Patent Grant
6905356
The present invention relates to electrical products, and more particularly, to electrical connectors for electrical systems and associated methods.
An electrical distribution system typically includes distribution lines or feeders that extend out from a substation transformer. The substation transformer is typically connected to a generator via electrical transmission lines.
Along the path of a feeder, one or more distribution transformers may be provided to further step down the distribution voltage for a commercial or residential customer. The distribution voltage range may be from 5 through 46 kV, for example. Various connectors are used throughout the distribution system. In particular, the primary side of a distribution transformer typically includes a transformer bushing to which a bushing insert is connected. In turn, an elbow connector may be removably coupled to the bushing insert. The distribution feeder is also fixed to the other end of the elbow connector. Of course, other types of connectors are also used in a typical electrical power distribution system. For example, the connectors may be considered as including other types of removable connectors, as well as fixed splices and terminations. Large commercial users may also have a need for such high voltage connectors.
One particular difficulty with conventional elbow connectors, for example, is that they use curable materials. For example, such a connector may typically be manufactured by molding the inner semiconductive layer first, then the outer semiconductive jacket (or vise-versa). These two components are placed in a final insulation press and then insulation layer is injected between these two semiconductive layers. Accordingly, the manufacturing time is relatively long, as the materials need to be allowed to cure during manufacturing. In addition, the conventional EPDM materials used for such elbow connectors and their associated bushing inserts, may have other shortcomings as well.
One typically desired feature of an elbow connector is the ability to readily determine if the circuit in which the connector is coupled is energized. Accordingly, voltage test points have been provided on such connectors. For example, U.S. Pat. No. 3,390,331 to Brown et al. discloses an elbow connector including an electrically conductive electrode embedded in the insulator in spaced relation from the interior conductor. The test point will rise to a voltage if the connector is energized. U.S. Pat. No. 3,736,505 to Sankey; U.S. Pat. No. 3,576,493 to Tachick et al.; U.S. Pat. No. 4,904,932 to Schweitzer, Jr.; and U.S. Pat. No. 4,946,393 to Borgstrom et al. disclose similar test points for an elbow connector. Such voltage test points may be somewhat difficult to fabricate, and upon contamination and repeated use, they may become less accurate and less reliable.
An elbow connector typically includes a connector body having a passageway with a bend therein. A semiconductive EPDM material defines an inner layer at the bend in the passageway. An insulative Ethylene Propylene Diene Monomer (EPDM) second layer surrounds the first layer, and a third semiconductive EPDM layer or outer shield surrounds the second insulative layer. A first end of the passageway is enlarged and carries an electrode or probe that is matingly received in the bushing insert. A second end of the passageway receives the end of the electrical conductor. The second connector end desirably seals tightly against the electrical conductor or feeder end. Accordingly, another potential shortcoming of such an elbow connector is the difficulty in manually pushing the electrical conductor into the second end of the connector body.
In an attempt to address the difficulty of inserting the electrical connector into the second connector end, U.S. Pat. No. 4,629,277 to Boettcher et al. discloses an elbow connector including a heat shrinkable tubing integral with an end for receiving an electrical conductor. Accordingly, the conductor end can be easily inserted into the expanded tube, and the tube heated to shrink and seal tightly against the conductor. U.S. Pat. No. 4,758,171 to Hey applies a heat shrink tube to the cable end prior to push-fitting the cable end into the body of the elbow connector.
U.S. Pat. No. 5,230,640 to Tardif discloses an elbow connector including a cold shrink core positioned in the end of an elbow connector comprising EPDM to permit the cable to be installed and thereafter sealed to the connector body when the core is removed. However, this connector may suffer from the noted drawbacks in terms of manufacturing speed and cost. U.S. Pat. No. 5,486,388 to Portas et al.; U.S. Pat. No. 5,492,740 to Vallauri et al.; U.S. Pat. No. 5,801,332 to Berger et al.; and U.S. Pat. No. 5,844,170 to Chor et al. each discloses a similar cold shrink tube for a tubular electrical splice.
Another issue that may arise for an elbow connector is electrical stress that may damage the first or semiconductive layer. A number of patents disclose selecting geometries and/or material properties for an electrical connector to reduce electrical stress, such as U.S. Pat. No. 3,992,567 to Malia; U.S. Pat. No. 4,053,702 to Erikson et al.; U.S. Pat. No. 4,383,131 to Clabburn U.S. Pat. No. 4,738,318 to Boettcher et al.; U.S. Pat. No. 4,847,450 to Rupprecht, deceased; U.S. Pat. Nos. 5,804,630 and 6,015,629 to Heyer et al.; U.S. Pat. No. 6,124,549 to Kemp et al.; and U.S. Pat. No. 6,340,794 to Wandmacher et al.
For a typical 200 Amp elbow connector, the elbow cuff or outer first end is designed to go over the shoulder of the mating bushing insert and is used for containment of the arc and/or gasses produced during a load-make or load-break operation. During the past few years, the industry has identified the cause of a flashover problem which has been reoccurring at 25 kV and 35 kV. The industry has found that a partial vacuum occurs at certain temperatures and circuit conditions. This partial vacuum decreases the dielectric strength of air and the interfaces flashover when the elbow is removed from the bushing insert. Various manufacturers have attempted to address this problem by venting the elbow cuff interface area, and at least one other manufacturer has insulated all of the conductive members inside the interfaces.
U.S. Pat. No. 6,213,799 and its continuation Application No. 2002/00055290 A1 to Jazowski et al., for example, discloses an anti-flashover ring carried by the bushing insert for a removable elbow connector. The ring includes a series of passageways thereon to prevent the partial vacuum from forming during removal of the elbow connector that could otherwise cause flashover. U.S. Pat. No. 5,957,712 to Stepniak and U.S. Pat. No. 6,168,447 to Stepniak et al. also each discloses a modification to the bushing insert to include passageways to reduce flashover. Another approach to address flashover is disclosed in U.S. Pat. No. 5,846,093 to Muench, Jr. et al. that provides a rigid member in the elbow connector so that it does not stretch upon removal from the bushing insert thereby creating a partial vacuum. U.S. Pat. No. 5,857,862 to Muench, Jr. et al. discloses an elbow connector including an insert that contains an additional volume of air to address the partial vacuum creation and resulting flashover.
Yet another potential shortcoming of a conventional elbow connector, for example, is being able to visually determine whether the connector is properly seated onto the bushing insert. U.S. Pat. No. 6,213,799 and its continuation Application No. 2002/00055290 A1 to Jazowski et al., mentioned above, each discloses that the anti-flashover ring on the bushing insert is colored and serves as a visual indicator that the elbow connector is seated when the ring is obscured.
U.S. Pat. No. 5,641,306 to Stepniak discloses a separable load-break elbow connector with a series of colored bands that are obscured when received within a mating connector part to indicate proper installation. Along these lines, but relating to the electrical bushing insert, U.S. Pat. No. 5,795,180 to Siebens discloses a separable load break connector and mating electrical bushing wherein the busing includes a colored band that is obscured when the elbow connector is mated to a bushing that surrounds the removable connector.
Accordingly, there exists several significant shortcomings in conventional electrical connectors, particularly for high voltage distribution applications.
In view of the foregoing background, it is therefore an object of the invention to provide an electrical connector that is useful particularly for relatively high voltage applications and that can be readily manufactured.
This and other objects, features and advantages in accordance with the invention are provided by an electrical connector comprising a connector body having a passageway therethrough and including a first layer adjacent the passageway, a second layer surrounding the first layer and comprising an insulative thermoplastic elastomer (TPE) material, and a third layer surrounding the second layer. The third layer preferably has a relatively low resistivity, and may also comprise a semiconductive TPE material. In some embodiments, the first layer may also comprise a semiconductive TPE material. The TPE material layers may be overmolded to thereby increase production speed and efficiency thereby lowering production costs. The TPE material may also provide excellent electrical performance and other advantages.
The passageway may have first and second ends and a medial portion extending therebetween. The first layer may be positioned along the medial portion of the passageway and spaced inwardly from respective ends of the passageway. For elbows and T-connectors, the medial portion of the passageway may have a bend therein. The first end of the passageway may also have an enlarged diameter to receive an electrical bushing insert for some embodiments.
For other embodiments, such as for an electrical bushing insert or some splices, the connector body may have a tubular shape defining the passageway. For an electrical bushing insert, the second layer may have an enlarged diameter adjacent the medial portion of the passageway.
In other embodiments, the connector body adjacent at least one of the first and second ends of the passageway may have a progressively increasing outer diameter. In still other embodiments, the connector body adjacent at least one of the first and second ends of the passageway body may alternately have a progressively decreasing outer diameter.
The first layer may have at least one predetermined property to reduce electrical stress. For example, the predetermined property may comprise a predetermined impedance profile. Alternately or additionally, the predetermined property may comprise a predetermined geometric configuration, such as one or more ribs adjacent the bend for connector embodiments including the bend.
The first layer may define an innermost layer, and the third layer may define an outermost layer. The connector may also include at least one pulling eye carried by the connector body. The connector body may be configured for at least 15 KV and 200 Amp operation. Each of the first and third layers may have a resistivity less than about 108 Ω·cm, and the second layer may have a resistivity greater than about 108 Ω·cm.
A method aspect of the invention is for making an electrical connector body having a passageway therethrough. The method may comprise providing a first layer to define at least a medial portion of the passageway; overmolding a second layer surrounding the first layer and comprising an insulative TPE material having a relatively high resistivity; and overmolding a third layer surrounding the second layer and comprising a material having a relatively low resistivity. The third layer may also comprise a semiconductive TPE material, and the first layer may comprise a semiconductive TPE material in some embodiments.
The present invention will now be described more fully hereinafter with reference to the accompanying drawings in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the illustrated 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. Like numbers refer to like elements throughout. Prime and multiple prime notation are used in alternate embodiments to indicate similar elements.
Referring initially to
The connector body 21 includes a first layer 25 adjacent the passageway 22, a second layer 26 surrounding the first layer, and a third layer 27 surrounding the second layer. In accordance with one important aspect of the connector 20, at least the second layer may comprise an insulative thermoplastic elastomer (TPE) material. The first and third layers 25, 27 also preferably have a relatively low resistivity. In some embodiments, the third layer 27 may comprise a semiconductive TPE material. In addition, the first layer 25 may also comprise a semiconductive TPE material. In other embodiments, the first layer 25 may comprise another material, such as a conventional EPDM.
By using relatively new electrical grade TPE materials, such as thermoplastic olefin materials, thermoplastic polyolefin materials, thermoplastic vulcanites, and/or thermoplastic silicone materials, etc., molding can use new layer technology. This technology may include molding the first or inner semiconductive layer 25 first, then overmolding the second or insulation layer 26, and then overmolding the third or outer semiconductive shield layer 27 over the insulation layer. Some of the suppliers for such materials are: A. Schulman—Akron, Ohio; AlphaGary Corp.
Leominster, Mass.; Equistar Chemicals—Houston, Tex.; M. A. Industries, Inc.—Peachtree City, Ga.; Montrell North America—Wilmington, Del.; Network Polymers, Inc.
Akron, Ohio Solutia, Inc.—St. Louis, Mo.; Solvay Engineering Polymers—Auburn Hills, MI; Teknor Aprex International—Pawtucket, R.I.; Vi-Chem Corp.—Grand Rapids, Mich.; and Dow Chemicals—Somerset, N.J. In other words, the TPE material layers may be overmolded to thereby increase production speed and efficiency thereby lowering production costs. The TPE material may also provide excellent electrical performance.
The use of a TPE material for the third layer 27 permits the entire outer portion of the connector 20 to be color coded, such as by the addition of colorants to the TPE material as will be appreciated by those skilled in the art. For example, a proposed industry standard specifies red for 15 KV connectors, and blue for 25 KV connectors. Gray is another color that TPE materials may exhibit for color coding. Of course, other colors may also be used.
In the illustrated connector 20 embodiment, a first connector end 21a adjacent the first end 22a of the passageway 22 has a progressively increasing outer diameter. The second connector end 21b adjacent the second end 22b of the passageway 22 has a progressively decreasing outer diameter. As will be appreciated by those skilled in the art, other configurations of connectors ends 21a, 21b are also possible.
As illustrated, the first layer 25 defines an innermost layer, and the third layer 27 defines the outermost layer. The connector 20 also illustratively includes a pulling eye 28 carried by the connector body 21. The pulling eye 28 may have a conventional construction and needs no further discussion herein.
The connector body 21 may be configured for at least 15 KV and 200 Amp operation, although other operating parameters will be appreciated by those skilled in the art. In addition, each of the first and third layers 25, 27 may have a resistivity less than about 108 Ω·cm, and the second layer 26 may have a resistivity greater than about 108 Ω·cm. Accordingly, the term semiconductive, as used herein, is also meant to include materials with resistivities so low, they could also be considered conductors.
Those of skill in the art will appreciate that although an elbow connector 20 is shown and described above, the features and advantages can also be incorporated into T-shaped connectors that are included within the class of removable connectors having a bend therein. This concept of overlay technology may also be used for molding a generation of insulated separable connectors, splices and terminations that may be used in the underground electrical distribution market, for example. Some of these other types of electrical connectors are described in greater detail below.
Referring now additionally to
A monitor point 30 is illustratively connected to the second portion 27b of the third layer 27′. In addition, a cover 31 may be provided to electrically connect the first and third portions 27a, 27c of the third layer 27′ yet permit access to the monitor point 30 as will be appreciated by those skilled in the art. For example, the cover 31 may have a hinged lid, not shown, to permit access to the monitor point 30, although other configurations are also contemplated.
By splitting or separating adjacent portions of the third layer 27′ or outer conductive shield, a reliable voltage source can be provided that can be used to monitor equipment problems, detect energized or non-energized circuits, and/or used by fault monitoring equipment, etc. as will be appreciated by those skilled in the art. By splitting and isolating the shield at various lengths and sizes, different voltages can provide feedback to monitoring equipment. The TPE materials facilitate this split shield feature, and this feature can be used on many types of electrical connectors in addition to the illustrated elbow connector 20′.
Turning now additionally to the illustrated elbow connector 20″ shown in
The TPE materials facilitate molded-in cold shrink technology for separable elbow connectors 20″, such as 200 and 600 Amp products, for example. Since the elbows 20″ are typically mated onto 200 or 600 Amp bushing inserts, the bushing side or first end 21a″ of the elbow need not be changed and a certain hardness/durometer and modulus can be maintained for the bushing side. But on the cable side or second end 21b″ of the connector body 21″ of the elbow connector 20″, the TPE materials will allow use of cold shrink technology to initially expand the cable entrance.
Referring now again to
To address the electrical stress in those connector embodiments including at least one bend, the first layer 40 may be molded or otherwise shaped to have the appearance of the embodiment shown in FIG. 5. In particular, the first layer 40 illustratively includes first and second ends 41, 42 with a bend at the medial portion 43. To reduce electrical stress at the bend, a series of spaced apart ribs 44 are provided to extend between the adjacent connector portions at the right or inner angle of the bend. Of course, the first layer 40 may be provided by molding a semiconductive TPE material as described above, but in other embodiments, this first layer 40 may be formed from other materials having the desired mechanical and electrical properties.
A second embodiment of a first layer 40′ is explained with particular reference to FIG. 6. In this embodiment, the first layer 40′ includes slightly differently shaped first and second ends 41′, 42′. In addition, only a single rib 44′ is provided at the right angle portion of the bend to reduce electrical stress thereat. The configuration of the ribs 44 or single rib 44′, as well as the configuration of the other connector body portions will be dependent on the desired operating voltage and current, as will be appreciated by those skilled in the art.
Of course, these stress control techniques can be used with any of the different electrical connector embodiments described herein. Typical 200 and 600 Amp elbow connectors, for example, may benefit from such stress control techniques as will be appreciated by those skilled in the art.
Referring now additionally to
In accordance with the illustrated connectors 50, 50′, this shortcoming is addressed by the connector body 51, 51′ having an outer end portion 51a, 51a′ adjacent the first end 52a, 52a′ of the passageway 52, 52′ with a flared shape, such as when abutting the shoulder 55, 55′ of an electrical bushing insert 54, 54′. In other words, the outer end 53, 53′ may abut the shoulder 55, 55′ without the sliding contact that would otherwise cause the partial vacuum.
In the illustrated embodiment of
As illustrated in the embodiment of
As also shown in the embodiment of the connector 50′ of
Another advantageous feature of the electrical connector 50′ is now explained. As noted in the above background, in many instances it is desirable to visually indicate whether the connector is properly and fully seated onto the electrical bushing insert 54′. The illustrated embodiment of the connector 50′ includes a colored band 57 serving as indicia to visually indicate to a technician that the connector has moved from the unseated position (
This indicator feature can be used, for example, for all elbows including 15, 25, 35 Kv 200 Amp devices, as well as many 600 Amp devices. Seating indicators exist in some prior art connectors, but these seating indicators are generally placed on the bushing insert. Accordingly, it may be difficult to see the indicator when the technician is positioning the elbow directly in front of the transformer. The seating indicators currently used typically employ a yellow band on the bushing that is covered up by the elbow cuff when the two portions are fully mated. After the products are mated together, the operator must view the side of the product to see if all of the yellow band is covered. In accordance with the indicator feature of the connector 50′, the elbow cuff or outer end 53 will flip up or flare when fully mated so that it can be viewed when directly in front of the technician. Thus, the technician need not approach the energized equipment to view the fully latched connector.
Referring now additionally to
The second and/or third layers 66, 67 may comprise TPE materials for the advantages as noted above. For example, the second layer 66 may comprise an insulative TPE material, and the third layer may comprise a semiconductive TPE material. As also shown in the illustrated embodiment, the second layer 66 may have an enlarged diameter adjacent the medial portion 62c of the passageway 62. Indeed this enlarged diameter medial portion may be formed by multiple layering of the insulative TPE material as indicated by the dashed lines 70, 70′, or by using other filler materials, for example, as will be appreciated by those skilled in the art. It may often be desirable to form successive relatively thin layers of the insulative TPE for the desired overall thickness and shape of the second layer 66. The first and third layers 65, 67, may also be formed of successive thinner layers in this connector embodiment, as well as the others described herein, and as will be appreciated by those skilled in the art.
A second embodiment of a bushing insert 60′ is shown in FIG. 12 and now described in greater detail. In this embodiment, the first layer 65′ is provided by a plastic material, such as a TPE material, for example. For example, the plastic material may be an insulative or semiconductive material. Those other elements of the bushing insert 60′ are indicated by prime notation and are similar to those discussed above with reference to FIG. 11.
The rib feature described above to reduce electrical stress may also be applied to the embodiments of the bushing inserts 60. 60′. In addition, a plurality of bushing inserts 60, 60′ may also be joined to a common bus bar, for example, to produce an electrical connector in the form typically called a junction as will be appreciated by those skilled in the art.
Referring now more particularly to
Other features and advantages of the present invention may be found in copending patent applications filed concurrently herewith and assigned to the assignee of the present invention and are entitled ELECTRICAL CONNECTOR WITH VISUAL SEATING INDICATOR AND ASSOCIATED METHODS, Ser. No. 10/438,764; ELECTRICAL CONNECTOR INCLUDING SPLIT SHIELD MONITOR POINT AND ASSOCIATED METHODS, Ser. No. 10/438,766; ELECTRICAL CONNECTOR INCLUDING COLD SHRINK CORE AND THERMOPLASTIC ELASTOMER MATERIAL AND ASSOCIATED METHODS, Ser. No. 10/438,777, ELECTRICAL CONNECTOR WITH ANTI-FLASHOVER CONFIGURATION AND ASSOCIATED METHODS, Ser. No. 10/438,777, the entire disclosures of which are incorporated herein in their entirety by reference. In addition, many modifications and other embodiments of the invention will come to the mind of one skilled in the art having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Accordingly, it is understood that the invention is not to be limited to the illustrated embodiments disclosed, and that other modifications and embodiments are intended to be included within the spirit and scope of the appended claims.
This application is based upon prior filed copending provisional application Ser. No. 60/380,914 filed May. 16, 2002, the entire subject matter of which is incorporated herein by reference in its entirety.
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|---|---|---|---|
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| 20020055567 | Romenesko et al. | May 2002 | A1 |
| Number | Date | Country | |
|---|---|---|---|
| 20040102091 A1 | May 2004 | US |
| Number | Date | Country | |
|---|---|---|---|
| 60380914 | May 2002 | US |
