Mexico’s Federal Electrical Commission needed a safe way to train new operators at its Laguna Verde Nuclear Power Plant in Veracruz, so it developed a stand-alone process simulator that allows trainees to practice a wide variety of plant operations and responses to incidents without putting the plant itself at risk.
Electric power plant owners have to face higher production and efficiency demands under tighter schedules these days. Furthermore, the need to be competitive in a globalized world requires them to observe and comply with more international standards and regulations; therefore, operation and maintenance personnel must be trained to deal with higher production requirements and be certified to comply with new international standards and regulations.
Plant owners and operators have much to gain by implementing appropriate personnel training. Comprehensive training programs are critical not only for plant owners but also for everyone involved in plant operations, as such programs can significantly improve not only safety but also plant performance in both functional and financial terms. Because time is always scarce, automated software systems that are flexible, scalable, easy to use, and easy to learn are the best for facilitating and enhancing the training process.
Training Requirements at Laguna Verde Nuclear Power Plant
Mexico’s National Electric Power Co., Comisión Federal de Electricidad (Federal Electrical Commission, or CFE by its acronym in Spanish), is the second-largest state-owned company in Mexico in terms of budget and employees. Currently, CFE generates, distributes, and markets electric power for almost 33.8 million residential and industrial customers, which currently represents almost 100 million people, and more than a million new customers are incorporated every year.
CFE operates several thermoelectric, hydroelectric, coal-fired, nuclear, geothermal, wind-powered, and combined cycle power generating facilities. It also has responsibility for the management, control, and development of Mexico’s electric grid, which has more than 742,000 kilometers of transmission and distribution power lines. The infrastructure to generate electric power consists of 177 generating plants with an installed total capacity of 51,081 MW.
Laguna Verde Nuclear Power Plant (LVNPP) is the only nuclear power plant in operation in Mexico. It belongs to CFE’s power generation division and is located in the state of Veracruz on the coast of the Gulf of Mexico. The plant has two independent power generation units with BWR-5 type reactors. The two 682.5-MW units provide a total plant capacity of 1,365 MW. The first unit started operation in August 1990; the second unit followed in April 1995.
LVNPP has developed several instruction and training programs to comply with recent international regulations. In order to further improve the quality of their training programs, the training department of LVNPP appointed the Enabling Technologies Division of the Instituto de Investigaciones Eléctricas (Electric Research Institute or IIE) to design and build a plant process simulator (SIMPRO) to facilitate and support the training and certification processes of the plant’s personnel. The plant process simulator consists of a physical reproduction (though a simplified version) of selected systems in the operating plant that are integrated with a digital control center.
Detailed Simulator 3-D Design
The development and use of virtual 3-D models is a common practice in industries that frequently design new products. Computer-aided modeling has been demonstrated to be a cost-effective and useful technique to develop virtual models that represent in a very realistic and detailed way the characteristics, operation, and performance of the elements or systems to be manufactured. This practice allows pre-visualization of the results and comparison against the expected functionality of the finished product, ahead of the manufacturing or construction stages.
These techniques have been adopted by designers in other fields, such as engineering, procurement, and construction. The use of 3-D modeling techniques has been accepted in plant design and construction because of the need to increase the reliability and security of the designs that will evolve into new industrial installations. Process, electrical power, oil, and gas plants are some examples of facilities that have applied 3-D modeling with excellent results in Mexico. For that reason, a plant design and 3-D modeling software system was used to design the plant simulator, which allowed the project engineering team to facilitate information flow among engineers of all disciplines involved in the design and construction.
The design and modeling software was deployed in a client-server configuration, where several users were able to retrieve, create, or update the plant design concurrently. Access to each plant area was carefully controlled by granting appropriate privileges to each engineer and designer.
All systems and components in the simulated plant were represented and their attributes stored in an external database linked to the items within the 3-D model; all the documentation and derived information is generated, retrieved, and graphically managed via the 3-D model of the simulated plant (Figure 1).
|1. Make the model. The simulated plant was first created as a 3-D model. Courtesy: IIE|
The 3-D plant design software was customized to organize the information and highlight the plant’s key elements. The software selected included the capability to automatically generate from the 3-D model the detailed engineering drawings and diagrams required to proceed to the construction stage, thus minimizing drafting time.
The 3-D model itself was utilized as a central source of engineering information across all disciplines involved in the design phase of the project, thus delivering a unified and integrated engineering solution to support engineers and constructors throughout the project. This approach delivered significant, compelling benefits since it reduced time, costs, and personnel effort by providing an easily accessible repository of valuable plant design information and up-to-date engineering documentation.
Additionally, the virtual model of the plant currently provides support to training programs and plant maintenance operations. The simulator virtual model has been employed to identify and evaluate problems that might have represented risks to personnel or equipment in the real site, such as plant layouts that would prevent fast reaction/runaway in case of an emergency evacuation. The model can be exploited, among other uses, to simulate and visualize critical operations on a real-scale, virtual site.
As mentioned above, 3-D modeling solutions, such as that used to create the simulator, facilitate efficient engineering design, data storage, and revision of information. This applies whether the data are produced via handover from engineering projects executed by third-party contractors, during construction or plant walkdown exercises, through concurrent engineering of small on-plant projects, or by legacy data integration from previous engineering records. However, integration and model validation is a very important phase that cannot be overlooked in a project of any magnitude, as it leads to enhanced engineering data and design integrity. In effect, model integration allows better coordination and decision-taking among all players and disciplines involved in the design and construction of any industrial plant, from engineering to commissioning, and from design to test and operations.
Plant design information is dynamic, because it often changes, especially during the detailed engineering revision stages when several final design decisions are taken. Besides, it is well known that plant design data is highly interdependent—the actions or decisions made in one plant discipline can affect many others, and this can be a serious problem when it is not properly managed. Therefore, adequate coordination and teamwork throughout the complex maze of partners, suppliers, and internal departments involved in the project is required. Leading companies have recognized this and have tried to manage it through the use of more-inclusive practices like formal review/approval workflows, but this practice has proven to have limitations, as it only deals with clear, highly visible interdependency problems.
Adequate management of the frequently changing engineering design basis throughout the different stages of a project is a key reason why model integration and design validation is an imperative step preceding construction; to facilitate this task, plant design management software systems deliver advantages for designers, plant owners, and operators.
Therefore, in order to act in accordance with best practices, and to avoid design change management problems, once all core elements of the plant’s virtual model were settled, the next step was to integrate all of them in a version for reviewing and validation. This integration and validation was carried out with the same software application used to model the elements for the plant simulator, but auxiliary third-party validation tools can also be employed to assist the review, validation, and construction of the facilities.
The Plant Process Simulator includes a physical reproduction of a section of the real nuclear power plant, which includes a pair of vessels, electric pumps, pipelines, control loops including valves, and associated instrumentation such as manometers, thermocouples, level gauges, flow indicators, transmitters, and limit switches (Figure 2).
|2. Reproduce reality. The simulator contains a reproduction of several elements of the plant control components and associated instrumentation. Courtesy: IIE|
This section of the simulator includes a motor control center with a cabinet designed to store the AC and DC distribution circuitry, the electric interrupters, breakers and all the mechanical and electrical protections found in a real plant. Both an air dryer and a compressor were included in order to supply instrumentation air to all pneumatic tools and devices available in the simulator; the compressor is capable of supplying air to the process, for instance, to simulate pressurized vessels.
The arrangement and layout of the mechanical and electrical equipment, pipelines, instrumentation, and control elements matches that of the real power plant, so trainees have the same “look and feel” as at the real site.
The “real plant section” of the simulator reproduces the process operations that take place in the plant and enables trainees to learn in a controlled, risk-free environment how to execute routine actions and corrective maintenance operations such as dismounting, disassembling, inspecting, and/or replacing a control valve from a pipeline following established procedures and utilizing the appropriate tools and protection equipment. This area provides a place where trainees are able to reinforce and put in practice concepts and abilities learned in manuals and written procedures. For their part, instructors are able to assess the performance of trainees in a secure scenario that mimics the real plant. In this manner, feedback is provided to trainees not only from instructors but also from the simulated process itself.
A human-machine (HMI) interface for the instructor was designed and supplied with the plant simulator (Figure 3).
|3. Visualize operations. The main display of the simulator HMI allows instructors to monitor process variables in real time and simulate plant disturbances and abnormal conditions. Courtesy: IIE|
The main HMI display contains a left panel that allows the user to remotely stop and start (as long as all required “ready-to-start” conditions are fulfilled) each of the pumps in the simulator. This panel also has several controls that allow the instructor to remotely cause disturbances and trigger events to simulate failures and/or abnormal conditions in the process. The right panel of the HMI makes it possible to monitor the process variables in real time and take remote control of each of the valves displayed.
The interface also integrates an application to remotely monitor in real time the motor control center’s electrical parameters such as voltage, current, power, and power factors. The simulator HMI logs all process variables and records the events that take place in the process as well as the sequence of actions taken by the operator trainee, so it facilitates the assessment of procedure compliance and the time needed by the trainee to restore the simulated scenario to normal operating conditions. Because this valuable information is recorded, statistics can be easily obtained to determine the effectiveness of newer training programs and teaching procedures. Control algorithms running behind the HMI are responsible for some of the protection trips that ensure safe operation of the real plant section of the simulator.
The plant process simulator currently provides several means to recreate abnormal plant conditions such as failure of valves, transmitters, and other equipment. However, it is desirable to combine such features in order to create a full set of programmable and triggered events that mimic the complex dynamics of the real plant process. This is being carried out in joint collaboration between CFE and IIE personnel.
Time restrictions always play an important role during projects, so there are several opportunities for improvements. The expected result is to have a comprehensive set of case studies available to enhance the training experience of CFE’s plant operators and maintenance technicians.
Many Benefits Gained
The plant simulator is a useful way to prepare and train crews to respond to various kinds of situations within the real power plant, as it can be used to provide failure-scenario mock-up tests. It also improves safety by eliminating the risks involved in assessing such tests in the real plant. Furthermore, the system automatically acquires and records all measurements required in a test session, so the accuracy of measuring the process variables is greatly improved.
The plant simulator can be set up to reproduce a selection of typical situations such as failure of equipment, instruments, and valves; system trips; and more complicated and critical scenarios an operator must be able to deal with, including those abnormal and emergency situations that are rare and uncommon.
— Jesús Vázquez Bustos and Octavio Gómez Camargo are with the Control, Electronics and Communications Department in the Enabling Technologies Division of the Instituto de Investigaciones Eléctricas, Cuernavaca, México.