Fault loop impedance determination in low-voltage distribution systems with non-linear sources

An increased penetration of distributed energy sources for example photovoltaics (PV) leads to new challenges regarding supply of buildings. Besides the common used supply by the public distribution network (large scale generators, transformers) the islanded supply of buildings becomes feasible. Apart from the advantage of a multivalent up to a fully independent power supply in low-voltage distribution systems, questions regarding the functionality of commonly used overcurrent protection devices occur, because of a low short circuit power of the distributed power generators and a too high loop impedance, which is load and time depending. Furthermore the established measurement procedure of the fault loop impedance has to be verified for application in islanded networks with non-linear sources (e.g. inverters).