Effects of dielectric liquids in electrical alternating fields [high voltage transmission lines]

Due to the high electric fields at the surface of conductors of high voltage transmission lines, effects appear, which are called corona discharges. The electrical and acoustic emissions of dry and moistened high voltage transmission line conductors have been examined and evaluated. For this purpose several systems for sound and partial discharge measurement were used in a parallel arrangement. Contrary to dry kept overhead line conductors, the conductors moistened with water showed a changed appearance in acoustic and partial discharge measurement, which suggests mechanical movements of water drops in the changing electrical field producing acoustic sound. This effect is well-known, but until now an exact analysis of the arising acoustic emissions was neglected. This paper details the spectral analysis method used to evaluate these corona discharge noises and also describes the partial discharge measuring system.