The operational characteristics of modern h.v. wood-pole lines

This paper is devoted to the study of the operation of h.v. wood-pole lines in which the insulator metalwork is not connected to earth. It deals distinctively with the two types of line of this kind, namely lines in which the metalwork is bonded, as by the use of steel cross-arms; and lines employing wood cross-arms in which the bonding as well as the earth connection is omitted. The paper deals with the insulating properties of complete line structures, as derived from their porcelain and wooden components; and then, from a consideration of the adverse agencies to which they are subjected, proceeds to conclusions regarding their operating characteristics. Some original experiments are described, and tentative conclusions submitted, regarding the effect of unearthed construction on the performance of insulators under conditions of fog and deposit. The nature and effect of lightning surges is also dealt with, and particularly the matter of surge asymmetry as a cause of interphase flash-over, and as a factor in the choice of the type of cross-arm. The paper emphasizes that, for the attainment of the best operating results, there should be a closer correlation between line design and local conditions than has usually obtained in the past.