EP1190424A1 - Cable electrique avec agent auto-obturant et procede pour empecher l'eau de toucher le conducteur - Google Patents

Cable electrique avec agent auto-obturant et procede pour empecher l'eau de toucher le conducteur

Info

Publication number
EP1190424A1
EP1190424A1 EP00908261A EP00908261A EP1190424A1 EP 1190424 A1 EP1190424 A1 EP 1190424A1 EP 00908261 A EP00908261 A EP 00908261A EP 00908261 A EP00908261 A EP 00908261A EP 1190424 A1 EP1190424 A1 EP 1190424A1
Authority
EP
European Patent Office
Prior art keywords
cable
conductor
insulation
installation
electrical cable
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
EP00908261A
Other languages
German (de)
English (en)
Other versions
EP1190424A4 (fr
Inventor
David Reece
Jonathan Waller
Nick Ware
Philip Sasse
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Southwire Co LLC
Original Assignee
Southwire Co LLC
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Southwire Co LLC filed Critical Southwire Co LLC
Priority claimed from PCT/US2000/000703 external-priority patent/WO2001052272A1/fr
Publication of EP1190424A1 publication Critical patent/EP1190424A1/fr
Publication of EP1190424A4 publication Critical patent/EP1190424A4/fr
Ceased legal-status Critical Current

Links

Classifications

    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A30/00—Adapting or protecting infrastructure or their operation
    • Y02A30/14—Extreme weather resilient electric power supply systems, e.g. strengthening power lines or underground power cables

Definitions

  • Insulated solid and stranded electrical cables are well known in the art.
  • Generally stranded cables include a central stranded conductor with a protecting insulation j acket disposed around the conductor.
  • the tougher cable is described as "ruggedized,” and generally consists of two layers: an inner layer of high molecular weight polyethylene and an outer layer of high density polyethylene. This design is more resistant to mechanical damage than one pass crosslinked polyethylene, but still can result in exposure of the aluminum conductor if sufficient impact is involved.
  • the mechanism of aluminum cable failure is the formation of hydrous aluminum oxide. As the aluminum oxide solids build up, the insulation in the vicinity of the puncture is forced to swell and splits open, making larger areas of the aluminum conductor surface available for electrolysis, thus increasing the leakage current and accelerating the corrosion process. Rapid loss of aluminum by AC electrolysis continues until ultimately the cable is open-circuited. A caustic environment is created at the aluminum, electrolyte interface, which dissolves the protective oxide film.
  • SUBSTITUTE SI IEET (RULE 26) The above margins of electrical performance were measured on new cables. They are far above what is needed to operate on a 600 V system since most of these cables operate at 120 V to ground.
  • One of the tests during compound and product development is a long term insulation resistance test performed in water at the rated operating temperature of the insulation. For crosslinked polyethylene cables the water temperature is 90°C. The insulation resistance must demonstrate stability and be above minimum values for a minimum of twelve weeks. If there is instability indicated, the test is continued indefinitely. Relative permittivity is measured at 80 v/mil and must meet specific values. Increase in capacitance and dissipation factor are also measured in 90°C water over a 14 day period. Insulation compounds used in present day cables easily meet these requirements.
  • Manufacturing defects in cable insulation are found during production by either of two methods.
  • the cable is sent through a spark tester, where 28 kV DC, or 17kV AC, is applied to the insulation surface. Any manufacturing defect resulting in a hole in the insulation will initiate a discharge, which is detected by the spark tester. Most manufacturers use this method.
  • Another test that is also often employed is a full reel water immersion test. In this test 21 kV DC, or 7 kV AC is applied to the cable after immersion for 1 hour or 6 hours, depending on whether the cable is a plexed assembly or single conductor, respectively. The actual voltages used for these tests are dependent on the wall thickness. The above values are for an 0.080 inch wall.
  • a critical current density is necessary to sustain the corrosion reaction. Below this 15 current density corrosion will be very slight, or almost imperceptible. Once the current density is high enough, the reaction can be swift. The necessary current density is below ImA/in 2 .
  • the current density of a damaged 600 V cable is influenced by the voltage, leakage resistance, and the area of exposed metal. Variables affecting this can include dampness of the soil, chemistry of the soil, degree of damage, etc.
  • a prior art attempt to minimize the flow of moisture or water within the interstitial spaces of a stranded conductor came in the form of compacted or compressed stranded conductors.
  • the stranded conductor itself was radially crushed in order to reduce the diameter of the conductor and to fill the interstitial spacing with metal from the individual wires themselves.
  • the drawback to this method is that even though some deformation of the individual wires does take place, and some of the interstitial spacing is filled, there is still the possibility of cable insulation damage through which moisture can enter the cable and contact the conductor.
  • Another attempt at correcting moisture flowing within interstitial space consisted of filling the interstitial space with a foreign substance which physically prevented the flow of the moisture or water within the conductor structure.
  • These substances typically comprised some type of jelly base and a polyethylene filler material. At slightly elevated temperatures, this compound becomes fluid and viscous and can be applied as the conductor is being formed.
  • the individual wires used to form the conductor are fed into an extrusion die where the moisture blocking compound is extruded onto and around each individual wire and, as the wires are stranded into the conductor, the interstitial space is filled with the jelly-like material. Upon cooling, the filler becomes very stable and immobile and does not flow out of the interstitial spaces of the stranded conductor.
  • the filling compound When the filling compound is applied within the interstitial spaces of the stranded conductor, it tends to remain in place.
  • the problems encountered in applying such a filling substance revolve around precise metering of the material into the interstitial spaces as the stranded conductor is being formed. If too much material is extruded into the conductor, the outer insulation will not fit properly. If too little material is applied, the interstitial spaces will not be filled and therefore will allow moisture to flow within the conductor.
  • Another drawback to this method of applying a moisture blocking material is that an extrusion head and an extrusion pump for applying the material is required for every individual layer of wires used to form the conductor.
  • U.S. Patent 4,273,597 shows a method of strand filling the interstitial spacing of a conductor with a powder. This is accomplished by passing the strands through a fluidized powder bed, where the interstitial spacing is filled with the powder. The stranded conductor then exits the opposite end of the bed where an insulating layer is applied which prevents the powder from vacating the interstitial spacing of the conductor.
  • U.S. Patent 4,563,540 describes a conductor which is constructed by flooding a waterproofing material among the individual conductors which make up the core of the stranded conductor. This flooded core is then wrapped with a plurality of different layers of shielding material which prevents the influx of moisture into the stranded conductor.
  • U.S. Patent 4,435,613 describes a conductor constructed of a plurality of layers of insulating material with the core (or conducting portion) of the conductor being filled with an insulating layer of polyethylene.
  • This polyethylene layer is contained by other rubber and plastic and epoxy compounds which produce a conductor having a waterproof construction.
  • U.S. Patent 4,129,466 deals with a method for the application of the filling medium which is applied to a stranded conductor.
  • This method comprises a chamber into which are passed individual wires that will be used to form the stranded conductor. These wires have a filling medium applied to them n the chamber. After the application of this filling medium, the conductor is passed through a chilling chamber where the filling medium is cooled and allowed to solidify within the interstitial spaces.
  • This method requires that the chamber containing the filling medium and the stranded conductor be both heated and pressurized. The heat applied to the chamber reduces the viscosity of the filling material, while the pressure assures introduction of the material into the interstitial spaces of the stranded conductor.
  • U.S. Patent 3,889,455 discloses a method and apparatus for filling the interstitial spacing of the stranded conductor in a high temperature flooding tank.
  • the individual wires are fed into a tank containing the filling material, the material having been heated to allow it to become less viscous.
  • the individual wires are stranded and closed within the confines of the flooding tank and the finished conductor is withdrawn from the opposite end of the flooding tank where it is passed through a cooling means.
  • the disadvantages experienced here involve the practice of stranding the conductor beneath the surface of an elevated temperature moisture block pool. No access, either visual or mechanical, to the conductor manufacturing process is practical.
  • U.S. Patent 3,607,487 describes a method whereby individual strands of wire are fed into a flooding tank which is supplied with heated filling material by a pump and an injection means.
  • the stranded conductor is withdrawn through the opposite end of the flooding tank, wiped in a wiping die, wrapped in a core wrapper and then passed through a binder where it is bound.
  • the bound, wrapped core is then passed through a cooler which sets the filling material.
  • the above described process is repeated through another flooding tank, another cooler, another binding machine, another flooding tank, another extruder, another cooling trough, and is eventually withdrawn from the end of the manufacturing line as a product having a plurality of layers of moisture blocking compound which protects the conductor core.
  • the disadvantages here comprise a complex manufacturing line whereby moisture blocking material is applied at many different locations, each having to be meticulously monitored and controlled in order for a proper conductor construction to be obtained.
  • the present invention relates to improvements in insulated solid and stranded cables.
  • a material which provides the cable with puncture, crack, and void self-sealing properties is included between the conductor and the insulation.
  • An additional water barrier material may also be included between the insulator and the conductor. Preferably, both materials are included in the cable. In this way, not only are the voids filled by the material, but the material will flow into any void, puncture, or crack formed in the insulation, thus preventing migration of moisture, with the added safety of the additional water barrier.
  • an additional water barrier such as a polymer sheet or film, is used, the self-sealing material is applied over such barrier between the barrier and the insulation, in which case the self-sealing material does not contact the conductor.
  • FIG. 1 is a cut-away, perspective view of a cable of the invention showing a stranded conductor, the insulation, and the material which provides the self-sealing effect;
  • FIG. 2 is an end view of the embodiment of the cable shown in FIG. 1;
  • FIG 3 is an end view of the cable shown in FIG. 2 having a break in the insulation with the break sealed by the material.
  • a central conductor of stranded wires of a good conductivity metal such as copper, aluminum, copper alloys or aluminum alloys; and (2) A layer of insulation around the stranded conductors which has been extruded thereover.
  • FIG. 1 shows a cable 11 comprising a conductor 12 of stranded wires of copper or aluminum or alloys thereof.
  • a layer 10 of material which provides the self-sealing effect encircles the conductor 12 and fills any spaces between conductor 12 and an insulation jacket 13 which encircles material 10 and conductor 12.
  • Insulation jacket 13 is of known material and is preferably an extruded polymeric material.
  • Preferred material 10 comprises a polymer which can be readily pumped at temperatures at least as low as 25°C.
  • the polymer will be a low molecular weight polymer such as low molecular weight isomer.
  • Other materials, or combinations of materials, with or without such polymers, having such characteristics may also be useful in the present invention.
  • a polymer which has been found to be particularly suitable is polyisobutene.
  • the preferred polymer of the present invention has very little or no significant Shore A hardness.
  • a test of determining whether or not the polymer has acceptable properties is the Penetrometer Test incorporated in ASTM D5 Penetration of Bituminous Materials. The 100 grams needle penetration value at 25°C should be greater than about 100 tenths of a millimeter.
  • the material is a dielectric, e., it is non-conductive and is not a semi-conductor;
  • the material causes the cable to be self-sealing, i.e.. it will flow, at ambient temperature, into insulation voids and/or cracks and prevent contact between the conductor and moisture which could cause cable failure; and (d) The material does not absorb moisture or swell upon contact with moisture.
  • the material used to fill the space between the conductor and the insulation is a compound of low molecular weight isomer or a low molecular weight copolymer of an isomer.
  • the material is polyisobutene.
  • the material of the present invention may optionally contain filler material, but is essentially free of any solvents or oils.
  • the cable 11 described in connection with FIG. 1 can be used without further layers encircling the insulation jacket 13.
  • the conductor and layers of insulation can be the same as those described in connection with FIG. 1.
  • the cable 14 illustrated in FIG. 2 is an end view of cable 11 illustrated in FIG. 1.
  • FIG. 3 is an end view of cable 11 shown in FIG. 1 and illustrates the self-sealing effect of material 10 which flows into a break in insulation 13, thereby preventing moisture from coming into contact with conductor 12.
  • thejacket tightly enclose the layers there within or enter into the spaces between the wires and protective materials, i.e.. the interior size of the jacket can be essentially equal to the exterior size of the elongated elements so that compression of the elongated elements, and hence, indentation of the layers there within including the insulation, is prevented.
  • the cable of the present invention is of particular advantage in that not only does the material fill the space between the conductor and the insulation as the cable is manufactured, but after the cable is placed in service the material will flow into any cuts or punctures formed as a result of damage during handling and installation of the cable or its use in service.
  • the stresses placed on the conductor and the insulation during handling and installation of the cable such as bending, stretching, reeling and unreeling, striking with digging and installation equipment can form cuts or punctures in the insulation and between the insulation and the conductor. Such cuts or punctures can also be formed after the cable has been placed in service as a result of damage from adjacent utilities, homer owners, or lightening strikes.
  • the cable of the present invention can provide acceptable service even after the insulation has been cut or punctured, exposing the conductor.
  • Both cable samples were placed inside separate 1 liter glass beakers containing tap water. Each cable sample was energized at 110V to ground with AC current. The sample which did not have the polyisobutene layer exhibited severe corrosion overnight. The sample containing the polyisobutene layer exhibited no corrosion after being energized and submerged for 4 weeks in tap water in the glass beaker.
  • the conductors from seven 600 V cable samples approximately 12 inches in length were coated with the polyisobutylene. A defect was made in the middle of each sample which exposed the conductor. Three untreated cables (without polyisobutylene) were similarly damaged to expose the conductor. Each of the cable samples was then placed inside a laboratory rectangular soil box, across and through the long sides of the box, which was then filled with soil. Each sample was energized at 1 10V to ground. The soil box was periodically watered to insure that the conditions leading to AC corrosion were present. Measurements of leakage current were taken to monitor the effect of the polyisobutylene layer on preventing corrosion. Periodically, the ability of each sample to carry 20 amps AC current was tested.

Landscapes

  • Insulated Conductors (AREA)

Abstract

La présente invention concerne un câble électrique comportant un conducteur central torsadé (12) entouré d'un isolant (10) constitué d'un matériau qui confère au câble (11) des propriétés d'auto-obturation, situé au moins entre les bords adjacents du conducteur torsadé (12) et l'isolant (10). De préférence, ce matériau est un matériau polymère fluide à une température d'au moins 25 °C à peine et présente une valeur de pénétration d'aiguille de 100 grammes supérieure à 100 dixièmes d'un millimètre à 25 °C.
EP00908261A 2000-01-12 2000-01-12 Cable electrique avec agent auto-obturant et procede pour empecher l'eau de toucher le conducteur Ceased EP1190424A4 (fr)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/US2000/000703 WO2001052272A1 (fr) 1999-01-11 2000-01-12 Cable electrique avec agent auto-obturant et procede pour empecher l'eau de toucher le conducteur

Publications (2)

Publication Number Publication Date
EP1190424A1 true EP1190424A1 (fr) 2002-03-27
EP1190424A4 EP1190424A4 (fr) 2003-07-02

Family

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Family Applications (1)

Application Number Title Priority Date Filing Date
EP00908261A Ceased EP1190424A4 (fr) 2000-01-12 2000-01-12 Cable electrique avec agent auto-obturant et procede pour empecher l'eau de toucher le conducteur

Country Status (2)

Country Link
EP (1) EP1190424A4 (fr)
CA (1) CA2332005A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2012127418A1 (fr) 2011-03-21 2012-09-27 Arjowiggins Security Support d'information ou papier comportant un matériau auto-réparant

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114141422A (zh) * 2020-09-03 2022-03-04 深圳市东佳信电线电缆有限公司 变压器连接用特种结构环保型电力电缆

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4095039A (en) * 1976-04-16 1978-06-13 General Cable Corporation Power cable with improved filling compound
EP0517287A2 (fr) * 1986-05-16 1992-12-09 Pirelli Cable Corporation Composition de remplissage pour câbles électriques et méthode de fabrication de ces câbles utilisant cette composition
EP0940819A1 (fr) * 1998-03-04 1999-09-08 PIRELLI CAVI E SISTEMI S.p.A. Câble électrique avec protection autocicatrisante
EP0947999A2 (fr) * 1998-03-31 1999-10-06 Pirelli Cable Corporation Appareil, systèmes et méthodes pour appliquer de la matière de remplissage et des particules absorbant de l'eau dans un conducteur toronné

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4095039A (en) * 1976-04-16 1978-06-13 General Cable Corporation Power cable with improved filling compound
EP0517287A2 (fr) * 1986-05-16 1992-12-09 Pirelli Cable Corporation Composition de remplissage pour câbles électriques et méthode de fabrication de ces câbles utilisant cette composition
EP0940819A1 (fr) * 1998-03-04 1999-09-08 PIRELLI CAVI E SISTEMI S.p.A. Câble électrique avec protection autocicatrisante
EP0947999A2 (fr) * 1998-03-31 1999-10-06 Pirelli Cable Corporation Appareil, systèmes et méthodes pour appliquer de la matière de remplissage et des particules absorbant de l'eau dans un conducteur toronné

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See also references of WO0152272A1 *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2012127418A1 (fr) 2011-03-21 2012-09-27 Arjowiggins Security Support d'information ou papier comportant un matériau auto-réparant

Also Published As

Publication number Publication date
CA2332005A1 (fr) 2001-07-12
EP1190424A4 (fr) 2003-07-02

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