Phase 1IEC

Short Circuit Current Calculator

IEC 60909 / ANSI/IEEE C37

Calculate 3-phase symmetrical, asymmetrical and peak fault currents for switchgear rating, breaker selection and busbar design. Based on transformer impedance and system data.

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Results are for guidance only. All calculations must be verified by a qualified electrical engineer before implementation. Always refer to the applicable local standard and authority having jurisdiction.
Standard:

Transformer Data

V
kVA
%

From transformer nameplate — typically 4-6% for distribution

MVA

Available from utility — leave blank if unknown

Cable Impedance (optional)

mΩ

For downstream fault calculation

mΩ

Typical: 5-20 for LV transformers

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