A quantitative evaluation of IEC61850 process bus architectures

The IEC 61850 standard plays an important role in the smart grid landscape by providing an unified way of accessing and exchanging data related to substations equipment. While large parts of the standard are widely adopted and integrated by the different vendors, the 9-2 part, or process bus, remains a challenge because of the number of opposite constraints that have to be addressed at the same time, such as scalability, reliability, real-time and cost efficiency. This paper does not provide the way to implement the process bus, but rather gives means to evaluate and compare different process bus solutions. In this study, we are performing a quantitative evaluation of different process bus architectures along the reliability, availability, performance and cost criteria. The performance criteria encompasses the evaluation with respect to the real time constraints as well as the overall load of the communication infrastructure. The cost criteria identifies the initial investment cost for a given solution and also evaluates the maintenance cost over the life time of the process bus. The main contributions of this paper are (a) to give a full evaluation by integrating all relevant criteria; (b) explicitly explain how the different evaluations are performed; (c) to integrate all elements for the reliability calculation, especially the optical fibres which are usually omitted but considered as the least reliable elements; (d) to evaluate the latest redundancy protocols for automation networks such as PRP and HSR; and (e) to evaluate architectures that take full advantage of IEC 61850 by deploying protection and control functions in innovative ways.