A Comparison Of The AC Breakdown Strength Of New And Used Poly-/spl alpha/ Olefin Coolant

The breakdown performance of an advanced synthetic dielectric coolant, poly-alpha olefin, is compared to conventional transformer oil over a range of temperatures from 10 to 50degC. The poly-alpha olefin oil is first benchmarked against conventional transformer oil, and then compared to poly-alpha olefin oil that has been exposed to a large number of high-energy discharges in order to establish the effects of oil age on performance. The results obtained from the standard ANSI D877 test procedure are compared to the results of a modified test procedure that incorporates sparging of the oil with dry nitrogen. Tests to determine the effects of nitrogen sparging on the water concentration of the poly-alpha olefin are analyzed. Concerns regarding the dependence of voltage breakdown values on oil viscosity are also discussed.