Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07F—ACYCLIC, CARBOCYCLIC OR HETEROCYCLIC COMPOUNDS CONTAINING ELEMENTS OTHER THAN CARBON, HYDROGEN, HALOGEN, OXYGEN, NITROGEN, SULFUR, SELENIUM OR TELLURIUM
  • C07F7/00—Compounds containing elements of Groups 4 or 14 of the Periodic Table
  • C07F7/02—Silicon compounds
  • C07F7/08—Compounds having one or more C—Si linkages
  • C07F7/18—Compounds having one or more C—Si linkages as well as one or more C—O—Si linkages
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
  • H01B7/00—Insulated conductors or cables characterised by their form
  • H01B7/17—Protection against damage caused by external factors, e.g. sheaths or armouring
  • H01B7/28—Protection against damage caused by moisture, corrosion, chemical attack or weather
  • H01B7/282—Preventing penetration of fluid, e.g. water or humidity, into conductor or cable
  • H01B7/285—Preventing penetration of fluid, e.g. water or humidity, into conductor or cable by completely or partially filling interstices in the cable
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
  • H01B3/00—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties
  • H01B3/18—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances
  • H01B3/30—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes
  • H01B3/46—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes silicones
• • 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

• the present invention relates to a method for preventing aluminum corrosion in restored electrical distribution cable. More particularly, the instant invention relates to a method of contacting the interior of the cable with a fluid mixture which comprises (A) a liquid anti-treeing agent and (B) a water-reactive compound or a water-reactive anti-treeing agent to obtain a fluid mixture with a boiling point ⁇ 90° C.
• a major problem associated with buried electrical distribution cable is its tendency over time to fail due to the progressive degradation of its insulation.
• the degradation of polymeric insulations in many cases can be correlated to the development and growth of water tree structures in the insulation material. These water tree structures have been studied extensively. Their development is known to occur when water present inside the insulation material is exposed to an electric field. Water trees grow in size over time usually spanning on the order of years. As they grow, they reduce the overall efficacy of the insulation. Eventually electrical stresses across the tree's branchlike structures discharge which leads to insulation failure. This failure mode is known to be a leading cause of failure in buried, aged, solid dielectric cables.
• certain tree retardants such as polydimethylsiloxane fluid or aromatic alkoxysilanes
• the restoration fluid can boil at the liquid to solid interface.
• Some alkoxysilanes, such as trimethylmethoxysilane, have low boiling points, which may allow the restoration fluid to boil at normal operating temperatures of the cable.
• This boiling action can disrupt and wear away the protective aluminum oxide layer on the aluminum strands in the cable. After this oxide layer is disrupted, corrosion agents can react with the aluminum to produce other corrosion products. The boiling action will continue to wash away the corrosion products leading to continued corrosion of the aluminum. This corrosion may, at times, lead to cable failure.
• the instant invention therefore relates to a method for enhancing the dielectric properties of an electrical cable having a central stranded conductor encased in a polymeric insulation, the cable having an interstitial void space in the region of the conductor, the method comprising supplying the interstitial void space of the cable with a fluid mixture comprising
• the in-service cable is typically of the type used in underground residential distribution and typically comprises a central core of a stranded copper or aluminum conductor encased in polymeric insulation.
• polymeric insulation As is well known in the art, there is usually also a semi-conducting polymeric conductor shield positioned between the conductor and insulation as well as a semi-conducting insulation shield covering the insulation, the latter being ordinarily wrapped with a wire or metal foil grounding strip and, optionally, encased in an outer polymeric protective jacket.
• the insulation is preferably a polyolefin polymer, such as polyethylene or a copolymer of polyethylene and propylene, or vinyl acetate.
• the term “in-service” refers to a cable that has been under electrical load and exposed to the elements for an extended period. In such a cable, the electrical integrity of the cable insulation has generally deteriorated to some extent due to the formation of water trees, as described above. It is also contemplated, however, that the instant method can be used for new cable as well as an in-service cable. Typically, after the cable has been in operation for an extended period, for example 7 to 15 years, the fluid mixture of the invention is introduced into the interstitial void space of the conductor.
• the method of introducing the fluid mixture into the interstitial void space of the conductor is carried out in the manner described in above and as cited in U.S. Pat. No. 4,766,011 to Vincent et al., which is hereby incorporated by reference.
• the method comprises filling the interstitial void space of the conductor with the fluid mixture of the present invention.
• the fluid mixture is allowed to remain in the cable interior for an appropriate period while it diffuses into the cable's polymeric insulation to fill the water trees, thereby enhancing the dielectric strength of the cable.
• the time required for the treatment is a function of such variables as cable size (insulation thickness), water content of the cable components and treatment temperature, less time being required when the cable has a thinner insulation and operates at a higher current load.
• the method may further comprise a step wherein water present in the conductor interstitial volume may be removed or its quantity reduced prior to the introduction of the fluid mixture. Typically, this is done by flushing a desiccant gas or liquid, such as air, nitrogen, ethanol or isopropanol, through the cable interior to either physically push out the moisture or mix with the water to facilitate physical removal.
• a desiccant gas or liquid such as air, nitrogen, ethanol or isopropanol
• a high velocity dry air stream may be used to blow out bulk water that has accumulated in the void space.
• Anti-treeing agent (A) can be selected from compounds known to prevent water trees in polymeric insulation when compounded into the insulation, and mixtures thereof. Such compounds as aromatic ketones (e.g., acetophenone), fatty alcohols (e.g., dodecanol) and organoalkoxysilanes, illustrate the range of suitable anti-treeing agents, which can be employed as component (A). It is preferred that component (A) be capable of reacting with water to polymerize in the cable insulation after diffusing therethrough. This tends to increase the lifetime of the treatment and precludes the need for perpetual maintenance of the dielectric enhancing fluid. Many such systems have been described in the patent literature and the interested reader is referred to U.S. Pat. No.
• the anti-treeing agent is of the type described in above cited U.S. Pat. No. 4,766,011 to Vincent et al.
• This compound is represented by the general formula (RO) x R 1 y SiAr (4-x-y) wherein R is an alkyl radical having 1 to 6 carbon atoms, R 1 is an alkyl radical having 1 to 6 carbon atoms, Ar is an aromatic group selected from the group consisting of phenyl and benzyl radicals, x is 1, 2 or 3, y is 0, 1 or 2 and (x+y) ⁇ 3.
• silanes may be exemplified by, but not limited to, phenyltrimethoxysilane, diphenyldimethoxysilane, phenylmethyldiethoxysilane and phenylmethyldimethoxysilane.
• An illustrative diffusion rate for the anti-treeing agent ranges from 5.6-5.9 ⁇ 10 ⁇ 8 .
• Compound (B) is selected from water-reactive compounds or water-reactive anti-treeing agents.
• the water-reactive compound (B) of the present invention is a low molecular weight liquid which is different from component (A), which reacts with water and which has a diffusion coefficient of at least about 1 ⁇ 10 ⁇ 7 cm 2 /sec at 50° C. in low-density polyethylene.
• the diffusion coefficient indicates the diffusion rate of the component.
• Component (B) may be selected from trialkylalkoxysilanes, dialkyldialkoxysilanes or organoborates.
• Component (B) can also be an orthoester having the general structure R 2 C(OCH 3 ) 3 , where R 2 is selected from hydrogen or a methyl radical.
• component (B) can be an enol ether of the general structure R 3 R 4 C ⁇ C(OR 5 )R 6 , where R 3 , R 4 and R 6 are independently selected from hydrogen or alkyl radicals having 1 to 3 carbon atoms and R 5 is —SiR 7 3 , in which R 7 is an alkyl radical having 1 to 2 carbon atoms.
• component (A) and component (B) there will be certain combinations of component (A) and component (B) that will not be suitable for the instant process due to the chemical interaction there between.
• component (A) is an alkoxysilane
• component (B) cannot be a borate since the latter would react with the silane to form products that would retard diffusion of component (A) in the insulation. Routine experimentation can be applied to determine whether a potentially reactive combination of (A) and (B) is suitable.
• the amount of compound (B) that is in the fluid mixture is an amount such that the boiling point of the fluid mixture is not ⁇ 90° C. For example, if too much of component (B) is added, since component (B) typically has a boiling point of ⁇ 90° C. and the boiling point of (A) is >90° C., the boiling point of the mixture would be reduced below 90° C. However, a sufficient amount of (B) is necessary to improve the diffusivity of the fluid mixture. Typically, the weight percent ratio of component (A) to (B) is 99.9/0.1 to 90.1/9.9.9.
• component (A) is present in about 95 parts by weight and component (B) is present in about 5 parts by weight, based on 100 parts by weight of the fluid mixture. Additionally, due to the presence of component (B), the fluid mixture of and used in the method of the present invention has a diffusion rate ⁇ than that of the liquid anti-treeing agent (A), such as phenylmethyldimethoxysilane.
• the liquid anti-treeing agent (A) such as phenylmethyldimethoxysilane.
• components (A) and (B) are selected from compounds which can form oligomers upon reaction with water, it is preferred that these components have a low water equivalent weight, this being defined as the weight of the compound required to react with one mole of water. This preference is suggested by the observation that the oligomers have significantly slower diffusion relative to the monomers and the intent is to limit the extent of oligomerization in the conductor region so that more of the fluid can penetrate the insulation as quickly as possible and react with the water therein.
• PhMe and TMM were blended in ratios listed in Table 1.
• PhMe contained a titanate as a hydrolysis catalyst and a blue dye.
• a corrosion agent was added to the silane blend in some cases to introduce a simulation of corrosion on the aluminum strands tested in these Examples (see below).
• the corrosion agents used in the Examples can include salts, bases above a pH of 8.5, acids below a pH of 4, water, alcohols, and the like so long as the corrosion agent is able to introduce the simulation of the corrosion on the aluminum strands.
• the blends were evaluated according to the experimental procedures below. Formulations C1-1 through C1-4 are comparative examples.
• PhMe and TME were blended in ratios listed in Table 2.
• PhMe contained a titanate as a hydrolysis catalyst and a blue dye.
• a corrosion agent was added to the silane blend in some cases to simulate an ample presence of a corrosion agent. The blends were evaluated according to the experimental procedures below.
• silane blends with and without the corrosion agent, were heated to boiling and the temperature was measured. Repeatability typically is within 3° C.
• D-Optimal Mixture Design was set up with 18 experiments.
• the corrosion agent was varied from 0-8% by weight, TMM or TME was varied from 0 to 30% by weight, and PhMe was varied from 62 to 100% by weight.
• the formulations were blended together in a bottle and shaken. The boiling point was then run. Design Expert Software was used to analyze the data and an equation was obtained. At this point, the boiling point can be calculated for any formulation between these % by weight ranges. Four formulations were then chosen, and boiling point tests were run to validate the equation to predict boiling point. The predicted boiling points were within experimental error of actual boiling points.
• Boiling Point ° C. C1-1 75 C1-2 62 C1-3 183 C1-4 77 1-1 134* 1-2 76* 1-3 108 1-4 72* 2-1 143* 2-2 75* 2-3 121* 2-4 72 *Calculated boiling points from DOE.
• Benz ovens were used to heat the formulations containing the silane and the corrosion agent and expose the formulations to the aluminum.
• the Benz oven uses 275 ml test tubes that fit into the slots in the oven. Water-cooled condensers were placed on top of the tubes to limit the evaporation of its contents.
• the formulations were loaded into the tubes. Thirty aluminum strands that were about 2 inches long (taken from an aged German electrical cable) were weighed on an analytical balance and placed in the tube. The tube was placed in the oven and heated to 70° C. for 72, 240 or 500 hours or to 90° C. for 72, 240, or 500 hours. The testing was done in triplicate. After the required time, the tubes were removed. The aluminum strands were separated from the fluid and corrosion products. Before weighing, the aluminum strands were rinsed with isopropanol and then acetone.
• 72 hr corrosion rates are typically higher than 240 hr or 500 hr corrosion rates cine the corrosion agent is depleted with time as the corrosion product is formed.
• Diffusivity (cm 2 /sec) (Permeability (g/cm 2 sec) ⁇ thickness (cm))/solubility (g/cm 3 )
• C1-4 and C1-2 The major difference between C1-4 and C1-2 is the presence of TMM, which reduces the boiling point, so boiling takes place during the lab corrosion test. Boiling of the fluid will cause cavitation, which can lead to corrosion. With TMM levels such that boiling does not occur (C1-4, 1-2, 1-4 at 70° C.), no corrosion takes place. However, as seen with C1-4 and 1-2, as the temperature increases above the boiling point of the fluid, boiling and thus cavitation will occur.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Physics & Mathematics (AREA)
• Spectroscopy & Molecular Physics (AREA)
• Insulated Conductors (AREA)
• Organic Insulating Materials (AREA)
• Manufacturing Of Electric Cables (AREA)
• Compositions Of Macromolecular Compounds (AREA)

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• 2006
  • 2006-04-28 US US11/912,863 patent/US20090114882A1/en not_active Abandoned
  • 2006-04-28 JP JP2008509228A patent/JP2008541341A/ja active Pending
  • 2006-04-28 AU AU2006242341A patent/AU2006242341A1/en not_active Abandoned
  • 2006-04-28 CA CA2606434A patent/CA2606434C/fr active Active
  • 2006-04-28 EP EP06758858A patent/EP1897098B1/fr not_active Not-in-force
  • 2006-04-28 KR KR1020077024985A patent/KR101363589B1/ko not_active IP Right Cessation
  • 2006-04-28 TW TW095115397A patent/TW200705465A/zh unknown
  • 2006-04-28 WO PCT/US2006/016644 patent/WO2006119196A1/fr active Application Filing
• 2007
  • 2007-11-06 ZA ZA200709571A patent/ZA200709571B/xx unknown
• 2011
  • 2011-03-22 US US13/069,252 patent/US20110171369A1/en not_active Abandoned

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