Condition monitoring of power transformers on BR

British Railways (BR) has some 5000 power transformers installed to supply traction power on AC and DC power systems, to supply power to stations and depots, to minimise telecommunication interference on AC systems and to step down voltage to electronic drives and traction motors on AC locomotives and electrical multiple units (EMU). Here, the author describes how improvements in oil quality for many fleets of transformers have been made by improved physical testing techniques and transformer failures have therefore reduced. The exercise has been of significant cost benefit in saving failures, preventing disruption, preventing fires and as an aid to planned replacement of assets, and the author expands on some of these areas