Alternative Liquid Dielectrics for High Voltage Transformer Insulation Systems

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Niharika Baruah1, Rohith Sangineni1, Mrutyunjay Maharana2, and Sisir Kumar Nayak1

1 Indian Institute of Technology, Guwahati, Assam, India

2 Xi’an Jiaotong University, Shaanxi, China

Transformers are the critical elements of the electrical grid and their effective operation is vital to the health of the whole network. It is of utmost importance to sustain the continuity of supply and prevent financial losses. The mineral oil (MO) is most generally used in the transformer as the dielectric fluid alongside the solid insulation like the pressboards and kraft papers. The development of environment friendly vegetable oils (VOs) or natural ester oils (NEOs) for transformers in place of MO gives us an alternative insulation system. MO is procured from the petroleum‐based fossil fuels and will deplete in the long run. Also, the biodegradability of MO is poor and hence causes environmental concern if spillage occurs. Alternatively, NEOs are achieving prominence because of their environment friendly nature, better biodegradability, higher fire and flash points. NEOs also have thermal conductivity better than MO; however, the viscosity is higher than MO, which is a disadvantage as it prevents flowability of the oil.

NEOs are derived from plant sources and there is a variety of them available in the market. Some of them are the linseed oil, castor oil, corn oil, Pongamia pinnata oil (karanji oil), soybean oil, punna oil, neem oil, Jatropha Curcas oil, palm oil, sunflower oil, olive oil, peanut oil, cottonseed oil, rapeseed oil (canola oil), coconut oil, hazelnut oil, and mustard oil [1–8]. The experimentation with NEOs for insulation purposes dates back to the twentieth century as these oils are readily biodegradable, have higher fire points, and are sustainable. The NEO also has higher water absorption capacity than the MO. A little concern over the use of NEOs made from edible oils like peanut and sunflower is that abundant use of NEOs can lead to a food crisis; therefore, these oils should preferably be made from nonedible seeds [9].