Automated computation of short-circuit current components and selection of high-voltage circuit breakers of substation switchgear CAD

The paper develops an algorithm for the automated calculation of short-circuit current components and the selection and verification of high voltage circuit breakers. The algorithms used to calculate the components of the short circuit current and check the circuit breakers are based on current guidelines. When developing the high-voltage circuit breakers checking algorithm, the attenuation of the aperiodic component of the short circuit current is taken into account. The least-squares method is used to determine the coefficients of a regression equation that describes the dependence of the normalized asymmetry of the disconnected current on the time of opening of the switch contacts. The article also shows that this regression equation estimates the normalized asymmetry with an error of under 5%. The authors have developed an algorithm that allows selecting and testing switches, based on the value of the periodic component of the short circuit current on the substation buses, the voltage class of its switchgear and the power of power transformers. This algorithm features a peculiar ability to export the nominal parameters of electrical equipment from the CAD database. It is implemented in step-down substations CAD, which allows automating the design of the electrical part of step-down substations along with obtaining a set of design documentation with a feasibility study for the decisions made, based on the terms of reference.