Electrical industry professionals are familiar with ester-based insulating oils, whether they are of vegetable or synthetic origin, for their excellent fire-resistance (class K oils) and for their biodegradability. These are the insulating fluids recommended both to eliminate the risk of transformer fire as well as to reduce the risk of pollution in the event of a leak.
High fire point vegetable insulating oils also have other less-known properties, which are extremely beneficial to transformers and their users.
The life of the electrical transformers is directly related to the good condition of the insulating papers. Natural or synthetic ester-based insulating oils have a better affinity to water than transformers' insulating papers, so they tend to "dry" them, slowing down their degradation and increasing their shelf life.
Naturally, the water saturation rate of an insulating oil ester is 10 times higher than that of a mineral oil. It can therefore accept much higher water contents, without its dielectric properties being significantly affected. With vegetable oils, the risk of free water at low temperatures is negligible, as well as the risk of induced electrical defects.
A serious problem in the degradation of mineral insulating oils is the formation of aggressive acids for insulating papers, and sludge that will create hot spots in transformers and risk of electrical defects. While degrading, vegetable oils produce log chain acids, which are much less aggressive for insulating papers, and very little sludge compared to mineral oils. Dielectric performance is also preserved.
Unlike mineral insulating oils, which the European REACH regulation considers to be hazardous to health in the event of aspiration, and which must be indicated by a hazard label bearing the label "may be fatal if swallowed or entered the respiratory tract", high-fire plant-based insulating oils do not require a hazard statement.
for example, to improve fire resistance properties. Insulating vegetable oils are miscible with mineral oils. The retro filling procedures with vegetable oils have been known and controlled for many years. Just take a few precautions, such as properly draining the mineral oil and sufficiently rinsing the transformer, as well as avoid using vegetable insulating oil in a breathing transformer. In case of uncertainty, do not hesitate to contact your supplier of insulating ester fluid, they will provide you with all the technical assistance to perform the retrofilling operation.