Protection of overhead line with inserted underground cable

This paper summarizes the main results of a study aimed at problem of the operation of the overhead line with inserted underground cable. Firstly the analysis of the risk of the cable insulation fault is presented and the study of protection applications follows. This study considers the situation of two cable sections inserted in an overhead line that is protected by surge arresters at both ends and is subjected to various types of faults. A digital model in EMTP ATP program was created for the analysis of this situation with respect to the real arrangement of the underground cables and overhead line in distribution network.