Quantitative Assessment of Stochastic Property of Network-induced Time Delay in Smart Substation Cyber Communications

Smart substation, in which various types of information are being exchanged on a communication network, is regarded as a typical cyber-physical system (CPS). The network-induced time delay, inherently stochastic, makes the performance of power system operation and protection unpredictable. This paper attempts to study the stochastic properties of end-to-end network-induced time delay in a time-critical smart substation CPS environment. The components in a smart substation CPS, including data flow, communication network, and intelligent electronic device (IED), are modeled. The data flow on the network is categorized into two different stochastic types according to their source: Poisson and Pareto data flow. The numerical simulation of the hybrid data sources on substation network is implemented to evaluate the stochastic property, by combining Monte Carlo method and queueing theory. The obtained distribution results are identified by using chi-square and Kolmogorov-Smirnov tests. It is identified that Normal distribution can best characterize the delay in smart substation, meanwhile, the proposed model is verified with the experiment. A typical 220kV smart substation is studied under various scenarios.