Compute electrical system fault currents quickly. Accurate engineering results calculated instantly.
An infinite bus represents a theoretical power system with constant voltage magnitude, constant frequency, and zero internal impedance. In practical power engineering, evaluating fault currents originating from an infinite bus assumption allows engineers to size switchgear, circuit breakers, and protective relays safely under worst-case scenarios. The short circuit level dictates the thermal and mechanical stresses equipment must withstand during transient faults.
The symmetrical fault current ($I_{sc}$) from an infinite bus system evaluated via short-circuit MVA is determined using the foundational equation:
$$I_{sc} = \frac{MVA_{sc}}{\sqrt{3} \times kV_{LL}}$$
When evaluated using percentage impedance (%Z), the system base impedance ($Z_{base}$) is calculated first:
$$Z_{base} = \frac{KV_{LL}^2}{MVA_{base}}$$
The total impedance is subsequently converted into absolute ohms to derive precise symmetrical and asymmetrical fault magnitudes based on the active X/R ratio.
Begin by selecting your preferred calculation mode from the first panel. Enter the proper system line-to-line voltage alongside your designated base MVA parameters. Input either the known Short Circuit MVA rating or specific percentage reactances depending on your available utility data. Designate your expected fault configuration type, click the calculation trigger button, and analyze instant results.
What is an infinite bus? It is an idealized voltage source where voltage parameters remain completely undisturbed regardless of connected load modifications or fault occurrences.
Why is the asymmetrical current higher? Asymmetrical currents incorporate DC transient offset components dictated directly by the circuit's underlying inductive reactance to resistance ratio.
How does voltage factor affect sizing? The voltage factor accounts for maximum operational voltage variations across utility networks before fault inception.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.