Suitability of Simple Methods Based on the Standard IEC 60909-0 for the Calculation of Three-Phase Short-Circuit Currents in Distribution Grids

Abstract:
In recent years, large amounts of renewable energies have been integrated into distribution grids, especially into medium-voltage grids. Short-circuit currents are important criteria for the design of electrical grids. The standard IEC 60909-0 for the calculation of short-circuit currents has been adapted in 2016 to take account of their increasing impact. However, it is uncertain to what extend these power plants influence short-circuit currents on different voltage levels. In this paper, the influence of power plants with inverter-based generators on three-phase short-circuit currents and their representation in the standard are investigated. Therefore, a method for calculating short-circuit currents exactly and an advanced method based on the aforementioned standard are introduced. To conclude, recommendations for adequate modelling of inverter-based generators for short-circuit current calculations on different voltage levels are given.