Reliability Evaluation of Distribution ArchitecturesConsidering Failure Modes and Correlated Events

Abstract: Power systems are in a phase of automation where intelligent components and sub-systems are employed to monitor, control and manage the grid. Quantifying the complex consequences on system reliability, from the integration of such automated and semi-automated equipment into the existing grid is important for maintenance optimisation and fault mitigation. This thesis identifies the  advanced approaches in power system reliability analysis with the potential to capture the complications and correlations in modern power grid after reviewing the traditional reliability evaluation methods.A method for modelling the different modes of failures, possible in a substation and feeder architecture along with the probable false tripping scenarios was developed. An improved Reliability Block Diagram based approach was designed to count in the traditionally unaccounted failure cases affecting both the primary grid and the protectionand control equipment. The effect and corresponding trend of additional feeder lines in a radial distribution system on the net interruption rate experienced at load ends of feeders are derived and modelled. Such real-world substation architectures are analysed and the aforementioned trends are compared with those from the practical grid. Thus, the analysis was able to identify and measure the complex hidden failure probabilities due to both unwanted operation of breakers and functional failure of protection systems.The measured probabilities were used to calculate the impact of protection and control equipment on system  reliability. The obtained results were verified by comparing it with the observations by energy researchers on ten years of protection system failure statistics. The application of the model and results, in optimal maintenance planning and power network optimisation are identified as the next step.