MXPA98008511A - Insulated glass / non-linear dielectric electric cable and product method - Google Patents

Abstract

The present invention relates to a cable (100, 1120) for transmitting electrical energy, it is constructed with a layer (104) of insulation and shielding material, comprising pre-impregnated strands, for example, glass strands (105), which transport a non-linear dielectric material, formed concentrically with respect to an electrical conductor (102). A portion of the layer (104) is moved by the braided material (116), pre-impregnated with a thermally conductive material to define a longitudinal thermal distribution channel (114) on the cable (100, 120). The layer (104) of non-linear dielectric material improves field control within the cable (100, 120) and also the temperature profile on the cable (100, 120), both of which improve performance and useful lifespan. In addition, the electric field and the electromagnetic interference (EMI) around the cable (100, 120), are reduced. The longitudinal thermal distribution channel (114) additionally improves the temperature profile on the cable (100, 12

Description

ELECTRIC CABLE ISOLATED GLASS / DIALECTIC NQ LINE !. AND TECHNICAL FIELD PRODUCTION METHOD The present invention relates in general to insulated cables for transmitting electric power and more particularly to cables using insulating and shielding material, generally formed concentric around a central conductor by means of braided material, for example glass, pre - impregnated with a non-linear dielectric material. The invention also relates to the manufacture of these cables, BACKGROUND A large variety of structures for insulated cables are known in the art. Typically, these cables include a core or core electrical conductor, such as copper, which can be either solid or stranded. One or more layers of material are then applied over the electrical conductor to form an insulated wire. It is a main function of the one or more cover layers, to electrically isolate the conductor. In addition, layers can also be provided to improve the thermal resistance of the cable, to provide fire resistance and reduced associated smoke release, if the cable is burned or heated at high temperatures, to provide resistance to the cable, to allow the cable to be peel easily for cable utilization, to provide abrasion resistance and the like. While a wide variety of materials have been employed for cable jacket layers, including glass and polymeric materials, recent investigations of so-called "smart materials" offer promise for further improvement of insulated cables. Intelligent materials are a class of more varieties that exhibit self-adaptive abilities in response to external stimuli in a way that they seem to have inherent intelligence in adapting to the stimulus. Of particular interest to insulating cables are nonlinear dielectric materials that have changing dielectric constants in response to changes in temperature and / or electric field. During investigations of temperature sensitivity of these nonlinear dielectrics, it has been suggested that nonlinear dielectric compounds can greatly improve field control in high voltage applications. Unfortunately, structures for such cables have not been described or suggested. There is a continuing need for improvements in insulated cables that extend both the operational characteristics and the service life of these cables. Preferably, new cable structures will improve field control within the insulated cables and also the temperature profile on the cable, both of which will improve performance and expected service life. DESCRIPTION OF THE UT UTION This need is met by the method and apparatus of the present invention, wherein a cable is constructed with a layer of insulating and shielding material comprising pre-impregnated strands, for example strands or glass strands, which transport a suitable non-linear dielectric material, formed concentrically with respect to the electrical conductor. A portion of the layer can be displaced by the braided material, pre-impregnated with a thermally conductive material, to define a longitudinal heat distribution channel on the cable. The non-linear dielectric material layer improves the field control within insulated cables and also the temperature profile on the cable, both of which improve the expected performance and life expectancy. In addition, the electric field and electromagnetic interference (EMI = Electro Magnetic Interference) around the cable are reduced. By including a longitudinal thermal distribution channel on the cable, the profile of the temperature on the cable is further improved. According to one aspect of the present invention, a cable for transmission of electrical energy comprises an electrical conductor with a layer of insulating and shielding material, generally concentric formed. The insulating layer in the shield comprises braided material, for example glass pre-impregnated with a non-linear dielectric material. A continuous coating covers the layer of insulating and shielding material for cable protection. The braided material may comprise continuous wicks and the dielectric material may be selected from the group consisting of barium titanate, titanic acid esters, rutile, titanium oxides and mixtures including barium titanate. The cable preferably also comprises an organic insulating layer selected from the group consisting of high density polyethylene, fluoropolymers and fluoroplastic formed between the electrical conductor and the layer of insulating and shielding material. The layer may further comprise an elastomeric polymer binding layer, for example neoprene, formed between the layer of insulating and shielding material and the continuous protective cover for holding the braided material of the insulation layer and the shielding with the cable. For applications where it is desired to ground, the cable can still further comprise an electrically conductive layer formed around the layer of insulating and shielding material. The electrically conductive layer can take the place of the elastomeric polymer binding layer or be used with the elastomeric polymer layer. For applications that require a water blocking barrier, the cable may further comprise a water blocking material formed between the electrically conductive layer or the elastomeric polymer layer and the continuous protective cover. The water blocking material may comprise a braided material, for example glass, pre-impregnated with super absorbent powder. The braided material forming the layer of insulating and shielding material can run generally parallel to the electrical conductor or can be wound around the electrical conductor at an angle with respect to the axis of the electrical conductor. The winding angle can vary between approximately 0 and 60 ° with respect to a longitudinal axis of the electrical conductor. The continuous protective coating may be selected from the group consisting of high density polyethylene, fluoropolymers and fluoroplastics. To improve the temperature profile on the cable, a portion of the layer of insulating and shielding material can be moved by the braided material such as glass, pre-impregnated with a thermally conductive material, to define a longitudinal thermal distribution channel on the wire. The displaced portion may be in the range from about 1% to 50% of the layer of insulation and shielding material. According to another aspect of the present invention, a method for forming cable for transmission of electrical energy may comprise the steps of: providing an electrical conductor; applying concentrically around the electrical conductor a layer of insulating and shielding material formed of braided material, for example glass, pre-impregnated with a non-linear dielectric material; and cover the layer of insulating and shielding material with a continuous protective coating. The step of applying concentrically around the electrical conductor a layer of insulating material and shield formed of braided material pre-impregnated with a dielectric material, can comprise the step of pre-impregnating the braided material with a non-linear dielectric material selected from the group that it consists of barium titanate, titanic acid esters, rutile, titanium oxides and mixtures that include barium titanate. The method for forming a cable for transmission of electrical energy may further comprise the steps of: forming an organic insulating layer between the electrical conductor and the layer of insulating and shielding material; forming a bonding layer of elastomeric polymer between the layer of insulating and shielding material and the continuous protective cover; forming an electrically conductive layer around the layer of insulating and shielding material; forming a layer of water blocking material between the electrically conductive layer or tie layer and the continuous protective cover; and forming a portion of the layer of insulating material and shielding of braided material pre-impregnated with a thermally conductive material, to define a longitudinal heat distribution channel on the cable. Thus, an object of the present invention is to provide an improved electrical cable that is uninsulated, at least in part by a layer of insulating and shielding material, comprising pre-impregnated yarns transporting a non-linear dielectric material and a method to produce the cable; and to provide said cable and method wherein a longitudinal thermal distribution channel is formed on the cable within the layer of insulating and shielding material. Other objects and advantages of the invention will be apparent from the following description, the accompanying drawings and the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a perspective view of a first embodiment of a cable for transmitting electrical energy according to the present invention, with successive layers removed to show the structure; Figure 2 is a sectional view of the cable of Figure 1; and Figure 3 is a perspective view of an alternative embodiment of a cable for transmitting electric power according to the present invention, with successive layers removed to show the structure. BEST MODE FOR CARRYING OUT THE INVENTION The present invention will now be described with reference to the drawings in which Figures 1 and 2 illustrate a first embodiment of an isolated cable 100 for transmitting electrical energy. It is noted that the invention of the present application can be incorporated into a variety of structures, with the most basic structure including a central electrical conductor 102, a layer 104 of insulating and shielding material formed generally concentric around the electrical conductor 102 by braided material , for example glass wires 105, as illustrated, pre-impregnated with a non-linear dielectric material and a protective coating 106 covering the insulating and shielding layer 104, to form the exterior of the cable. While barium titanate and mixtures that include barium titanate for the non-linear dielectric material are currently preferred, other non-linear dielectric materials may be employed in the present invention, including for example titanium, rutile and titanium oxide esters. The braided material may comprise continuous threads, continuous wicks, continuous tape or the like, which will also be referred to herein as threads or braided material. While the braided material is illustrated to run in parallel with the central electrical conductor 102, it can also be braided, sewn or any combination of braiding and parallel stitching, the various noted shapes of braided material being interspersed, in layers, to form a structure sandwich or similar. It is currently preferred to use braided glass material for layer 104; however, other inorganic as well as organic materials may be employed in the present invention, including for example textile fibers, polytetrafluoroethylene fibers, polypropylene fibers and aramid fibers. It is noted that some of these fibers tend to melt at elevated temperatures such that their use is limited to low temperature applications. In the first illustrated embodiment, the electrical conductor 102 is covered with a jacket or liner 108 made for example of high density polyethylene, suitable non-conductive materials based on rubber, polytetrafluoroethylene or other fluoropolymers and fluoroplastics. The liner 108 improves the flexibility of the cable 100 and the movement between the electrical conductor 102 and the layer 104 of insulating and shielding material. The glass strands 105 finally employed to form the layer 104 of the insulating and shielding material are prepared by impregnating with suitable materials, such as thermoplastic polymers or thermosets, to protect the wires against self-abrasion. The glass threads are then coated with organic or inorganic fillers which exhibit a non-linear dielectric constant as a function of applied field and / or temperature intensity. The filler material increases the thickness of the glass threads and changes the dielectric properties of the glass threads to make them proportional to the dielectric properties of the fillers. The thickness of the layer 104 varies, depending on the cable that is produced and is determined based on the nominal power of the cable. In addition to insulation and shielding, the glass strands or filaments of the layer 104 contribute to the strength of the cable 100. The glass wires 105 thus prepared are generally concentrically formed around the electrical conductor 102 on the coating 108, to form the layer 104 of the insulating and shielding material. The glass strands 105 may be formed on the coating 108 of the electrical conductor 102 in a variety of ways including crosslinking, braiding, helical superposition and parallel placement. The required flexibility of the insulated cable 100 that is formed can be influenced in a certain proportion by the angle of the glass strands 105 with respect to the longitudinal axis A of the cable 100. Preferably, the angle of the glass strands 105 with respect to the longitudinal axis A is between 0 and 60 °. Whichever way they are applied, the glass strands 105 of the layer 104 are held in place within the mechanical cable 100, chemically or through another attachment mechanism. In the illustrated embodiment of Figures 1 and 2, glass yarns 105 of layer 104 are held in place by a tie layer shown as a jacket or liner 110 made of neoprene or other elastomeric polymer. As previously noted, the layer 104 of insulation and shielding material incorporated in the cable 100, exhibits a non-linear dielectric constant as a function of the field strength and / or temperature applied. When using the annotated materials, the dielectric constant is a function of both the field strength and applied temperatures, both of which improve the performance of the 100 cable. Improved performance is obtained since in areas where the electric field is increased, the The dielectric constant of the layer 104 is also increased thereby reducing the dielectric stress in the layer 104 and homogenizing the field distribution. Also, an increase in the electric field is accompanied by an increase in temperature that also increases the dielectric constant, thus supplementing more the improved performance of the insulated 100 wire. Often insulated cables are required that offer a water blocking barrier, particularly for communications applications. While water blocking greases can be injected into a cable to prevent water penetration, these greases create handling problems and thus the so-called "dry cables" or cables that perform blockage of water without fats are preferred. To perform the dry water blockWater-swellable or swellable powders, such as sodium salts of polyacrylic polymers, are used to replace fats. While water-swellable powders can be used directly within a cable, preferably glass or other fiber strands are pre-impregnated with a water-soluble powder and then incorporated into a cable to prevent water from penetrating the cable.

Water blocking is provided in the insulated cable 100 by a layer 112 of water blocking material formed of the liner 110 and the liner 406. In the embodiment illustrated in Figures 1 and 2, the layer 112 of water blocking material is formed by braided material 113, for example glass or aramid fibers distributed on the market under the trademark Kevlar ™ (Keviar is a trademark of The DuPont of Neumours and Company, Inc.), pre-impregnated with water-swellable dust. This braided material 113 is commercially available from a variety of sources. In the first illustrated embodiment of the invention, a longitudinal thermal distribution channel 114 is formed on the insulated cable 100, to further improve the performance of the cable 100. Channel 114, which is thermally conductive, distributes heat from the sites of its first temperature on the cable 100 to sites of lower temperature, thereby better anticipating the heat produced within the cable 100. As illustrated, the longitudinal thermal distribution channel 114 is formed by displacing a portion of the layer 104 of insulation material and of shielding with braided material 116, such as glass, pre-impregnated with a thermally conductive layer such as graphite, nickel or titanium. Preferably, the thermal distribution channel 114 displaces between 1% and 50% of the layer 104 of the insulation and shielding material. The heat distribution channel 114 is illustrated as continuous and generally centered within the layer 104 of the insulation and shielding material in Figures 1 and 2. However, the heat distribution channel 114 can be located anywhere between the coating 108 of the electrical conductor 102 and the coating 110, and may be discontinuous or randomly distributed through the layer 104, as is the case for the alternating mode of the cable 120 of Figure 3 which will now be described. Elements of the cable 120 that we only saw that those of the cable 100 will be numbered the same as in Figures 1 and 2. To avoid repetition and unnecessary lengthening of the description of the present invention, the elements of the cables 100 and 120 that are equal, not it will be described with respect to the cable 120. The differences between the cable 120 and the cable 100 are the supply of an electrically conductive layer 122, which is formed with respect to the layer 104 of insulation and shielding material and the formation of the layer 104 itself. In particular, the electrically conductive layer 122 provides grounding for the cable 120, while grounding is generally required for high voltage cables, for example cables that carry 15 kilovolts or more. The grounding layer 122 can be formed by using copper tape, electrically conductive polymeric film, electrically conductive fibers or tapes that are woven or otherwise formed around the layer 104. For cables operating at low voltages, typically no it requires grounding such that the first illustrated mode can be preferred as the least expensive. Whether or not there is a ground connection, and therefore the electrically conductive layer 122 is required, it depends on the specific components of a cable and the operating voltage or voltage, and can be determined empirically through tests on the cable. The layer 104 of insulation and shielding material is formed using components described above. In the alternate embodiment of Figure 3, layer 104 comprises an inner layer 104A of insulation and shielding materials as previously described without any interspersed thermal distribution. An outer layer 104B is formed on the inner layer 104A to complete the layer 104. The outer layer 104B also comprises insulation and shielding material; however, between mixing is the thermal distribution channel 114. As illustrated, heat distribution heat 114 is randomly distributed through the outer layer 104B, but may take other forms as previously described and will be suggested by those skilled in the art. the specialty, from the description of the present application. Having thus described the invention of the present application in detail and by reference to preferred embodiments thereof, it will be apparent that modifications and variations are possible without departing from the scope of the invention defined in the appended claims.

Claims (26)

1. CLAIMS 1. - A cable for transmitting electrical energy, characterized in that it comprises: an electrical conductor; a layer of insulation and shielding material formed generally concentric around the electrical conductor by braided material, pre-impregnated with a non-linear dielectric material; and a continuous protective coating that covers the layer of insulation and shielding material.
2. 2. - A cable for transmission of electric power according to claim 1, characterized in that the braided material comprises continuous wicks.
3. 3. - A cable for transmission of electrical energy according to claim 1, characterized in that the braided material comprises glass.
4. 4. - A cable for transmission of electrical energy according to claim 1, characterized in that the dielectric material is selected from the group consisting of barium titanate, titanic acid esters, rutile, titanium oxides and mixtures including barium titanate .
5. 5. - A cable for transmission of electrical energy according to claim 1, characterized in that it also comprises an organic insulating layer formed between the electrical conductor and the layer of insulation material and shielding.
6. 6. - A cable for transmission of electrical energy according to claim 5, characterized in that the organic insulation layer is chosen from the group consisting of high density polyethylene, fluoropolymers and fluoroplastic.
7. 7. - A cable for transmission of electrical energy according to claim 5, characterized in that it further comprises an electrically conductive layer formed between the layer of insulation material and shielding and the continuous protective coating.
8. 8. - A cable for transmission of electrical energy according to claim 5, characterized in that it also comprises an elastomeric polymer binding layer, formed between the layer of insulation material and shielding and the continuous protective coating.
9. 9. A cable for transmission of electrical energy according to claim 8, characterized in that the bonding layer is formed of neoprene.
10. 10. - A cable for transmission of electrical energy according to claim 9, characterized in that the bonding layer further comprises an electrically conductive layer formed with respect to the layer of insulation material and shielding.
11. 11. A cable for transmission of electrical energy according to claim 8, characterized in that it also comprises a layer of water blocking material formed between the elastomeric polymer layer and the continuous protective coating
12. 12. - A cable for power transmission electrical device according to claim 11, characterized in that the layer of water-blocking material comprises a braided material pre-impregnated with super-absorbent powder.
13. 13. - A cable for transmission of electric power according to claim 1, characterized in that the braided material runs generally parallel to the electrical conductor.
14. 14. - A cable for transmission of electrical energy according to claim 1, characterized in that the braided material is wound around the electric conductor at an angle ranging between approximately 0 and 60 ° with respect to a longitudinal axis of the electrical conductor.
15. 15. - A cable for transmission of electrical energy according to claim 1, characterized in that the continuous protective coating is chosen from the group consisting of high density polyethylene, fluoropolymers and fluoroplastic.
16. 16. - A cable for transmission of electrical energy according to claim 1, characterized in that a portion of the layer of insulation and shielding material comprises braided material pre-impregnated with a thermally conductive layer to define a channel of longitudinal thermal distribution over the wire.
17. 17. - A cable for transmission of electrical energy according to claim 16, characterized in that the portion comprises between approximately 1% and 50% of the layer of insulation and shielding material.
18. 18. Method for forming a cable, for transmission of electrical energy, characterized in that it comprises the steps of: providing an electrical conductor; applying concentrically around the electrical conductor a layer of insulating material and shield formed of braided material, pre-impregnated with a non-linear dielectric material; and cover the layer of insulation material and shielding with a continuous protective layer.
19. 19. Method for forming a cable, for transmission of electrical energy according to claim 18, characterized in that the step of concentrically applying a layer of insulation material around the electrical conductor and shield formed of braided material pre-impregnated with a material dielectric, comprises the step of pre-impregnating the braided material with a non-linear dielectric material, selected from the group consisting of barium titanate, titanic acid esters, rutile, titanium oxides and mixtures including barium titanate.
20. 20. Method for forming a cable, for transmission of electrical energy according to claim 19, characterized in that it also comprises the step of forming an organic insulating layer between the electrical conductor and the layer of insulation material and shielding.
21. 21. Method for forming a cable, for transmission of electrical energy according to claim 20, characterized in that it further comprises the step of forming an electrically conductive layer between the layer of insulation and shielding material and the continuous protective coating.
22. 22. Method for forming a cable for transmission of electrical energy according to claim 21, characterized in that it further comprises the step of forming a layer of water blocking material between the electrically conductive layer and the continuous protective coating.
23. 23. Method for forming a cable, for transmission of electrical energy according to claim 22, characterized in that it also comprises the step of forming a portion of the layer of insulation material and shielding of braided material, pre-impregnated with a material thermally conductive, to define a longitudinal thermal distribution channel on the cable.
24. 24. Method for forming a cable for transmission of electrical energy according to claim 20, characterized in that it also comprises the step of forming a bonding layer of an elastomeric polymer between the layer of insulation material and shielding and the protective coating continuous.
25. 25. Method for forming a cable for transmission of electrical energy according to claim 24, characterized in that it further comprises the step of forming a layer of water blocking material between the bonding layer and the continuous protective coating.
26. 26. Method for fprmar a cable, for transmission of electrical energy according to claim 25, characterized in that it also comprises the step of forming a portion of the layer of insulation material and shielding of braided material pre-impregnated with a material thermally conductor to define a longitudinal thermal distribution channel on the cable.