Oil-to-Gel insulation: A novel eco-efficient insulation concept

Oil filled power products are susceptible to oil leakage resulting in environmental damage, downtime and ongoing maintenance costs. The environmental component of the aforementioned problem in traction transformers is presently mitigated by the usage of metal oil reservoirs, able to host the full amount of the insulating fluid upon leakage or failure. This, however, results in increased weight and cost. The present contribution describes the modification of ester oils, used as electrical insulation in power products (e.g. traction transformers), with low amounts of additives (<10 wt.%), in order to induce a thermo-reversible “oil-to-gel” transition. The oil remains in the liquid state at operational temperatures (essential for heat dissipation through convection) and gels below a certain temperature (selected to be few degrees higher than the maximum environmental temperature the product experiences). In the event of a leakage, the ester oil gels fast diminishing any environmental related hazard (gel does not penetrate the soil but stays on its surface and can be easily removed thereafter leaving behind clean, non-contaminated soil). Spillage experiments presented here provide proofs for a significantly reduced environmental damage upon leakage and for improved safety, since small leakages can be self-sealed or retarded. Finally, key physical properties of the insulation oil are studied (rheological, electric/dielectric) in relation to the presence of the additives.