Thermal Analysis of 11 kV PILC Belted Cable

Abstract

Worldwide, electrical networks depend on large Medium Voltage (MV) Paper Insulated Lead Covered (PILC) underground cables.  Most of those cables were installed in past decades, with an expected lifespan of forty to seventy years. Toddy, most of these cables have exceeded their design service increasing the probability of MV network failures. In addition, during service, these cables are subjected to multiple stresses such as electrical, mechanical, and thermal stresses. The majority of their failures are attributed to thermal stress effects. The operational reliability of MV cables is influenced by thermal behaviour over time. This paper study a comprehensive thermal model of a three-phase, belted 11 kV PILC cable system based on the Finite Element Method (FEM).  Taking into account the ampacity, cable structure, installation layout, and the thermal characteristics of the soil under specific ambient conditions.  Thermal behavior is investigated within constant load and cyclic daily loading. Power loss is determined and included in the thermal analysis.  The thermal effect of each cable component is determined. The results demonstrated a significant time-varying temperature gradient within the cable. It indicates that the thermal characterization of PILC cables is highly sensitive to the operation load and the that cable performance significantly influenced by temperature variations over the cable layers. This research provides knowledge, modelling and analysis of underground MV PILC cable thermal behaviour. Leading to improving assessments and network lifespan extension.