Automation of Methodology for Analysis of Overcurrent Protection Functions in Electrical Power Systems

This paper addresses a proposal for the optimization and automation of the methodology of selectivity analysis in protection relays by fault sweeps, to improve selectivity and evaluate the operation times and coordination margins in a complex network composed by a large amount of overcurrent units. Through the operating times of the protection devices, it can be quickly identified the lack of coordination that may occur in the relays of the network for several topological conditions. The coordination times are obtained by a set of injected failures in the assets delimited by the scope of the selectivity study, and through an automatic systemic analysis it is sought to generate a diagnosis of the most critical points in which there is no correct selectivity within protection functions. The automation strategy of this work is designed and evaluated in DIgSILENT PowerFactory and Python computational tools. Through the scripting and automation module, a Python script is executed in the PowerFactory environment, and in this way the protection relays and the measurement transformers are modeled by assigning their respective settings and directionality. Finally, an analysis is carried out with criteria of the good setting of protection devices created by experts in the field, and a calculation file is generated with the optimized operating times of the protection devices and an analysis of selectivity between the overcurrent functions of the system.