Abstract
Five transformer oil samples were collected from Western Region of Saudi Arabian from Electricity Companies during operation. The efficiency of transformer oils as insulation and cooling in power station was evaluated by studying their physicochemical and electrical characteristics. The sulfur compounds in transformer oils were evaluated via X-ray sulfur meter. Also, the dissolved gases in the studied transformer oils were vacuum extracted and analyzed by capillary gas chromatography. The excitation transformers have low dielectric strength compared with the other oil samples may be due to water contamination, reflecting the low efficiency of this oil as electrical insulator and decrease its safety around high-voltage equipment.