Green tapchanger — OLTC filled with ester oil

On Load Tap Changer (OLTC), is a Transformer accessory intended for voltage regulation. Historically mineral oil is used as the dielectric liquid for OLTC. Considering the new global emphasis on biodegradable solutions, various alternative dielectric liquids such as Silicone oil, High Molecular Weight Hydrocarbons (HMWH), Poly Chlorinated Biphynyl (PCB), Ester oil etc., were considered. It is also important to consider economics while providing biodegradable solutions. Based on study of the performance of various dielectric liquids mentioned above, option of ester oil was found to be suitable. Detailed study of the properties of the mineral oil vis-à-vis the natural ester oil was carried out. Extensive experiments were conducted for both the oils at CTR — India Research and Development Center, supported by the state of the art test facilities, for different aspects of Tapchanger and the test results compared.