Cableizer ®

Phase-to-ground fault current

Definition according to Schneider Electric Cahier technique 158 (2000), chap. 2.1 + 3.3)

This type of fault brings the zero-sequence impedance Zo into play. Except when rotating machines are involved (reduced zero-sequence impedance), the short-circuit current Isco is less than that of a three phase fault. Calculation of $I_{sco}$ may be necessary, depending on the neutral system (system earthing arrangement), in view of defining the setting thresholds for the zero-sequence (HV) or earth-fault (LV) protection devices.

$I_{k3} = \frac{c Un}{\sqrt{3} \lvert Z_{(1)} \rvert}$, $I_{k0} = I_{k1} = \frac{c Un \sqrt{3}}{\lvert 2 Z_{(1)} + Z_{(0)} \rvert}$ $\rightarrow$ $I_{k0} = \frac{3 \lvert Z_{(1)} \rvert}{2 Z_{(1)} + Z_{(0)}}$

Symbol
$I_{k0}$
Unit
A
Formulas
$\frac{3|Z_1|}{|2Z_1+Z_h|} I_{k3}$
Related
$I_{k3}$
Three-phase symmetrical fault current [A]
$Z_1$
Positive sequence impedance [$\Omega$/m]
$Z_h$
Zero-sequence impedance [$\Omega$/m]
Used in
$I_{ka}$
Complex conductor current a [A]
$I_{kb}$
Complex conductor current a [A]
$I_{kc}$
Complex conductor current c [A]
$I_{kx}$
Split fault current [A]