Central or Local Compensation of Earth-Fault Currents in Non-Effectively Earthed Distribution Systems

Centralized Petersen coil earthing in networks with extensive use of underground cable involves flow of large quantities of reactive earth fault current. In networks with long radial cable feeders this creates problems involving active losses and active and reactive earth fault current. One possible solution to the problem is the use of local compensation. This paper aims at understanding the limitations of traditionally compensated networks and compares these to networks that are locally compensated. This is done through analytical calculations and PSCAD simulations that are combined with results from a project studying cables in Swedish distribution networks. In addition, basic PSCAD simulations are used to clarify how the rating and placing of the distributed compensation units affects active earth fault current and investment costs.