PCBs management strategy of pole mounted transformers – a statistical model approach

£722 million to £1.4 billion is needed to replace ~180,000 pole mounted transformers (PMTs) in Great Britain (GB), due to the risk of Polychlorinated Biphenyls (PCBs). Recent legislative updates in Europe (2019) and in the UK (2020, 2021) meant the need for removal of PCBs contaminated oil filled assets by 31 December 2025. The biggest challenge lies with PMTs as these are not easily accessible and currently impractical to sample/test. This means the 180,435 PMTs that are in-service across the GB would need to be replaced by the legislative deadline, triggering astronomical cost and diverting investments away from Net Zero transition, prematurely replacing assets, worsening supply chain bottleneck issues as well as causing significant disruptions to electricity supply. The main author has led and delivered a statistical model that groups the ∼180,000 PMTs into 12,660 cohorts/families, based on 211 distinct manufacturers and 60 years of manufacture. Setting a required statistical confidence, a set of minimum required sample size and acceptance/rejection criteria is selected for each cohort to inform the risk of PCBs contamination. This is the core of the GB electrical utilities’ strategy for managing PCBs in PMTs and has realised savings of £324 million to £647 million to date.