Decentralized earth fault compensation in MV-grids -challenges and solutions

Decentralized earth fault compensation coils (EFCC) in resonantly grounded medium voltage networks are becoming increasingly
popular. Their installation imposes several requirements on the earthing system in terms of equipment and personnel safety
as well as the functionality of the ground-fault protection devices. Based on two practical examples of networks (urban and rural),
the challenges and their possible solutions are presented and verified by on-site measurements. Due to the impressed current of
the distributed EFCC, the earth potential rise (EPR), the touch voltage, the transmitted voltages to neighboring stations and to the
low voltage installation (PEN conductors) have to be analyzed. The role of cable shields in relation to earthing and the influences
on the distribution of the zero sequence currents discussed. In addition, this work investigates the currents flowing on the interconnecting
cables between two different network areas under fault conditions with different distributions of compensation. The
cable shields grounded at both ends are loaded by flowing zero sequence currents. This leads to additional heating of the cables.
It is analyzed which zero-sequence currents are permanently permissible in order to avoid a maximum insulation temperature
and to prevent additional aging of the cables