Impact of protective structures on EHV cable transient behaviour: Comparison between FEM, EMTP and measurements

Reliability of underground Extra High Voltage (EHV) cable systems is undermined by third party mechanical damages. In order to prevent long and expensive outages, the Italian TSO equipped some cable lines of strategical importance with additional protective structures. The presence of highly permeable and conductive material surrounding the cable installations has risen concerns about potential variations in the transient behaviour. The objective of this paper is to model a 380 kV single-core land cable system, by means of the Finite Element Method (FEM) software COMSOL and compare simulation results with measurements. The series impedance matrix as well as modal attenuations and velocities are significantly affected over a wide frequency range, whereas the self input impedance does not show any substantial changes either in short or open circuit conditions.