**2. Training simulators**

92 Fossil Fuel and the Environment

the largest 100 accidents in the hydrocarbon-chemical processing industry cost \$7.52 billion in losses; operator error accounted for 21% of these events at an average of \$75 million per loss". The modern distributed control systems of the power plants provide to the operator with the elements to get a power generation stable, safe and reliable, but as a consequence, there is a reduction of the operator's confidence to carry out unusual manoeuvres, e.g. a start-up in manual mode or the requested actions after a feed water pump trip. Training simulators help operators to practice this type of manoeuvres. The main advantage of a simulator as a training tool is that the operator does not need to touch the actual unit to learn to operate it in a broad range of possible scenarios. These scenarios include normal operations like unit start-up from cold iron to full load and shutdown. Also can be defined scenarios for malfunctions in which the trainee practice the suitable operative actions when in the simulated unit there are events like: trips of pumps and turbine, tube ruptures, and "faulty" instrumentation. In other words, the operators use the simulator to practice their normal operation procedures and to practice infrequent evolutions and faulted conditions. Therefore, one of the most important parts of the training programmes of power plant operators is carried out trough simulators, a big number of these simulators are of the type called full-scope, these simulators incorporate detailed modelling of those systems of the referenced plant with which the operator interfaces in the actual control room environment. Usually, replica control room operating consoles are included (International Atomic Energy Agency [IAEA], 2004). In these simulators, the responses of the simulated unit are identical in time and indication to the responses received in the actual plant control room under similar conditions. A significant portion of the expense encountered with this type of simulators is the high fidelity simulation software that must be developed to drive it. The completeness of training using a full-scope simulator is obviously much greater than that available on other simulator types since the operator is performing in an environment that is identical to that of the control room. Experienced operators can be effectively retrained on these simulators because the variety of conditions, malfunctions, and situations offered do not cause the operator to become bored with the training or to learn it by rote (Instrument Society of America [ISA], 1993). Therefore, full-scope simulators are recognized worldwide as the only realistic method to provide real-time and hand-on training of operators. Also the simulators can be utilized to validate the normal operating procedures, to conduct

engineering studies and to train plant technical supporting personnel.

However, the expense of developing this kind of simulators, the necessity of training a bigger number of the operation staff and the search of better training has driven the development of different training tools, for instance, there are part-task simulators, where the users are only trained in a particular system of the power plant (e.g. feed-water system, steam turbine, etc.). There are also compact simulators, where the users can practice the majority of the main operation actions required in a power plant, but the operation interfaces are of a generic type and not necessarily are similar to the ones the operators utilize in their actual power plant. In many cases, the part-task and compact simulators are portables, so they are transported to the power plants, in this way, the operators can practice onsite, these simulators can be utilized with the assistance of an instructor, in a free-hands context, or with the guidance of an expert system. In spite of the shortcomings of these simulators , there are some clearly identified benefits of using a variety of training simulators, which are: the ability to train on malfunctions, transients and accidents; the reduction of risk to plant equipment and personnel; the ability to train personnel on actual According to The Free Dictionary (thefreedictionary, 2008), a simulator is defined as "any device or system that simulates specific conditions or the characteristics of a real process or machine for the purposes of research or operator training". In the context of training of power plant operators, a simulator is a system composed of a Human Machine Interface (HMI) which replicates the operation consoles of the actual plant and a computer that executes mathematical models, which "replicate" unit performance. These simulators are based on the mathematical modelling of dynamic systems and their expected responses have a real-time functioning. Usually the training sessions are guided by an instructor which establishes the initial condition, starts the simulation, and supervises the actions of the trainees. This concept is shown in a simplified way in Figure 1.

Fig. 1. Schematic representation of a training simulator.
