Customer: BAA AirportsMidel filled Transformers for Dusty Environments - Heathrow Airport
Location: Heathrow Airport

Application: Distribution Transformers
Highest Voltage: Various
Rating: Various

Date: 1990s onwards

Heathrow airport is one of the world’s busiest hubs, serving millions of customers a year. Throughout the airport distribution transformers provide power for critical services.

Originally all these transformers were cast resin but there were issues concerning airborne contamination, in the form of fabric dust. The transformers were located close to the baggage handling area and since the luggage was regularly moved on and off the conveyors a large amount of fabric dust was released into the air. This, combined with general dust from the movement of many staff and passengers, resulted in a build up on the surface of the transformers. This was further complicated by the cast resin design because of the airflow over the coils and the static fields around them.

The build up of dust on the transformer could potentially cause overheating and electrical issues, therefore the units had to be regularly cleaned. Initially, the operator tried to reduce the maintenance burden by installing filters on the transformers so that the dust would be trapped but these quickly clogged up and needed regular maintenance to keep the air flow high.

Deciding that cast resin transformer were not a suitable option the user sought fluid filled transformers that would not be affected in the same way by dust build up. Mineral oil could not be used as it is not fire safe, so MIDEL filled transformers were specified. MIDEL transformers were the perfect replacement because they are housed in sealed tanks and not exposed to dust build up and they do not have external static fields to attract fabric particles from the air.

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