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This is how expensive power failures can be averted

Published Apr 01, 2011

Transformers are the bridge between your computer, TV and washing machine at home and the nuclear power station. They also form a link between companies and the same power station. When the transformer breaks down, it costs society and businesses a lot of money. Researchers at KTH have now started working on a new method making it possible to keep track of the transformer’s condition which means we can avoid unnecessary and costly power failures.

A fault at one of Vattenfall’s many transformers a year ago caused a multi-hour power failure in Lilla Edet. 2,700 customers were without power, which included Inland Knauff’s cardboard factory. The site manager Åke Andersröd stated that the power failure cost the company millions, according to the local newspaper TTELA.

This is merely one example among many in recent years where faulty transformers have caused problems. Even the power companies are affected when transformers break down as they are forced to pay out substantial amounts in the form of damages to customers. Customers, in turn, risk losing everything from food which can spoil to information not saved onto hard disks when the power fails.

An important step towards a more reliable power supply is now being developed as KTH researchers Martin Norgren, senior lecturer in theoretical electrical engineering, and Hans Edin, senior lecturer in electrical power systems, have started to identify the problem. By placing sensors (antennae) which transmit and receive microwaves which bounce off the various parts of the transformer it is possible to read off how the transformer "feels" and how much wear it has so far been exposed to.

"If you want to keep track of the transformer’s aging process, you need to be able to see the material's fine structures, and that is why you have to use waves that have a short wavelength. With this information we can hopefully understand how to avoid costly power failures in the future and know when a transformer needs to be replaced," says Martin Norgren.

At the same time it may seem that it is really only a question of taking the transformers out of service and examining how they are functioning. But it may be very expensive to disconnect and examine them, connect up reserve transformers and redirect the power.

What Martin Norgren and Hans Edin already know is that no one has previously chosen to diagnose the transformer’s physical condition through the use of microwaves. More specifically, tests using microwaves can analyse the object’s materials, insulating properties and its conductivity.

"This method has not been tested on the transformers before, it is a new idea. The methods we use have been tested however in other areas," says Martin Norgren.

He adds that if the research is successful, it may mean that in future it will be possible to receive continuous information about the transformer’s condition, this is for example particularly important during solar flares which may expose the transformers to considerable strain.

"We are currently working on a feasibility study with prototypes whereby we will test these principles in order to prove that this works. We are also in the midst of recruiting a doctoral student to assist with our research," says Martin Norgren.

For more information, contact Martin Norgren at 08-790 74 10 or martin.norgren@ee.kth.se.

Peter Larsson