Wednesday, 6 April 2016

Stuart Foster, UK Water Industry Sales Manager, ABB writes: As the saying goes, prevention is better than cure. This certainly proved to be the case for Southern Water when it came to minimising the risk of harmonic distortion occurring at a major new wastewater and sludge treatment works.

The incidence of harmonics has become more prominent in recent years due to the increase of non-linear loads such as fluorescent lighting and variable-speed drives (VSD). Harmonic distortion can strike anywhere, but it is particularly prevalent in industries troubled with weak networks, including water.

Over 90 ABB industrial drives were needed at the new treatment works near Brighton, which, once completed, would treat 95 million litres of wastewater each day from Brighton and the surrounding areas. This meant it was essential to take appropriate evasive action in the planning stage for the new facility to avoid major problems with harmonic distortion occurring once it was in operation.

The drives would be incorporated into seven motor control centres (MCCs) - five in the main works and two at pumping stations in Brighton and nearby Telscombe Cliffs. The main criterion for the drives was to minimise the harmonics produced by the large motors employed in the pumping stations.

MCS Control Systems, which supplied the MCCs for the site, called in ABB authorised value provider, Sentridge Controls, to provide the solution. Sentridge Controls found that a combination of low harmonic and 6-pulse drives, ranging from below 1 kW up to 560 kW, would provide the best solution, providing the right level of harmonics mitigation while keeping costs to a reasonable level.

The drives brought other benefits, too. Lack of space within the works meant it was important to minimise the size of the MCCs. The ABB drives offered the smallest footprint possible at these power ratings. Meanwhile, the large drives were rack mounted and fitted with wheels to make them easier to install in the MCC cabinets.

The ABB drives also have built in Profibus capabilities, making it easy for the facility’s control system to communicate with the drives.

According to Steve Poole, Managing Director of MCS, this mean the ABB drives provided the best combination of capabilities and price for this application, providing a “simple, cost-effective and low risk solution”.

For advice on finding the best harmonics mitigation solution for your water or wastewater plant, visit ABB’s new dedicated harmonics website

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