Preventing harmonic currents from flowing through a power system is the best way to ensure clean voltage waveforms essential for the correct operation of process equipment.

For a large oil extraction facility, all 690V variable frequency drives (VFDs) were installed within the same switchgear and MCC lineup.

The harmonic currents from these drives were cancelled by mirror-image harmonic currents provided by the active filters. In order to ensure failure-free operation, an additional back-up active filter unit was provided for each busbar. The active filters ensured that the current flowing through the transformers into the power system had no harmonic content and the resulting voltage waveform was perfectly sinusoidal.

The VFDs and related line reactors were installed in groups of 12 with six at the front and six at the rear.o

Schneider Electric France is based in Grenoble, France. www.schneider-electric.com