US3300575A

US3300575A - Conductor suspension assembly

Info

Publication number: US3300575A
Application number: US503764A
Authority: US
Inventors: Short Herbert Douglass
Original assignee: Lacal Industries Ltd
Current assignee: Lacal Industries Ltd
Priority date: 1965-10-23
Filing date: 1965-10-23
Publication date: 1967-01-24
Anticipated expiration: 1984-01-24

Description

1967 H. D. SHORT 3,300,575

CONDUCTOR SUSPENSION ASSEMBLY Filed Oct. 25, 1965 INVENTOR. H. D. SH ORT fmww hza ATTORN EYS United States Patent 3,300,575 CONDUCTOR SUSPENSION ASSEMBLY Herbert Douglass Short, Newmarket, Ontario, Canada,

assignor to Lacal Industries Limited, Newmarket, Ontario, Canada Filed Oct. 23, 1965, Ser. No. 503,764 3 Claims. (Cl. 174-144) This invention relates to a high voltage electricity con ductor suspension assembly.

In the transmission of electrical energy it is common to transmit each phase by groups of spaced apart conductors. The phases or groups are spaced apart and are often at potential differences in the order of over 400 kv. The conductor groups are supported by conductor suspension assemblies at towers at spaced apart points along the line. This invention relates to such a conductor assembly and has as its principal object the reduction of corona losses in transmission by the provision of an assembly that has a higher corona inception voltage. Corona effect is usually most pronounced at the towers.

Corona losses in the high voltage transmission of electrical energy can be very substantial and tend to limit the voltage that a line can be operated at under many conditions. .Corona may be described as a manifestation of ionization formed in air at breakdown of the air due to high potentials. It represents a loss of electrical power from the transmission line and must be kept within tolerable limits. At the same time it is desired to transmit as much power as possible over a given line.

It will be apparent that any device that has the effect of raising the ionization ignition or corona inception voltage of a line will increase the line efliciency because it will raise the operating voltage for a given tolerable corona loss.

It is well known that corona is most apparent at sharp edges in a piece of conducting equipment and designers usually try to eliminate sharp edges where corona is a factor to be designed for. This invention eliminates the effect of sharp edges in a suspension clamp by the unique expedient of providing a spheroidal shielding link to connect each conductor clamp of the assembly to the suspension plate, such spheroids being of sufiicient dimensions to function as electrostatic shields thereby reducing the intensity or concentration of the electric field and at the same time increasing the electrostatic capacity of the insulators immediately adjacent to the suspension assembly which in turn reduces the voltage distribution across the insulators and hence their susceptibility to corona formation.

Generally speaking, a conductor suspension assembly according to this invention comprises a suspension plate, a plurality of conductor clamps each having jaws with a jaw axis adapted to align with the axis of a conductor in use and a spherical link menrber connecting each of said conductor clamps to said suspension plate with its jaw axis substantially parallel to the jaw axis of the other of said plurality of conductor clamps. The invention will be clearly understood after reference to the following detailed specification read in conjunction with the drawings.

In the drawings:

FIGURE 1 is an illustration of a conductor suspension assembly according to the invention with one clamp and its link in exploded form and with one link broken away;

FIGURE 2 shows a portion of a clamp, and

FIGURE 3 illustrates the connection of a link to an arm of the plate.

The conductor suspension assembly shown comprises a suspension plate adapted for suspension from a transmission tower in the usual way and preferably made from aluminum according to standard practice. There are four metal similar conductor clamps carried by plate 10', each "ice comprising cooperating

jaws

12 and 14 operable into and out of clamping arrangement with respect to each other by bolts 16 and nuts 18. In use cable is gripped in the longitudinally extending cylindrical cavity 20, the axis of which is herein defined as the jaw axis.

It will be noted that the cross-section of the conductor clamps is oval in shape and that the jaw axis, which coin ides in use with the longitudinal axis of a cable gripped within the jaw, is located towards the outer end of the jaw cross-section. These clamps have been designed with a view to having the cross-section thereof conform to an equipotential surf-ace of the electrostatic field created by four current carrying conductors mounted in the assembly. The shaping of the cross-section of the clamps with a view to having their outer surface correspond to the equipotential surface of the electrostatic field created has been described and claimed in my copending United States application Serial No. 376,186, filed June 18, 1964.

A metal spheroidal shielding link 22, in this case essentially spherical, connects each of the clamps to the plate 10. In the embodiment illustrated the shielding link 22 is cast integral with the jaw section 12. It has a socket [formed in its free end and is joined to the plate 10 by means of a bolt 24 that extends through one side of the sphere, through a hole 26 in an arm of plate 10 and into a threaded bore 25 in the other side of sphere 22. Bolt 24 preferably has a lock washer under its head.

The socket into which arm 26 extends is formed to per mit a certain amount of pivotal movement between the parts, as will be apparent from FIGURE 3, to permit variation of the angle of inclination of the conductors carired thereby at the towers in use.

In use four conducting cables, constituting a bundle, are retained by the four clamps of the assembly which is suspended from a transmission tower of a power transmission system. The four cables each commonly carry current of one of three phases in a three phase system and adjacent and similar assemblies carry similar conducting cables of the other phases.

It is well understood that under such conditions loss due to corona increases with the intensity of the electrostatic field at the surface of conducting bodies. Thus, if the bodies have sharp points, the intensity of the electric field at those points is most likely to be quite high and corona will manifest itself at those points, as the transmitting potential increases. By increasing the surface area of such points by rounding the body the intensity of the electric field at the surface is reduced and the voltage at which corona effect becomes apparent is raised.

This invention employs a spheroidal connecting device for connecting the clamp to the plate and is thought to be the ultimate type of connection for connecting the clamp to the plate from the point of view of reducing corona loss. The diameter of the spheroidal link 22 must be large enough to result in a surface area that reduces the intensity of the electrostatic field at the surface of the sphere to a point where no objectionable corona effect exists when each of the assembly clamps has a conductor clamped therein and the desired operating transmission voltage exists. It will be apparent that as the transmitting volt-age increases that the size of the sphere 22 will have to be increased in order to reduce the electrostatic intensity at the surface of the sphere to a value that will eliminate or reduce corona losses to the desired level. Thus, the surface area of the sphere 22 shields the sharp points of the connection of the clamp to the plate that would otherwise exist if the sphere were not incorporated. For example, the bolt 24 the head of which is embedded in one side of the sphere 22 would if unshielded by the sphere 22 present a rather sharp corner at which the electrostatic field surrounding the conducting cables in use would tend to be intensified. Corona would tend to form at this and other sharp points at the connection first. However, by providing the shielding sphere the electric field intensity is reduced at this point for *a given voltage and it is a matter of choice to select the size of the sphere that will reduce the intensity to a point that will eliminate corona at this point in any given design.

A sphere 22, having a diameter of about 3% inches, has proved satisfactory in eliminating corona effect in tests where a bundle of conductors carried in the assembly as illustrated at spacings of about 19 inches from each other in the horizontal and vertical direction was operated at a voltage of 310 kilovolts to ground at a distance of 10 feetto ground.

The shape of link connector 22 has been illustrated as spherical but itis not intended that the invention be so limited. A link of a shape approaching the shape of a sphere i.e. spheroidal would fulfill the purpose of an eflective shield for the sharp edges. Thus an ellipsoidal or similar solid of revolution of a curve is contemplated. The essence of the invention is a link having a rounded but not necessarily round outline that will result in a surface area to reduce electrostatic field intensity and act as an efficient corona shield.

What I claim as my invention is:

1. A high voltage conductor suspension assembly for a bundle of conductors of a single phase comprising a suspension plate, a plurality t conductor clamps, each having jaws with a jaw axis adapted to align with the axis of a conductor in use, and a spheroidal corona shielding link members between each clamp and said conductor plate having a spheroidal interconnecting part electrically connecting each of said conductor clamps to said suspension plate with the jaw axis of each of said conductor clamps substantially parallel to the jaw axis of each of the other of said plurality of conduct-or clamps.

2. A high voltage conductor suspension assembly as claimed in claim 1, in which said spheroidal member is formed from a common piece of material with said respective clamp.

3. A high voltage conductor assembly as claimed in claim 1 in which said spheroidal member is spherical.

References Cited by the Examiner UNITED STATES PATENTS 2,806,897 9/ 1957 Sheadel et al 174144 X FOREIGN PATENTS 65 3,027 11/1962 Canada. 685,503 1/1953 Great Britain. 63,677 2/ 1913 Switzerland.

OTHER REFERENCES Ohio Brass Advertisement, Electrical World, vol. 143,

No. 11, March 14, 1955, page 11.

LARAMIE E. ASKIN, Primary Examiner.

Claims

1. A HIGH VOLTAGE CONDUCTOR SUSPENSION ASSEMBLY FOR A BUNDLE OF CONDUCTORS OF A SINGLE PHASE COMPRISING A SUSPENSION PLATE, A PLURALITY OF CONDUCTOR CLAMPS, EACH HAVING JAWS WITH A JAW AXIS ADAPTED TO ALIGN WITH THE AXIS OF A CONDUCTOR IN USE, AND A SPHEROIDAL CORONA SHIELDING LINK MEMBERS BETWEEN EACH CLAMP AND SAID CONDUCTOR PLATE HAVING A SPHEROIDAL INTERCONNECTING PART ELECTRICALLY CONNECTING EACH OF SAID CONDUCTOR CLAMPS TO SAID SUSPENSION PLATE WITH THE JAW AXIS OF EACH OF SAID CONDUCTOR CLAMPS SUBSTANTIALLY PARALLEL TO THE JAW AXIS OF EACH OF THE OTHER OF SAID PLURALITY OF CONDUCTOR CLAMPS.