More than £1 million has been saved during the first year of using a human machine interface (HMI) at Innogy’s combined cycle gas power plant at Little Barford, Cambridgeshire. The system, from ABB Automation, has cut downtime by improving the handling of the existing HMI system, eliminating spurious system shutdown.
Neil Coles, control systems engineer at Little Barford, explained: ‘With the old system, the response was not fast enough to react to the operator trying to take control of a function and consequently we could have emergency shutdown of the plant. Some types of electrical fault can, for safety reasons, cause the breaker for the 400kV line, which connects the site to the grid, to drop out. This causes every motor and valve across the site to fail, generating four to five alarms each, resulting in thousands of alarms flooding the system.
‘Because the memory buffers of the old interface were not large enough to handle all these alarms simultaneously, they would flash up as much as half an hour later or be lost to the system and the operator could miss an essential alarm. Many megawatts were lost this way. Depending on the electricity pool price at the time, this could cost between £10 and £100 per MWh.’
Since the new system was installed, Coles and his team have been able to recover the situation on three occasions. The HMI was able to deal with these severe situations, which should mean trips are now hopefully a thing of the past.
‘Eliminating the first trip we saved some £500,000, the second time, £200,000, and on the third occasion, £300,000,’ said Coles. ‘This represents a fantastic return on investment of over 180% in the first year.’
The new HMI features a large screen display system, with mouse control replacing the original trackerball and SVGA graphics in multiple windows, enabling the operator to view all the relevant information simultaneously.
Little Barford has two frame 9F gas turbines on separate shafts and one steam turbine, run by the steam generated from the exhaust gases of the gas turbines, with a total output of 680MW. The ABB automation system, comprising 5,500 I/Os, controls the heat recovery steam generators, feed water controls, and interfaces to various packaged units around the plant.