Powerline Monitoring

ISOSTROSE – Localization of ground faults on 110 kV overhead powerlines with a wireless sensor system mounted at the conductor

© Fraunhofer ENAS
Overhead high voltage power line with PLM system for ground fault detection and localization.
© Fraunhofer ENAS
Overhead high voltage power line with PLM system for ground fault detection and localization.

Despite all precautions, such as regular pruning of trees or regular inspections of the overhead transmission lines, ground faults cannot completely be avoided in the power distribution network of the 110 kV high voltage level. Ground faults are usually caused by trees pressed in the direction of the overhead line by strong wind. But even bird nesting or damaged and polluted insulators can trigger short-term ground faults. An occurring ground fault always affects the entire galvanically connected subnetwork. At best, with the help of electronic protective devices mounted in substation the error can be limited to a single overhead line. However, these can be up to 70 kilometers long in Germany. The logistical and financial effort as well as the time necessary for troubleshooting is enormous.
In the ISOSTROSE project (funded by BMWi / BMBF), a rope-based wireless monitoring system for the localization of ground faults was developed in cooperation with the partners MITNETZ Strom, LTB, First Sensor and Fraunhofer IZM. The centerpiece of the self-sufficient system is a ground fault sensor developed by Fraunhofer ENAS. The ground fault detection is implemented via various independent principles. On the one hand the voltage drop and the maximum current flowing at the moment of the ground fault is used. On the other hand the error is detected by the high-frequency electromagnetic wave caused by the briefly flowing ground fault current. The localization is done via the distributed wireless sensor system. Since mid-November 2017, a field test is running at an 110 kV power line in the Harz mountains. Several ground faults have already been detected.