Effect of AC Interference on HV Underground Cables Buried Within Transmission Lines Right of Way

Issues and interest of AC interference from Overhead Transmission Lines (OHTL) to nearby co-located facilities not only involve pipelines, communication cables and transportation infrastructures but also to nearby High Voltage (HV) underground cables. In this paper, the effects on a three phase AC 275kV underground cable running in parallel to three phase AC double circuit of 275kV OHTL are studied using Current Distribution, Electromagnetic Interference, Grounding and Soil Structure Analysis (CDEGS) software program. The underground cable under study is placed within the OHTL Right of Way (ROW) where the modelling, simulation and analysis of both systems are presented in order to assess induced voltage on the sheath of an underground cable. This paper investigates the case when OHTL and underground cable were energized during steady state operation with respect to different length and parallelism of both systems. During the operation of both systems, induced sheath voltage on the cables has increased and voltage distribution changed significantly which can stress the sheath itself. The induced voltage on underground cable sheath has been reduced to tolerable sheath standing voltage as specified by international standard by proposing some mitigation techniques.