Enter the short-circuit MVA at each point of interconnection and the plant size. See the short-circuit ratio, weak-grid flags, the largest plant each site can host, and what it would cost to strengthen a weak site.
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Short-circuit MVA should exclude inverter-based resources (as NERC defines SCR). Plants with the same group label are also screened together (WSCR).
Set the SCR you want each plant to have. Plants below it are marked in the results with two ways to get there: a smaller plant, or a synchronous condenser at the point of interconnection. Flags stay on the standard screening bands above. Enter your own costs; this calculator includes no cost data.
| Plant | SCR | Flag (screening bands) | Max size, no flag (MW) | Target check | Condenser (MVA) | SCR after condenser | Total cost |
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* Incomplete: a needed cost rate is blank.
How it is calculated. SCR = short-circuit MVA ÷ plant MW. WSCR = Σ(SCMVAᵢ × Pᵢ) ÷ (ΣPᵢ)², assuming the plants in a group are fully interacting (ERCOT/NERC). Max size (largest plant before a weak flag) = SCMVA ÷ weak threshold. Condenser MVA = max(0, MW × target SCR − SCMVA) × (X″d + Xt), assuming the condenser is at the point of interconnection. Default flag bands follow HVDC planning practice (IEEE Std 1204-1997); there is no universal weak-grid threshold.
Screening only. Results do not replace interconnection studies, detailed positive-sequence or EMT analysis, or the transmission provider's requirements. SCR-based metrics assume grid-following inverters and do not replace the inverter manufacturer's minimum SCR. Cost screening excludes network upgrades, which are often the largest interconnection cost.
To calculate short-circuit MVA from a network model, scan every bus, and compare methods, use the full SCR-Screen tool. Created by Shaibu Ibrahim, P.E. · MIT License.