Assessing Short Circuit Levels as a Measure of System Strength in Future Grids with Uneven Distribution of Inertia and High Percentages of IBR

Abstract

In power system analysis the system strength and suitability for connection of Inverter Based Resource (IBR) generation and disturbing loads is considered in terms of fault level and Short Circuit Ratio (SCR). This paper shows that with the increasing penetration of IBR and changes to the distribution of system inertia, such an approach overestimates system strength. This paper proposes an alternative approach using time domain Root Mean Square (RMS) / Electromagnetic Transient (EMT) simulation methods to analyse the system's ability to deliver energy over time in relation to small perturbations. This is demonstrated through the use of a test network, where uneven inertia distribution and increased fault levels due to IBR are shown to give misleading results.