Power Transformers with PCB-Contaminated Mineral Oil: The Natural Ester Fluid as a Replacement Alternative

The 2001 Stockholm Convention was convened to draft a global treaty for the regulation of persistent organic pollutants (POPs) and established an agreement to carry out the total removal of contaminated sources of PCBs (one of the POPs) by 2025 and their total destruction by 2028. PCBs were the basis of synthetic oils used as electrical insulating fluid in transformers. Decontamination processes using several chemical-physical treatments removes PCB present in the molecules of the contaminated insulating fluid. Natural ester insulating liquid can be a substitute alternative to replace PCB-contaminated mineral oil. A real case will be presented with a 16 MVA 88 kV power transformer with PCB-contaminated mineral oil and the field process to exchange it by a new natural ester fluid.