Search

US-12624221-B2 - Composition for coating an overhead conductor comprising a reflective agent and a photocatalytic agent

US12624221B2US 12624221 B2US12624221 B2US 12624221B2US-12624221-B2

Abstract

A composition for coating an overhead conductor is disclosed comprising: (i) a reflective agent; (ii) a photocatalytic agent comprising ≥70 wt % anatase titanium dioxide (TiO 2 ) having an average particle size (“aps”) ≤100 nm; (iii) a non-aqueous solvent; and (iv) one or more alkyl silicate binders.

Inventors

  • Niall COOGAN
  • Barry Johnston

Assignees

  • Cable Coatings Limited

Dates

Publication Date
20260512
Application Date
20201126
Priority Date
20191126

Claims (20)

  1. 1 . A composition for coating an overhead conductor comprising: a reflective agent comprising rutile titanium dioxide having an average particle size of ≤100 nm, sodium aluminosilicate (AlNa 12 SiO 5 ), or copper oxide (CuO); a photocatalytic agent comprising ≥70 wt % anatase titanium dioxide (TiO 2 ) having an average particle size (“aps”)≤100 nm; a non-aqueous solvent; and one or more alkyl silicate binders.
  2. 2 . The composition as claimed in claim 1 , wherein the reflective agent comprises rutile titanium dioxide having an average particle size of ≥100 nm.
  3. 3 . The composition as claimed in claim 1 , wherein the composition comprises from about 5 to about 25 wt. % reflective agent, from about 1 to about 5 wt. % photocatalytic agent, from about 24 to about 60 wt. % non-aqueous solvent, and from about 20 to about 70 wt. % alkyl silicate binder.
  4. 4 . The composition as claimed in claim 3 , wherein the composition comprises from about 10 to about 20 wt. % reflective agent, from about 2 to about 4 wt. % photocatalytic agent, from about 28 to about 55 wt. % non-aqueous solvent, and from about 30 to about 60 wt. % alkyl silicate binder.
  5. 5 . The composition as claimed in claim 1 , wherein the reflective agent comprises a white filler.
  6. 6 . The composition as in claim 5 wherein the white filler comprises: (i) magnesium oxide (MgO); (ii) calcium oxide (CaO); (iii) aluminum oxide (Al 2 O 3 ); (iv) zinc oxide (ZnO); (v) calcium carbonate (CaCO 3 ); (vi) aluminum silicate (Al 2 SiO 5 ); (vii) kaolin (Al 2 O 3 .2SiO 2 ); (viii) titanium dioxide (TiO 2 ); or (viii) barium sulphate (BaSO 4 ).
  7. 7 . The composition as claimed in claim 1 , wherein the solvent comprises xylene, xylol or dimethylbenzene having the formula (CH 3 ) 2 C 6 H 4 , toluene having the formula (CH 3 )C 6 H 5 , ethanol having the formula C 2 H 5 OH, isopropanol having the formula CH 3 CH(OH)CH 3 , 2-ethoxyethanol having the formula C 2 H 5 OC 2 H 4 OH or 2-ethoxyethyl acetate having the formula CH 3 C(O)OC 2 H 4 OC 2 H 5 .
  8. 8 . The composition as claimed in claim 1 , wherein the one or more alkyl silicate binders are pre-hydrolysed to between 75-100% hydrolysis.
  9. 9 . The composition as claimed in claim 1 , wherein the alkyl silicate binder comprises methyl silicate, ethyl silicate, propyl silicate, butyl silicate, pentyl silicate, hexyl silicate, heptyl silicate or octyl silicate.
  10. 10 . The composition as claimed in claim 1 , wherein the alkyl silicate binder is non-fluorinated.
  11. 11 . The composition as claimed in claim 1 , further comprising a curing agent.
  12. 12 . The composition as claimed in claim 1 , further comprising a flexibility agent and/or a rheology agent.
  13. 13 . The composition as claimed in claim 1 , wherein the composition comprises from about 1 to about 5 wt. % photocatalytic agent.
  14. 14 . An overhead conductor at least partially coated with a composition as claimed in claim 1 , wherein, in use, the composition is cured so as to form a coating or film on at least a portion of the overhead conductor.
  15. 15 . The overhead conductor as claimed in claim 14 , wherein the coating or film has a thickness in the range of from 20 to 120 μm.
  16. 16 . The overhead conductor as claimed in claim 14 , wherein the coating or film has an average thermal emissivity coefficient E≥0.90 across the infrared spectrum 2.5-30.0 μm; and/or wherein the coating or film has an average solar reflectivity coefficient R≥0.80, across the solar spectrum 0.3-2.5 μm; and/or wherein the coating or film is substantially white in colour and has a L*≥80, L*≥85, L*≥90 or a L*≥95.
  17. 17 . An electric power or distribution system comprising one or more overhead conductors as claimed in claim 14 .
  18. 18 . A method of coating or applying a film to an overhead conductor comprising: applying a composition as claimed in claim 1 to at least a portion of an overhead conductor; and allowing the composition to cure solely by moisture curing so as to form a coating or film on at least a portion of the overhead conductor.
  19. 19 . The method as claimed in claim 18 , wherein the step of allowing the composition to cure by moisture curing does not involve heating the composition above ambient temperature.
  20. 20 . A kit for forming a composition for coating an overhead conductor comprising: a first part comprising: (i) a reflective agent comprising rutile titanium dioxide having an average particle size of ≥100 nm, sodium aluminosilicate (AlNa 12 SiO 5 ), or copper oxide (CuO); (ii) a photocatalytic agent comprising ≥70 wt % anatase titanium dioxide (TiO 2 ) having an average particle size (“aps”)≤100 nm; and (iii) one or more alkyl silicate binders; and a second part comprising: (i) a non-aqueous solvent; wherein, in use, the first and second parts are mixed together to form a composition which is applied to at least a portion of an overhead conductor in order to form a coating or film on at least a portion of the overhead conductor.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a National Stage application of PCT/GB2020/053002, filed Nov. 26, 2020, which claims benefit of Application No. GB 1917214.7 filed on Nov. 26, 2019 and claims benefit of Application No. LU101578 filed on Dec. 30, 2019, which are incorporated by reference herein in their entirety. None. FIELD OF THE PRESENT INVENTION The present invention relates to electric overhead conductors. Various preferred embodiments relate to high voltage electric overhead conductors which have a single coating for the purpose of reducing the temperature of the conductor thereby reducing the resistance of the conductor (as electrical resistance is temperature dependent) and hence reducing power losses in the conductor (since power loss is dependent upon electrical resistance). The single coated high voltage electric overhead conductor includes a photocatalytic self-cleaning agent provided in a non-aqueous solvent based alkyl silicate binder. BACKGROUND Various different types of high voltage electric overhead conductors are known comprising aluminium cables suspended between pylons. The various different types of known high voltage electric overhead conductors can be divided into two groups. The first group comprises conductors which have a maximum operating temperature of 80° C. The second group comprises conductors which have a higher maximum operating temperature in the range 150-250° C. There are various particular problems associated with high voltage electric overhead conductors and these problems can become particularly acute with high voltage electric overhead conductors which are operable at elevated operating temperatures in the range 150-250° C. Such conductors may, for example, be installed in particularly hot regions of the world such as Southern USA, the Middle East and Australia. High voltage electric overhead conductors which are installed in particularly hot regions of the world suffer from the problem that the overhead conductors are exposed to significant solar heating due to intense sunlight for a majority of the year. An overhead electric conductor which is subjected to sustained solar radiation throughout the year presents a number of significant operational challenges to a utility company seeking to manage an overhead power transmission or distribution line or network. As will be understood by those skilled in the art, the temperature of a high voltage electric overhead conductor will tend to increase due to two main factors. The first factor is that there will be Ohmic losses due to the transmission of electric current through the conductor which will result in Joule heating of the conductor. The second factor is that the conductor will be subjected to relatively intense solar radiation (i.e. sunlight) and hence will be heated by solar radiation. It will be apparent that both factors will play a role in elevating the temperature of the conductor. It will also be understood that there are also a number of other potential factors which will tend to decrease the temperature of the conductor. For example, a conductor may lose energy by emitting infra-red (heat) radiation. A conductor may also lose energy by conduction or by convection (e.g. due to air currents, wind etc.). However, as a practical matter, energy losses due to conduction are fairly minimal and energy losses due to convection depend upon the geographic location where the conductor is installed. It will be understood by those skilled in the art that the predominant cooling mechanism by which an overhead electric conductor will lose energy is via radiation i.e. by radiating heat energy and in particular infra-red radiation in the infrared wavelength range 2.5-30.0 μm. Accordingly, to a first approximation the temperature of a high voltage overhead electric conductor will increase due to the combined effects of Joule heating and solar radiation with this temperature increase being offset by energy loss due to the conductor emitting infra-red radiation. For illustrative purposes, a bare overhead aluminium electric conductor may be considered having an average solar absorptivity coefficient A of 0.5 across the solar spectrum 0.3-2.5 μm. It will be understood that the bare aluminium conductor will have a corresponding average solar reflectivity coefficient R of 0.5. Accordingly, a bare aluminium electric conductor exposed to solar radiation (i.e. sunshine) will absorb approx. 50% of the incident solar radiation. The net effect of the conductor absorbing approx. 50% of incident solar radiation over a sustained period of time coupled with significant Joule heating of the conductor will cause the temperature of the overhead conductor to rise up to a maximum rated operating temperature. Dependent upon the geographic location of the conductor energy losses due to air currents (i.e. wind) may be low or negligible. The maximum operating temperature of the conductor may be either 80° C. or in the range 1