Comparative analysis of HVAC cable metallic sheath modelling approaches for network studies

Abstract

This paper discusses high voltage ac underground cable sheath layer modelling for network studies in EMT type program. In EMT studies, the cable compound sheath layer is considered as a single solid layer, therefore the simplified sheath layer representation is needed. This paper presents developed approaches for cable sheath modelling. The approximations made in sheath parameters can lead to inaccuracies in study results. Therefore to determinate the sheath modelling accuracy, network power flow, short-circuit and lightning surge studies are analyzed. The network bus voltages are observed and compared at various sheath modelling approaches. Network power flow study shows no major variation in results when different modelling approaches are used. However, the short- circuit and lightning surge study results show that chosen cable sheath modelling approach has significant effect to the network bus voltage values. The needed extent of network modelling area is also analyzed in this paper. At cable networks, the considered modelling area needs to be wider than for OHL networks. The extent of modelling area should be decided corresponding to the total length of cable lines. Cable sheath modelling approach recommendations for network studies are provided in this paper.