Devonport is the largest naval base in Western Europe, and the electrical estate reflects 50 years or more of organic growth across multiple voltage levels and two different frequencies. There was no single earthing design that the survey could be measured against, so each substation had to be assessed on its own merits.

Aurora carried out a site wide survey covering the 33 kV, 11 kV (50 Hz) and 6.6 kV (60 Hz) systems, taking in over a hundred substations from modern installations through to assets several decades old. The survey identified the high risk areas requiring immediate remedial action and set out a longer term path forward, including the route to a Global Earthing System (GES) classification for the site.