The master station (MTU) is one of the most important components in a SCADA control system, in that sense it should be clear about the functions performed by this team within the system and what criteria it.

The master unit MTU RTU sends information to each using a common medium of communication and a common protocol. Both the master station and RTU basically have the same communications equipment. The difference is that the master station MTU is the only one who can start the conversation. This communication is initiated by a program within the MTU that can be triggered by a manual instruction given by the operator or by the MTU program. 99% of the messages are automatically initiated by MTU as part of their routine control.

Many MTU use proprietary protocols depending on the Provider. This protocol must be compatible with all stations to connect to the network. In this type of technology is known as a closed architecture, which is characterized by having to use only equipment supplier.

Figure 1

Example of a communication module for a master station:

When working with teams of open technology, it believes it can work with different suppliers at the time of system design. This is mainly because the standard is shared among providers.

SETTING A SCREEN OF A PROCESS

Adequate information to display the status of remote stations, it is necessary that all the elements necessary field are connected to the RTU. That way, the MTU may obtain such information.

Figure 2

Below is an example that consists of a simple process for controlling a fuel supply line.

Figure 3

The RTU 1 monitors the status of the pump, which can be turned on or off. You can control the on and off the pump. Similarly you can open and close the valve and identify the state of the valve. Additionally there is the aggregation of data flow through the pipe and low pressure alarm on the line.

In the RTU 2 we have only one control block the valve. It controls the opening and closing the valve and monitors the status of it. As is the case of RTU1 monitors the status of the minimum pressure in the process line.

The RTU3 has the same function as the RTU1 just do not have a pump to control.

It has a simple system for monitoring the Scada system. It seeks to prevent leaks in the supply line of the process. Detection can be performed by the difference between the tote tote entry and the exit. It also has a continuous monitoring of pressure drop on the line in case of a fuel leak. If any of these conditions is presented in the data table of the master station is activated an alarm to take direct action on the process. In this case send a signal to close the valves in a sequential process. If no confirmation is received that the valves are closed, the MTU back to send the shutdown signal. If the problem persists, give an alarm signal the operator to take direct action on the process.

The MTU on failure and lose communication with the RTU's communication should recover automatically. If communication can not be reached to establish a routine can be activated to send stop. This RTU is that? S send close their valves and stop the flow.

The process status display is made from a monitoring station consisting of a PC monitoring software that displays the status of computers in graphic form.

Figure 4

Below is the codes that are sent to RTU1 for process control.