Understanding the impacts of networks and parallel redundancy protocol for process bus applications

In a digital substation, process bus (PB) refers to a local-area communication network used to interface critical information, such as sampled values and trip signals, between primary equipment and protection and control devices. To improve protection system reliability of a digital substation, an engineered network is required for the PB. An ideal PB network must be robust and resilient. Robustness can be achieved by characterization of the network path, such as latency, packet delay variation (PDV) also known as jitter, packet loss rates, and bandwidth usage. Resiliency is usually achieved by incorporating redundancy or duplication. Parallel Redundancy Protocol (PRP) is a natural choice for PB, especially for transmission substations; however, redundancy can be ineffective if not constantly supervised and will hide failures in plain sight. In this paper, we outline a method for achieving robustness and resilience by closely analyzing PB network characteristics. We also discuss safe deployment of redundancy using PRP technology on PB applications.