SVL (Sheath Voltage Limiter) – Contextual Evaluation of IEC 60099-4 Type Tests in Link-Box Applications

Abstract

In high-voltage underground cable systems, the management of sheath voltages is of critical importance for system reliability and insulation coordination. This study provides a technical perspective to guide energy authorities by interpreting how the test requirements of Sheath Voltage Limiters (SVLs)—used within link boxes—should be understood in the context of their specific application, as defined in IEC 60099-4. Unlike conventional surge arresters that operate continuously under energized outdoor conditions, SVLs in link boxes are protection devices that function only during transient overvoltage events and are located in enclosed, protected environments. Therefore, certain type tests, such as environmental and mechanical endurance tests, are explicitly stated in IEC 60099-4 as not mandatory or may be exempted for link box applications. However, since SVL manufacturers generally design their products for both outdoor and enclosed system use, all type tests are typically performed during production. This practice has led to a common perception among energy authorities, utilities, and industry stakeholders that the same testing requirements apply to all SVLs, regardless of their installation environment. Consequently, some tests that are technically unnecessary for enclosed and protected applications are often considered obligatory. This paper emphasizes the importance of correctly interpreting and applying the exemption clauses in IEC 60099-4, taking into account the physical location, operating conditions, and housing design of SVLs within link boxes.