SCADA: Master Station

What Is It

Master Station is one of the three components of a SCADA system. The term in a small system refers to a single computer responsible for communicating with the field equipments. In a large SCADA system, master station consists of multiple servers, distributed software applications and disaster recovery sites. Master station server and software communicate with, apart from the field equipments like RTU/PLC, HMI software running in the workstation of control room or at other place.

Presenting The Information

Information to the operating personnel is generally presented graphically by the SCADA system. This graphic representation is known as a mimic diagram. This enables the operator to have a schematic representation of the controlled plant. For example, it shows a graphic of a pump connected to a pipe from which the operator can see both running of the pipe as well as the volume of fluid being pumped through the pipe at the given moment. The operator can switch off the pump depending on the need. The flow rate of fluid in the pipe decreases over real time as shown by the HMI software. Process elements are usually represented by schematic symbols and line graphics of mimic diagrams. The process equipment is represented in animated symbols by digital photograph.

HMI Workstation

There is a drawing program in a typical SCADA system with HMI package. The operators or system maintenance people use this drawing program to make changes in the way of representation of these points in the interface. An on-screen traffic light representing actual traffic light state in the field is an example of a simple representation. A multi-projector display to represent in a skyscraper position of all the elevators is an example of a complex representation. Platforms like LINUX were not much used earlier on account of its dynamic development environment. However now all major operating systems like LINUX, UNIX and OPENVMS are used for master station servers and also HMI workstations.