Returning transformers to service

The customer was a large UK Distribution Network Operator

Following a tap changer failure on a 132kV transformer approx 25,000 litres of insulating oil from the main tank of the transformer needed to be removed. The area around the transformer was environmentally sensitive so oil replacement, involving two sets of tankers, was deemed higher risk and a temporary hold on site option was deemed more suitable.

The EOS engineer met with the customer to assess site access, conduct environmental and work specific survey for RAMS.

EOS dispatched an oil flushed and certified road tanker to site for an 8:00am drain which went according to plan. The tanker was fitted with a desiccant dehydrating breather so the oil remained in good condition for the 12 hours or so it was out of the transformer.

Because the core and windings had been exposed to atmosphere the best advice was to refill the transformer through an EOS Mobile Processing Unit and circulate the oil for two complete “passes” once it was filled. This was duly done and the transformer successfully returned to service.