The present invention relates to electrical cables and, more particularly, to connections and covers for electrical transmission cables.
Covers are commonly employed to protect or shield electrical power cables and connections (e.g., low voltage cables up to about 1000V and medium voltage cables up to about 65 kV). Mastic is commonly used to provide electrical stress relief in areas proximate connectors that might otherwise present voids or other undesirable irregularities.
One application for such covers is for splice connections of metal-sheathed, paper-insulated cables such as paper-insulated lead cable (PILC). A PILC typically includes at least one conductor surrounded by an oil-impregnated paper insulation layer, and a lead sheath surrounding the conductor and insulation layer. Alternatively, the metal sheath may be formed of aluminum. In some cases, it is necessary to contain the oil. It is known to use a heat shrinkable sleeve made of a polymer that does not swell when exposed to the oil. Examples of such heat shrinkable sleeves include heat shrinkable oil barrier tubes (OBT) available from TE Connectivity. The sleeve is placed over the oil impregnated paper and heat is applied to contract the sleeve about the insulation layer. Mastic or other sealant material may be used at each end of the sleeve to ensure an adequate seal and containment of the oil.
According to embodiments of the present invention, a cable connector system includes an electrical cable, a connector, a flow block member and a flowable sealant. The electrical cable includes a primary conductor and an insulation layer surrounding the primary conductor. The insulation layer has an insulation terminal end and the primary conductor extends beyond the insulation terminal end. The connector defines a conductor bore, an entry opening communicating with the conductor bore, and a connector end face surrounding the entry opening. The flow block member defines a passage extending therethrough. The primary conductor extends through the passage and the entry opening and into the conductor bore. The primary conductor is mechanically and electrically coupled to the connector. The flow block member is thereby mounted on the primary conductor and interposed between the insulation terminal end and the connector end face. The sealant surrounds the flow block member and adjacent portions of the insulation layer and the connector. The flow block member inhibits flow of the sealant into the conductor bore through the entry opening.
According to method embodiments of the present invention, a method for forming a protected electrical connection assembly includes: providing an electrical cable including a primary conductor and an insulation layer surrounding the primary conductor, wherein the insulation layer has an insulation terminal end and the primary conductor extends beyond the insulation terminal end; providing a connector defining a conductor bore, an entry opening communicating with the conductor bore, and a connector end face surrounding the entry opening; providing a flow block member defining a passage extending therethrough; inserting the primary conductor through the passage and the entry opening and into the conductor bore such that the flow block member is thereby mounted on the primary conductor and interposed between the insulation terminal end and the connector end face; mechanically and electrically coupling the primary conductor to the connector; and applying a sealant to surround the flow block member and adjacent portions of the insulation layer and the connector, wherein the flow block member inhibits flow of the sealant into the conductor bore through the entry opening.
According to embodiments of the present invention, a cable connector system kit for use with an electrical cable including a primary conductor and an insulation layer surrounding the primary conductor, wherein the insulation layer has an insulation terminal end and the primary conductor extends beyond the insulation terminal end, includes a connector, a flow block member and a flowable sealant. The connector defines a conductor bore, an entry opening communicating with the conductor bore, and a connector end face surrounding the entry opening. The connector is adapted to mechanically and electrically couple with the primary conductor. The flow block member defines a passage extending therethrough and adapted to receive the primary conductor. The flowable sealant can be applied about the connector and the insulation layer. The connector and the flow block member are relatively configured and constructed to be assembled into a connector system wherein: the primary conductor extends through the passage and the entry opening and into the conductor bore, the primary conductor being mechanically and electrically coupled to the connector; the flow block member is thereby mounted on the primary conductor and interposed between the insulation terminal end and the connector end face; the sealant surrounds the flow block member and adjacent portions of the insulation layer and the connector; and the flow block member inhibits flow of the sealant into the conductor bore through the entry opening.
Further features, advantages and details of the present invention will be appreciated by those of ordinary skill in the art from a reading of the figures and the detailed description of the preferred embodiments that follow, such description being merely illustrative of the present invention.
The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which illustrative embodiments of the invention are shown. In the drawings, the relative sizes of regions or features may be exaggerated for clarity. This invention may, however, 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.
It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another region, layer or section. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the present invention.
Spatially relative terms, such as “beneath”, “below”, “lower”, “above”, “upper” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the exemplary term “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90° or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.
As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless expressly stated otherwise. It will be further understood that the terms “includes,” “comprises,” “including” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. It will be understood that when an element is referred to as being “connected” or “coupled” to another element, it can be directly connected or coupled to the other element or intervening elements may be present. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.
Unless otherwise defined, 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. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of this specification and the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
As used herein, “monolithic” means an object that is a single, unitary piece formed or composed of a material without joints or seams.
With reference to
The connector system 101 can be used to electrically and mechanically couple or splice a pair of electrical power transmission cables. The spliced cables may include polymeric insulated cables, paper-insulated lead cables (PILC), or one of each. In the embodiment illustrated in
The cable 30 (
In the illustrated embodiment, the three conductors 32 of the cable 30 are each spliced to a respective one of three polymeric cables 60. As shown in
However, it will be appreciated that polymeric cables of other types and configurations may be used with the connector system 101. For example, the polymeric cable may include three conductors, each surrounded by a respective polymeric insulation and a respective semiconductive elastomer, and having a metal shield layer collectively surrounding the three conductors and a polymeric jacket surrounding the shield layer.
In the illustrated embodiment, three connector systems 101 are employed (one for each phase), as shown in
The connector system 101 includes a mechanical and electrical connector 130 (
According to some embodiments and as shown, the connector 130 (
Each bolt 144 includes a shank 146 and a head 148. The head 148 may be configured to operably engage a driver to be forcibly driven by the driver. The shank 146 includes a threaded section 146A configured to threadedly engage an associated one of the bolt bores 142. The shank 146 also includes a breakaway section 146B between the threaded section 146A and the head 148. Each bolt 144 is adapted to be screwed down into its respective bolt bore 142 to clamp a conductor 32, 62 in the underlying conductor bore 136A or 136B. The head 148 on the bolt 144 is configured to shear off of the threaded shank 146A at the breakaway section 146B when subjected to a prescribed torque. According to some embodiments, the bolt 144 is formed of copper or aluminum.
The spacer inserts 149 are each optionally positioned in a respective one of the bores 136A, 136B. In
The flow block members 150, 150′ may be constructed and configured in the same manner. Accordingly, the description of the flow block member 150 below may likewise apply to the flow block member 150′. However, the flow block members 150, 150′ need not be identical.
With reference to
The flow block member 150 may be formed of any suitable material. According to some embodiments, the flow block member 150 is formed of a resiliently deformable material. According to some embodiments, the flow block member 150 is formed of an elastomeric material. According to some embodiments, the flow block member 150 is formed of silicone rubber. Other suitable elastomeric materials may include ethylene-propylene-diene-monomer (EPDM) rubber, butyl rubber or nitrile rubber. However, silicone rubber may be particularly advantageous because silicone rubber is stable over a wide service temperature range, is highly resistant to oil absorption, and will not degrade when subjected to oil.
According to some embodiments, the flow block member 150 has a Young's Modulus of in the range of from about 1 to 20 MPa and, in some embodiments, from about 1 to 5 MPa.
According to some embodiments, the flow block member 150 has a Shore A hardness in the range of from about 10 to 90.
The flow block member 150 may be formed using any suitable technique. According to some embodiments, the flow block member 150 is molded or extruded and, according to some embodiments, injection molded. Alternatively, the flow block member 150 may be stamped. According to some embodiments, the flow block member 150 is monolithic and the body 152 and tab 156 are unitarily molded or otherwise formed such that they form a unitary structure.
According to some embodiments, the flow block member 150 is formed of a closed cell polymeric foam. According to some embodiments, the closed cell foam is an oil-resistant base polymer such as silicone. In some embodiments, the elasticity/compressibility of the closed cell foam is in the range of from about 20 to 70 percent to accommodate a wide application range. In some embodiments, the individual cells of the foam have a size or sizes in the range of from about 0.5 to 1 mm. In some embodiments, the exposed surfaces of the flow block member 150 are smooth and may be substantially non-porous. In other embodiments, at least some of the exposed surfaces are rough or have exposed open cells (e.g., as obtained from cutting a foam block, bar or tube into pieces). According to some embodiments, the polymer foam has a low tension set and high application temperature. According to some embodiments, the closed cell foam flow block members are extruded and cut or sliced into substantially flat rings, which form the body of the flow block member.
The mastic 170 (
The mastic 170 may be any suitable sealing mastic. According to some embodiments, the mastic 170 is resistant to chemical attack from oil, and resistant to migration of oil therethrough. According to some embodiments, the mastic 170 is formed of nitrile rubber, epichlorhydrin rubber, or fluorinated rubber.
The cover system 104 may further include three tubular oil barrier tubes (OBTs) 110 (
Each OBT 110 (
The breakout 112 (
The stress control tubes 114 (
The three heat shrinkable tubes 116 (
The breakout 117 (
The re-jacketing sleeve 118 (
The constructions of the connector system 101 and the cover assembly 102 may be further appreciated in view of methods for forming the connection assembly 104 (
With reference to
As shown in
Each cable 60 is prepared by cutting each layer 62, 64, 65, 66 and 68 such that a segment of each layer 62, 64, 65 and 66 extends beyond the next overlying layer 64, 65, 66 and 68 as shown in
The following procedure can be executed for each of the cable core 40/polymeric cable 60 pairs in turn.
In the exemplary connection, the size (outer diameter) of the conductor 32 is in a range better accommodated by the full bore 136B, and therefore, the installer will not install a spacer insert 149 in or, if pre-installed, will remove the spacer insert 149 from the conductor bore 136B. Also, in the exemplary connection, the size (outer diameter) of the conductor 64 is in a range better accommodated by a conductor bore smaller in size than the full bore 136A, and therefore, the installer will install the spacer insert 149 in or, if pre-installed, will retain the spacer insert 149 in the conductor bore 136A.
With reference to
The bolts 144 overlying the bore 136A are driven into the bore 136A via their heads 148 until sufficient torque is applied to shear the head 148 off at the breakaway section 146. The intruding bolts 144 may tend to forcibly radially displace the conductor 64 in the offset direction O with respect to the bore centerline CL-CL. At this time, the end segment of the conductor 62 is secured in the bore 136A by the remainder of each bolt 144, as shown in
According to some embodiments, the gap width W1 is the same as or less than the relaxed width W2 (
According to some embodiments, the relaxed height H1 (
According to some embodiments, the relaxed inner diameter D2 (
According to some embodiments, the relaxed outer diameter D3 (
The cable core 40 is likewise coupled to the connector 130. In the same manner, the flow block member 150′ is mounted on the conductor 32 and the conductor 32 is secured in the connector bore 136B by the corresponding shear bolts 144 to thereby capture the flow block member 150′ between the terminal edge or face 110B of the OBT 110 and the connector end face 140B, as shown in
The mastic 170 is then wrapped about the cable core 40, the flow block member 150′, the connector 130, the flow block member 150 and the polymeric cable 60 as shown in
According to some embodiments, the mastic 170 overlaps the insulation 64 by a distance L2 (
The stress control tube 114 is then mounted around the connector 130, the mastic 170 and adjacent portions of the cables 30, 60. The stress control tube 114 overlaps a portion of the semiconductive layer 65 on one end and a portion of the OBT semiconductive layer 110A on the other end.
Each of the other cable pairs can be connected and covered in the same manner as described above using respective connector systems 101.
The heat shrinkable tubes 116 are then mounted around the connections such that they overlap the neutral conductors 66 on one end and a grounding conductor (not shown) on the other end, as shown in
The assembly can thereafter be grounded, shielded and re-jacketed in known manner, for example. For example grounding braids can be connected to the shield layers 68 of the polymeric cables 60 and the metal sheath 30 by clamps or the like. The entire joint assembly can be covered by the re-jacketing sleeve 118 (
The connector system 101 can provide significant advantages and overcome or mitigate problems commonly associated with similar connections of the known art. Because the inner diameter of the conductor bore 136A, 136B of the connector 130 is greater than the outer diameter of the received conductor 62, 32, a significant gap G will often be created between the conductor and the bore wall 135 at the opening 138A, 138B. In connector systems of the prior art, this gap presents a passage through which the mastic 170 at the joints between the insulation 64 or OBT 110 and the connector 130 can flow into the conductor bore 136A, 136B. Notably, this mastic 170 is relied upon to provide electrical stress relief at the joint 107. The unintended loss of the mastic 170 into the connector 130 can therefore risk failure or degradation of the splice due to electrical stresses.
Various environmental parameters may encourage or induce flow of the mastic 170 into the conductor bores. In service, environmental and electrical resistance heating of the connection and conductors heats the mastic 170, thereby softening and reducing the viscosity of the mastic 170. With reference to
The connector system 101 according to embodiments of the present invention can prevent, limit or inhibit such unintended and undesirable flow, displacement or extrusion of the mastic 170 into the conductor bores 136A, 136B. The flow block members 150, 150′ block or dam the gaps G at the openings 138A, 138B so that the mastic 170 is retained about the joints 107 (
In the case of the joint between the connector 130 and the cable 30, the mastic 170 may also be relied upon to prevent or inhibit oil from leaking from the cable 30 (e.g., by sealing the open end of the OBT 110). By preventing or inhibiting displacement of the mastic 170, the connector system 101 (in particular, the flow block member 150′) can preserve the integrity of the mastic oil stop seal to retain the oil in the PILC cable 30 even when relatively high oil internal pressures are induced, such as by increases in temperature or placement of the connection at lower elevation than other parts of the cable 30.
Forming the flow block members 150, 150′ of silicone rubber may be particularly advantageous for multiple reasons. Silicone rubber is extremely stable across a wide temperature spectrum including the temperature range (from about −40° C. to 250° C.) typically experienced by electrical power transmission connectors. Silicone rubber is highly resistant to attack by and absorption of oil such as the oil contained in the cable 30. Silicone rubber is tear resistant. As discussed above, the resilience of silicone rubber can enable significant cable diameter range taking.
However, according to further embodiments, the flow block members 150, 150′ may be formed of other materials. According to some embodiments, the flow block members 150, 150′ are formed of a polymeric material, and in some embodiments an elastomeric material, other than silicone rubber. According to some embodiments, the flow block members 150, 150′ are formed of nylon. According to some embodiments, the flow block members 150, 150′ are formed of PTFE (e.g., Teflon). According to some embodiments, the flow block members 150, 150′ are formed of metal (e.g., copper).
According to further embodiments, the flow block members 150, 150′ may be formed without insert tabs 156. In particular, the flow block members may be formed by extruding and cutting a tube of the flow block member material into flat rings.
The insert tab 156 of each flow block member 150, 150′ can assist the installer in positioning the conductor 62, 32 in the bore 136A, 136B. The insert tab 156 may serve to positively locate the flow block member 150, 150′ relative to the connector 130 and the conductor 62, 32. The insert tab 156 can brace or reinforce the body 152 to resist axial deflection that may otherwise permit mastic 170 to flow past the flow block member 150, 150′ into the bore 136A, 136B.
With reference to
The connector system 201 includes strips of metal mesh 210, which may be dispensed from a roll 211 (
With reference to
With reference to
The connector system 401 includes a pair of spring clamps 410 (
With reference to
The connector system 501 includes a pair of split rings 510 (
With reference to
With reference to
The connector system 701 includes flow block members 750, 750′ (
In use, the flow block members 750, 750′ may be installed in the same manner as described above for the flow block members 150, 150′, except as follows. The flow block member 750 is slid onto the conductor 62, which is in turn inserted into the bore of the connector 130. At this time, the cover flap 760 may be positioned around the body 752 or an adjacent portion of the connector 130. The cover flap 760 is then pushed, slid, rolled or otherwise extended out over the cable insulation 64 as shown in
According to some embodiments, the relaxed inner diameter of the resilient cover flap 760 is less than the outer diameter of the insulation 64 so that the cover flap 760 is elastically expanded and exerts a persistent radially compressive load on the insulation 64.
The flow block member 750′ and its cover flap 760 may be installed on the cable 30 in the same manner such that the cover flap 760 overlaps the OBT 110 as shown in
According to some embodiments, a supplemental layer of mastic may be applied to (e.g., wrapped around) the insulation 64 and/or the OBT 110 adjacent the associated flow block member 750, 750′ prior to extending the cover flap 760 thereof. The cover flap 760 is then extended so that the deployed cover flap 760 surrounds the supplemental mastic layer (which is interposed between the cover flap 760 and the insulation 64 or OBT 110).
The cover flaps 760 can serve to secure the flow block members 750, 750′ on the cables 60, 30. The cover flaps 760 can also serve to prevent or inhibit the flow of the mastic into the gap between the insulation 64 and the block member 750, or into the gap between the OBT 110 and the flow block member 750′, and through the through passages 754 around the conductors 62, 32.
With reference to
With reference to
The inner and outer subbodies 857, 859 can be selectively separated at the separation line 855. According to some embodiments, the body 852 is frangible at the separation line 855 and the subbodies 857, 859 are separated by tearing along the separation line 855. According to some embodiments, the body 852 is cut (e.g., using a knife blade) along the separation line 855 to separate the subbodies 857, 859.
The inner subbody 857 defines an inner passage 857A for the cable conductor 32, 62 having a first diameter D5. When the subbody 857 is removed, the outer subbody 859 defines a passage 859A for the conductor 32, 62 having a diameter D6. It will be appreciated that the diameter D6 is greater than the diameter D5.
In use, for a conductor 32, 62 having an outer diameter in a first range, the flow block member 850 is mounted thereon with the inner subbody 857 in place within the outer subbody 859. However, for a conductor 32, 62 having an outer diameter in a second range greater than the first range, the inner subbody 857 is removed and the outer subbody 859 is mounted on the conductor 32, 62. Accordingly, the flow block member 850 can be properly fitted to a greater range of cable sizes.
In some embodiments, the connector 130 may be provided without an oil block wall 134, in which case the two conductor bores 136A, 136B may form parts of a bore that passes fully through the connector body 132.
Connector systems according to embodiments of the invention may be used for any suitable cables and connections. Such connector systems may be adapted for use, for example, with connections of medium voltage cables (i.e., between about 8 kV and 46 kV).
While the connections to PILCs have been described herein with reference to PILC-to-polymeric cable transition splices, connector systems as disclosed herein may also be used in PILC-to-PILC splices and polymeric cable-to-polymeric cable splices. Connector systems according to embodiments of the invention may also be configured for non-splice cable terminations and elbows, for example, for PILC cables and polymeric cables.
The foregoing is illustrative of the present invention and is not to be construed as limiting thereof. Although a few exemplary embodiments of this invention have been described, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention. Therefore, it is to be understood that the foregoing is illustrative of the present invention and is not to be construed as limited to the specific embodiments disclosed, and that modifications to the disclosed embodiments, as well as other embodiments, are intended to be included within the scope of the invention.
Number | Name | Date | Kind |
---|---|---|---|
3770871 | Goodman | Nov 1973 | A |
4262167 | Bossard et al. | Apr 1981 | A |
4701574 | Shimirak et al. | Oct 1987 | A |
5201914 | Hollick | Apr 1993 | A |
5422438 | Lamome | Jun 1995 | A |
6284976 | Pulido et al. | Sep 2001 | B1 |
7952020 | Yamamoto et al. | May 2011 | B2 |
8404975 | Chang | Mar 2013 | B2 |
20030127242 | Pilling et al. | Jul 2003 | A1 |
20130056268 | Bumgarner | Mar 2013 | A1 |
Entry |
---|
“Aluminum Shearbolt Connector” Instruction Sheet 408-8990, Jul. 5, 2006 Rev D, Tyco Electronics Corporation (2 pages). |
“HVS-T-1580E-S 15kV Class Trifurcating Transition Splice for 3/C PIL to 3 1/C Extruded Dielectric (Poly/EPR) Power Cables” Raychem PII 54917, Rev AJ, PCN 307937-000, Effective Date: Mar. 13, 2007 (18 pages). |
“General Instructions for Installation of Straight Bolted Connector on Splices” UE-1.0.9, Oh & Ug Distribution System Standards, Date: Oct. 3, 2008 (1 page). |