PCB contaminated distribution transformers: problems and solutions

As required by European and Italian legislation, a systematic screening of the power distribution transformers in service was made by ENEL. This screening was related to a number of about 300,000 medium to low voltage transformers, with rated power from 50 to 630 kVA. The screening has shown that a certain number of transformers were contaminated with various degrees of PCBs. An economical evaluation was made to compare the different solutions to the problem: continuation of service without any intervention; decontamination; direct disposal; or disposal after treatment. The influence of the content of PCB and of the size of the transformer on the solution to be adopted was analyzed and technical evaluations of the various decontamination procedures were made. On the basis of the research activity performed, guidelines for solving the PCB problem for distribution transformers in Italy were drawn, by means of the setting up of technical specifications for verifying the adequacy of dehalogenation and/or decontamination methods and of the qualification of the decontamination service suppliers