Minimum voltage rating of sheath voltage limiters in underground cable systems: The influence of corrugated cable sheaths

Sheath voltage limiters (SVL) are a critical component of an underground cable´s protection system. SVLs must be sized such that, under steady state fault conditions, no conduction through the arrester occurs. This could otherwise lead to a catastrophic failure. A SVL failure [1] under steady state fault conditions prompted an investigation into the adequacy of traditional approaches used to model cable sheaths and underground cable networks. Injection tests have demonstrated that the type of sheath used has a large influence over the sheath voltage profile under faulted conditions. This is particularly evident with corrugated sheaths. In this paper, two common types of corrugated sheaths are investigated - the helically corrugated sheath (HCS) and the annularly corrugated sheath (ACS). The paper establishes improved models for each type of sheath and compares these models to sheath voltage profiles obtained from injection tests on three different types of underground cable systems.