Cable fault current calculator

Electrisim

Transformer and network

Rated power S_rT

kVA

Secondary voltage U_n

Line-to-line.

Short-circuit voltage u_k

Transformer X/R

Network fault level S″_kQ

MVA

At the transformer’s primary. Leave empty for an infinite source.

Voltage factor c_max

Voltage factor c_min

Cable

Conductor

Cross-section

Length

Parallel cables per phase

Reactance X

Ω/km

Typically 0.07–0.09 Ω/km for low-voltage multicore cables.

Conductor temperature at the end of the fault

°C

For the minimum current (IEC 60909): 160 °C for PVC, 250 °C for XLPE.

Maximum three-phase fault current at the cable end

—

Minimum line-to-earth: —

Check the inputs: positive values, and a temperature between 20 and 400 °C.

Peak current i_p at the cable end: —
Three-phase at the transformer terminals: —
Minimum line-to-earth at the cable end: —
Earth-fault loop impedance Z_s: —
Cable impedance per phase at 20 °C: —
R/X at the fault (maximum case): —

Maximum: IEC 60909 with c_max and the cable resistance at 20 °C. Minimum line-to-earth: TN system, Dyn transformer, protective conductor the same size as the phase conductors, c_min and the resistance at the end-of-fault temperature. Motor contributions are not included.

Free calculator by Electrisim · How it works