A) THE MASTER OR MASTER STATION
Receives data from the condition of field equipment that is sent by the remote station (RTU). Processes information and sends commands to the remote stations to maintain process variables within the established parameters. The master station depending on the Scada system to implement can be a PC with software for monitoring and control. In many cases it chooses to work with a PLC with communication skills that would accomplish the task of reading the information from the remote units.
Figure 3 - Master or Station Master
B) O RTU REMOTE UNITS
Control all input and output signals of the field as valves, measurement equipment, motors. Monitor the condition of field devices and store the states of the alarms. Send alarm states and field teams and receive commands from the master station.
Figure 4 The master station interrogates the RTU via a survey or polling process
Some authors classify units RTU is silly and intelligent units. At the beginning of the SCADA system installed units was common that only fools were in charge of sending information to the master station and the station made the decision and is transmitted to the RTU.
At present, the RTU silly have been replaced by the RTU smart are basically small PLC's that are capable of communications and are responsible to control processes locally and then the master station is informed of the action taken by the RTU to to update their registration data.
Other authors classify the RTU on the number of input and output signals handled by each team. RTU is considered a less than 100 signal I / O and small, up to 500 I / O as medium and over 500 I / O and large.
C) TELEMETRY NETWORK
Set the exchange of information between the master station and remote units. When we talk about telemetry we refer primarily to three components:
The topology used: Corresponds to the geometric arrangement of the nodes. Among the main ones is the point to point, point to multipoint, and so on.
Transmission mode: It's how information travels between the different network nodes. You can have two main modes: Full Duplex and Half Duplex.
The medium used: It is the type of medium used to send and receive information. It may be a dedicated physical line, through the atmospheric environment, through the power lines, etc..
Figure 5 - Telemetry Network
D) MONITORING STATION
Allows graphic display of process status, ie gives the operator control functions and monitoring of the plant. The process is represented by synoptic stored in the computer generated from the process and incorporated into the SCADA editor or imported from another application when configuring the package.
Figure 6 - Supervision Station
Some monitoring software:
RSView32, Rockwell Software.
InTouch, Wonderware.
WinCC of Siemens.
LS-B/Win Choirs of Siemens.
SYSMAC SCS Omron.
FIXDMACS, Omron-Intellution.
SCADA software must be able to offer the following services:
Ability to create alarm panels, which require the operator to recognize the presence of a stop or alarm condition, with logging.
Generation of signal historical plant, which can be turned over for processing on a spreadsheet.
Implement programs that modify the control law or even the entire program on the PLC, under certain conditions.
Programmable numerical arithmetic that allows high resolution on the computer's CPU and not on the PLC, less specialized, and so on.
