Comprehensive Analysis of Lightning Performance of the Oil-Wedge Type Electrode Model Immersed in Selected Dielectric Liquids

(Vi) and breakdown voltage (LIBV) of the oil-wedge type electrode model immersed in selected dielectric liquids. The choice of the model is a response to the industry need to evaluate the liquids in conditions that are closer to a real insulating structure of the power transformers than typically used point-to-sphere and point-to-plane configurations. Two dielectric liquids made from GTL (Gas-to-Liquids) feedstock, namely Diala S4 ZX-I and Diala S5 BD are compared in terms of above-mentioned parameters with inhibited mineral oil Diala S3 ZX-I. Vi parameter is determined based on registration of light emitted by developing discharges while LIBV is determined based on the voltage waveform recorded using digital oscilloscope. Twenty-five models are prepared for each testing procedure at given voltage polarity and given dielectric liquid. This allows for in-depth statistical analysis and for determination of 1% probability of

Vi or LIBV, respectively. In addition, through successive calculations of the 1% probability of

Vi and LIBV after 10, 15 and 20 testing procedures, it is assessed the impact of sample number on the analyzed parameters. The results show that both GTLs behave similarly in terms of considered quantities and are characterized by higher Vi and LIBV than evaluated mineral oil.

Statistical analysis shows however that reliability of the results increases with increased number of measurement procedures, especially for Vi parameter.