Protection of MV covered conductor lines against overvoltages and fault arcs

Reduction of the line and tower dimensions is a common tool to insert overhead lines into the environment. Recently such trends occurred in the field of MV networks, as well. When applying covered conductors shorter phase-to-phase distances can be allowed than with bare conductors. Important application areas of covered conductor system are the lines passing through forests (allowing narrow corridor), inhabited areas or line crossing. This paper analyses the processes resulting in damaging the cover and conductor, reports on the laboratory studies aiming at selecting the suitable arc protecting devices, establishing their pros and cons. Authors report on the laboratory tests for understanding the complex flashover mechanism of the insulator-covered conductor arrangement. Follow current tests were carried on by thin wire arc initiation and in a synthetic circuit.