US1876577A

US1876577A - austin

Info

Publication number: US1876577A
Authority: US
Publication date: 1932-09-13
Anticipated expiration: 1949-09-13

Description

Sept. 13, 1932. A. o. AUSTIN 1,876,577

WOOD SUPPORT FOR CQNDUGTORS Filed Junel. 1926 2 Sheets-Sheet l j Fly] mcnfoz Chrome/a s Sept. 13, 1932. Av O ug- 1,876,577

WOOD SUPPORT FOR CONDUCTORS Filed June 1. 1926 2 Sheets-Sheet 2 umznto'c W m aw 81 fl e the insulating characteristics the burning of poles has Patented Sept. 13, 1932 UNITED STATES PATENT OFFICE ARTHUR 0. AUSTIN, OF BARBERTON, OHIO, ASSIGNOR, BY MESNE ASSIGNIE'IEPT'IS, TO THE OHIO BRASS COMPANY, OF MANSFIELD, OHIO, A CORPORATION OF OHIO WOOD SUPPORT FOR CONDUGTORS Application filed. June 1,

This invention relates to wood structures or poles for supporting transmission lines or other conductors and has for its object the provision of means for taking advantage of of the wood structure while preventing in ury to the wood by leakage currents, discharges, lightning or other causes to which such structures have heretofore been subjected.

The invention is exemplified in the combination 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 drawings- F 1 is an elevation of a pole structure having one embodiment of the present invention applied. thereto.

Fig. 2 is a View similar to Fig. 1 showing the invention applied to a somewhat different arrangement of the parts carried on the pole.

In transmission work it has long been known that the insulation in an ordinary wood pole is frequently suflicient to prevent flash over during lightning and eliminates much bird trouble. The frequent shattering t poles during electrical storms as well as caused its use to be abandoned in many cases, although the dang of arcs to ground has been increased by I to a metal structure or the conversion of the pole to the equivalent of a metal structure by use of a ground wire or ground leads runuii down the pole. If the insulation furnished by a wood pole can be made use of without danger of shattering, the effective insulat'on of even a moderate voltage line may be n'iuch higher than that of even the highest vol age line using groun ded metal structures.

Fig 1 shows a rausmission pole having a body 10 upon which are mounted cross-arms 11 and 12. The concuctors 13 are carried by insulators 142 which are attached to the crossarms by pins 15. The sky wire 16 is shown mounted on an insulator and

17 and 18. 'il'he pole also equipped with an arcing rod 19 which is connected to the braces 20. A sky or charging wire 16 may be tied in directly 1926. Serial No. 112,744.

to the down lead or jumper 19 or it may be connected only in ca se a discharge takes place across the gap 21. During electrical storms the line may be struck by lightning or the release of a bound charge may set up a very high potential or voltage in the conductors 13 which will cause arcing to braces 20 or a flash-over of the insulators it they are mounted on a grounded structure. Since the sky wire or charging wire 16 will have approximately the same voltage induced on it at the time of release of a bound charge as that induced upon the conductors 13 the electrical charge on this conductor may be used to charge up the structure, thereby reducing the dilierence in potential between the conductors 13 and the conducting

parts

19 and 20 of the supporting structure. This, however, can only take place when the jumper or lightning rod 19 is not grounded and there is an insulating section in the supporting structure in the path to ground.

In most cases, the sky or charging wire 16 is not necessary as the structure may be charged by the lightning rod 19 so that the difference in potential between the conductors 13 and the structure will be little more than that produced by the normal operating voltage. Where the lightning rod 19 is used it is necessary that this terminate preferably near the top of the structure. If this mem ber terminates close to the side of the structure there is danger that it will discharge into the pole or structure or that an are from the end will burn the structure. The light ning rod 19 should be such that it will shunt the section of the pole so that discharge cannot take place inside the pole and shatter same. In order to insure safe operation it is necessary, however, that considerable care be given to the lower end of this member which should preferably terminate in a cischarge member which will screen the pole. The lower end should preterabl terminate in one or more flaring members 22 whose distance from the pole increases as they proceed in the general direction of the pole. Where this is carried out properly a dis charge will start from the lower end of the and will not ailect the pole. This discharge will go to ground or a corresponding member 23 which is grounded may be placed below so that the discharge will take place between the members 22 and In general, a distance between the

members

22 and 23 of from 1 to feetwill require for arcing a voltage equivalent to that of flash-over of the usual range of insulators found in transmission practice. The gap between the

members

22 and 23 tends to increase the effective insulation between conductors and ground over the effective insulation where the rod 19 is directly grounded by a low resistance conductor and in favorable cases the effect of the gap is equivalent to increasing the insulation for the conductor by the resistance to flash-over volt-age of the gap. This is particularly true for high frequency disturbances.

lVhere the wood structures and arrangements or" conductors are such that the lightning rod 19 will not sufiiciently charge up the structure, this charging may be supplemented by the shy or counter E. M. wire 16. If this is tied directly into the down lead 19 there 's danger that a bird or squirrel may produce a short circuit. It, however, it is insulated and connection to ground is only made though a gap 21 it does not reduce the effective insulation of the system for birds or squirrels. lVhere the sky wire, is not sectionalized, it is advisable to insulate it, otherwise multiple paths to ground at the various structures will make it possible for a bird or squirrel to starta short circuit by shunting an insulator supporting a conductor wire 13.

In many cases leakage and charging current over the insulators has caused burning of the wooden structure and made it necessary to do away with the insulator furnished by the wood structure. This, however, may be taken care of with the improved construction. Where leakage conditions are severe, the insulator supports 15 may be bonded together by conductors 24. In general, the leakage and charging current will be equalized for most systems. In some cases, however, due to a faulty insulator or greater leakage owing to a lower surface resistance or difference in location of the conductor, there may be an unbalanced current or volt age which will'cause burning of the wood structure in going to ground. In order to prevent c amage to the insulating zone the pole this section is shunted by a member 25. The resistance may be made up in any suitable manner depending upon the degree of resistance necessary. Tfi hcre conditions are such as to cause heavy unbalanced leakage over the insulators, it may be advisable to use a rather low resistance. In general, however. a resistance of several thousand ohms will carry away the unbalheavy induced charge resis r anced current. A resistance of this magnitude will have a very high IR drop in the case of high frequency discharge or in the case of impact or the release of a bound charge as with lightning. These resistances may be made with a higher resistance wire placed in an insulating tube filled with a non-corrosive electrolyte or oil. F or the iigher resistances an insulating tube may be used of proper cross-section filled with water and alcohol or other suitable mixture which will not freeze and damage the tube.

In case the line is grounded by the conductor fallin on a metal arm :20 or through the insulator puncturing, the resistance, if high, will not withstand the discharge for any considerable length of time. In this case, however, it will usually evaporate the conducting fluid and may clear the line until such time as repairs can be made. In many cases the resistance member, however, can be so proportioned that it will operate the circuit breaker and clear the line so that there will be no danger of destroying the structure. Many different applications are possible making use of the principles involved. In general, itis desired tohave the lightning or the bound charge raise the voltage of the metal parts at the top of the structure so that the difference in potential between the conductors and the supporting members will not be sullicient to cause the insulators to flash-over. This may be aided by the use of a lightning rod or antenna projecting well above the conductors or by a charging or static wire. lVhere these are not used the electrostatic capacity between the conductors 13 and the upper portion of the supporting structure must be suliicient so that the potential of this portion of the supporting structure will be raised by the disturbing charge sufficiently to counteract the increase in the stress between the conductor 13 and their supports.

In a system where the insulators are mounted on metal arms on a wood pole, the bonding may be already affected by the cross-arms. A common arrangement of this type is shown in. Fig. 2.

In the form shown in this figure a wood pole 26 is provided with cross-arms 27 and braces 28. Insulators 29 are mounted on pins supported by the cross-arms and braces. The metal supporting parts attached to the insulators are connected by jumpers 31. The pole has an insulating Zone 32 located below the cross-arms. This insulating Zone is pro tected by the screen and discharge points and 34c. The screen 34- is connected to ground by a jumper 35. rshunting resistance 36 may be provided to take care of unbalanced leakage conditions. This resistance protects the insulated zone 32 from burning as previously explained. If a part or all of the insulators 29 are shunted by a bird or squirrel so that a discharge can take place between the conductor 37 and the cross-arm 27, a power are is likely to result if the metal arms are grounded in the ordinary way by a conductor running down the pole. Where the arms are grounded in the ordinary way by a con ductor running down the pole, it is evident that a voltage which will cause an arc to strike from the conductor 37 to the cross-arm or the supporting pin 30 is likely to result in a power are.

The construction shown in Fig. 2 reduces, if not entirely eliminates, the danger of power are for most operating conditions. here the insulated section 32 has a high resistance, a bird shunting the insulator may not draw enough current to cause a heavy power arc to pick up so that although a slight discharge may be started there would be no interruption. Where the resistance 36 is high, the amount of current which can be drawn will be limited and in some cases, even though a power are starts, the resistance may be depended upon to clear the arc and reestablish service. 'Where the resistance of the pole is low enough or it is impregnated or painted with a low resistance material, no shunting resistance 36 is necessary to prevent burning due to unbalanced leakage. It is evident that a series of gaps rather than a single gap may be used to protect the pole. here the screening action is suflicient and the distance between the ends of the members 33 and 84 is reduced so that a discharge will take place across their ends before discharge will take place along or through the pole, it will be effectively protected from shattering during electrical storms and at the same time the insulated zones will add materially to the insulation to ground and prevent flash-over between conductor and arm.

Where the insulating section 32 is sufficient to prevent an arc to ground, a discharge between the conductor 37 and the cross-arm will do no damage, for as soon as the crossarm and conductor are raised to approximately the same potential, the arc will die out. This is particularly true where the resistance to ground is high. If, on the other hand, conductors on different phases flash to the arm at the same time, a short circuit will usually result regardless of the insulation to ground. It is evident that as the potential difference between the conductor 37 and the cross-arm 27 or pin 30 becomes less, the danger of flash-over will be reduced. The release of a bound charge due to the discharge of a cloud overhead will produce a high momentary voltage on the conductors 87. A portion of this charge will be transferred to the cross-arms owing to the electrostatic capacity of the insulator. This will result in a voltage drop across the insulating section of the pole. In general, however, the electrostatic capacity of the metallic portion of the structure to ground is too high to get the best results. This is further aggravated by leakage through the resistance element 36, particularly where the latter is relatively low to take care of heavy leakage on the insulators. If the charge on the cross-arms can be increased so as to raise the potential at the same time as the maximum potential exists on the conductors 37, it is evident that the condition will be improved. This may be materially improved by using a static or charging wire 38 mounted on an insulator 39. The pin 40 supporting the insulator is bonded to the cross-arms by a jumper 31. By giving this insulator a relatively high electrostatic capacity the static wire 88 will tend to raise materially the potential of the metallic structure supporting the insulators. In this case the static wire 38 can be made use of to equalize the potential on the supporting structure and the conductor, but since there is no direct contact between the metallic structure and the upper part of the pole, there will be no direct path to ground through the static wire in case an insulator flashes-over due to an abnormal surge or due to shunting of the insulator by a bird or squirrel. The static wire 38 can be sectionalized between supporting structure so that a large or small section will be available for charging the pole, as desired, or it may run the entire length of the system without grounding or ground occasionally. While the static wire will tend to keep down the bound charge used in the manner shown, it will tend to charge the section of the structure above the insulating Zone and thereby tend to reduce the dif ference in potential between the conductor and supporting structure which tends to cause an arc to ground.

I claim- 1. In combination, a wood pole having an insulator supported near the top thereof, a transmission line carried by said insulator, a lightning rod projecting above said pole and insulated from said transmission line and a discharge member connected with said lightning rod near the top of said pole, said discharge member being inclined gradually away from said pole and terminating at a point spaced away from the surface of said pole and a grounded member fo'ming an arcing gap from said point to ground.

2. A conductor support comprising a wood pole, an insulator mounted on said wood pole, a transmission line carried by said insulator, a lightning rod projecting above said pole, a conductor connected with said lightning rod and shunting a portion upon the top of said pole and a high resistance leakage conductor connecting said lightning rod with ground the resistance of said leakage conductor being sufliciently great to provide a leak age path to ground from said conductor having a conductivity commensurate with that of the leakage path from said transmission line to ground.

8. A conductor support comprising a wood pole, an insulator mounted on said pole near the top thereof, a transmission line carried by said insulator, a lightning rod carried by said pole and projecting above the top thereof and insulated from said transmission line, a conductor connected wi h said lightning rod and shunting a pole, an arcing horn connected with said lightning rod and inclined outwardly away from the surface of said pole for directing an arc to ground away from said surface a grounded member forming with said horn an arcing gap and a high resistance leakage conductor extending from said lightning rod to ground.

i. A conductor support comprising a wood pole having cross-arms thereon, insulators mounted on said cross arms, transmission lines carried by said insulators, metallic members mounted on said pole adjacent said transmission lines but insulated therefrom, a lightning rod extending upwardly from said metallic members and shunting a portion of said pole adjacent said conductors, said pole having an insulating section below said lightning rod and a hi h resistance leakage path shunting said insulating section the resistance of said leakage path being great enough to retard the escape. thereover of an abnormal charge on said metallic members sinhciently that the time required for such escape is approximately that required for a like charge on said transmission line to become dissipated.

5. A conductor support comprising a wood pole, an insulator mounted on said pole near the top thereof, a transmission line carried by said insulator, a lightning rod connected with said pole and extending above the top thereof but insulated from said transmission line and from ground and shunting a portion of the top of said pole, said pole having an insulat'ng section below said lightning rod. means for directing the discharge over said insulating section away from the surface thereof and a high resistance leakage path shunting said insulating section.

6. A wood pole having an insulator mounted thereon, a transmission line. carried by said insulator, a charge receiving element mounted on said pole adjacent said transmission line but insulated therefrom, a charging conductor mounted on said pole and insulated from said charge receiving element and means forming a discharge gap between said charging conductor and charge receiving element.

7. A conductor support comprising a wood pole, a plurality of insulators mounted on said pole, a metallic element mounted on said pole adjacent said insulators, transmission portion of the top of said.

conductors carried by said insulators, a charging conductor mounted on said pole, means forming a, discharge gap between said charging conductor and metallic element and means for directing discharge from said metallic element away from the surface of said pole. V

8. A transmission line support comprising a wood pole having cross-arms thereon, insulator pins secured to said cross-arms, insulators mounted on said pins, transmission conductors mounted on said insulators, means for electrically connecting said insulator pins said connecting means and pins being insulated from ground and a high resistance leakage conductor extending from said connecting means to ground, the resistance of said leakage conductor being sufficient to retard escape of an abnormal charge from said connecting means for a period commensurate with that required for the escape of a similar charge from said transmission conductor.

9. A transmission line comprising a wood pole having cross-arms thereon, pins mounted on said cross-arms, insulators carried by said pins, transmission conductors mounted on some of said insulators, a charging line mounted on one of said insulators, means for electrically connecting said insulator pins, an arcing member spaced from said pole and connecting with said pin connecting means a grounded member forming an arcing gap from said arcing member to ground and means forming an arcing gap between said charging conductor and pin connecting means.

10. A transmission line support comprising a pole having cross-arms mounted thereon, insulators mounted on said cross-arms, a lightning rod extending above said pole, transmission line conductors carried by a portion of said insulators, a charging conductor carried by one of said insulators, means for forming a discharge gap between said charging conductor and lightning rod, a high resistance leakage conductor connected with said lightning rod and bridging a portion of said pole and arcing horns also bridging a portion of said pole.

11. In combination, a wood pole, a pair of cross-arms mounted on said pole, metallic braces for said cross-arms, insulator pins carried by said cross-arms, insulators mounted on said pins, three transmission line conductors carried by respective insulators on said pins, a charging conductor carried by a fourth insulator, a lightning rod mounted on said pole and projecting above the top thereof, said lightning rod, braces and insulator pins being electrically connected, arcing horns forming a discharge gap between said charging conductor and the connecting metallic parts on said pole, discharge horns gradually inclined out- S i MW Wardly from said pole and forming an arcing gap from said metallic parts to ground 1n spaced relation to the surface of said pole and a high resistance leakage conductor shunting the portion of said pole.

12. In combination, a Wood pole, an insulator mounted thereon, a transmission line carried by said insulator, a lightning rod mounted on said pole, a charging conductor mounted on said pole, a metallic charge receiving member mounted on said pole in the vicinity of said conductor but insulated therefrom and from ground and connected with said lightning rod, means forming a discharge gap between said conductor and metallic member, means forming a leakage path of several thousand ohms resistance between said metallic member and ground, and a discharge gap spaced from said pole and arranged parallel with the high resistance portion of said leakage path.

In testimony whereof I have signed my name to this specification on this 27th day of May, A. D. 1926.

ARTHUR O. AUSTIN.