US1744353A

US1744353A - Support for transmission lines

Info

Publication number: US1744353A
Application number: US32711A
Authority: US
Inventors: Arthur O Austin
Original assignee: Ohio Brass Co
Current assignee: Ohio Brass Co
Priority date: 1925-05-25
Filing date: 1925-05-25
Publication date: 1930-01-21
Anticipated expiration: 1947-01-21

Description

Jan. 21, 1930. A. o. AUSTIN 1,744,353

SUPPORT FOR TRANSMISSION LINES Filed May 25. 1925 4 Sheets-Sheet 1 T I 15. I T

Fir. I I I Fit 2 [,INVENTOR.

QLZZMCQML A TTORNEYJ Jan. 2.1, 1930. A, o, AU TIN 1 1,744,353

SUPPORT FOR TRANSMISSION LINES Filed May .25. 1925 4 Sheets-Sheet 2 VINVENTOR.

ATTORNEYS Jan. 21, 1930. A. o. AUSTIN SUPPORT TRANSMISSION LINES Filed May 25 1925 4 Sheets-Sheet- 5 I N VEN TOR.

ATTORNEYS Jan. 21, 1930. us'rm 1,744,353

SUPPORT FOR TRANSMISSION LINES Filed May 25.- 1925 4 Sheets-Shet 4 J N VEN TOR.

M (QM A TTORNEYJ Patented J... 21, 1930 UNITED STATES PATENT OFFICE ARTHUR O. AUSTIN, OF BAIBZ BERTON, OHIO, ASSIGNOB, BY MESNE ASSIGNMENTS, 'lO THE OHIO BRASS COMPANY, OF MANSFIELD, HIO,'A CORPORATION 01 NEW JERSEY SUPPORT FOR TRANSMISSION LINES Application me May 25,

This intention relates to electrical trans mission lines and especially to wooden supports therefor and has for its object the provision of means whereby advantage may be taken of the insulating properties of wood supports for the lines and, at the same time, utilize means for against lightning.

The invention is-exemplified in the com- ]0 bination and arrangement of parts shown in the accompanying drawings and described in the following specification. and it is more particularly pointed out in the appended claims. In the drawingsf I Fig. 1 is an elevation of a wood pole showing one embodiment of the present invention applied thereto.

Fig. 2 is a view looking from the. right of Fig. 1.

Fig. 3 is a view similar to Fig. 1 showing another embodiment of the present invention.

Fig. 4.- isan elevation showing another form of the invention.

Fig. 5 is a side elevation of the embodiment shown in Fig. 4.

Fig. 6 is a view similar to Fig. 5 a side elevation, of a modification.

On transmission lines it is common prac- 'tice to use wood poles or towers for carrying the insulators andhigh voltage conductors. Thesewood poles are used for practically all voltages from very low voltages to extremely high voltages. Practically the only time a transmission line is subjected to extremely high voltages is during lightning storms or for high frequency'or transient con ditions on the line. While a wood pole will usually not'withstand a high voltage for any 40 length of time where the conductor is direct ly on the wood, under high frequency condi tlons where the conductor is supported on an insulator it will withstand a very high volta e and is a comparatively eflective insulator. If the insulation of the pole under the highest showing desirable to make use of this insulation for protecting the structure ground which may be caused by birds,

eliminated by 1925. Serial No. 32,711.

voltage conditions existing on the line can be added to the insulator, a very high degree of insulation may be obtained. ere a wood structure already exists it is the insulation in the structure for the most severe conditions may be even greater than that furnished by the insulator itself unless the latter is of very'large size. It will be seen that if the insulation of the pole or wood structure canbe utilized, it .is of very great economic importance. As the flash-over voltage of the system is increased, the number a of arcs to groundwill be rapidly diminished. From this it is-evident that where efiective use of the wood structure may be made, a a line of a very high degree of reliability may be installed at comparatively low cost. It is also desirable to utilize the insulation in wood structure, particularly where pin type insulators are used in order to reduce the arcs to squirrels, straw or weeds shunting out the insulation furnished by, the insulator. It is evident tliat where the insulation of a wood structure is utilized that the entire insulation cannot be cut out by birds, although the path around the insulator may be readily shunted by a bird or squirrel, or by small objects such as straw or weedsblowing along the conductor up to the insulator.

In many localities it is not necessary to provide any protection for the wood structure. In other sections, however, the storms may be so severe that lightning will shatter or destroy the supporting wood structure. This can be running a ground lead or lightning rod along the ole. This, however, practically converts t e structure into a steel structure, particularly where the insulator 85 support is tied into the ground lead electrically so that the advantage of the insulation in the wood structure is lost.

In this invention it is desired to utilize the insu ation furnished. by the wood structure 90 and, at the same time, eliminate thedanger of shattering the same. This may be accomplished in different ways, although the principal may be the same. c

Figure 1 shows a wood pole 10, upon which cross arms 11 are mounted, supporting insulators 13. A ground wire 14 is supported and insulated by an insulator'15 and extends from pole to pole along the line. The conductors 16 carrying current are supported by the insu-. lators 13 in the usual manner.

If in the ordinary practice the ground wire is carried down along the pole, a discharge will tend to take placefrom the conductors 16 to the braces 17 and thence to ground through the ground lead which would be in contact or very close to these braces. By moving the ground lead 18 out from the pole, but in the direction of the line, it will be possible largely to eliminate the short circuit of the insulation furnished by the pole. This is shown to better advantage in Figure 2. While this method has beenused quite efiectively,it still does not make use of the fullinsulation of the pole, as the voltage which the conductors will carry is limited by the voltage which will establish an are between the conductor and the ground lead 18. While it would be possible more fully to utilize the insulation of the pole by providing greater clearance between the conductors 13 and the ground lead 18, this greatly increases the cost of the structure,

tends to increase bending moments on the arm and torsional moment on the structure. In addition, the arcing voltage does not increase in proportion to the distance, but falls off quite rapidly-for the greater distances so that the method is rather ineflicient.

y In the present invention, a high flash-over voltage is obtained, particularly for high frequency conditions with rather small clearances, which makes it applicable not only to new lines, but it can be usedfor improving the eflective insulation of existing lines without changing clearances.

The ground or static wire 14 will tend to carry ofi the charge of lightning and may otherwise dissipate the energy of the surge. This will travel alon the ground wire 14 and to ground through t e ground or earth connection 18. Since the lead 18 is at ground or earth potential, the electrical stress which may be placed on conductors '13 will either be limited by the insulation provided by the pole, by the structure and the insulator 15 supporting the ground wire or by the break-down of the air between the conductor 16 and. the

- ground lead 18.- It is comparatively easy to use a large enough insulator 15 for supporting the ground wire 14 that the limit in voltage for severe high frequency conditions will be the breakdown of the air between the conductor 16 and the ground lead 18. As'pointed out, it is exceedingly costly to increase the flash-over voltage by increasing this distance.

mounted on the structure, it is quite'efiicient.

In order to increase the'voltage which the conductors will carry without arcing to ground, it is proposed to equip the conductor adjacent the ground lead 18 with an insulated control or conductor cage shown in previous Patents Nos. 1,611,871 and 1,664,100. This tends to control the electrostatic field and permitsa higher high frequency voltage on the line before discharge will occur between the conductor and the ground lead 18. Where there are several conductors on the structure they may set up a very strong field so that a discharge tends to start from the ground lead 18 rather than conductor 16. This is particularly true where conductors 16 are of large diameter and the ground lead 18 of small diameter. Under conditions of this kind, flashing or discharge voltage may be increased by applying a conductor cage to the ground lead or by covering same with insulation, such as a porcelain or fibre tube or even rubber or other insulation which will withstand the weather. The ground lead beingat earthpotential and generally very much below the corona point, {)nay be simply wrapped with varnished camr1c. Another efi'ective method of preventing discharge from the ground lead 18'where the field is quite strong, is by the use of insulated controls 20 or'insulation on the conductor as shown by 19. To prevent discharge from the conductor insulated controls 21 are placed so as to raise the discharge voltage between the conductor 16 and the down lead 18. The discharge voltage between the conductor and down lead may be raised by increasing the effective diameter of the conductor by a cage having an approximately uniformly distributed roughness, by an insulated tube or by insulated controls. The insulated control is shown at 21, conductor cage at 22 and insulation over the conductor at 23. The effectiveness of the combination depends upon the relative insulation furnished by: the structure, insulators, the size of conductors, ground lead and the clearance between conductors and ground lead. In many cases the fiash-over-voltage for severe high frequency surges may be easily doubled compared to conditions where the ground lead simply runs down the pole. In addition, it may easily increase the flash-over voltage by avery appreciable percentage where, the ground lead is brought down away from the pole but between the conductors.

In many types of existing construction, the flash-over voltage may be easily increased 50% by the application of insulated controls to the conductor or conductor and ground wire over that where no insulated control is applied to either.

Another method of accomplishing the same results which reduces the number of wire in either case would be at 31, Where Where the field set up the strain insulator 30 is used, ample clear ance would, of course, be provided by leaving off the cross arm or raislng the point of attachment high enough so that flash-over would not occur between the cross arm or braces and the ground wire 13 or the down lead 25. Both the strain insulator 30 and the ground wire insulator 29 may be used together, although in general one or the other is all that is necessary. Where the strain insulator is used, heavy bending moment is eliminated from the pin insulator 29. If no guying is necessary, the ground lead 25 may be attached to the conductor 31 some distance out from the insulator. If, however, mechanical support is necessary, it is usually necessary to bring the ground lead down in the plane of the structure. It is evident that there is likely to be a strong tendency to cause discharge from the conductor 33 to the ground lead 25, particularl under high frequency conditions. The ash-over or areover voltage between the conductor 33 and the ground lead 25 would limit the voltage which may be applied to the system. By the use of insulated controls 34 so as to raise the flash-over voltage between the conductor 33 and the ground lead 25, a very much higher flash-over voltage can be placed on thevconductors without causing an arc to ground. by the conductor and controls is quite strong or the voltage very high, discharge may be started from the ground lead 25', particularly where the latter is small in diameter.

/ The voltage at which this discharge will start can be materially increased by the use of a conductor cage, insulated control or the application of insulation as previously explained and as indicated by the cage 35.

A somewhat difierent modification is shown in Figure 4. In this instance the circuit is composed of four conductors 36 mounted on two structures. While three conductors only may be used for the three phase transmission circuit, the fourth conductor provides a spare and permits of repairs or may be used in case of failure of one of the other conductors.

Where a high degree of insulation is possible,

the fourth conductor circuit or even a three conductor circuit may provide a higher degree of reliability than two circuits having lower insulation and the cost will be very much less.

It is apparent from the above discussion that one of the chief difliculties in utilizing the insulation of the wood structure is to revent discharge between conductor and t e ground lead, particularly where a ground or static wire is used. In Figure 4 a type of construction is shown which gives good clearance for the conductor, good mechanical strength and reduces the number of ground leads. The ground or static wire 37 .from the two structures may be cross connected by the lead 38 and the earth or ground connection made through the down lead 39. Arcing voltagebetween conductors 36 located below the cross lead 38 may be raised by the application of insulated controls 40 which, with the field set up by the insulator, may be quite effective in raising the flashover voltage. If the ground lead 38 is near the top of the insulator support, it may be advisable to use an insulated control 41 to prevent discharge from the'charging current between the insulator support and-the lead 38.v In general, however, this clearance may be made quite effective. Where the cross lead is small or the field set up by the conductors 36 tends to start discharge from the lead 38, the discharge voltage from the lead may be raised by the insulation, an insulated control or a cage, as previously explained. This is indicated by 42.

It is usually advisable to bring the ground lead down some distance out from the structure so as not to shunt insulation furnished by the wood structure. Discharge between the conductors 36 and the down lead 39 prevented by insulated controls as previously explained. The discharge voltage of the down lead 39 may be raised by covering the down lead with insulation 44, by the application of insulated controls 47 or conductor cages 48 as previously explained. It is evident that the down lead may be brought down outside of or between the structure by a lead 45. This latter method is very eflicient where there is considerable clearance between the two structures. Where the clearance is large, no additional means may be required. It is evident that by controlling the distance or flash-over between the ground lead and conductors or attachments that this clearance may be used as a safety valve to control the voltage which may be applied so as not to damage the wood structures under very severe conditions. In this case it may be advisable to provide some arcing protection for the ground lead such as coiling the wire 46. The coil may be used to increase the effective diameter and the voltage at which discharge occurs from the ground lead in a strong field, or may be used to increasethe efiective diameter of the conductors themselves and to protect same from power arcs.

Various types of structures may be used without changing the principle. In this conmay be 1: non it may be said that structure made from wood poles presenting a narrow face to the conductor make the problem of increasing the flash-over voltage much more simple, as it is only necessaryto prevent discharge from the conductor fora comparatively short dis tance.

1. The combination with a wood support of a high potential transmission line Carried on said support, a ground wire carried by said support, a lead connected with said ground Wire, and a flux control device for reducing the tendency to discharge between said transmission line and lead.

2. In combination a wood support for a high potential transmission line, an insulated ground wire on said support, a lead from said ground wire spaced away from said support, and a flux control member on said lead.

3. The combination with a high potential transmission line of a wood support for said line, a ground wire mounted on said support, a lead from said ground wire spaced away from said support, and a flux control device ilisposed in the field adjacent said lead and 4. The combination with a high potential transmission line of a support for said line, a ground wire mounted on said support and insulated therefrom, a lead extending to ground from said ground wire and passing said transmission line in spaced relation thereto, and a flux control member on said lead adjacent said transmission line for minimizing the tendency to discharge between said line and lead.

5. The combination with a high potential transmission line of a support therefor, an insulated ground wire on said support, a lead extending from said ground wire in spaced relation to said support and passing said transmission line in spaced relation thereto, and a flux control member on said transmission line for controlling the field in the vicinity of said lead.

6. In combination a high potential transmission line, a wood support for said line, an insulator for attaching said line to said support, an insulated ground wire on said support, a lead from said ground wire extending to ground in spaced relation withsaid support and passing said transmission line in spaced relation thereto, and flux control devices on said lead and transmission line for preventing flash-over from said transmission line to said lead.

7 In combination'a wood pole, a pair of cross arms on said pole arranged one above the other, insulators on the lower one of said cross arms at opposite sides of said pole, an insulator on the u per one of said cross arms on one side of sai pole, high potential transmission lines supported respectively by said insulators, a ground wire mounted on said.

wire mounted on said pole and extendingsubstantially parallel to said transmission' line, a lead connected with said ground wire at a point thereon spaced away from said pole and extending downwardly past said transmission line, and a flux control device for distributing the flux in the electrostatic field adjacent said lead and transmission line to prevent discharge from said transmission line.

9. In combination, a'support having a cross arm thereon, a high potential transmission line mounted on said cross'arm atone side of said support, a ground wire mounted on said support substantially in alinement with the axis thereof and insulated by said support from ground, a lead connected with said ground wire at a point spaced from said support and extending downwardly to ground in spaced relation to said transmission line, and flux control members 'for preventing discharge from said transmission line and ground wire at the points thereof where said lead and transmission line are closest together.

10. In combination, a supporting pole of insulating material, a cross arm on said pole, high potential transmission lines carried by said cross arm at opposite sides of said pole, a ground wire mounted on said pole substantially in the plane thereof parallel with said said transmission line, a lead connected with said ground wire, at a point spaced from said pole and extending downwardly between said transmission lines, and a flux control device for controlling the field of force where said transmission lines and ground wire pass one another.

11. In combination, a wood pole, a cross arm on said pole, metallic bracing for said cross arm, insulators supported from said cross arm at opposite sides of said pole, high potential transmission lines supported by said insulators, an insulator mounted on said pole above said cross arm and between the vertical planes of said transmission lines, a conductor supported on said last-namedinsulator and extending parallel with said transmission lines, a ground lead connected with said conductor and extending downwardly between said transmission lines, said lead being spaced from said pole and extending-downwardly between said transmission lines and having its lower end grounded, and means on said transmission lines and ground lead adjacent the points wherethey most closely approach one another for increasing the efifective diameter thereof to curtail formation of discharge streamers at points on said transmission lines adjacent said ground lead thus tending to prevent discharge between said transmission lines and ground lead.

In testimony whereof I have signed my name to this specification on this 21st day of May A. D. 1925.

ARTHUR O. AUSTIN.