Breaker Duty In The Ibr Era: When Old Rules Meet New Currents

The IEEE C37.010-2016 (IEEE Application Guide for AC High-Voltage Circuit Breakers > 1000 Vac Rated on a Symmetrical Current Basis) outlines a conservative methodology for calculating the maximum short-circuit duty for circuit breakers, widely adopted in commercial short-circuit analysis tools. While effective for systems dominated by synchronous machines, this approach does not adequately reflect the fault current behavior of inverter-based resources (IBRs), which differ significantly in response characteristics. This paper examines the implications of these differences and encourages a fresh look at established practices, offering perspectives that may inform future refinements to industry standards as power systems continue to evolve.