IEC 60909-0:2016 · National Annex · Electrical

IEC 60909 Short-Circuit Current

Full IEC 60909-0:2016 fault level analysis with national annex selection, impedance correction factors K_T and K_G, and generator contributions. I"k · ip · κ · Ib (μ) · Ith (m/n).

National Annex / Standard:
IEC 60909 VDE 0102 (DE) BS 7639 (UK) GB/T 15544 (CN) JIS C 4620 (JP) IS 13234 (IN)
c_max = 1.10 (LV) / 1.10 (HV)
System One-Line Diagram
SUPPLY Un · Z_Q Z_src R + jX TR K_T=— CABLE r·l x·l FAULT BUS G K_G F FAULT CURRENTS · IEC 60909 I"k = — ip = — κ = — Ib = — Ith = — μ = — R/X = — Z_k = — NA = IEC c = — Fault= 3ph K_T = —
R/X: —
κ: —
Z_k: — Ω
NA: IEC
c: 1.10
System Parameters
kV
Line-to-line nominal voltage
Hz
s
For thermal equivalent current (0.5 s typical)
Network Infeed (Source)
Ω
Ω
Impedance of the supply network at PCC
Transformer (optional)
MVA
%
kW
Leave 0 to use R/X ≈ 0.05 approximation
Cable (optional)
Ω/km
Ω/km
km
Synchronous Generator (optional)
MVA
pu
Typical: 0.12–0.25 pu
R/X
Typical: 0.05–0.15
⚡
Select national annex, enter parameters, and click Calculate.
Includes K_T (transformer) and K_G (generator) impedance correction factors.
Standards & National Annexes
IEC 60909-0:2016
International standard. c_max = 1.10 (LV + HV). Defines equivalent voltage source method, κ factor, m/n factors, K_T and K_G correction.
VDE 0102 (Germany)
German national implementation of IEC 60909-0. c_max = 1.05 for LV networks (≤ 1 kV), 4.5% lower maximum fault currents. Standard for switchgear selection in Germany and Austria.
BS 7639 (UK)
British standard for short-circuit calculation, harmonised with IEC 60909-0. Same c-factor table as IEC. Used alongside Engineering Recommendation G74 for UK distribution networks.
GB/T 15544 (China)
Chinese national standard harmonised with IEC 60909. Symmetrical component method, same c-factors. Required for grid fault level studies in China. Supplemented by DL/T 5222 for power system planning.
JIS C 4620 (Japan)
Japanese switchgear standard referencing IEC 60909 method for rated short-circuit withstand current. 50/60 Hz mixed grid. Used with IEC 62271-200 for LV/MV switchgear selection.
IS 13234 (India)
Indian standard for three-phase fault level calculation based on IEC 60909 method. 50 Hz grid. Used with IS 13118 for switchgear selection across HV/MV/LV levels.

Frequently Asked Questions

What is the difference between /tools/short-circuit-iec and this calculator?
This flagship adds national annex selection (VDE 0102 LV cmax = 1.05, BS 7639, GB/T 15544, JIS C 4620, IS 13234), impedance correction factors K_T for transformers and K_G for generators (IEC 60909 §3.6.1 and Eq. 12a), and synchronous generator contribution with μ factor for breaking current.
What is K_T and when does it matter?
K_T is the impedance correction factor for transformers per IEC 60909 Eq. (12a): K_T = 0.95 × cmax / (1 + 0.6 × x_T). It accounts for the tap changer position and pre-fault voltage deviations. For high-voltage transformers (u_kr ≥ 10%) the correction can reduce Z_T by 3–5%, increasing I"k.
What is K_G and how is it applied to generators?
K_G is the generator impedance correction factor per IEC 60909 §3.6.1 Eq. (18): K_G ≈ (Un × cmax) / (U_rG × (1 + x"d × sinφ_rG)). It corrects for the generator operating voltage and load angle before the fault. Applying K_G increases the effective impedance, reducing the generator's short-circuit contribution.
What is the μ factor for breaking current?
μ is the factor for near-generator breaking current per IEC 60909 §4.5. For far-from-generator faults (the common case for networks without local generators), μ = 1 and I_b = I"k. For near-generator faults, μ < 1 because the AC component decays between fault inception and breaker opening: μ ≈ 0.84 + 0.26 × exp(−0.26 × I"k/I_rG).
What is VDE 0102 and how does it differ from IEC 60909?
VDE 0102 is the German national implementation of IEC 60909-0 under DIN VDE 0102. The key difference is cmax = 1.05 for low-voltage systems (≤ 1 kV) instead of the IEC default of 1.10. This means VDE 0102 calculates 4.5% lower maximum fault currents at LV — important for switchgear selection in Germany and Austria.
How does this compare to ANSI/IEEE C37 methods?
IEC 60909 uses the equivalent voltage source method (c × Un/√3 at the fault point), giving a single worst-case current without load-flow precalculation. ANSI/IEEE C37 uses a voltage divider approach with pre-fault Thevenin equivalent. Both methods are internationally accepted; IEC 60909 is standard in Europe, Middle East, Asia and Africa while ANSI/IEEE dominates North America.