Intermountain Power Service Corp. replaced its vintage hard panel simulator with a new simulator designed around its modern distributed control system.
By James Burr, Intermountain Power Service Corp.
Intermountain Power Service Corp. (IPSC) at its Intermountain Generating Station in Utah has begun training operators with its new full-scope, high-fidelity simulator that incorporates the latest “virtual stimulation” of the plant controls with an object-oriented process model and instructor station. The new simulator was installed in January 2005 at a cost of approximately $1 million. Since then, the simulator has been undergoing system software upgrades and final model and controls checkout. The two-unit station is in the process of upgrading its distributed control system (DCS), making the new simulator necessary.
IPCS’s new simulator is much improved from the $6 million, high-fidelity hard panel simulator it installed in 1985. The differences in development, installation and performance illustrate just how far simulator technology has advanced in the past 20 years. In the original simulator, the DCS controls were emulated with software and hardware. For the new simulator, IPSC chose a “virtual stimulation” where the actual DCS software runs on several Windows-based PCs. This greatly reduced the hardware cost, while still allowing operator trainees to use actual DCS hardware stations and graphics. As fossil-fueled power plants continue to take advantage of technology improvements and upgrade their control rooms, an increasing number of high-fidelity simulators based on virtual stimulation designs, such as the one discussed here, will likely be installed throughout the country.
Background
The Intermountain Power Project was conceived in the 1970s by several Utah municipalities. By 1980, 36 different entities had come together to build a two-unit plant near Delta, Utah. The entities included 23 municipalities and six rural electric associations in Utah, six municipalities in California and Utah Power & Light. Los Angeles Department of Water and Power (LADWP) was designated as the operating agent for building, operating and maintaining the plant. The project also included a direct current (DC) converter station where a segment of the plant output is converted to DC and sent to California.
LADWP contracted with Black & Veatch and Bechtel for the design and construction of a coal-fired power source. The plant owners wanted a highly reliable design that would insulate them from supply fluctuations that might occur over 30 years. The reliability concern drove a design that resulted in two units rated at 750 MW each. Surplus capability was implicit in redundancy. For example, each unit was designed with eight coal pulverizers but could reach the rated load with only six. This design ultimately became valuable in paying down the owner’s debt during the 2002 California energy crisis. During this period, and for the next few years, each of these units produced nearly 900 MW of electricity.
The push for high availability also drove an investment in extensive training for plant personnel and operators. LADWP specified that a high-fidelity, near-replica simulator be built and used to develop skilled control room operators.
As plant construction began, IPSC was formed to secure labor resources and to be the plant operator. The project was approved with the agreement that Utah coal and Utah labor would be utilized to the maximum extent possible. General Physics was contracted to start training staff recruited from the surrounding area and from other sources. The initial training courses covered basic academics and principles of steam electric generation. These courses were found to be overly simplistic and were later upgraded by the plant training staff.
The simulator entered service around one year before the plant came online in June 1986. Many of the early trainees are still at the plant and are able to compare the 1985 simulator with the new SimSci-Esscor simulator installed in 2005.
Justification: 1985 vs. 2005
In 1985, the need to train multiple people who had little or no experience operating fossil-fueled power plants justified the simulator purchase. Most of those who would guide the new units through startup to full operation had never operated a fossil-fueled boiler or steam turbine. They had little basis for comparing simulator responses to actual plant responses. Their goals were to familiarize themselves with the control panel, gain an understanding of plant responses and learn how to start and operate the plant.
Justifying a new simulator in 2005 proved quite different than justifying the original simulator. The new simulator’s main objective is to configure and debug the new DCS controls before they are installed. A second objective is operator training; preparing plant operators to cope with the changes implicit with the installation of a cathode-ray tube (or CRT) only DCS and removal of the old control panel. Also, the simulator will become a tool to aid in engineering studies on plant equipment and operation modifications.
Plant personnel are convinced that the simulator is a proactive tool that will minimize the time required to change the DCS control system, a process which began in April 2006 and was expected to take four weeks. Two groups are concerned with these changes, the instrument and control (I&C) group and experienced control room operators.
The I&C staff has two goals. The first is to discover and correct any control logic errors, and the second is to discover early on any graphic errors that could inhibit operator reactions.
I&C engineers used the simulator to preview how the new controls will interact with the plant. The new controls underwent several refinements as they were tailored to the simulator plant model. Thus, the IPSC simulator is able to accept repeated direct downloads of actual DCS graphics and logic.
Most of the operators who will be trained have nearly 20 years of operating experience on the IPSC units, so they are familiar with the likely responses. The operators’ goals are to become familiar with the new graphical interface and appreciate how new control logic will affect plant response. Because of their knowledge, these operators clearly impose stringent requirements on both the accuracy of the process model and the DCS representation.
Software
Bringing a realistic process model together with the exact details of DCS configuration in the shortest time possible is important to fossil plant simulator clients in 2006, because lost production threatens economic survival. The process model/instructor station environment software (Dynsim Power from the SimSci-Esscor unit of Invensys Process Systems) and the DCS representation software (ABB Industrial IT virtual-stimulation) support this requirement at a level of detail and with an ease of use that was not imaginable in 1985.
1985 Simulator Features
The large hard-panel simulator supplied by Electronic Associates Inc. (EAI) in 1985, shown in Figure 1, cost approximately $6 million. The simulator included several graphic screens that generated representations of Foxboro and General Electric displays.
 Figure 1. IPSC’s 1985-vintage hard-panel simulator. |
The total development time for the EAI simulator was approximately two years. The software that represented the process model (Babcock & Wilcox drum boiler and GE steam turbine generator) and control system logic was written mostly in FORTRAN and included some assembler-language code. The software required compiling and linking executable code each time the plant model or the control model were changed. In the first years of operation, modifications to the models were performed by the vendor. Because modifications or model changes are required each time the real plant’s control system is changed, modifications to the simulator model are required through the life of the simulator. After the first years of operation, the IPSC staff was able to perform many of the changes without the vendor’s assistance. But often, obtaining a realistic response on the simulator was not achievable because of approximations in both the plant and control models. All documentation was distinct from the process model and control system representation code.
Comments from current plant operators who were trained on the original simulator confirm that the plant model predictions often differed significantly from the actual plant response. The staff recognized several areas of discrepancy once they became familiar with plant data and had operating experience. This is not surprising because the simulator vendor most likely lacked access to plant operating transients for validation exercises.
“The simulator was good for teaching new staff that had never operated a power plant,” said one trainee, who is now a senior operator. It helped develop skills of finding controls and information quickly, placing plant equipment in operation and developing operator responses to equipment failures and malfunctions. “But in many aspects,” the senior operator said, “the models lacked the realism of the plant and did not provide the desired training experience.”
2005 Simulator Features
The estimated cost of the 2005 simulator is about $1 million. This includes the process model software and hardware and a suite of ABB Industrial IT hardware and software. The simulator operating console is shown in Figure 2.
 Figure 2. IPSC’s 2005-vintage virtual stimulation simulator, installed in 2005. |
SimSci-Esscor’s Dynsim Power software is used to represent the process model. It is object-oriented with a JAVA graphical user interface (Figure 3). The object set that was used to build the boiler, turbine and balance-of-plant models has been used in more than 70 fossil plant simulators. Tests using data taken from the actual plant were used to validate static and dynamic process model responses. This validation process helped ensure that the simulator had the high-fidelity required for control logic testing and advanced operator training.
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The object-oriented “engine-based” nature of Dynsim Power, together with the virtual-stimulation ABB Industrial IT simulator solution, support the integration and testing of these two simulator segments. The SimSci-Esscor architecture also supports acceptance of repeated control system configuration downloads without the repeated compilation and linking steps required in the 1985 simulator.
The Dynsim software allows the process model and ABB control system representation to be easily maintained by the same IPSC staff that normally maintain the ABB system in the plant. Therefore, there is little need for a dedicated simulator maintenance technician. If plant equipment changes occur, the drag-and-drop graphical user interface (GUI) supports changes that can be made simply by opening the particular object and editing its parameters. Because Dynsim is object-oriented, these changes can be made “on-the-fly” while the simulator is running and the DCS is interconnected. This is like changing equipment in an operating plant while it is running. The feature also permits rapid tuning of the controls, which should cut maintenance time, and in turn, maintenance cost.
IPSC personnel specified the virtual-stimulation simulator where actual DCS software runs in emulated DCS controllers, thus hardware costs are reduced and the simulator still uses the actual DCS control software. In addition, IPSC started simulator development well before DCS installation to allow enough time for DCS logic testing and operator training.
The past 20 years of computer evolution have brought about personal computers that run at 3.4 GHz and support both DCS system implementation and simulator implementation. Software evolution has brought about concepts such as object-oriented programming, which make products like Dynsim a reality on the same personal computers. In addition, 20 years of progress have included the Internet’s development and proliferation. The simulator vendor can now maintain and make model edits remotely via the Web. These developments are brought together in the new IPSC simulator and provide a final result that is powerful and easy to maintain. The new simulator will be able to serve the needs of both the high-fidelity checkout of the new ABB Industrial IT control system and the advanced operator training in a single solution that cost approximately 17 percent as much as the 1985 simulator.
Author
James Burr, PE, is a systems engineer for Intermountain Power Service Corp. (IPSC), at the Delta, Utah, power generating facility. In addition to the positions held during his 21 years with IPSC, Burr managed engineering responsibilities for Westinghouse Idaho Nuclear Co. at the Idaho National Engineering Lab. Mr. Burr earned his bachelor’s degree in chemical engineering from Brigham Young University and is a registered professional engineer in Utah. He is also a long-standing member of the Institute of Electrical and Electronics Engineers (IEEE).