IEC 61850 Process Bus Benefits

Process bus based applications offer some important advantages over conventional hard wired analog circuits. The first very important one is the significant reduction in the cost of the system due to the fact that multiple copper cables are replaced with a small number of fiber optic cables.

Using a process bus also results in the practical elimination of CT saturation because of the elimination of the current leads resistance.The impedance of the merging unit current inputs is very small, thus resulting in a significant reduction in the possibility for CT saturation and all associated with it protection issues. Process bus based solutions also improve the safety of the substation by eliminating one of the main safety related problems - an open current circuit condition. Since the only current circuit is between the secondary of a current transformer and the input of the merging unit located right next to it, the probability for an open current circuit condition is very small. It becomes non-existent if optical current sensors are used.

Last, but not least, the process bus improves the flexibility of the protection, monitoring and control systems. Since current circuits can not be easily switched due to open circuit concerns, the application of bus differential protection, as well as some backup protection schemes becomes more complicated. The above is not an issue with process bus, because any changes will only require modifications in the subscription of the protection IEDs receiving the sampled analog values over IEC 61850 9-2.