Electrical and Mechanical Considerations in 765kV (Insulator) Hardware Assembly Design

Starting in 1969, American Electric Power (AEP) built a 765kV transmission network that amounted to over 2,000 circuit miles by 1984. The system utilized four—conductor bundles of Rail and Dipper conductors. Operational experience with the network revealed issues around audible noise due to corona from the lines. In 1990, when the need arose to expand the network, it was decided that audible noise issues would be addressed by utilizing a new bundle design that consisted of a 6-conductor bundle using Tern conductors. The intent of the design change was to eliminate corona and thus resolve the audible noise issues associated with previous designs. The new design would also allow the use of non-ceramic insulators, which are susceptible to damage from long term exposure to corona. The move to the 6 x Tern phase bundle posed significant mechanical and electrical challenges to the engineers involved in hardware development. This paper describes the extensive electrical testing programs carried out to prove the performance of the new 6-conductor bundle design.