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Active filters ensure reliable emergency power at Spain’s newest airport

02 November 2013

Interruptions to power supplies at airports can cause serious failures in aeronautical navigation systems, runway lighting and the like. Emergency generators must therefore be able to start up instantly and keep crucial systems online.

Two Danfoss VLT Advanced Active Filter units are helping to reduce the effects of grid disturbances and secure the power supply to Spain’s newest air transport hub, the Region de Murcia International Airport.

The new international airport in Murcia is expected to become the gateway to a wide range of Spanish destinations with significant growth potential. With an annual capacity of three million passengers, the airport is currently equipped to handle 23,000 landings and take-offs per year.

Spanish contractor, SAMPOL, was responsible for the implementation of the new filter system, which reduces the reactive current on emergency generator start-ups. As SAMPOL already had experience with Danfoss filters in connection with a similar challenge at Fuerteventura Airport in Spain, it returned to the company in 2012 for similar help with the power supply protection systems at the new airport. 

The start-up of an emergency generator is the most critical part of its operation, as Danfoss business development manager, Sergej Kalashnikow, explains:

“We want to avoid reactive currents because they place an additional load on the generator and grid, which prevents the power source from providing the rated power. Before the Danfoss filters were installed the lagging reactive current reached 600KVAr due to the length of the power cables at the airport.

This is well above the expected maximum of 120kVAr. As a result, the generator did not work correctly, and in the worst case the generator would not start up at all, ultimately causing the entire emergency system to fail.”

Active or passive?
Issues related to reactive currents are typically solved by using passive components such as inductors. However, the most efficient way is to use filters that handle currents actively, without causing negative effects such as resonances, which often appear when using a passive alternative.

For the Murcia project, the Danfoss Advanced Active Filters were installed on the secondary side of the auxiliary services transformer. This is a medium voltage dual secondary coil transformer where one of the coils is used to power auxiliary service equipment and the other powers the filters. Combined, the filters guarantee that the reactive currents always stay well below 120kVAr when the generator starts up.

The new filters were installed in October 2012 and passed the final tests in January 2013, much to SAMPOL’s satisfaction.

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