In the case of cables of design I and II, the earth fault current $I_Ce$ flows from the faulty conductor T, for example, to the sheath or shield and from there via the conductor-sheath capacitance per unit length to the intact conductors R and S that are at the full delta voltage.
The currents caused by the conductor-conductor capacitance per unit length only flow in the conductors and have no influence on the earth fault current. They are generated by the delta voltage both in undisturbed operation and in the event of an earth fault and are therefore of the same magnitude in both cases.
In the case of design III cables, currents with the same phase position as the corresponding phase currents flow in the sheaths or shields. The currents of the healthy phases are therefore equal to zero in the middle of the cable and at both ends of the cable they reach half the value of the phase currents at the feeding end of the cable. If the fault is in the immediate vicinity of the end of the feeder, the earth fault current is almost equal to the current in the faulty phase.
Note: refer to table 14.7 in $C_b$ for design I, II, III (called Bauform).
| $3U_e \omega C_E$ | three-phase system |
| $2U_e \omega C_E$ | two-phase system |
| $U_e \omega C_E$ | single-phase system |
