Short circuit ratio (electrical grid)

For other uses, see Short circuit ratio (disambiguation).

In an electrical grid, the short circuit ratio (or SCR) is the ratio of: the short circuit apparent power (SCMVA) in the case of a line-line-line-ground (3LG) fault at the location in the grid where some generator is connected, to: the power rating of the generator itself (GMW).

Since the power that can be delivered by the grid varies by location, frequently a location is indicated, for example, at the point of interconnection (POI):

SCR is used to quantify the system strength of the grid (its ability to deal with changes in active and reactive power injection and consumption).[1] On a simplified level, a high SCR indicates that the particular generator represents a small portion of the power available at the point of its connection to the grid, and therefore the generator problems cannot affect the grid in a significant way.[2] SCMVA is defined as a product of the voltage before the 3LG fault and the current that would flow after the fault (this worst-case combination will not happen in practice, but provides a useful estimation of the capacity of the circuit). SCMVA is also called a short circuit level (SCL),[3] although sometimes the term SCL is used to designate just the short-circuit current.[4]

  1. ^ NERC 2017, p. 1.
  2. ^ Ramasubramanian 2019, p. 6.
  3. ^ Burton et al. 2001, p. 572.
  4. ^ Henderson et al. 2023, p. 1.