Abstract: An electrically insulating cross-arm for a tower for high-voltage power networks. The cross-arm includes an insulating structural member for attachment to the tower body and to support a conductor cable. The insulating structural member comprises a solid rigid spine extending along a long axis having cross sectional profile, normal to the long axis, having a second moment of area of its cross sectional profile about every axis normal to the long axis and dissecting its centroid has a value of A2/2? or more, where A is the area of the cross sectional profile. The structural member provides resistance to bending and compressive buckling and allows conductors to be safely supported at reduced tower height. T and Y shaped cross sections provide water run-off and inhibition of organic growth. The structural members are also generally useful as insulator members in high voltage power networks.

Abstract: An electrically insulating cross-arm for a tower for high-voltage power networks. The cross-arm includes an insulating structural member for attachment to the tower body and to support a conductor cable. The insulating structural member comprises a solid rigid spine extending along a long axis having cross sectional profile, normal to the long axis, having a second moment of area of its cross sectional profile about every axis normal to the long axis and dissecting its centroid has a value of A2/2? or more, where A is the area of the cross sectional profile. The structural member provides resistance to bending and compressive buckling and allows conductors to be safely supported at reduced tower height. T and Y shaped cross sections provide water run-off and inhibition of organic growth. The structural members are also generally useful as insulator members in high voltage power networks.

Abstract: A safety harness for use on power transmission pylons has a main section with at least a portion thereof being electrically conductive, and a coupling for connecting that portion to earth. The harness may include a lower support section, with the main section having shoulder straps and an upper back portion. The electrically conductive portion is normally located in at least one of shoulder and waist areas of the main section. The earth connection can be made through a lanyard extending from the harness to the respective pylon.

Abstract: An optical cable for use in an overhead optical transmission system in which the cable is supported along the route of the system by means of towers, masts or other upstanding supports that are also employed to support electrical power cables, includes one or more optical fibers and an electrically insulating jacket (8). The cable includes an array of elongate conductive elements (10, 12) each of which extends along a portion of the cable, adjacent conductive elements axially overlapping each other with overlapping portions circumferentially spaced apart to form a composite conductive path that extends along the cable and is interrupted when the cable is dry. Adjacent conductive elements (10, 12) are resistively coupled to each other when the surface of the cable is wet to form a continuous electrically conductive path along the cable. Such a form of cable has the advantage that the dry-band arcing under wet conditions is reduced by disrupting the geometry that allows such bands to form.

Abstract: A linear element (1,61) suitable for extending between, and being supported by, towers of an overhead electrical power transmission system, includes one or more electrically semiconductive components (54, 62) that cause the element to have a linear resistance of 0.05 to 100 Mohms m.sup.-, and which exhibit a negative temperature coefficient of resistance. The element may be a rope used for stringing up conductors of the system or it may be an optical cable. Preferred materials for forming the semiconductive components include carbonaceous fibre tows formed from pyrolised acrylonitrile fibres. The element has a controllable and reproducible resistance for reducing or eliminating dry-band arcing.

Abstract: An overhead electrical power and optical transmission system, comprising overhead electrical phase conductors (2) extending between and supported by towers (10), and at least one optical cable (1) that extends between and is supported by, the towers. Each optical cable has a resistive element (12) that is removably supported thereby and which extends from a tower (10) where it is earthed part of the way along the span of the optical cable, and the resistive element has the necessary length and conductivity such that if a dry band (6) occurs on the cable at the end of the element, the potential difference (VG') across the band is insufficient to form an arc, such that any induced current is insufficient to sustain any arc that may occur across the dry band.

Abstract: A method of installing an optical cable in an overhead power transmission line by supporting an optical cable, which has an overall protective sheath of electrically insulating material, in long lengths between towers employed to support at least one electric power transmission line which is on load and, after the optical cable has been so installed and while the overhead electric power transmission line is on load, providing on or in the supported optical cable at least one longitudinally continuous path which extends throughout substantially the whole length of the supported optical cable and which is sufficiently electrically conductive to carry along the cable any currents that may be capacitively induced. The method enables a cable that will not be subject to dry-band arcing to be installed without danger to personnel during installation.

Abstract: In an overhead optical transmission system in which an optical cable is freely supported between towers employed to support overhead electric power transmission lines and in which each end of the suspended length of optical cable is secured to a tower by means of a metal termination fitting which surrounds and is clamped on a part of a length of the optical cable at or near this end, each metal termination fitting of the cable over a part of the length of the fitting extending to the end of the fitting remote from the tower and an immediately adjacent part of the length of the optical cable are surrounded by a shield of an electrically conductive metal or of a semi-conductive plastics material sufficiently conductive to reduce arcing and/or joule heating.