3. Conclusion

Mineral oil, which is a non-renewable resource and therefore likely to run out in the future, is still widely used as a liquid insulator in many applications, thanks to its dielectric properties and low cost. However, the trend for the future is to replace it with "green" renewable liquids in all possible applications. This is the case for transformers (traction, distribution), where mineral oil can be advantageously replaced by vegetable oil (or a synthetic organic ester). What's more, if the risk of fire is considered unacceptable, only these liquids can be used (class K). Silicone oil is also class K, but is only slightly biodegradable. Numerous studies are underway to validate the use of these "green" liquids for power transformers.

Power cables impregnated with liquids (polyolephins, alkylbenzenes, etc.) are usually replaced by buried extruded polymer cables...