The research of alternative EHV mineral transformer oils for the replacement of SHELL diala oil

For the replacement of SHELL Diala oil on extra high voltage (EHV) transformers, alternative of Kelamay oil (a kind of petroleum product) are chosen. Various electric performances, physical and chemical properties of Kelamayi and SHELL Diala EHV transformer oil are tested according to international standards and other related standards. In this paper, some important parameters are measured such as oil-flow electrification, dielectric breakdown voltage, particle count, kinematic viscosity, oxidation stability, solidification point, dissipation factor, gassing tendency and volume resistivity. Moreover, the properties of mixed oils are also tested. The results show that the special Kelamayi EHV transformer oils typed KI50GX and KI50AX are superior to the commercial SHELL Diala GX transformer oil in general properties. As the excellent performances, the two Kelamayi oils can be used as alternative oils for the SHELL Diala transformer oil. The properties of mixed oils meet the requirement of qualities according to GB/T14542-2017 standard.