SCADA Data Communication

Even with the reduced amount of wire when using a PC to IED system, there is usually a lot of wire in the typical SCADA system. This wire brings its own problems, with the main problem being electrical noise and interference.

Interference and noise are important factors to consider when designing and installing a data communication system, with particular considerations required to avoid electrical interference. Noise can be defined as the random generated undesired signal that corrupts (or interferes with) the original (or desired) signal. This noise can get into the cable or wire in many ways. It is up to the designer to develop a system that will have a minimum of noise from the beginning. Because SCADA systems typically use small voltage they are inherently susceptible to noise.

The use of twisted pair shielded cat5 wire is a requirement on most systems. Using good wire coupled with correct installation techniques ensures the system will be as noise free as possible.

Fiber optic cable is gaining popularity because of its noise immunity. At the moment most installations use glass fibers, but in some industrial areas plastic fibers are increasingly used.

Future data communications will be divided up between radio, fiber optic and some infrared systems. Wire will be relegated to supplying power and as power requirements of electronics become minimal, even the need for power will be reduced.