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Steam turbine automation

A new turbine controller brings Lielahti power plant into modern times , Update 2012

Manually or automatically? If today’s operators are asked this question, they will definitely choose the latter one. At the Lielahti power plant in Tampere, Finland, the partly manual startup of the steam turbine will soon be history.

Pls feel free to ask for more information. We also appreciate your feedback in all automation related issues.

“It feels as if this AEG turbine was only recently lifted into its place – although it was 25 years ago,” laughs Technical Specialist Lasse Vuorio at Tampereen Energiantuotanto Oy.

At the time of the interview, the turbine was down and partly dismantled of its old hydraulic pipings. The era of mechanical control had ended, and a new one was about to begin.

“The turbine control had been built very skillfully using technology of the past, and it functioned well. However, today’s regulations have changed; the target for controls and interlockings is to improve reliability and safety both in disturbance situations and during normal operation. With the new automation, turbine control takes a leap into our modern times,” he continues.

The construction of the AEG steam turbine control equipment will be simpler when the mechanical controls are dismantled,” says Lasse Vuorio of Tampereen Energiantuotanto Oy.

Part of an extensive renewal project

The changes in steam turbine control are part of a large LASU project in which automation and electrification at the Lielahti power plant have been extensively renewed. Metso was chosen as the main supplier for the plant, which started energy production in 1988 and is fueled by natural gas. The original installations will be replaced with modern technology to extend the automation lifetime by about twenty years. The automation renewal project will be finished in autumn 2011.

Metso’s comprehensive delivery includes the dismantling of the old Damatic automation system and a new-generation automation system with integrated steam turbine controls.

Tom Bäckman, Product Manager, Turbine Controllers, at Metso.

“Earlier, the turbine was controlled with mechanical-hydraulic speed control and load controllers whose control motors were managed from the control room. Now, we will simplify the turbine hydraulics by removing the mechanical controllers and limiters,” explains Tom Bäckman, Product Manager, Turbine Controllers, at Metso. He has also designed the hydraulic changes at the Lielahti steam turbine.

In addition to the speed and load controllers, the inlet pressure controller as well as the backpressure and wheel chamber pressure limiters were removed while modernizing the hydraulics. Two electric-hydraulic converters will be installed in their place to control the turbine’s control valves through the Metso DNA automation system. All turbine startup logics, controls and necessary limiters will be implemented through the main automation system.

The turbine’s hydraulic protection will remain as it is, but will be connected to Metso DNA-HIMA turbine protection. According to the power plant’s wishes, also the mechanical overspeed protection will stay in place and will be accompanied by a new electric overspeed protection with 2/3-voting.

No more manual control

Lasse Vuorio has been working with steam turbines for over forty years and has seen how technology develops sometimes in small steps and sometimes in major leaps. He has – as also do the power plant operators – high expectations for the new steam turbine control.

“Usability will improve and become easier. For example, startup can be performed directly from the control room without the need to go to the turbine hall. You no longer need to control from memory or raise rotations by hand. Also, during normal startups and shutdowns, you just push the button and follow the trends, whereas earlier you had to do manual adjustments little by little.”

Due to new technology, changing different control modes (inlet pressure, backpressure and load) will be easier. In the future, the operators will see significantly more turbine control and process measurements and signals on the control room displays than before. Also, they will get more information and faster about possible alarms, enabling easier troubleshooting.

The power plant runs with several shifts and operators. Each has his own way to manage the process.

“Now there will be no differences between the shifts, as everybody operates according to the same trends. The limiting values cannot be exceeded,” Vuorio points out.

Good experiences at other plants

Tampereen Energiantuotanto chose Metso’s turbine control based on the experiences gained at its Naistenlahti 1 and Naistenlahti 2 power plant units, which have run with a turbine controller for a few years.

“They have functioned well, and using the turbine with them is easy. At Naistenlahti, the major benefit came from changing over from water hydraulics to oil hydraulics and making control directly part of the main automation, which simplified things a lot,” Vuorio tells.

Although not all that much time has passed since the turbine controllers were installed in Naistenlahti, technology has moved forward. Especially the hydraulics automation and interlockings have developed.

Pls feel free to ask for more information. We also appreciate your feedback in all automation related issues.