A Low Cost I&C Training Solution for any Plant

1.0 SIMULATOR DESCRIPTION

This type of I&C training simulator consists of the following major components:

• Dynamic process model running on a personal computer
• Control hardware including:
  • A PLC to provide instrument-level signals
  • Controllers (duplicates of those in the plant) to provide control action
• Software interface between the process model and the PLC

The process model calculates levels, pressures, temperatures, flows, and other process variables. These variables are passed to the PLC hardware, which generates instrument-level signals (e.g., 4-20 mA, 0-10 VDC). These output signals are wired to the inputs of the controllers. An identical approach is used for data traveling in the opposite direction, for outputs from the controllers that will be used to control variables such as valve positions in the process model.

1.1 Process Model

The process model that drives the simulation is created using the ProTRAX modeling system. ProTRAX is a modular, dynamic simulation code designed for use on personal computers running under a Windows® operating system. Individual modules, each representing a piece of plant equipment, are connected together in the same configuration as the plant. Once configuration is complete, data is entered into the model. Required data consists of physical and operating data, or design data, from the plant.

A typical I&C training simulator model for a nuclear application might include the following process/control equipment:

• Condensate pumps and condensate booster pumps and their motors
• Reactor feedwater pumps
• Reactor level and minimum flow loops
• Coolant recirculation pumps
• Reactor level, suction pressure, and miscellaneous feedwater transmitters

In addition, the process model will include all of the necessary tanks, pumps, pipes, valves and motors to fully simulate the selected portion of the plant. A sample portion of a typical process model is shown in Figure 1.

Figure 1 - Typical Process Model

The hardware controllers regulate most of the loops in this type of simulation, but there are numerous local controls that are not part of these loops. These local controls can also be modeled using ProTRAX. A complete set of SAMA modules, which can be used to simulate controls, are part of the ProTRAX software system. Controls can either be built in a separate model or can be built directly into the process model.

1.2 Hardware Description

Plant control hardware can include programmable computing stations and programmable indicating controllers. Each station/controller in the trainer contains exactly the same logic program that exists in its field counterpart. Simulator stations and controllers are cross-linked as in plant panels. All of the hardware (controllers, PLC hardware, and process model computer) is mounted in a portable enclosure. Front and rear views of a typical hardware cabinet are shown in Figures 2 and 3.

Hardware is used to generate and receive signals from the controllers. I/O types to be used in the signal generator can include any type of analog and digital inputs and outputs. An Ethernet base controller is used as the CPU to control I/O. This controller acts as a slave and adjusts outputs/reads inputs via Ethernet from the process models running on the instructor station.

Figure 2 - Hardware Cabinet - Front View

Figure 3 - Hardware Cabinet - Rear View

One feature that provides additional training capability is the ability of the I/O module to sense 0 V. Most I/O in control systems is set up as 1-5 V or 4-20 mA. If the signal generator can produce 0 V, this allows for the simulation of signal failure and the resulting alarms and diagnostic messages.

An instructor station, which provides the graphical interface to the simulator, consists of a rack-mounted computer with a remote monitor and a wireless keyboard and mouse. The computer runs Windows® operating systems and executes the real-time process model.

1.3 Process Model/PLC Interface

Several different interfaces between the process model and the hardware are possible with this type of simulator. These include:

• OPC client/server
• COM Objects
• Active X Objects
• Vendor Libraries

For a recent nuclear application, TRAX used an interface based on a vendor library that provided robust operation and high data throughput. Data was transferred via the interface over an Ethernet link from the instructor station to the Ethernet base controller.

2.0 TESTING SCENARIOS

Much of the training typically performed on simulators is geared toward operator training. This type of simulator, which targets I&C technicians, allows for hands-on troubleshooting of control and instrumentation problems that may occur within the plant. Students can use controller diagnostic tools and multi-meters to check signals and diagnose problems. This is done while the control system is operating a live (simulated) plant process.

As an example, a “bad” measurement signal can be simulated in a number of different ways, allowing multiple training opportunities:

• A step change in the transmitter bias
  This could result in a signal selector choosing a different signal for control, an alarm light on the controller or station, or a runback.
• A gradual or integrating bias change
  Several process problems can occur over a period of time. The end result may be similar to what is seen in a step change, but several alarms and process swings will occur on the way.
• The signal going to 0 V for a 1-5 V I/O point
  On the controller stations, this will result in several control errors. In addition, the station diagnostic will indicate a bad point.
• Failing power to a controller or station
  This would simulate a hardware station failure leading to several alarms and runbacks.

The instructor station provides the graphical user interface for simulator operation and initiation of training scenarios. A typical instructor screen is shown in Figure 4. From this screen the instructor can make adjustments to the process model. From here, the instructor can also initiate several malfunctions, including turning off power to selected controllers/stations.

Other screens provide the capability to:

• Implement step changes and incremental changes
• Enter a bias target to which the systems will ramp/integrate after the “set” button is clicked
• Input step changes to a level measurement
• Fail one or more of the level transmitters
• Initialize the process model to full, half, or low load
• Start or stop any of the process pumps
• Initiate runbacks

Figure 4 - Main Instructor Screen

3.0 CONCLUSION

A portable, versatile I&C training platform can be developed. This type of training tool will work with a PLC or DCS-based control system, or for stand-alone controllers. It can be applied to any type of power or process plant. The required hardware/software interface can be customized, or can use an industry standard such as OPC.

The major advantages of this type of simulator include:

• Affordable
• Short construction time
• Simple to operate
• Hands on operation
• Targets specific need
• Cost effective training with immediate employee improvement
• Lower risk to plant equipment and operations

The cost of having poorly trained personnel is extremely high. Both new and existing employees need training on the I&C problems they will face in the plant. Part task simulators fill this need by providing targeted training that efficiently trains employees to manage the complex tasks they are expected to control.

The bottom line is that targeted training on this type of platform reduces the risk of plant or equipment failure due to personnel error.