Patent Grant
9343204
The present disclosure is generally related to overhead distribution and transmission insulators and more particularly is related to electrical insulator apparatus and methods of retaining an electrical conductor with an electrical insulator apparatus.
Insulators are used with electrical transmission and distribution systems to isolate and support electrical conductors above the ground for overhead power distribution and transmission. Tie-wire and clamping mechanisms are used to secure and hold electrical conductors that are strung between utility poles in a variety of common configurations, such as roadside (tangent) or road crossing (angled) spans between the utility poles. For tangent and small angle configurations, typically up to 5°, the electrical conductors are supported on the top portion of the insulator, known as the top saddle. On angled configurations, typically greater than 5°, the electrical conductors are supported on the side portion of the insulator, known as the neck or side saddle. For the most part these needs have been met by use of a tie-wire, a pre-formed tie-wire, a clamp-top fitting, or an integral vise-top.
Tie-wire is a low-cost material, but may not achieve the desired conductor grip strength due to variation in hand-tying methods by installation personnel. It may also lack consistency in grip strength from one location to the next although the same tying method is utilized. Another deficiency of tie-wire is the required method of wrapping the wire about the neck of the insulator effectively reduces the electrical resistance path to ground. Preformed tie-wire overcomes the tie-wire deficiency in strength and consistency, but shares the issue of reducing the resistance path to ground. Preformed tie-wires carry a higher per unit cost and also require several different models to accommodate the wide range of conductor sizes and configurations used in the field.
Clamp-top fittings typically consist of a metal bracket for attachment to the insulator neck and an additional metallic assembly to keep and clamp the conductor. Clamp-top fittings generally accept a wide range of conductor sizes, but still require multiple models to cover the full range of conductor sizes and insulator neck sizes. There is a high per unit cost and a high installation cost when compared to ties. Their top saddle position also raises the conductor some distance (e.g. 3-inch) above the normal conductor mounting position which can increase the moment (force) applied to mounting hardware in small angle configurations. This has the drawback of forcing the user to shift the installation to a side-saddle position, with an associated reduction in resistance path to ground and dry-arc distance, for small angles that would otherwise be accommodated in the top saddle position by tie-wire methods.
Vise-top insulators are generally formed on insulator bodies having opposing jaws positioned at the top of the insulator body. The opposing jaws include at least one jaw piece that is adjustable relative to the other jaw piece, such that the jaw pieces can be clamped on an electrical conductor therebetween and retain it in place. Vise-top insulators overcome many of the deficiencies cited for devices above by accommodating a wide range of conductor sizes in a single model. However, the conductor grip strength is generally less than that of preformed ties and clamp-top fittings.
There has long been a need to reliably and economically secure a wide range of electrical conductor sizes to the insulator. Conventional insulators and associated ties or clamps, as cited above, generally accommodate the reliability aspects of tangent configurations. However, for angled configurations typically greater than 5° the electrical conductors are supported on the side saddle and these conventional insulators often are unable to provide the necessary mechanical and electrical support to ensure safe and proper functioning of the electrical conductor over the expected lifetime. They are also unable to provide the flexibility within one device to accommodate the wide range of conductor sizes, types, configurations and grip strength requirements.
Thus, a heretofore unaddressed need exists in the industry to address the aforementioned deficiencies and inadequacies.
Embodiments of the present disclosure provide an electrical insulator apparatus. Briefly described, in architecture, one embodiment of the apparatus, among others, can be implemented as follows. An insulator body is formed about a central axis, the insulator body having an internal cavity and a plurality of spaced fins positioned along an exterior of the insulator body. A first jaw portion is positioned on the insulator body. A second jaw portion is connected to the first jaw portion. At least one fastener is connected between the first and second jaw portions. A jaw platform has a platform surface, wherein the platform surface is formed at least partially between the first and second jaw portions, and wherein a plane substantially aligned with the platform surface intersects the internal cavity.
The present disclosure can also be viewed as providing an electrical insulator apparatus for side-saddle mounting of a conductor. Briefly described, in architecture, one embodiment of the apparatus, among others, can be implemented as follows. An insulator body is formed about a central axis, the insulator body having an threaded internal cavity sized to receive a mounting pin. A plurality of spaced fins is positioned radially about the threaded internal cavity along an exterior of the insulator body. A first jaw portion is formed integral with the insulator body. A second jaw portion is movably engaged to the first jaw portion. A jaw platform is formed between the first and second jaw portions and having a substantially planar platform surface, wherein the first jaw portion, the second jaw portion, and the jaw platform form a conductor-receiving notch, and wherein a plane substantially aligned with the substantially planar platform surface intersects the internal cavity. A first threaded fastener is engaged between the first and second jaw portions in a position above the substantially planar platform surface. A second threaded fastener is engaged between the first and second jaw portions in a position below the substantially planar platform surface.
The present disclosure can also be viewed as providing methods of retaining an electrical conductor with an electrical insulator apparatus. In this regard, one embodiment of such a method, among others, can be broadly summarized by the following steps: securing the electrical insulator apparatus to a utility fixture, wherein a pin affixed to the utility fixture engages with an internal cavity of an insulator body of the electrical insulator apparatus; and retaining a portion of the electrical conductor within a receiving notch formed on the insulator body between a first jaw portion, a second jaw portion, and a jaw platform, wherein the portion of the electrical conductor contacts a platform surface of the notch, wherein a plane of a platform surface of the jaw platform is aligned to intersect the internal cavity, wherein the portion of the electrical conductor applies a longitudinal force against the pin within the cavity.
Other systems, methods, features, and advantages of the present disclosure will be or become apparent to one with skill in the art upon examination of the following drawings and detailed description. It is intended that all such additional systems, methods, features, and advantages be included within this description, be within the scope of the present disclosure, and be protected by the accompanying claims.
Many aspects of the disclosure can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the present disclosure. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views.
The apparatus 10 may be used to retain electrical conductors, which are used in systems for the transmission and distribution of electrical power. The apparatus 10 may be used to both install and retain electrical conductors along various electrical fixtures, such as utility poles, towers, or other fixtures. The apparatus 10 may be affixed or fastened to any part of the utility fixture, such as to a cross member of the utility fixture. The apparatus 10 may be used in conjunction with any number of other devices that are known and available within the art, and it should be appreciated that other variations beyond this disclosure are also possible. In particular,
The insulator body 20 is used to isolate electrical conductors from a utility fixture. The insulator body 20 is formed about the central axis 22, such that the central axis 22 is positioned approximately through the center point of the insulator body 20. In other words, the central axis 22 may be characterized as running along a length of the insulator body 20, such that is traverses through the ends of the insulator body 20. The insulator body 20 may be constructed from a variety of different materials that are commonly known and readily available within the art. The size of the insulator body 20 may vary depending on the size or voltage rating of the electrical conductor that it is designed to retain.
The internal cavity 24 of the insulator body 20 may be sized to engage with a mounting pin (not shown) which is affixed to a utility structure, such as a cross-arm of a utility pole. The internal cavity 24 may have varying diameters along its length and any portion thereof may have internal threading for engagement with external threads of a mounting pin. While the internal cavity 24 may have different lengths relative to the insulator body 20, it may commonly traverse into the insulator body 20 past the spaced fins 26 and in to an upper portion of the insulator body 20, terminating at a position proximate to the first jaw portion 40. The insulator body 20 may include any number of spaced fins 26 positioned thereon in a variety of configurations. The number or size of the plurality of spaced fins 26 may vary depending on the design of the insulator body 20. For example, the insulator body 20 may have one, two, or three or more fins 26 radially positioned about the insulator body 20 and spaced relative to one another. The size of the fin 26, in particular, the distance from the tip of the fin 26 to its center, may vary between the fins 26 on the insulator body 20.
The first jaw portion 40, second jaw portion 50, and jaw platform 70 may collectively form a notch for receiving the electrical conductor, and are used to secure the electrical conductor to the insulator body 20. The notch formed by the first jaw portion 40, second jaw portion 50, and jaw platform 70 is positioned on an upper portion or upper area of the insulator body 20. While a lower portion or lower area of the insulator body 20 may be affixed to a utility fixture via a mounting pin. The first jaw portion 40 may be positioned removably to or integral with the upper portion of the insulator body 20. Similarly, the second jaw portion 50 may be connected to the first jaw portion 40 with a fixed connection or a movable connection. Commonly, the second jaw portion 50 is movably connected to the first jaw portion 40, thereby allowing the second jaw portion 50 to provide a clamping function relative to the first jaw portion 40, allowing for the electrical conductor to be clamped between the first and second jaw portions 40, 50.
The jaw platform 70 is formed between the first and second jaw portions 40, 50, and has a platform surface 72 as a base surface on which an electrical conductor can be placed. In this configuration, the electrical conductor can be secured between the first and second jaw portions 40, 50, and the platform surface 72 of the jaw platform 70. The platform surface 72 may be a substantially planar surface, such that it is substantially formed along the plane 74. It is noted that the substantially planar surface may include a number of features that are not planar, such as a textured surface, a slight curvature, or other features, none of which detract from the general positioning of the platform surface 72 along the plane 74.
The at least one fastener 60 is connected between the first and second jaw portions 40, 50. The fastener 60 may include a threaded fastener that is threadedly engaged with a threaded hole 42 positioned within at least one of the first jaw portion 40 and the second jaw portion 50. In
As is shown in
The second jaw portion 50 may have a hole 52 therein which the threaded fastener 60 can engage with or traverse through. The hole 52 may be aligned with the hole 42 of the first jaw portion 40. A contact face 54 of the second jaw portion 50 may oppose the contact face 44 of the first jaw portion 40, and may extend towards the platform surface 72. When the second jaw portion 50 is fixed to the jaw platform 70, the contact face 54 of the second jaw portion 50 may be formed integral with the jaw platform 70. When the second jaw portion 50 is movable relative to the first jaw portion 40 or the jaw platform 70, the contact face 54 may terminate proximate to the platform surface 72. As is described further relative to other figures of this disclosure, while the second jaw portion 50 may connect to the first jaw portion 40 with the threaded fastener 60, it may also slidably engage with the jaw platform 70.
The platform surface 72 positioned along the plane 74 may be formed at an angle with respect to the insulator body 20 and the central axis 22. The central axis 22 intersects the plane 74 at the upper portion of the insulator body 20. The intersection of the central axis 22 and the plane 74 may be a perpendicular or angled, depending on the design of the apparatus. As is shown in
When the apparatus 10 is positioned to hold an electrical conductor that is being strung along a curve or a bend in the electrical conductor path, the electrical conductor may also produce lateral forces exerted on the first and second jaw portions 40, 50, and the jaw platform 70. For this angled construction, the electrical conductor's horizontal tensions on each side of the insulator body 20 induce a horizontal cantilever force. The plane 74 that is substantially aligned with the platform surface 72 intersects the internal cavity 24 within the insulator body 20. The proximity and the level positioning of the platform surface 72 of the jaw platform 70 with respect to the internal cavity 24 may reduce detrimental moment and any long term creep. By positioning the plane 74 of the platform surface 72 to intersect the internal cavity 24, the cantilever force of the electrical conductor may be fully absorbed by the mounting pin (
The apparatus 10 may provide significant benefits in retaining electrical conductors along angled paths by allowing the lateral forces created by the electrical conductor to be transferred primarily to the mounting pin within the internal cavity 24. When the platform surface 72 is angled relative to the central axis 22, as is discussed relative to
Examples of using the apparatus 10 relative to the requirements of industry standards are provided. As an electrical conductor is held by the apparatus 10, the weight of the electrical conductor will create a downward force, generally directed centrally to the jaw platform 70. The alignment of the plane 74 of the platform surface 72 with the internal cavity 24 is a primary factor when analyzing the acting conductor loads. In a tangent construction and a steady state, the only load acting on the platform is the conductor's weight. Due to the close proximity of the platform surface 72 to the central axis 22, the moment induced by this vertical load is extremely small and has no impact during the lifetime of the insulator.
The following load calculation for a tangent construction is provided as means of clarification. A large conductor and Heavy Loading Zone conditions, in accordance with National Electrical Safety Code (NESC), are applied for the calculation:
Vertical load (Lv) is given by the formula:
LV=Total Linear Weight×Span
LV=2.28×250=570 lbf
Thus, the acting vertical load upon the apparatus 10 is approximately 600 lbf for a Heavy Loading Zone condition of a tangent configuration.
Common mounting pins, such as Joslyn Catalog No J606Z, J203Z & J207Z, may be used to install the apparatus 10 on the utility fixture. Finite Element Analysis (FEA) may be used to simulate the acting force on the mounting pin and the resultant deflection. FEA with cast steel key mechanical properties, representative of the described mounting pins, shows that for a vertical load of 600 lbf and a standard 6″ mounting pin, a deflection angle of 0.86° may occur, which is significantly less than the 10° deflection allowed by industry design practice.
This example considers the compliance with the National Electrical Safety Code (NESC) Section 27, table 277-1 “Allowed percentages of strength rating” for insulators, where the maximum allowed service load acting on the insulator is 40% of its published rated value. Within the industry, the bending strength is typically rated to 3000 lbf, hence the 40% NESC allowance computes to 1200 lbf maximum permissible service load. The same FEA analysis as in Example 1 shows that for a vertical load of 1200 lbf, a corresponding mounting pin deflection angle of 1.75° may occur.
In another example, the most stringent case is compliance with the State of California General Order GO 95, Rule 44.1 Table 4 “Minimum Safety Factor” for Grade of Construction “A”. The minimum safety factor for Line insulators' mechanical loads for Grade “A” is to be 3. The vertical load to consider is then the actual load in Example 1 multiplied by the safety factor which computes to approximately 1800 lbf. The FEA simulation performed as in Example 1 shows that a pin deflection angle of 2.67° may occur which is considerably less than the 10° deflection that is allowed by industry design practice.
Considering the same Heavy Loading Zone conditions in the previous examples with the additional condition of 40 mile/hour wind and fixing the maximum mounting pin permissible deflection to 10°, the maximum allowable Line Angle for an angled construction is calculated for common conductor sizes as follows:
These calculations show that large line angle configurations for heavy loading conditions are possible with the present disclosure. The mechanical strength and the size of the mounting pin are the limiting factors. Increasing the diameter or choosing a higher Young's modulus for a metal pin will thus increase the permissible line angle while still satisfying the 10° maximum pin deflection limitation.
As a point of comparison to the present disclosure, conventional insulators within the industry support the electrical conductor in a top-saddle position for tangent, small angle configurations, e.g., less than 5°, or configurations with lateral wind forces. The top saddle is centered at some distance above the mounting pin, typically 0.50 inch or more, and the additional wind load component and related conductor blow angle cause a resultant moment and a mounting pin deflection angle larger than that of the present disclosure. The allowable line angle values in the above example exceed the allowable angles calculated for conventional insulators supporting the electrical conductor in a top-saddle. When conventional insulators are used for angled configurations, e.g., greater than 5°, the conductor is commonly placed in a side-saddle position. Similar to the top-saddle position, this side-saddle position in conventional insulators is positioned a distance above the mounting pin. The lateral force of the conductor applied to the conventional insulator above the mounting pin substantially increases the cantilever forces applied to the conventional insulator to undesirable levels. Furthermore, the side-saddle position places the electrical conductor closer in proximity to the utility fixture, when compared to its top-saddle position, and therefore presents the disadvantage of reduced electrical performance.
Thus, the alignment and position of the platform surface 72 of the jaw platform 70 in relation to the internal cavity 24 of the apparatus 10 may be sufficient tangent or angled accommodation of the electrical conductor in accordance to industry standards and provide many benefits over conventional insulators.
As is shown in
As can also be seen, the jaw platform 170 having the platform surface 172 may have outer edges that are terminated by two horizontal beams 176, 178. The two horizontal beams 176, 178 may resist uplift motion of the second jaw portion 150 when it is secured in place to the first jaw portion 140 with one or more fasteners (not shown). Additionally, the two horizontal beams 176, 178 may eliminate flexural stress on a fastener engaged with a hole 180 within the jaw platform 170. Below the jaw platform 170, two braces 182, 184 may connect between the insulator body 120 and the jaw platform 170 to provide long term support and creep resistance capability that the jaw platform 170 may be susceptible to under a constant weight (vertical load) of the electrical conductor supported by the apparatus 110. Beneath the platform surface 172, the hole 180 may be positioned within a lateral jaw face 186. The lateral jaw face 186 may protrude beyond the jaw platform 170 to increase fastener thread engagement length when accommodating a large conductor.
As is shown in
By tightening the fasteners, the conductor is secured on the platform surface 172 (
Common construction practice for conductor grip strength is to apply the safety rules as described in NESC Section 26 for longitudinal strength. To achieve the NESC strength values, it may be desirable to select a material for the liner member 192 harder than the conductor in order to resist deflection under load and with textured surface or raised features to improve grip strength. The inorganic material as described in this disclosure, preferably with an undulating face pattern (
In addition to providing the aforementioned hardness and the necessary grip strength, the material selected for the liner member 192 should be chemically inert and stable over time. The liner member material properties are also selected to eliminate galvanic reactions with electrical conductors. An aspect of the present disclosure is to provide compatibility with all types of conductors, such as aluminum, copper and covered, and to provide UV resistance and chemical stability in the presence of moisture and contaminants (e.g. dust, salt, fertilizer or other airborne matter) for the expected lifetime (e.g. 30 years, 40 years, or 50 years, as non-limiting examples). In the outdoor environment, where high humidity and salt-fog conditions may be common, galvanic reaction is expected between metals if their Anodic Index (AI) differs by 0.15 or more. Typical AI values for common materials used in the industry are provided in Table 3:
Given the large AI differences between these materials, none can be a suitable universal liner member 192 for all types of conductors aforementioned. Thus, it is preferable for the liner member 192 to be constructed from a material different from a material of the first and second jaw portions 140, 150, and selection of a non-metallic, electrically non-conductive material is preferred. For example, the liner member 192 may be a ceramic type material such as Aluminum Oxide (85% to 99.9% purity), Silicon Nitride, Cordierite, Mullite, Steatite, Zirconium Oxide or some other suitable material. The liner member 192 may be an organic based composite such as UV-stabilized abrasive-filled rubber, glass fiber filled Nylon, or other suitable material.
As is discussed with respect to
In accordance with this disclosure, the offset distance X between the central axis 222 and the fin axis 227 may be a value such as to balance or optimize the resistance path to ground, hereinafter referred to as leakage distance, as measured from the jaw platform 270 across the body of the apparatus 210 to the inner internal cavity 224, in all directions across the plurality of spaced fins 226. As an example, the offset distance X may be 0.50 inch or other desired value (e.g. 0.20 inch, 0.40 inch, 0.60 inch or any other suitable value). The offset distance X may vary depending on the size or voltage rating of the electrical conductor that it is designed to retain. For example, the offset distance X may be selected to adjust the leakage distance for a range of conductor sizes (e.g. No. 6 AWG to 2/0 AWG, No. 1/0 AWG to 4287 kcmil, 336 kcmil to 795 kcmil, or any other suitable range) or for a range of system voltages (e.g. 5 kV to 15 kV, 15 kV to 25 kV, 25 kV to 35 kV or any other suitable range). Conventional devices have fins that are coaxial with an insulator device. The non-coaxial positioning of the fins 226 to the insulator body 220 of the apparatus 210 provide improved leakage distance over these conventional devices, in addition to providing a sufficient tangent or angled accommodation of the electrical conductor.
The apparatus 210 of
The positional nature of the jaw platform 270 with respect to the insulator body 220 may allow for the apparatus 210 to be used to string electrical conductors in various configurations, namely along paths that include bends and curves. In other words, the apparatus 210 may also serve an additional function as an installation tool suitable for the conductor prior to securing in place. For example, the apparatus 210 may allow for stringing electrical conductors along paths with bends or curves that are greater than 6°, or greater than other angles, such as greater than 20°, 30°, or 45° when used with suitable mounting hardware. When the apparatus 210 is used to angularly string an electrical conductor, the force that the electrical conductor 214, 216 applies to the apparatus may be transferred into the insulator body 220 via the first jaw portion 240 and the jaw platform 270, such that the force is applied angularly to the insulator body 220. The positioning of the jaw platform 270 with respect to the insulator body 220 and the internal cavity 224 may help counteract the force applied by the electrical conductor 214, 216 better than a conventional insulator device, e.g., a vise-top insulator, since the insulator body 220 may have a greater resistance to lateral forces created by the electrical conductor due to the bend in the stringing path.
As is discussed with respect to
In all four illustrations the vector force components are represented and expressed as a function of the angle θ, where V is the vertical force in the tangent case and C is the cantilever force in the angled case. For θ>90°, in the tangent configuration of
The apparatus 410 includes a rail 412 formed on the insulator body 420 which the first jaw portion 440, second jaw portion 450, and the jaw platform 470 can be positioned along. In
As is shown by block 502, the electrical insulator apparatus is secured to a utility fixture, wherein a pin affixed to the utility fixture engages with an internal cavity of an insulator body of the electrical insulator apparatus. A portion of the electrical conductor is retained within a receiving notch formed on the insulator body between a first jaw portion, a second jaw portion, and a jaw platform, wherein the portion of the electrical conductor contacts a platform surface of the notch, wherein a plane of a platform surface of the jaw platform is aligned to intersect the internal cavity, wherein the portion of the electrical conductor applies a longitudinal force against the pin within the cavity (block 504). The method may include any additional step, process, or function, including any disclosed relative to any figure of this disclosure. For example, the plane of the platform surface may be angled substantially between 60° and 150° relative to a central axis of the insulator body and the longitudinal force applied against the pin may be dependent on an angle size of the angle. The longitudinal force may be 500 lbf or greater.
It should be emphasized that the above-described embodiments of the present disclosure, particularly, any “preferred” embodiments, are merely possible examples of implementations, merely set forth for a clear understanding of the principles of the disclosure. Many variations and modifications may be made to the above-described embodiment(s) of the disclosure without departing substantially from the spirit and principles of the disclosure. All such modifications and variations are intended to be included herein within the scope of this disclosure and the present disclosure and protected by the following claims.
This application claims benefit of U.S. Provisional Application Ser. No. 61/647,754, entitled, “Angled Insulator For Electrical Conductors And Methods Of Using The Same” filed May 16, 2012, the entire disclosure of which is incorporated herein by reference.
| Number | Name | Date | Kind |
|---|---|---|---|
| 3586758 | Harmon et al. | Jun 1971 | A |
| 4134574 | Jean et al. | Jan 1979 | A |
| 4178470 | Jean et al. | Dec 1979 | A |
| 4258228 | Jean et al. | Mar 1981 | A |
| 7432449 | Kim | Oct 2008 | B2 |
| 7588224 | Bernstorf et al. | Sep 2009 | B2 |
| Number | Date | Country | |
|---|---|---|---|
| 20130306355 A1 | Nov 2013 | US |
| Number | Date | Country | |
|---|---|---|---|
| 61647754 | May 2012 | US |
