WO2007133202A1

WO2007133202A1 - Integrated outdoor termination for a high voltage cable

Info

Publication number: WO2007133202A1
Application number: PCT/US2006/018367
Authority: WO
Inventors: Zhou Ming Yang
Original assignee: G & W Electric Company
Priority date: 2006-05-11
Filing date: 2006-05-11
Publication date: 2007-11-22
Also published as: MX2008014201A; EP2016595A4; CA2650516A1; CA2650516C; CN101479814A; EP2016595A1; CN101479814B; BRPI0621663A2

Abstract

An integrated outdoor terminal is disclosed that reduces the effects of environmental and electrical stresses by integrating a first portion, second portion and plurality of sheds into a one-piece insulation body. The first portion includes an integrated first connector for connecting the outdoor terminal to a high voltage cable. The second portion functions as a stress cone and connects with a second terminal for connecting with ground. The first portion has a generally cylindrical shape and the stress cone has a generally conical shape. The first portion transitions into the second portion without any abrupt changes in cross-sectional area, thus avoiding an increase in electric fields. The integrated outdoor termination may be prefabricated using a material such as silicone. The sheds extend approximately perpendicular to and may be uniformly distributed along the longitudinal axis of the insulation body. By uniformly distributing the sheds, the risk of flashover is avoided.

Description

INTEGRATED OUTDOOR TERMINATION FOR A HIGH VOLTAGE CABLE

BACKGROUND

[001] In many cases, electric power is transmitted through cables located outdoors. In order to reduce power losses caused by the resistance in the cables, the power is often transmitted at voltages exceeding 5OkV. In order to end the cables, a transition must be connected between the cable conductor and the ground. Such a transition must be able to withstand the voltage drop between the cable conductor and ground. These transitions are generally referred to as "terminations." Due to the high voltages of the cables and the fact that the cables and terminations are located outdoors, the terminations are subject to electrical and environmental stresses. The environmental stresses include water, dirt, snow, wind and fluctuations in temperature. The electrical stresses are generally caused by the termination itself and include high electric field intensity, leakage current ("leakage") and flashover. [002] Outdoor terminations generally include a sub-assembly structure. In a sub-assembly structure, multiple components are assembled to form the termination. An example of an outdoor termination for a high voltage cable with a sub-assembly structure is shown in Figure 2. The outdoor termination 200 includes three components; two insulation kits 202, 204 and a stress cone 208. The first insulation kit 202 includes a first terminal 212 for connecting the termination 200 to a high voltage cable (not shown). The high voltage cable enters the termination 200 through the first terminal 212. The portion of the cable housed by the first insulation kit 202 is stripped back to the insulation and connected to the first terminal 212 via a connector. The stress cone 208 includes a second terminal 214 for connecting a ground cable to ground (not shown). The second terminal 214 includes an entrance housing through which the ground cable enters the termination 200, and a clamp that connects the ground cable to the second terminal 214.

[003] The two insulation kits 202, 204 include multiple sheds 206. The sheds 206 reduce the dirt and/or water that accumulate on the termination, which reduces leakage and the occurrence of flashover. The two insulation kits 202, 204 are connected together and the second insulation kit 204 is connected to the stress cone 208. The outdoor termination 200 may be prefabricated and assembled before use. [004] To improve the mechanical and electrical performance of the termination, the insulation body may be fabricated from silicone. Silicone provides anti-dirt and anti-water capabilities and may reduce flashover and arcing in the termination. In addition, silicone can extend the range of temperatures and other environmental factors that the termination can withstand.

[005] Even with the advantages provided by silicone, terminations with a sub-assembly structure still suffer from the effects of electrical and environmental stresses. For example, the highest electrical field intensity of the termination 200 occurs at the junction between the insulation kit 204 and the stress cone 208. Because there are no sheds at this location, dirt and water accumulate causing flashover, particularly when the environment includes rain or humidity. Further, the lack of sheds causes current leakage at the junction between the insulation kit 204 and the stress cone 208 and the junction between the insulation kits 202, 204.

SUMMARY

[006] An integrated outdoor terminal is disclosed that reduces the effects of environmental and electrical stresses to which it is subjected by integrating a first portion, second portion and plurality of sheds into a one-piece insulation body. The first portion, second portion and sheds may be molded together into a single piece so that the insulation body does not include cross-sectional seams. The first portion includes an integrated first connector for connecting the outdoor terminal to a high voltage cable. The second portion connects with a second terminal for connecting with ground. The second portion functions as a stress cone. [007] The first portion has a generally cylindrical shape and the stress cone has a generally conical shape. The first portion transitions into the second portion without any abrupt changes in cross-sectional area, thus avoiding an increase in electric fields. The integrated outdoor termination may be prefabricated using a material such as silicone. [008] The sheds extend approximately perpendicular to and may be uniformly distributed along the longitudinal axis of the insulation body. By uniformly distributing the sheds, the risk of flashover is avoided. BRIEF DESCRIPTION OF THE DRAWINGS

[009] The invention can be better understood with reference to the following drawings and description. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. In the figures, the same reference symbols designate the same parts, components, modules or steps, unless and to the extent indicated otherwise.

[0010] Fig. 1 is an isometric view of an outdoor termination;

[0011] Fig. 2 is an exploded isometric view of an outdoor termination according to the prior art;

[0012] Fig. 3 is a front plan view of an outdoor termination; and

[0013] Fig. 4 is a cross-sectional view of the outdoor termination of Fig. 3.

DETAILED DESCRIPTION

[0014] Integrated terminations for high voltage cables that are suitable for outdoor use (each an "integrated outdoor termination") are presented. The integrated outdoor termination includes one-piece, which generally eliminates seams and discontinuities between what would otherwise be separate components. Therefore, the integrated outdoor termination reduces the effects of environmental and electrical stresses. Fig. 1 illustrates an example of an integrated outdoor termination 100. The integrated outdoor termination 100 generally includes a first portion 116 and a second portion 114 that functions as a stress cone. The integrated outdoor termination 100 may also include a plurality of sheds 112 extending approximately perpendicular to the external surface 120 of the insulation body 110. The first portion 116, stress cone 114 and sheds 112 are completely integrated so as to form a one- piece insulation body 110.

[0015] The integrated outdoor terminal 100 may also include a first terminal 102. The first terminal 102 may be integral with the first portion 116 and enables the integrated outdoor terminal 100 to connect with a high voltage cable (not shown). The first terminal 102 may include an unshielded crimped-on connector (not shown). To connect the high voltage cable with the termination 100, the insulation on the high voltage cable may be stripped back and the crimped-on connector crimped onto the cable. However, the first terminal 102 may include other types of connectors. The integrated outdoor terminal 100 may also include a second terminal 104 that may be integrated with the stress cone 114 (only a portion of which is shown), which connects the integrated outdoor terminal 100 with ground (not shown). [0016] The first portion 116 may include a generally cylindrical shape and the stress cone 114 may include a shape that is generally conical. Where the insulation body 110 transitions from the first portion 116 to the stress cone 114, the stress cone 114 includes a cross-sectional diameter that is about equal to that of the first portion 116 and increases in the direction of the second terminal 104. Thus, an abrupt change in diameter between the first portion 116 and the second portion 114, which can lead to increased electrical fields, may be avoided. In addition, the cross-sectional diameter of the stress cone 114 may reach its greatest value at a point between the first portion 116 and the second terminal 104, and then may decrease in the direction of the second terminal 104. However, the cross-sectional diameter of the stress cone 114 is generally larger, in all locations, than the cross-sectional diameter of the first portion 116.

[0017] The insulation body 110 generally includes sheds 112 located along and integral with its external surface 120. Thus, both the first portion 116 and the stress cone 114 generally include multiple sheds 112. The sheds 112 may be uniformly distributed along the longitudinal axis 126 of the insulation body 110. By uniformly distributing the sheds 112, particularly those sheds 112 in the area of greatest electric field density 122, the risk of flashover, such as that caused by rain and accumulation of dirt, is avoided. [0018] To create the one-piece integrated outdoor termination 100, the first portion 116, second portion 114 and the sheds 112 are molded together to form a single piece. Thus, the insulation body 110 generally does not include cross-sectional seams within the first portion 116 or between the first portion 116 and the stress cone 114. The integrated outdoor termination 100 may be prefabricated using a material such as silicone. [0019] An example of an integrated outdoor termination is shown in Figs. 3 and 4. A shown in Fig. 4, the integrated outdoor termination 300 includes a longitudinal axis 378 and may be approximately symmetrical along this axis 378. The terminal includes a first portion 316, a second portion 314, and multiple sheds 312. These elements are integrated with each other to form a single-piece insulation body 310. The insulation body 310 is integrated with the first terminal 302 and the second terminal 304 to form the integrated outdoor termination 300 as a single-piece. In addition, the first terminal 302, first portion 316, second portion 314 and the second terminal 304 are integrated so that the transitions among their outer surfaces are generally smooth and without approximately coaxial seams or discontinuities. Thus, because the outdoor termination 300 includes one, generally smooth piece, leakage due to seams and/or discontinuities is avoided.

[0020] The sheds are integrated with the outer surface 320 of the insulation body 310 so that they may be distributed along the outer surface 320 and approximately perpendicular to the longitudinal axis 378 of the terminal 300. The sheds 312 may be uniformly distributed. Because the termination 300 includes a single-piece, sheds 312 may be located along the second portion 314, which functions as a stress cone, and along the transition between the first portion 316 and the second portion 314. Thus, leakage and flashover may be reduced in these areas, which typically experience the highest electric field intensity. [0021] The insulation body 310, first terminal 302 and second terminal 304 include a bore 360 for receiving a high voltage cable and a ground cable. The first terminal 302 may include a crimped-on connector that crimps onto the high voltage cable. The second terminal 304 includes a connector 370 and a ground bore 374. The ground bore 374 may receive ground cable with its insulation exposed and the bore may receive the ground cable with its conductor exposed. The connector 370 secures the ground cable to the second terminal 304. [0022] Fig. 3 includes exemplary dimensions, in millimeters, for an integrated outdoor termination 300 suited for 138 kilovolts (kV) applications. However, the integrated termination 300 may be scaled for higher voltage classes, such as, 220 kV and 500 kV or scaled down for applications at lower voltages such as 69 kV. The total length of the integrated outdoor termination 300, including the first 302 and second 304 connectors is approximately 1400 mm. The diameter of the first terminal is approximately 86 mm, the distance from the end of the second connector 304 (only a portion of which is shown) to the first shed on the stress cone 314 is approximately 141 mm, and the widest part of the stress cone 314, including the shed 312 is 332 mm. The sheds 312 of the termination 300 form an angle of 8 degrees from a horizontal line approximately perpendicular to the longitudinal axis 326 of the termination 300. The end portion 311 of the sheds 312 is generally concave with respect to the second connector 304 so that the end portion 311 points towards the second connector 304 with a radius of approximately 2.5 mm. The sheds 312 include a generally convex portion 321 with a radius of approximately 12 mm, which provides a transition from the sheds 312 into the exterior surface 320 of the insulation body 310. Further, the sheds 312 extend from the exterior surface 320 of the insulation body 310 by 45 mm or 70 mm and are approximately equally spaced along the exterior surface 320 of the insulation body 310 by approximately 48 mm to approximately 52 mm. [0023] While various embodiments of the invention have been described, it will be apparent to those of ordinary skill in the art that many more embodiments and implementations are possible within the scope of the invention. Accordingly, the invention is not to be restricted except in light of the attached claims and their equivalents.

Claims

CLAIMSWhat is claimed is:

1. A one-piece termination for a high voltage cable comprising: a stress cone configured to connect with ground; and a portion integrated with the stress cone and configured to connect with the high voltage cable.

2. The termination of Claim 1 further comprising a first terminal integrated with the portion.

3. The termination of Claim 2, wherein the first terminal is configured to receive the high voltage cable.

4. The termination of Claim 1 further comprising a second terminal integrated with the stress cone.

5. The termination of Claim 4, wherein the second terminal is configured to receive a ground cable.

6. The termination of Claim 1 further comprising a plurality of sheds.

7. The termination of Claim 6, wherein the plurality of sheds is integrated with the portion.

8. The termination of Claim 6, wherein the plurality of sheds are approximately uniformly distributed along the portion.

9. The termination of Claim 6, wherein the plurality of sheds is integrated with the stress cone.

10. The termination of Claim 6, wherein the plurality of sheds are approximately uniformly distributed along the stress cone.

11. The termination of Claim 1 , wherein the portion includes an approximately cylindrical shape.

12. The termination of Claim 1, wherein the stress cone includes an approximately conical shape.

13. The termination of Claim 1 further comprising silicone.

14. The termination of Claim 1, wherein the portion smoothly transitions into the stress cone.

15. The termination of Claim 1, wherein the high voltage cable is configured to support a voltage of at least approximately 69 kV.

16. A termination for a high voltage cable comprising: a stress cone configured to connect with ground; a portion configured to connect with the high voltage cable; and a plurality of sheds; wherein the stress cone, portion and plurality of sheds are integrated to form a single piece.

17. A method for fabricating a termination for a high voltage cable, the method comprising: molding a stress cone configured to connect with ground; molding a portion configured to connect with the high voltage cable; and molding a plurality of sheds; wherein the stress cone, portion and plurality of sheds are molded to form a single integrated piece.

18. The method of Claim 17, wherein the termination is fabricated prior to installation.