Communication is an essential part of an effective SCADA system. If the different parts of the system cannot communicate securely in common procedural language, the system cannot control the processes as it is designed to.
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Use of a Supervisory Station
A supervisory station within a SCADA Industrial Control System refers to the combination of servers and software that are responsible for communicating with all of the field equipment, such as sensors, RTUs, and PLCs, as well as the HMI software that is being used. How the station is set up depends on the size and complexity of the SCADA system. It may range from a single control PC to multiple servers. Dual-redundant units that provide continuous control and monitoring in the event of a server malfunction or breakdown may also be used to increase system integrity.
Developing Communication Infrastructure and Methods
One of the problems with the traditional communication systems used within SCADA systems is that they are open, and therefore are at risk from security breaches. These traditional communication approaches use a combination of radio and direct wired connections. Even those that use SONET/SDH often share a network with other applications putting them at risk of bandwidth issues and even unintentional security breaches.
Satellite-based communication is increasingly used as a solution for mitigating such risks, with one of the main benefits of the approach being a self-contained system. It can also be safeguarded with built-in encryption and customized to the specific availability and reliability requirements of the SCADA system operator.
The Importance of an Operational Philosophy
The costs associated with the failure of the control system are extremely high for some installations. For this reason, hardware for certain SCADA systems is extremely rugged and able to withstand extremes of temperature, vibration, and voltage. Reliability of the most important systems is enhanced through the inclusion of redundant communication channels and hardware, which may include multiple fully-equipped control centers. This allows a failing part to be identified quickly and for its function to be taken up by backup software automatically and without interruption to the system. In many cases, the failed part can also be replaced without any interruption to the process.
The reliability of such systems can be statistically calculated and specified as the mean time to failure. This is a modified version of Mean Time Between Failures (MTBF). In such highly reliable systems, the mean time to failure is often calculated in centuries.
