Short-Circuit Ratio

SCR. The ratio between short circuit apparent power from a 3LG fault at a given location in the power system to the rating of the location.

Last Updated:  November 29, 2025

Version:  1.0.0

Generated:  December 04, 2025

Definition by NERC

Source: p1

SCR is defined as the ratio between short circuit apparent power (SCMVA) from a 3LG fault at a given location in the power system to the rating of the inverter-based resource connected to that location. Since the numerator of the SCR metric is dependent on the specific measurement location, this location is usually stated along with the SCR number.

$ SCR_{POI} = \frac{SCMVA_{POI}}{MW_{VER}} $

Where $SCMVA_{POI}$ is the short circuit MVA level at the POI without the current contribution of the inverter-based resource, and $MW_{VER}$ is the nominal power rating of the inverter-based resource being connected at the POI.