Calculator #002 IEC 60909-0 IEC 60909-1 MV 1 kV to 33 kV Sequence networks

Short-Circuit Current Calculator — MV, 1 kV to 33 kV (IEC 60909)

Positive / negative / zero sequence calculation of I″_k3, I″_k2, I″_k1, peak i_p and κ at every busbar of a user-defined network. Multiple parallel sources per circuit (infinite bus, transformer, manual Z, or known I″_k); segments of type cable / OHL / transformer with parallel conductors; earthing model selector (TN / TT / IT / resistance / reactance / isolated); maximum and minimum regimes computed independently. All computation runs in your browser — no data leaves the page.

Working below 1 kV? The companion tool #012 Short-Circuit — LV up to 1 kV carries the rules IEC 60909-0 reserves for low-voltage systems: the peak current by the equivalent-frequency method c), minimum currents with the conductor at θ_e, motor groups and busbar trunking as elements, and validation against the worked 400 V example of IEC TR 60909-4 clause 3. This calculator still accepts low-voltage inputs, but the low-voltage tool is the one written for them.

Developed by the ieccalc.com engineering team

Questions and corrections — forum

Join the discussion —
Electrical Designers Middle East

Project settings (applied to all circuits)

Region preset

System

Network voltage

Frequency, Hz

Earthing / neutral model (for I″_k1)

R_n, Ω (resistance / TT)

X_n, Ω (reactance / Peterson)

Ambient θ_a, °C

Conductor θ_op, °C (for I″k_min)

IEC 60909 voltage factor c: LV (U ≤ 1 kV) c_max = 1.05, c_min = 0.95. MV/HV: c_max = 1.10, c_min = 1.00. I″_{k_max} uses R at 20 °C, I″_{k_min} uses R at the conductor operating temperature set above. Z₂ = Z₁ (static network, far from generator).

PRO — unlimited project size

The free tier carries the whole calculation — every standard, every check and the full .docx report — for up to 3 circuits in one project. PRO removes that limit so a complete installation fits into a single file. An admin invitation unlocks it for your account.

Glossary & abbreviations

Input data and network schema are intentionally compatible with Calculator #001 (voltage drop): identical field names for U, freq, system, region, segments/elements[].L, .series, .S, .R_km, .X_km, .material, .n_parallel, .theta_ref_R. Future calculators in the series will follow the same contract so a project can be started in one tool and continued in another.

Built-in validation tests

#	Case	Quantity	Expected	Computed	Status

Reference values computed by hand from IEC 60909-0 formulae; I″_k1 test uses the three-sequence-network approach (|Z1 + Z2 + Z0|) and compares to the canonical limit cases (Z0 = Z1 → I″k1 = I″k3; Z0 = 3 Z1 → I″k1 = 0.6 I″k3).