Stochastic latency assessment in substation automation systems

This paper deals with stochastic latency in modern substation automation systems based on IEC61850. In order to meet the real-time requirements of mission-critical protection functions, latency evaluations are necessary to assess the expected performance level. A thoroughly-analyzed system under various contingencies ascertains that the communications design architecture is sufficiently fast and reliable. The presented methodology is demonstrated via a case study related to anti-islanding protection of a power plant. The base case latency and stochastic latency were calculated and compared. This investigation reveals that a failure in the communications network can compromise the performance of the protection function without proper mitigation strategies such as utilizing devices with higher reliability, considering redundant parts, equipping network devices with monitoring and indication systems, and deploying GOOSE as opposed to ARQ.