Assembly for mitigating dry-band arcing in distribution line insulators

Abstract

To provide a cover configured for a polymer insulator for a distribution line, which mitigates dry band arcing from occurring along the insulator.SOLUTION: An assembly 300 for mitigating dry band arcing includes: a polymeric insulator 100 for a power distribution line; and a cover 200. The cover 200 has a main body or a shroud part 201. The main body 201 includes a side wall 202 and an upper wall 206 which define a cavity 203. The cavity 203 receives one or more of annular sheds or skirts 118 of an insulator 100. The main body 201 of the cover 200 covers one or more of the annular sheds 118 at an upper part of the insulator 100. In other words, the cover 200 is attached to an upper end of the insulator 100.SELECTED DRAWING: Figure 4B

Description

[Technical Field]

[0001] The present invention relates to covers for power distribution line insulators, and more particularly to covers and assemblies configured to mitigate dry band arcing in polymeric power distribution line insulators. [Background technology]

[0002] Support structures, such as utility poles, are often used to suspend power transmission lines, such as distribution lines, above the earth's surface. These support structures are typically located outdoors and can be in a variety of different configurations for suspending one or more lines. Composite polymer insulators are used to support power conductors and secure the power conductors to the support structures. In particular, composite polymer insulators are commonly used to support and attach high-voltage (HV) power lines. As used herein, "high voltage" refers to power lines operating at voltages of 69 kilovolts (kV) or greater. Composite polymer insulators typically include an elongated, electrically insulating core, an electrically insulating housing surrounding the core, and end fittings attached to the ends of the core. See, for example, Figures 1A and 1B. The core provides mechanical strength. The end fittings may be formed from metal (e.g., steel) and configured to couple the ends of the insulator to the cable and / or support. The core may be formed from a fiberglass composite material (e.g., fiberglass reinforced resin). The housing may be formed from an elastomeric material (e.g., silicone rubber). The housing may be attached to the core by molding (e.g., injection molding) or by inserting the core into a pre-formed housing.

[0003] The housing may include radially outwardly protruding sheds. The sheds help maximize the creepage distance (or leakage distance) of the insulator by increasing the surface distance from one end of the insulator to the other, and help remove environmental contaminants (e.g., salt, pollutants, dust) from the insulator in wet conditions (e.g., rain). Creepage or leakage distance refers to the shortest distance along the surface of the insulator between its conductive ends. Environmental contaminants can have a strong effect on insulator performance. The more contaminants there are on the insulator's surface, the more likely leakage current will occur because many of the contaminants are conductive. It is desirable to have an insulator shape that helps prevent current from "leaking" along the insulator's surface from an energized electrical circuit to ground. Current leakage can cause damage and eventual failure of the insulator. Summary of the Invention [Problem to be solved by the invention]

[0004] One problem with the aforementioned transmission lines, particularly distribution lines transmitting high-voltage power, is dry-band arcing. Dry-band arcing is a common phenomenon observed in composite polymer insulators for these distribution lines, especially in contaminated (e.g., dirty, wet) service areas. When the insulator becomes wet, a thin film of water can form on the surface and small leakage currents can begin to flow. When this thin film of water evaporates due to increased ambient temperature, a "dry band" forms on the insulator's surface. The dry band impedes current flow, and a voltage gradient appears across the dry band. The voltage gradient exerts electrostatic stress across the surface, causing further water evaporation and an increase in the dry band width, thus creating a larger voltage gradient and resulting in small arcing. Dry band arcing can produce visible arcing and audible noise, and often results in customer complaints. These dry band arcing events can last for days to weeks under certain environmental conditions, for example, when there is a lot of dew / humidity. [Means for solving the problem]

[0005] Embodiments of the present invention relate to covers configured for use with polymeric insulators for power distribution lines to help mitigate dry band arcing along the insulator. In some embodiments, the cover helps prevent a film of water from forming on the housing and / or annular shed of the insulator, thereby helping to mitigate conditions that can result in dry band arcing. Additionally, in some embodiments, the cover increases the creepage or leakage distance along the surface of the insulator between the conductive ends of the insulator, thereby helping to mitigate current leakage that can cause damage and / or ultimate failure of the insulator.

[0006] A further embodiment of the present invention relates to an assembly configured to mitigate dry band arcing. The assembly includes a polymer insulator for electric power distribution lines, the polymer insulator having a core, two end fittings attached to opposite ends of the core, and a housing circumferentially surrounding the core. The housing includes upper and lower end fittings that respectively overlap the respective end fittings and a series of axially spaced annular sheds that protrude radially outward from the outer surface of the housing. The assembly further includes a cover having a body including side walls and a top wall, the side walls and top wall together defining a cavity. A lower edge of the side walls defines a lower opening, and the top wall includes an upper opening, both of which communicate with the cavity. At least a portion of the upper end of the housing is received through the top opening of the cover, and one or more of the annular sheds are received within the cavity of the cover.

[0007] A further embodiment of the present invention relates to a cover for an insulator for electrical distribution lines. The cover comprises a body including a side wall and a top wall. The side wall and top wall together define a cavity. A lower edge of the side wall defines a lower opening communicating with the cavity, and an upper surface of the top wall of the cover is tapered or angled. The cover further comprises a collar extending upward from the top wall, and an upper edge of the collar defines an upper opening communicating with the cavity. The upper opening is configured to receive at least a portion of the insulator housing, and the cavity is configured to receive one or more annular sheds extending radially outward from the insulator housing.

[0008] A further embodiment of the present invention relates to a method for mitigating dry band arcing in polymeric insulators for power distribution lines. The method includes: (a) providing a polymeric insulator for electric power lines having a core, two end fittings attached to opposite ends of the core, and a housing circumferentially surrounding the core, the housing including upper and lower ends respectively overlapping the respective end fittings and a series of axially spaced annular sheds protruding radially outward from the outer surface of the housing; (b) providing a cover having a body including side walls and a top wall, the side walls and top wall together defining a cavity, the lower edges of the side walls defining a lower opening, the top wall having an upper opening, and the lower and upper openings communicating with the cavity; (c) pressing the cover downward onto the insulator's housing so that one or more annular sheds of the insulator are received in the cavities of the cover; and (d) continuing to press the cover downward until at least a portion of the upper end of the housing is received through the upper opening of the cover.

[0009] Further features, advantages, and details of the present invention will become apparent to those skilled in the art upon review of the following drawings and detailed description of the preferred embodiments, which are merely illustrative of the invention.

[0010] The invention will now be described, by way of example only, with reference to the accompanying drawings, in which: [Brief explanation of the drawings]

[0011] [Figure 1A] FIG. 1 is a perspective view of a typical polymer insulator for power distribution lines. [Figure 1B] FIG. 2 is a side cross-sectional view of the insulator of FIG. [Figure 2] FIG. 2 is a side view of a cover of a polymer insulator for electric power distribution lines according to an embodiment of the present invention. [Figure 3] 1B is an enlarged side view of the cover of FIG. 2 attached to the insulator of FIG. 1A. [Figure 4A] FIG. 3 is a perspective view of an assembly configured to mitigate dry band arcing using the cover of FIG. 2 in accordance with an embodiment of the present invention. [Figure 4B] FIG. 4B is a cross-sectional side view of the assembly of FIG. 4A. [Figure 5A] FIG. 1 is a perspective top view of an alternative cover for a polymeric insulator for electrical distribution lines according to an embodiment of the present invention. [Figure 5B] FIG. 5B is a side cross-sectional view of the cover of FIG. 5A. [Figure 5C] FIG. 5B is an exploded perspective view of the cover of FIG. 5A. [Figure 6A] FIG. 6 is a perspective view of another assembly configured to mitigate dry band arcing using the cover of FIGS. 5A-5C, in accordance with an embodiment of the present invention. [Figure 6B] FIG. 6B is a cross-sectional side view of the assembly of FIG. 6A. [Figure 7] FIG. 10 is an exploded perspective view of another assembly configured to mitigate dry band arcing in accordance with an embodiment of the present invention. [Figure 8A] FIG. 8 is a perspective view of the assembly of FIG. 7. [Figure 8B] FIG. 8B is a cross-sectional side view of the assembly of FIG. 8A. DETAILED DESCRIPTION OF THE INVENTION

[0012] The present invention will now be described more fully hereinafter with reference to the accompanying drawings, which show exemplary embodiments of the invention. In the drawings, the relative sizes of areas or features may be exaggerated for clarity. However, this invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0013] When an element is referred to as being "coupled" or "connected" to another element, it is understood that the element can be directly coupled or connected to the other element, or intervening elements may be present. In contrast, when an element is referred to as being "directly coupled" or "directly connected" to another element, there are no intervening elements present. Like numbers refer to like elements throughout. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0014] Additionally, spatially relative terms such as "below," "lower," "bottom," "above," and "upper" may be used herein for ease of description to describe the relationship of one illustrated element or feature to another. These spatially relative terms are intended to encompass different orientations of the device during use or operation in addition to the orientation shown. For example, if the illustrated device were inverted, elements described as "below" or "beneath" another element or feature would then be oriented "above" that other element or feature. Thus, the exemplary term "below" can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations), and the spatially relative descriptors used herein may be interpreted accordingly.

[0015] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms unless the context clearly dictates otherwise. It will be further understood that the terms "comprises" and / or "comprising," as used herein, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0016] Unless otherwise specified, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms as defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant art, and will not be interpreted as an idealized or overly formal meaning unless expressly stated herein.

[0017] Hereinafter, embodiments of the present invention will be described in more detail with reference to FIGS. 1A to 8. FIG.

[0018] As previously mentioned, a known composite polymer insulator 100 is shown in Figures 1A and 1B. The insulator 100 can be used to mechanically separate and electrically isolate a first component from a second component. Typically, one component is a power transmission conductor and the other component is a power transmission conductor or a supporting structure. Generally, the insulator 100 has a longitudinal axis LL of the insulator and opposite axial ends 102A, 102B.

[0019] In some embodiments, insulator 100 forms part of an electrical power distribution system, such as, for example, a utility power distribution system. It will be understood that insulator 100 can be used in any application or electrical power distribution system in which composite polymer insulators of this type can be used. The support structure can take other forms, and the configuration of insulator 100 can be modified to accommodate different applications. For example, insulator 100 can be incorporated into a system as a standoff insulator between a conductor and a bracket. In other embodiments, insulator 100 is secured to and between two elongated conductors (e.g., power lines) by a coupling such that insulator 100 spans the distance between the conductors, mechanically separating and electrically insulating the conductors from one another.

[0020] As shown in FIGS. 1A and 1B, the insulator 100 includes a core 110 and a housing 112 (see also, e.g., FIGS. 4B, 6, and 7). The core 110 has a longitudinal axis LC-LC coaxial with the longitudinal axis LL of the insulator 100. The core 110 may be cylindrical and extend from a first or upper end 110A to an opposite second or lower end 110B. The core 110 may be formed from any suitable dielectric or electrically insulating material. End fittings 104, 106 are attached to opposite ends of the core 110. The end fittings 104, 106 may be formed from any suitable material and are typically formed from metals such as steel, cast or ductile iron, aluminum, or stainless steel.

[0021] Housing 112 circumferentially surrounds core 110. Housing 112 includes an upper end or upper mating portion 114 and a lower end or lower mating portion 116. Upper mating portion 114 overlaps end fitting 104, and lower mating portion 116 overlaps end fitting 106. A series of axially spaced annular sheds or skirts 118 project radially outward from the outer surface of housing 112. Housing 112 may be formed from any suitable dielectric or electrically insulating polymeric material, such as silicone rubber, ethylene vinyl acetate (EVA), ethylene propylene diene monomer (EPDM) rubber, or other suitable rubber or other elastomeric and / or polymeric materials. These components of insulator 100 are well known to those skilled in the art and need not be described in further detail herein.

[0022] Generally, the end of the insulator 100 that is connected to the power line (e.g., the top end 102A) has a higher electrical energy (higher voltage) than the opposite low-voltage or grounded end of the insulator 100 (e.g., the bottom end 102B). In other words, the electrical stress on the insulator 100 decreases along the longitudinal axis LL of the insulator as you move from the highly current-carrying (voltage) top end 102A to the low-voltage or grounded bottom end 102B. Dry band arcing is likely to occur adjacent the highly current-carrying top end 102A of the insulator 100.

[0023] 2 illustrates a cover 200 for an insulator 100 according to an embodiment of the present invention. As described in further detail herein, according to an embodiment of the present invention, the cover 200 can be configured for use with the insulator 100 of the power distribution line described herein (i.e., the assembly 300 shown in FIGS. 3-4B) to help mitigate dry band arcing along the insulator 100, for example, proximate the high voltage top end 102A of the insulator 100.

[0024] As shown in FIGS. 2-4B , the cover 200 includes a body or shroud portion 201. The body 201 includes a sidewall 202 and a top wall 206 that together define a cavity 203. In some embodiments, the sidewall 202 is cylindrical. As shown in FIG. 4B , the cavity 203 in the cover 200 is configured to receive one or more of the annular sheds or skirts 118 of the insulator 100. For example, as shown in FIGS. 3 and 4B , in some embodiments, the cavity 203 is sized and configured to receive two or three of the annular sheds 118 of the insulator 100. In other embodiments, the cavity 203 is sized and configured to receive four or more of the annular sheds 118 (see, for example, FIG. 6 ). Generally, the body 201 of the cover 200 covers one or more annular sheds 118 on top of the insulator 100, i.e., the cover 200 is attached to the upper end 102A of the insulator 100. The inner diameter (D) of the cavity 203 of the cover 200 may vary to accommodate different size sheds 118. For example, in some embodiments, the inner diameter of the cavity 203 may be from about 2 inches to about 7 inches.

[0025] A lower edge of side wall 202 defines a lower opening 207 that communicates with cavity 203. In some embodiments, top wall 206 includes an upper opening 205 that also communicates with cavity 203. In some embodiments, body 201 further includes a collar 204 extending upwardly from top wall 206. In some embodiments, an upper edge of collar 204 defines upper opening 205 that communicates with cavity 203. In some embodiments, upper opening 205 is sized and configured to form an interference fit with upper joint 114 of insulator 100. In some embodiments, cover 200 may be formed as a unitary or single piece. Cover 200 may be formed from silicone rubber, EVA, EPDM, or other suitable rubber or other elastomeric and / or polymeric material. In some embodiments, cover 200 is formed by injection molding.

[0026] 2, 3, and 4B, in some embodiments, the top surface of the top wall 206 may be tapered or angled. In some embodiments, the top wall 206 may be frusto-conical. For example, in some embodiments, the top surface of the top wall 206 may taper downward from the collar 204. The tapered or angled top surface or frusto-conical shape of the top wall 206 may allow water and / or other environmental contaminants to flow away from the top wall 206 and away from the insulator 100. As previously discussed, when the insulator 100 becomes wet, a film of water may form on the surfaces (e.g., the housing 112 and / or the annular shed 118) and small leakage currents may begin to flow. As this water film evaporates due to increased ambient temperature, a "dry band" forms on the surface that impedes current flow, creating a voltage gradient across the dry band. This voltage gradient exerts electrostatic stress across the surface, causing further evaporation and an increase in the dry band width, creating a larger voltage gradient and resulting in small arcs (i.e., dry band arcing). When placed on the insulator 100 (e.g., as part of the assembly 300 shown in FIGS. 3-4B ), the cover 200 helps prevent a water film from forming on the housing 112 and / or shed 118 of the insulator 100, thus helping to mitigate conditions that could result in dry band arcing. Additionally, the cover 200 increases the creepage or leakage distance along the surface of the insulator 100 between the conductive ends of the insulator 100, thereby helping to reduce current leakage that could cause damage and ultimate failure of the insulator 100.

[0027] As shown in FIGS. 4A and 4B , in some embodiments, the cover 200 can include an annular flange edge 208A extending radially outward from the top wall 206. In some embodiments, the cover 200 can further include a second annular flange edge 208B extending radially outward from a lower edge of the side wall 202. In some embodiments, the annular flange edges 208A, 208B can have a width of about 3 inches to about 10 inches. The annular flange edges 208A, 208B further increase the creepage or leakage distance along the surface of the insulator 100. Additionally, the annular flange edges 208A, 208B help direct the flow of water and / or other environmental contaminants away from the surface of the cover 200 and away from the insulator 100 (i.e., help water roll off the cover 200).

[0028] The cover 200 can be attached to the insulator 100 to form the assembly 300 in the following manner: In some embodiments, the cover 200 is factory-installed to the insulator 100. In other embodiments, the cover 200 can be field-retrofitted to an existing insulator 100. Factory installation of the cover 200 depends on the type of insulator 100, and the cover 200 can be installed before or after the end fittings 104, 106 are attached to the core 110 of the insulator 100. In the case of an overmolded insulator, the cover 200 is installed after the end fittings 104, 106 are attached to the core 110 of the insulator 100 and the polymer housing 112 is molded around the core 110. For non-overmolded insulators (i.e., insulators in which the housing 112 is molded to the core 110 before the end fittings 104, 106 are assembled), before the end fittings 104, 106 are attached to the core 110 of the insulator 100, the cover 200 is pressed downwardly onto the housing 112 so that the one or more annular sheds 118 are received in the cavity 203 and a portion of the upper end 114 is received through the top opening 205. Once the upper end 114 is received through the top opening 205, an interference fit can be formed between the cover 200 and the insulator 100, and in some embodiments, between the upper end 114 and the top opening 205. The interference fit helps prevent water from entering the top of the housing 112 and / or shed 118 through the top opening 205 of the cover 200. In some embodiments, the polymer material forming cover 200 provides cover 200 with some flexibility, allowing smaller diameter top opening 205 to deflect or stretch to accommodate insertion of larger diameter top end 114 of housing 112. Once top end 114 is positioned within top opening 205 of cover 200, the resilience of the polymer material of cover 200 allows top opening 205 to return to its original diameter, thereby securing cover 200 to insulator 100. Retrofitting of cover 200 occurs after end fittings 104, 106 have been assembled and can be accomplished by stretching cover 200 over an existing end fitting 104 attached to top end 110A of core 110, or by using a two-piece cover, such as cover 400, described in more detail below.

[0029] 5A-5C, an alternative cover 400 for insulator 100 is shown in accordance with an embodiment of the present invention. FIG. 6 illustrates an assembly 500 configured to mitigate dry band arcing using cover 400 shown in FIGS. 5A-5C in accordance with an embodiment of the present invention. The characteristics and / or features of cover 400 or assembly 500 may be similar to those described above with respect to cover 200 or assembly 300 shown in FIGS. 2-4B, and for purposes of describing FIGS. 5A-5C and 6, redundant description may be omitted herein.

[0030] The cover 400 differs from the cover 200 described herein in that the cover 400 includes a two-piece construction. The two-piece construction allows the cover 400 to be retrofitted to an existing insulator 100, for example, an insulator 100 already installed in the field. As shown in FIGS. 5A-5C , the cover 400 includes two substantially identical members 400A, 400B configured to engage and couple with one another. As shown in FIG. 5A , when the members 400A, 400B are engaged with one another, the cover 400 includes a side wall 402 and a top wall 406. The top wall 406 has an upper opening 405 configured to receive the upper end 102A of the insulator 100. In some embodiments, the cover 400 further includes a collar 404 extending upwardly from the top wall 406. In some embodiments, the cover 400 may include an annular flange edge 408 extending radially outward from the lower edge of the side wall 402 and / or the top wall 406. The annular flange edge 408 further increases the creepage or leakage distance along the surface of the insulator 100. Additionally, the annular flange edge 408 helps direct the flow of water and / or other environmental contaminants away from the surface of the cover 400 and away from the insulator 100 (i.e., helps water roll off the cover 400).

[0031] In some embodiments, each member 400A, 400B includes a transition wall 411 that includes a plurality of securing features 410. The transition wall 411 is coupled to or integral with the side wall 402, the top wall 406, and the collar 404 (if applicable). As described in more detail below, the transition wall 411 of each member 400A, 400B provides a contact surface for the members 400A, 400B to engage and secure together in the insulator 100.

[0032] FIG. 5B illustrates one of the members 400A. In this embodiment, members 400A and 400B are mirror images of each other; therefore, at times, only one of the members 400A will be described in detail, with the understanding that such description equally applies to the other member 400B. As shown in FIG. 5B, member 400A has a body or shroud portion 401A. Body 401A includes a side wall 402A and a top wall 406A that together define a cavity 403A. In some embodiments, body 401A further includes a collar 404A extending upwardly from top wall 406A. In some embodiments, body 401A includes a transition wall 411A that is coupled to or integral with side wall 402A, top wall 406A, and collar 404A.

[0033] In some embodiments, the side wall 402A includes one or more annular recesses 409A, 412A. The recesses 409A, 412A allow the cover 400 to fit over the shed 118 of the insulator 100 and also provide additional creepage distance. The body 401A (e.g., the transition wall 411A) includes multiple locking features 410 configured to engage with corresponding locking features 410 on the other body 401B. In some embodiments, the locking features 410 may include snap-fit ​​features such as ball or cylinder snap-ins or extension snap-ins. In some embodiments, rivets or screws formed from a non-conductive material may be used to secure the bodies 401A, 401B of the cover 400 to one another. Alternatively, in some embodiments, the bodies 401A, 401B of the cover 400 can be glued or otherwise sealed to one another. When the bodies 401A, 401B (e.g., transition walls 411) of each member 400A, 400B are engaged (i.e., secured to one another), the respective cavities 403A, 403B together define the main cavity 403 of the cover 400. Similar to the cavity 203 of the cover 200 described herein, the main cavity 403 of the cover 400 is configured to receive one or more of the annular sheds or skirts 118 of the insulator 100 (see, e.g., FIG. 6 ). Generally, the cover 400 covers one or more annular sheds 118 on top of the insulator 100, i.e., the cover 400 is attached to the upper end 102A of the insulator 100.

[0034] In some embodiments, the lower edges of the side walls 402A, 402B together define a lower opening 507 that communicates with the main cavity 403. In some embodiments, the top walls 406A, 406B cooperate with one another to define an upper opening 405 that also communicates with the main cavity 403. In some embodiments, the upper edges of the collars 404A, 404B cooperate with one another to define an upper opening 405 that also communicates with the main cavity 403. Similar to the cover 200 described herein, in some embodiments, the upper surfaces of the top walls 406A, 406B may be tapered or angled to allow water and / or other environmental contaminants to flow away from the cover 400 and away from the insulator 100. The cover 400 may be formed from silicone rubber, EVA, EPDM, or other suitable rubber or other elastomeric and / or polymeric material. In some embodiments, the cover 400 is formed by injection molding.

[0035] The cover 400 can be attached to an existing insulator 100 to form the assembly 500 in the following manner: The two members 400A, 400B are aligned such that the inner surfaces of their respective top walls 406A, 406B are positioned above the top shed 118 of the insulator 100 and the corresponding fastening features 410 on each member 400A, 400B are aligned. The two members 400A, 400B are pressed together (e.g., pressed or glued together) so that the corresponding fastening features 410 on the transition walls 411 engage and secure the two members 400A, 400B to one another. In some embodiments, the two members 400A, 400B are secured together with a room-temperature vulcanizing silicone (RTV) sealant to help prevent moisture between the two members 400A, 400B. 6 , when the two members 400A, 400B are pressed together, at least a portion of one or more annular sheds 118 are received in the respective cavities 403A, 403B such that the mated members 400A, 400B of the cover 400 cover at least one or more of the annular sheds 118 of the insulator 100. In some embodiments, a portion of the upper end 114 of the housing 112 of the insulator 100 is received through the top opening 405. When the two members 400A, 400B are mated together, the upper end 114 is received through the top opening 405 formed in the top wall 406 of the cover 400.

[0036] When the cover 400 is placed on the insulator 100 (e.g., as part of the assembly 500 shown in FIG. 6 ), it helps prevent a film of water from forming on the housing 112 and / or shed 118 of the insulator 100, thus helping to mitigate conditions that could result in dry band arcing. Additionally, the cover 400 increases the creepage or leakage distance along the surface of the insulator 100 between the conductive ends of the insulator 100, thereby helping to mitigate current leakage that could cause damage and / or ultimate failure of the insulator 100.

[0037] 6 and 7, an assembly 600 configured to mitigate dry band arcing is shown in accordance with an embodiment of the present invention. The characteristics and / or mechanisms of assembly 600 may be similar to those described above with respect to assemblies 300, 400 shown in FIGS. 2-4B and 5, and for purposes of describing FIGS. 6 and 7, duplicate descriptions may be omitted herein.

[0038] Assembly 600 differs from assemblies 300, 400 in that assembly 600 includes a three-piece cover 700. Similar to the two-piece cover 400 described herein, the three-piece construction of cover 700 allows cover 700 to be retrofitted to existing insulators 100, for example, insulators 100 already installed in the field.

[0039] 7 and 8, similar to the cover 200 described herein, the cover 700 includes a body or shroud portion 701. The body 701 includes a side wall 702 and a top wall 706 that together define a cavity 703. In some embodiments, the side wall 702 is cylindrical. As shown in FIG. 8, the cavity 703 of the cover 700 is configured to receive one or more of the annular sheds or skirts 118 of the insulator 100. Generally, the body 701 of the cover 700 covers the one or more annular sheds 118 on top of the insulator 100, i.e., the cover 700 is attached to the upper end 102A of the insulator 100.

[0040] The lower edge of the side wall 702 defines a lower opening 707 that communicates with the cavity 703. In some embodiments, the top wall 706 includes an upper opening 705 that also communicates with the cavity 703. In some embodiments, the body 701 further includes a collar 704 extending upwardly from the top wall 706. In some embodiments, an upper edge of the collar 704 defines the upper opening 705 that communicates with the cavity 703. In some embodiments, the top wall 706 or the collar 704 includes an annular lip 709 around the upper opening 705. In some embodiments, the body 701 of the cover 700 may be formed as a unitary or single piece. The cover 700 may be formed from silicone rubber, EVA, EPDM, or other suitable rubber or other elastomeric and / or polymeric material. In some embodiments, the cover 700 is formed by injection molding. As shown in Figures 7 and 8, in some embodiments, the top surface of the top wall 706 may be tapered or angled. For example, in some embodiments, the top surface of the top wall 706 may taper downward from the collar 704. The tapered or angled surface of the top wall 706 may allow water and / or other environmental contaminants to flow away from the top wall 706 and away from the insulator 100.

[0041] 7, the cover 700 further includes two collar members 710A, 710B. In this embodiment, the collar members 710A, 710B are mirror images of each other, and therefore, only one collar member 710A may at times be described in detail, with the understanding that such description equally applies to the other collar member 710B.

[0042] Each collar member 710A, 710B includes an arcuate sidewall 712A, 712B and a flange edge 714A, 714B extending radially outward from a lower edge of the respective sidewall 712A, 712B. The arcuate sidewalls 712A, 712B of the collar members 710A, 710B are sized and configured to receive the upper end 114 of the insulator 100 therebetween. The sidewalls 712A, 712B are also sized and configured to be received through the top opening 705 of the body 701. As described in more detail below, the flange edge 714A, 714B of the collar members 710A, 710B is configured to engage or contact a lip 709 present around the top opening 705 of the body 701.

[0043] The cover 700 can be attached to an existing insulator 100 to form the assembly 600 in the following manner. Similar to the cover 200 described herein, in some embodiments, the cover 700 is factory-installed to the insulator 100. In other embodiments, the cover 700 can be field-retrofitted to an existing insulator 100. Factory installation of the cover 700 depends on the type of insulator 100, and the cover 700 can be installed before or after the end fittings 104, 106 are attached to the core 110 of the insulator 100.

[0044] For non-overmolded insulators (i.e., insulators in which the housing 112 is molded to the core 110 before the end fittings 104, 106 are assembled), the side walls 712A, 712B of the two collar members 710A, 710B are aligned with at least a portion of the upper end 114 of the housing 112 of the insulator 100 between them. The body 701 is pressed downward onto the housing 112 so that the one or more annular sheds 118 are received in the cavity 703, and the side walls 712A, 712B of the collar members 710A, 710B and a portion of the upper end 114 of the housing 112 are received through the top opening 705. The body 701 is pressed downward until the flange edges 714A, 714B of the collar members 710A, 710B engage or contact the annular lip 709 of the body 701. The top wall 706 of the body 701 and / or the collar 704 exert a radially inward force on the side walls 712A, 712B of the collar members 710A, 710B, thereby securing the top end 114 of the housing 112 between the side walls 712A, 712B.

[0045] For an overmolded insulator, the cover 700 is applied after the end fittings 104, 106 are attached to the core 110 of the insulator 100 and the polymer housing 112 is molded around the core 110. The side walls 712A, 712B of the two collar members 710A, 710B are aligned with at least a portion of the upper end 114 of the housing 112 of the insulator 100 between them. The cover 700 is stretched over the existing end fitting 104 attached to the upper end 110A of the core 110 and over the two collar members 710A, 710B. The body 701 is pressed downward until the flange edges 714A, 714B of the collar members 710A, 710B engage or contact the annular lip 709 of the body 701. The top wall 706 of the body 701 and / or the collar 704 exert a radially inward force on the side walls 712A, 712B of the collar members 710A, 710B, thereby securing the top end 114 of the housing 112 between the side walls 712A, 712B.

[0046] When cover 700 is placed on insulator 100 (e.g., as part of assembly 600 shown in FIG. 6 ), it helps prevent a film of water from forming on housing 112 and / or shed 118 of insulator 100, thus helping to mitigate conditions that could result in dry band arcing. Additionally, cover 700 increases the creepage or leakage distance along the surface of insulator 100 between its conductive ends, thereby helping to mitigate current leakage that could cause damage and / or ultimate failure of insulator 100.

[0047] In some embodiments, similar to cover 200 described herein, cover 700 may include one or more annular flange edges extending radially outward from top wall 706 and / or from the lower edges of the side walls to further increase the creepage or leakage distance along the surface of insulator 100 and to help direct the flow of water and / or other environmental contaminants away from the surface of cover 700 and away from insulator 100.

Claims

1. An assembly (300) configured to mitigate dry band arcing, comprising: The assembly comprises: A polymer insulator (100) for a power distribution line; a cover (200); The polymer insulator (100) for power distribution lines comprises: a core (110); two end fittings (104, 106) attached to opposite ends of the core; a housing (112) formed from an electrically insulating polymeric material and circumferentially surrounding the core, the housing including upper and lower ends (114 and 116) respectively overlying respective end fittings in a direction transverse to the axial direction of the core, and a series of axially spaced annular sheds (118) projecting radially outward from an outer surface of the housing; The cover (200) includes a body (201) including a side wall (202) and a top wall (206), the side wall and the top wall together defining a cavity (203), a lower edge of the side wall defining a lower opening (207), the top wall including an upper opening (205), the lower opening and the upper opening communicating with the cavity; At least a portion of the upper end of the housing is received in the upper opening of the cover through the upper opening, one or more of the annular sheds are received in the cavity of the cover, and a portion of the end fitting (104) that overlaps with the upper end of the housing and overlaps in the direction transverse to the axial direction of the core is received in the upper opening of the cover; the upper opening of the cover is configured to form an interference fit with the upper end of the housing of the insulator; An assembly in which the overlapping portion of the end fitting, the upper end of the housing, and the cover are stacked in this order from the side of the upper end (110A) of the core in the direction intersecting the axial direction.

2. The assembly of claim 1 , wherein the cover further includes a collar (204) extending upwardly from the top wall.

3. The assembly of claim 2 , wherein an upper edge of the collar defines the upper opening that communicates with the cavity.

4. The assembly of claim 1 , wherein an upper surface of the top wall of the cover is tapered or angled.

5. The assembly of claim 1 , wherein the cover is formed as a unitary or single piece.

6. The assembly of claim 1 , wherein the cover further includes a first annular flange edge (208A) extending radially outward from the top wall.

7. The assembly of claim 1 , wherein the cover further includes a second annular flange edge (208B) extending radially outward from the lower edge of the side wall.

8. A cover (200) for an insulator (100) for a power distribution line, the cover comprising: a body (201) including a sidewall (202) and a top wall (206), the sidewall and the top wall together defining a cavity (203), a lower edge of the sidewall defining a lower opening (207) communicating with the cavity, and an upper surface of the top wall of the cover being tapered or angled; a collar (204) extending upwardly from the upper wall, the upper edge of the collar defining an upper opening (205) communicating with the cavity; the upper opening is configured to receive at least a portion of a housing (112) formed from an electrically insulating polymer material of the insulator and at least a portion of an end fitting (104) attached to the core (100) of the insulator overlapping with the at least a portion of the housing (112), the at least a portion of the housing (112) being configured to overlap with the at least a portion of the end fitting (104) in a direction transverse to the axial direction of the core, and the cavity is configured to receive one or more annular sheds (118) extending radially outward from the housing of the insulator; the upper opening of the cover is configured to form an interference fit with the upper end (114) of the at least a portion of the housing of the insulator; The at least a portion of the end fitting, the upper end of the housing, and the cover are configured to be stacked in this order from the upper end (110A) side of the core in the direction intersecting the axial direction of the core. cover.

9. A method for mitigating dry band arcing in polymer insulators for power distribution lines, , the method comprising: providing a polymer insulator (100) for electric power distribution lines, the insulator comprising a core (110), two end fittings (104, 106) attached to opposite ends of the core, and a housing (112) formed of an electrically insulating polymer material circumferentially surrounding the core, the housing including upper and lower ends (114, 116) respectively overlapping the respective end fittings in a direction transverse to the axial direction of the core, and a series of axially spaced annular sheds (118) projecting radially outward from an outer surface of the housing; providing a cover (200) including a body (201) including a side wall (202) and a top wall (206), the side wall and the top wall together defining a cavity (203), a lower edge of the side wall defining a lower opening (207), the top wall including an upper opening (205), the lower opening and the upper opening communicating with the cavity, the upper opening configured to form an interference fit with the upper end of the housing of the insulator; pressing the cover downward onto the housing of the insulator so that one or more annular sheds of the insulator are received in the cavity of the cover; the cover is continuously pressed downward until at least a portion of the upper end of the housing and a portion of the end fitting (104) that overlaps with the upper end of the housing and overlaps in the direction intersecting the axial direction of the core are received in the upper opening of the cover through the upper opening of the cover, so that the overlapping portion of the end fitting, the upper end of the housing, and the cover are stacked in this order from the upper end (110A) side of the core in the direction intersecting the axial direction; A method comprising:

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