**4.4 Performance criteria and acceptance procedures**

Usually the fidelity of a simulator is mainly based on the behaviour of a group of variables called critical parameters. These parameters are related with conservation principles of mass and energy of the power plant and they will be selected only if they can be accurately measured. Any other variable not selected as critical parameter and which is observable in the operator HMI is called no critical. Typical critical parameters are:


108 Fossil Fuel and the Environment

uses the operation diagrams to control and monitor the whole process, with them he operates pumps, fans valves, and also he can modify set points of automatic controls and carry out any feasible operation in a similar way as he would do in the actual power plant. When the trainee needs to perform an action, he selects the suitable pictogram with the cursor, and then a pop-up window appears with the corresponding operation buttons. At any time the trainee can open all the pictograms he wants, and can do this in any operation console. The operation diagrams also have value windows; they show a pop-up window with the value of one variable (e.g., boiler drum level, turbine speed, etc.) and its operation range. The trainee easily visualizes the off-service equipment because it is shown in white and the equipment on-service has a specific colour depending on its working fluid. To this end, green equipment handles water, blue equipment handles air, red equipment handles steam, and so on. Figure 12 shows the operation diagram of combustion gas, where it is

One important improvement of this kind of HMI is its capacity to show to trainee more information (temperatures, pressures, flow rates, etc.) compared to former control board simulators so it is expected that this kind of features help the operator to analyze in a better way a particular phenomena. In the bottom of the diagram displayed in Figure 12

open a pop-up window to start a motor.

Fig. 12. Interactive process diagram


According to the previous classification, the criteria to assess the performance of the simulator can be summarized in the following three points:


The acceptance procedures define the required tests to carry out before a simulator can be ready to use it as a part of the training programmes for operators, the execution of these procedures is also a way of verifying if the simulator meets with its specification and scope. These procedures include exhaustive tests of all the hardware and software involved, the required tests can be summarized as:

Fossil Fuel Power Plant Simulators for Operator Training 111

where: *w* is the flow, *K* is the valve conductance, *Ap* is the valve position, *ρ* is the density, *Pi*

In the case of elements like pumps and fans, an approach based in the operation curves of the actual equipment is preferred because it gives a complete representation of the flowpressure behaviour to any operation speed. For instance, in the case of a centrifugal pump, from the nominal data of the head-volumetric flow rate curve (H vs. q), the application of a

where: *∆H* is the head developed by the pump, *q* is the volumetric flow rate and a*, b, c* are the coefficients obtained from the least squares fitting. The application of the pump affinity laws and the relationship for the developed head transforms the former equation in another one in terms of the flow, discharge pressure and pump speed, which is more

�� � �� � � ��� � � � � � � ��

where: *w* is the flow, *Pi* and *Po* are the inlet and outlet pressures, *ρ* is the density, *Ω* is the angular speed and *A, B, C* are the transformed coefficients depending on pump nominal data. On the other hand, capacitive elements are those which have a storage effect in the process (tanks, metal walls, etc). In this case the equations of the element are based on the lumped parameters approach; this approach simplifies the description of the behaviour of spatially distributed physical systems into a topology consisting of discrete entities that approximate the behaviour of the distributed system under certain assumptions, e.g. perfect mixing, which assumes that there are no spatial gradients in a given physical envelope, so the outlet stream has the same conditions of the fluid inside a control volume. In this way, to model a tank of constant volume with a single-phase fluid, the mass conservation equation yields:

> <sup>0</sup> <sup>0</sup> ; *i o t*

<sup>0</sup> <sup>0</sup> ; *ii o <sup>t</sup>*

<sup>0</sup> <sup>0</sup> ; *i i*

*t*

where *ρ* is the density, *t* is the time, *wi and w*o are the inlet and outlet flows and V is the

where *U* is the total internal energy, *hi* and *h* are the inlet and outlet enthalpies and *Q* is the heat flow rate. For an incompressible fluid, the internal energy is equal to its enthalpy, and

*dh wh h Q h h*

*dU wh wh Q U U dt* (5)

(6)

(4)

*d w w dt V* 

volume. The energy conservation equation with no work is expressed as:

with the assumption of perfect mixing, equation (5) is transformed in:

*dt V*

and *Po* are the inlet and outlet pressures.

suitable for the simulation.

least squares fitting gives the following expression:

� � � ������� � ��� (1)

�� � � � � � � � �� (2)

� (3)


The general requirements of fossil fuel power plant simulators are well defined by the Instrument Society of America (ISA) and the Electric Power Research Institute (EPRI). These entities provide extensive guides related to the design, development, fabrication, performance, testing, training, documentation and installation of power plant simulators.
