An ABB active filter is providing a dramatic improvement in network harmonic distortion at the new Padstow foreshore pumping station
South West Water is currently investing around £1 billion in ‘Clean Sweep’ - the largest coastal clean up operation of its kind in Europe. One of the places that has already seen the benefit is the traditional Cornish fishing village of Padstow. The project, which includes a new foreshore pumping station, is helping to safeguard the beautiful coastline which contrasts a rugged landscape with sandy beaches and an abundance of wildlife.
Western Power Distribution, the local DNO (distribution network operator) was concerned that the drives installed in the pumping station could give rise to unacceptable harmonic distortion on the local network. So in mid-2004 ABB was called in to carry out an investigation and implement a solution.
Many of the common loads in industrial and commercial applications are non-linear, such as variable speed drives, rectifiers, UPS-systems, computers, etc.
These loads draw a current from the source that does not follow the voltage wave shape and hence introduce potentially harmful distortion into the power network. This can lead to overheating of cables, motors and transformers, damage to sensitive equipment, tripping of circuit breakers and blowing of fuses as well as premature ageing of the installation.
ABB PQF (power quality filter) active filters have been developed to provide a reliable and cost-effective solution to this problem by continuously monitoring the current in real time to determine what harmonics are present.
They then inject harmonic currents in the network with exactly the opposite phase to the components that are to be filtered. The two harmonics effectively cancel each other out so that the feeding transformer sees a clean sine wave.
The traces from Padstow provide a dramatic illustration. First, we see the unfiltered 400V AC three-phase supply with serious distortion of the current waveform - instead of two crossover points per cycle, there are six.. The second set of traces show the effect of energising the ABB solution (a 70A active filter type PQFL) - there is a considerable improvement to the waveform and a 60 percent reduction in the current distortion.