Drives save Aberthaw power station £350,000 oil costs 19 October 2012

Aberthaw Power Station in Wales is reporting savings of £350,000 per year on its oil costs, following the installation of ABB variable-speed drives.

The power station, operated by RWE npower, just west of Cardiff, is coal-fired, with a capacity of 1,600MW.

To light each of its three boilers, the power station uses 36 oil injecting lances, half mounted on each side of the vessels. Oil from the lances is blown into the boiler by fans at two rates – high flow to light the coal and low to sustain the burn.

Previously, the fans were driven by direct-on-line motors, which made it difficult to get the correct oil flow rate, according to Kevin Smyth, assistant electrical engineer at the power station.

"The flame size is dependent on the oil-to-air ratio – too much air and the flame will blow out, while too little air and there is the danger of too much oil entering the boiler, causing potentially dangerous combustion conditions," he explains.

As part of an energy saving drive as well as a plan to improve the power station's environmental credentials, Smyth looked into using variable-speed drives instead.

"We looked at several vendors' products," says Smyth, "but only the ABB drive had the required robustness.

"The power station is a very challenging environment with a lot of coal dust and water, so we needed a drive that offered an IP66 enclosure. We also needed a drive with high heat dissipation."

ABB Drives Alliance member, APDS, of Bristol, recommended 7.5kW ABB standard drives, so 32 were installed on selected lances, with a plan to install 16 more, their location depending on the required oil flow rates.

"With the drives, we can run the motors at either of two speeds," explains Smyth. "50 Hz corresponds to the high or normal flow rate, used for lighting the boiler. This flow rate will normally be used for 10 hours. The 35 Hz speed is used to maintain a flow rate that sustains the burn – the duration depending on the coal type."

And Smyth concludes: "As well as saving £350,000 on oil costs, we anticipate that savings could rise even further as oil prices escalate and we are also improving our environmental credentials."

Brian Tinham

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