The design of overhead electric lines for improved reliability

Overhead electric lines are affected by wet snow and ice accretion in two principal respects. Conductors and support systems become more highly stressed and the aerodynamic properties of conductors, which affect the normal limits, are disturbed by wet snow or ice accretion and under such conditions the risk of conductor clashing is much greater. The author reports on work undertaken in the UK in the following areas: the development of methods of producing severity maps for the UK for levels of wet snow accretion and associated wind pressures which are likely to be experienced on low level lines erected on terrain of varying heights; a new method of modelling the clashing of conductors which are covered with wet snow and exposed to a gusty wind; a new basis for the specification of overhead line design loads; and the development of an inexpensive failure containment device and a simple failure containment policy aimed at reducing the risk of cascade line failure