Partially underground transmission circuits: safety issue for current and future power systems

An underground cable is often used as the interface between an overhead line and a substation where it is impractical to obtain an overhead right of way or to avoid environmentally sensitive areas. The transition from an overhead line to the underground cable usually takes place at cable sealing end compounds or transition stations. At the moment there is not adequate information in the national as well international standards on safety at these installations. This paper describes the earthing assessment of a 132 kV cable sealing end compound. A fault transfer phenomenon at the cable sealing end compound is discussed and simulated using the computer method. It is demonstrated that cable sealing end compounds can exhibit higher earth potential rise (EPR) for either end substation fault instead transitions points fault when such faults are fed by a combination of overhead line and underground cable. The analysis steps presented in this paper can be used as a guide for future works within this area.