New results of earth fault tests: earthing the faulted phase in isolated and compensated networks

This paper presents the test results of the method "faulted phase earthing" (FPE) in isolated and compensated MV-networks. The task of the project is to create similar advantages for cable networks and mixed networks as the earth fault compensation for the overhead line network. First, the main advantages of earth fault compensation for overhead lines compared to low-resistance and solid earthing are listed. Subsequently, standardization for the operation of compensated networks as overhead line networks has been adapted over the past decades. The main advantage of self-extinguishing of the arc without intervention of the protection or the operating personal is no longer given for cable networks. The proportion of cable is steadily increasing in the existing networks, and the overhead line part is being partially reduced. As a result, earth fault compensation is increasingly coming into question, and networks are often converted to low-resistance earthing. New findings regarding the arc suppression behaviour of the earth fault compensation in future networks are presented and a solution combining ‘Faulted Phase Earthing’ is shown. The paper uses real earth fault measurements to describe and discuss the function of the FPE and the positive effects of the FPE on a compensated or isolated system in detail.