Application Update: Integrated plant control system

Westar Energy natural gas peaking plant helps address variable wind power input and balance electricity flow in a smarter grid with integrated plant controls, for 12% less cost than expected.

07/06/2011


Emporia Energy Center, Courtesy: Westar EnergyTo meet a growing need for electricity in Kansas, Westar Energy, the largest electricity provider in the state, has developed an energy plan that includes investing in a wide range of power generation options, including both renewable and traditional-fueled generation.

“The Emporia Energy Center was designed with Westar’s many different needs in mind. The project took into consideration current and future wind energy expansions, environmental stewardship, future customer load growth, and recent and future energy market changes,” said Larry Graves, plant manager at Emporia Energy Center. “Westar chose to construct a facility that would allow the opportunity to generate a minimum of 10 megawatts, if one [aeroderivative gas turbine] were to run at minimum load, through the full plant base load operation of 665 megawatts.” GE LM6000 Sprint aeroderivative turbines at Emporia Energy Center have a GE Mark VI turbine control system; Courtesy: GE Energy

Quick-start gas turbines

To support that overall energy plan, Westar Energy built and is operating a new, simple-cycle power plant at the Emporia Energy Center near Emporia, Kansas. The facility is designed as a natural gas peaking plant intended to operate during periods of highest customer demand, primarily on hot summer days, using aeroderivative gas turbines.

The quick-start capability of the aeroderivative turbines at the Emporia Energy Center also makes this plant, along with other Westar facilities, an enabler of the renewables fleet at Westar. In addition to the gas-fired and coal-fired generation, the Emporia Energy Center is designed to help Westar address variable wind energy conditions from the nearly 300 megawatts of wind power the company buys or generates in Kansas.

The Emporia plant was completed two months ahead of schedule and under budget, resulting in an installed cost per kilowatt that is 12 percent lower than planned. Although designed for 625 megawatts, the plant today is rated at 665 megawatts, enough to power 400,000 Kansas homes.

Phase I of the energy center began generating energy to meet customer needs when it was completed in June 2008. Phase II was completed in late February 2009, about two months earlier than anticipated. Total cost of the project was about $305 million, about $13 million less than originally projected.

A unique feature of the project is the combination of aeroderivative and heavy-duty gas turbines in one integrated system. The plant includes four aeroderivative gas turbines, each site-rated at 41 megawatts; and three heavy-duty gas turbines, each site-rated at 154 megawatts.

Westar Energy needed to ensure that the plant automation and distributed control system (DCS) would effectively integrate with the turbine-generator controls. In addition, Westar wanted to use as many common features as possible, thereby reducing interfaces, shortening engineering and installation cycles, and providing a straightforward upgrade path for the future.

Westar Energy’s goal was to achieve short-cycle project execution and reduce capital costs, in addition to lowering maintenance costs. Integrated plant control systems are a key factor in achieving each of those goals.

The turbine supplier installed a total plant control system to meet Westar Energy’s schedule and performance goals. The three heavy-duty gas turbines were delivered with a turbine control system, the four aeroderivative turbines were delivered with a different turbine control system from the same manufacturer, and a distributed control system also was delivered for the plant control system. 

The control system helps to improve plant performance by integrating the controls for the turbines and balance-of-plant (BOP) equipment into an integrated system featuring the newest control technology. The high reliability of the control system is critical to the plant’s ability for quick start-ups to support the demands of peaking duty, as well as to serve as backup power for Westar’s wind generation.

The control, protection, and monitoring system uses a distributed architecture that supports local I/O on turbine skids and integration of remote monitoring systems with category five or fiber-optic 100 MB Ethernet. Dual redundant controllers and simplex I/O are used for the DCS. Triple redundant controls are used for turbine controls and safety systems. The I/O is distributed in simplex, dual, or triple redundant configuration as needed for the application.

The control system has a common time-coherent database. This database also contains data from other controls in the integrated control system, such as the excitation, static starter, and PLCs. A common database simplifies system configuration and provides quality data for operations and diagnostic analysis.

Integrated control advantages

The integrated plant control system includes:

  • Main control room cabinets, human-machine interfaces, engineering workstation, and plant historian
  • Main DCS cabinets, I/O cabinets, and network switches.

Using common hardware throughout the plant decreases spare parts and training costs, as well as time and expenses associated with start-up. While a common hardware platform reduces spare parts costs, there is value in having an integrated one-control system for all plant equipment. The common interface to all of the equipment operator screens, process data, alarms and events, trips, and trend data helps to increase the operator’s productivity and operational awareness. System tools can analyze data more thoroughly with one database.

This approach eliminates the traditional integration of plant and unit level controls, which in turn reduces system complexity, start-up problems, commissioning time, and project risk. These features contribute to simplified life-cycle maintenance and training for the plant equipment and personnel.

A centrally located control system makes it possible to see the plant operations from any control console in the plant. This allows an operator who may be physically located at the Unit 1 terminal to view and control functions for all the other units.

Integrating the BOP control shifted the coordination of unit and plant controls to the turbine and automation supplier, including an integrated factory acceptance test (FAT).

Power plant design experience coupled with advanced control technology extends the benefits to plant-wide operation. The automatic generation control system sends a signal to the DCS from outside the plant so the units respond to that signal.

In addition to improving plant performance through the total plant control system, Westar was also interested in quick start-ups and high efficiency. The aeroderivative gas turbines can achieve base load operation in about 8 minutes, adding flexibility to the Westar generation portfolio. In 2008, the plant had expectations of operating most substantially in the summer months. 

2008 Operating Data Emporia Energy Center

 

Unit #

 

Service Hours

 

Unit Starts

 

1

 

1025

 

131

 

2

 

1044

 

128

 

3

 

1127

 

141

 

4

 

1116

 

145

 

5

 

382

 

56

 

6

 

Not commissioned

 

7

 

Not commissioned

 

Source: Westar

With the fast start-up, low heat rates, and low startup cost of the aeroderivative turbines, the operating profile approaches more of an intermediate operating capacity than peaking. The heavy-duty gas turbines operate on a peaking profile with current expectations of <40 starts per year each, as shown in the table with 2009 operating results. 

2009 Operating Data Emporia Energy Center

 

Unit #

 

Service Hours

 

Unit Starts

 

1

 

2036

 

230

 

2

 

2199

 

250

 

3

 

2191

 

246

 

4

 

2101

 

240

 

5

 

293

 

57

 

6

 

457

 

73

 

7

 

408

 

60

 

Source: Westar

The Emporia Energy Center was originally staffed with one plant manager and three gas turbine technicians. After about a year of operating at a higher than anticipated load profile, two additional technicians were added to accommodate extended run times. Automation allows the expanded energy center to safely provide more service per scheduled human hours. Also, Graves said, the facility “can put up to 165 megawatts on the grid in less than 10 minutes with the remaining 500 megawatts following within 20 minutes and is capable of creating a spinning reserve pool or regulating energy of greater than 300 megawatts for the function of managing Westar’s wind energy program or any other system contingency that may arise. The flexibility of Emporia Energy Center is nearly endless.”

Controls: Integration benefits

Integrated controls:

  • Simplify plant operations and maintenance
  • Reduce spare parts inventory
  • Shift coordination of unit and plant controls to GE’s scope
  • Integrate FAT of unit and plant control in factory
  • Lessen installation cost and risk
  • Lessen initial and ongoing training
  • Lower life-cycle cost
  • Improve operator productivity and plant awareness with lower training costs.

Project elements, technologies at Emporia Energy Center

  • Three GE 7FA gas turbines with a GE Mark* VIe turbine control system
  • Four GE LM6000 Sprint aeroderivative turbines with a GE Mark VI turbine control system
  • GE Mark VIe DCS plant control system with dual redundant Mark VIe controllers and simplex I/O
  • Triple redundant Mark VI/VIe controls are used for turbine controls and safety systems
  • GE coordinated unit and plant controls and conducted an integrated factory acceptance test (FAT)
  • Black and Veatch engineering services 

- Edited by Mark T. Hoske, Control Engineering, CFE Media, www.controleng.com.

www.bv.com 

www.ge-energy.com 

www.westarenergy.com 

http://www.controleng.com/channels/process-control.html



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