of the reactance. The resistance or heating element may be of any suitable type and may be a non-inductive resistance, if desired. In general, it will be necessary to provide at protecting gap 23 between the two jumpers 18 and 19 so that a surge or transient on the transmission line will be relieved by jumping across this gap when it strikes the impedance. This gap may be at any point between the jumpers and may be between the jumpers and the ends of the clamp, if desired; the insulation be tween the conductor and clamp seat providing the necessary air gap. lVhere the current flowing through the conductor is entirely too large to carry through the insulators conveniently, a shunt 24 may be used which will divide the current.

In the modification of the invention shown in Figs. 2 and 3, a clamp 25 of usual or any suitable form is employed for the cable 14 and the iron mass for producing impedance in the conductor is provided by laminated iron rings 26 having the laminations held together and in place about the conductor 14 and clamp 25 by bolts 27 The lamina lions may be split radially and overlapped if desired for convenience of assembly. The laminated structure of the collars 26 will prevent or limit induced currents in the iron. The operation is similar to that of the device of Fig. 1.

In Fig. i a soft iron wire or ribbon is wound about the clamp 29 and insulated from the clamp by a wrapping or layer of insulation 30. The wrapping 28 produces the necessary impedance between the taps 18 and 19 to cause the heating current to flow through the heating coil as in Fig. 1. Since the clamp forms a part of the conductor through the wrapping, the taps 18 and 19 may be attached to the ends of the clamps beyond the wrapping. This in some cases will form an easier means of attachment for the leads. The clamp may be made longer than is usual if found desirable for providing snfhcient space for the wrapping 28.

Another arrangement for securing a hiat ing current, as shown in Figs. 5 and 6, is by means of a transformer in. which the main conductor passes through the magnetic core, and the heating element is connected to a suitable secondary. In this arrangement the conductor 14 passes through a magnetic core 31. The magnetic core 31 may be made in sections or C shaped so that it may be readily slipped over the conductor. It is also constructed so that it will not have a short circuit turn which will tend to offset the current flowing in the main conductor or in the secondaries running to the heating elements. This core is preferably made up of laminated iron or any other suitable mechanical construction. The core is preferably provided with a clamp or seat 32 for holding the conductor. By properly supporting this. little difiiculty is found in making provision against a short circuit turn. lVhile the scat may be combined with the magnetic core 31. it is necessary to insulate the conductor in this case. In order to provide energy for the heating element 33, the magnetic core is equipped with secondaries 3 1- and These se ondaries may be provided with limiting gaps 36, or a limiting gap may be placed around the magnetic circuit of the main conductor as in Fig. 1. With this arrangement. it is possible to provide the necessary heat in the insulator. even though the conductor 1A may carry a rather small current. The scheme is also applicable where the conductor carries a large current as it is not necessary to carry current leads of heavy current carrying capacity to the heating element of the insulator. The ratio of turns between secondary and primary will, of course. depend upon the condit ons wh ch are likely to exist on the system. The secondar may be provided with suitable taps or coils which may be connected so as to control the amount of energy going to the heating elements in any of the well-known ways.

One method of controlling the current is by the size of the magnetic core or by controlling the size of an air gap placed in this core. As the size of the core is reduced or the air gap increased, the amount of energy going to the heating element will be reduced in accordance with well-known laws. The gap may be provided in any convenient place. An air gap is shown at 37 or, if desired, this air gap may be placed in any other convenient position. il here the magnetic core 31 is made from C shaped punchings which provide an opening only sufficient to pass the conductor, the air gap may be varied by use of an adjustable wedge 38. Another method of regulating the amount of current is to slit part of the punchings so as to control the effective gap or flux in the magnetic circuit. Any or all of the above schemes may be used to control current as desired.

The same scheme for heating the insulator may be applied to bushings or to pin insulators. Wall entrance bushings or busses operating in circuit breakers may be provided with a magnetic circuit either inside or outside of the bushings. The current may then be forced through suitable heating ele ments placed within the bushing in the same manner as shown in Figs. 1 or 2. In a bushing the heating element may be placed inside of a tubular member 39 so that the conducting tubular member provides an electrostatic screen.

While the various species of the invention described above show means for applying heat to a liquid inside of the insulator, this heat may be applied to a conducting member in the insulator. Arrangements of this kind are shown in Figs. 7 and 8. In Fig. 7, an insulator is provided with a suitable attachment 39 and flanges A0. The insulator may be built up of a plurality of shells nested together if desired and provided with closed ends so that the flow of current between the lower attachment 41 and the upper attach ment will be forced over the surfaces of the various insulating shells or members. In this form, the heating element 42 is placed around the support member 41. The heatelement 42 is attached to the transformer or conductor supplying the heating current in the above cases. It is evident that where the member all has good heat conductivity. the heating element might be placed outside of the insulating shell and the member 41 depended upon to distribute the heat up into the insulator and to the adjacent shells. The heat may be supplied to the n'icinber 41 by heat generated in the element A2 or by heating currents set up in the member ll. or a combination of the two.

Where heavy current is flowing, an insulator composed of an insulating member ha ring a closed end or one composed of a number of nested shells may be heated with a central member either directly or through iii-J conduction. Where the current is heavy in the main line, the reactance produced by the magnetic element a3, Fig. 7, or the transformer 44, Fig. 8, may be usedto cause the current to fiow through legs and 51 of a split pin or attaching means in the insulator. The members 50 and 51 are attached to the leads from the source of heating current. The members 50 and 51 can constitute the heating means. The heat may be generated almost entirely in one member or in both, as desired, or may be caused to flow around a heating element as in Fig. 7. As the mem bers 50 and 51 are usually of steel, they may be made of such section that the resistance or resistance and eddy currents in these members will supply the necessary heat for warming the insulator. If desired, thermostat elements 52 may be provided which will shunt the current flowing in the members 50 and 51 so that excessive heating would not occur. The members 50 and 51 may be for the most part surrounded by an air space or if desired the space between these members and the insulating members may be filled with oil or any suitable compound or liquid which will more readily transfer heat. Vhere the drop in potential is small, itis not necessary that this liquid or medium be an insulating medium of high resistance. If an electrolyte is used, an increase in the temperature would decrease its resistance, thereby automatically shunting the current. In general, if a liquid is used, it is desirable that it be one which will not freeze under operating conditions.

I claim:

1. The combination with a transmission line, of an insulator for supporting said line, an impedance interposed in said line, a heating element for said insulator, and taps connected with said line at opposite sides of said impedance for supplying current to said heating element.

2. The combination with a conductor, of an insulator for supporting said conductor, said insulator comprising a tubular, dielectric member having a reinforcing member disposed inside of said dielectric member, and a heating element disposed inside of said tubular, dielectric member.

3. The combination with a transmission line, of a mass of ferrous metal disposed about a portion of said transmission line for offering impedance to current flowing in said line, an insulator for supporting said line, leads connected with said line at opposite sides of said mass of ferrous metal, and a heater for said insulator connected with said leads and energized by current flowing therein.

4. The combination with a transmission line, of an insulator for supporting said line, a mass of ferrous metal forming a clamp for connecting said insulator and line, said'line being insulated from said clamp, a heater for said insulator, and leads connected with said line at opposite sides of said clamp for supplying current to said heater.

5. The combination with a transmission line, of an insulator for supporting said line, a mass of iron surrounding a portion of said line adjacent said insulator, said mass being insulated from said line, a heater for said insulator, leads connected with said line at opposite sides of said metal mass for supplying current to said heater, and an arcing gap for limiting the voltage in said line between the opposite sides of said mass.

6. The combination with an insulator, of a conductor supported by said insulator, an impedance interposed in said conductor, a heater for said insulator, leads connected with said conductor at opposite sides of said impedance for supplying current to said leads, a shunt path about said impedance, and an arcing gap for limiting the voltage between portions of said conductor at opposite sides of said impedance.

7 The combination with a transmission line, of a suspension insulator for supporting said line, a heating element connected with one of the units of said suspension insulator, a clamp for connecting said line to said insulator, and a transformer associated with said line adjacent said clamp for supplying current to said heating element.

8. The combination with an insulator, of a transmission line carried by said insulator, a magnetic core surrounding said line, a secondary winding associated with said core, and a heating element connected with said winding for heating said insulator.

9. The combination with a transmission line, of an insulator for supporting said line, a magnetic core member surrounding said line, a secondary winding associated with said core member and energized by the magnetic field set up therein by current flowing in said line, and means for adjusting the field in said core member to regulate the current in said secondary winding.

10. The combination with a suspension insulator, of a conductor carried thereby, a magnetic core member surrounding said conductor and having an opening therein providing an air gap in the field of said core member, means for adjusting the length of said air gap, a heating element for said insulator, and a secondary Winding connected to said core member for energizing said heating element.

11. The combination with an electric conductor, of an insulator for supporting said conductor, and means for diverting energy from current flowing in said conductor for heating said insulator, the current diverted being a function of the current flowing in i ductor, of an insulator for supporting said conductor, said insulator having an attachment member secured thereto and forming a resistance path for electrical current, and means for supplying current to said attachment to heat said insulator.

13. The combination With an electric conductor 01"" an insulator for supporting said conductor, a pin secured to said insulator, a solid heat conducting member extending into said insulator, and means for heating said member to supply heat by conduction to said insulator.

14. The combination With an electric conductor, of an insulator for supporting said conductor, a bifurcated pin secured Within said insulator, and means for circulating electricity through the legs of said pin to heat said insulator.

In testimony whereof I have signed my name to this specification this 9th day of December, A. D. 1929.

ARTHUR O. AUSTIN.

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