Erdschlüsse bei Mittelspannungskabeln und die elektrische Beeinflussung im Bereich von Swimmingpools

In the case of earth faults in medium voltage cables, potential rises and thus step and touch voltages can occur in the immediate vicinity of the fault location due to the injection of currents into the ground. These have to be examined with regard to personal safety. A special situation arises when a fault occurs in the vicinity of a swimming pool since people could be barefoot in this area. There are smaller contact resistances to the ground for barefoot people than for people with footwear leading to larger body currents. This situation is assessed in terms of its hazard potential, taking the relevant standards into account.

This paper focuses on the following question: Under which conditions can the proximity of a swimming pool to a buried cable result in a hazard to humans in the event of an earth fault in compensated medium voltage networks (20 kV and 30 kV), and, if necessary, what measures should be taken by the operators of these cables?Two different fault scenarios are analyzed in detail: a cable fault in the vicinity of a swimming pool and a fault in the area of a cable transition tower with transferred potential via the cable accompanying earth electrode.

The main parameters influencing the fault current are investigated with respect to the effects on step and touch voltages.

The investigations show that in most of the fault scenarios considered, no hazard is to be expected for humans with regard to step and touch voltages. Only the special fault scenario with transferred potential via cable accompanying earth electrodes in areas with soil resistivities higher than 1000 Ωm have to be investigated in more detail.