Medium-voltage shielded busbar long-term ageing test method

Abstract

Classical air insulated switchgear busbar consist in a simple metal component using the ambient air as dielectric insulating medium: its sensibility to the external conditions is very high and dielectric failure is likely to occur. An innovative modular MV busbar, similar in principle to the MV cable shielded accessories, has been designed to reduce the internal arc probability and increase the reliability of medium-voltage (MV) switchgear. The live part is overmolded by a first insulating rubber layer which is also overmolded by a second conductive rubber, connected to the earth. The study proposes a validation method to assess the lifetime of this technology, by providing a complete review of the ageing behaviour. The use of several ageing models (parametric and non-parametric) is discussed. Physical and chemical ageing is followed up at various temperatures during more than 12,000 h both on material samples and on real parts. The choice of an end-of-life criteria based on a dielectric test is discussed and compared with a more classical criteria. In the end, this study review all the steps to perform a complete ageing study of a real industrialized component.