Investigating the Physiochemical Effects of Verdigris Contamination found on a Polymeric Cable Sealing End

A cable sealing end is a crucial power system component as it is responsible for the vital task of successfully terminating cables. Recent reports on the diagnosis of ex-service units have led us to investigate possible contaminations that could impact the dielectric properties of a cable sealing end. Verdigris, often blue/green in color, is one such contaminant that is observed on the surface of a cable stalk. This investigation aims to understand the possible cause of this contamination and its impact on the dielectric liquid used inside a polymeric cable sealing end. To achieve this, the current study is devised in two parts. First, a sample of the verdigris is scraped off from the cable stalk surface and analyzed. The elemental composition of the blue verdigris is analyzed using energy-dispersive X-ray methods on a scanning electron microscope. Second, sonication ageing tests are performed on samples of silicone oil that have been contaminated with verdigris. Elemental analysis shows traces of carbon, oxygen, sodium, silicon, tin and copper contaminations as the primary components of the verdigris present in different percentage. The results from the second half of the study obtained shows an increment in dielectric permittivity and moisture measurements, whereas not much change was reflected in the UV-vis analysis when compared with fresh oil sample.