Liquides isolants en électrotechnique

Insulating liquids have been used from the very beginning of the development of high-voltage electrical equipment. In general, liquids are associated with solid insulators, and their main role is to replace air in the cavities of solids to improve resistance to partial discharges and insulation breakdown. In some cases, notably in transformers and some power cables, the insulating liquid is primarily a heat-transfer fluid, used to evacuate the heat generated at the heart of the device.

Until the late 1960s, insulating liquids posed no environmental or toxicity problems. The discovery of worldwide pollution by polychlorinated biphenyls (PCBs) put the finger on the insulating liquid family as a whole, and made it the target of media attention. The result was growing suspicion of them, and their use became increasingly restricted and subject to regulation by national authorities. It is this phobia that has prompted research into "green" substitutes, notably based on vegetable oils.

A general presentation of insulating liquids in electrical engineering and a study of their main physico-chemical properties are given in the previous article. . You can also consult the table of notations and symbols.