Transformer maintenance reduced at Heathrow airport


Customer: BAA Airports
Location: London Heathrow Airport
Date: 1991 onwards

Application: Distribution Transformers
Highest Voltage: Various
Rating: Various



One of the busiest airports in the world

Heathrow airport is one of the world’s busiest hubs, serving millions of customers a year. Throughout the airport there are distribution transformers providing power for critical services. Originally all these transformers were cast resin but there were some problems which prompted the user to look for a solution.


Airborne contaminants increases overheating risk

The key issue was 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 lead to 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 they 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.


A more suitable ester filled transformer solution

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 after contacting M&I Materials, 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.

The MIDEL solution has been so successful that during the latest terminal 5 expansion MIDEL filled transformers were used once more.




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