The chemistry of interfacial tracking

Interfacial tracking occurs in a wide range of high voltage apparatus and frequently leads to electrical breakdown. A review of the chemistry of interfacial tracking along interfaces consisting of crosslinked polyethylene (XLPE), ethylene-propylene rubber (EPR) cable compound, and silicone rubber (SR) termination compound is given. Interfacial tracking experiments were conducted on the interfaces commonly encountered in cable accessories, including XLPE/EPR, XLPE/SR, EPR/EPR, and EPR/SR. The tracking products were analyzed using FTIR and GCMS. XLPE and EPR showed carbonization and an increase in cyclic and smaller chain hydrocarbons produced from radicals originating from hydrogen abstraction and chain scission. Oxidation of XLPE was observed with evidence of a Norrish type II photochemical reaction. SR showed evidence of SiO₂ production along with lower molecular weight silicones. Tracking across an interface containing SR resulted in erosion of the SR side of the interface.