Algorithms for intermittent fault detection with high-impedance neutral-to-ground regimes

The massive integration of new production plants using decentralized renewable energy resources (DER) implies an expansion of the electrical distribution power grid with construction of more transmission lines and substations. With this expansion t he probability of occurrence of permanent and intermittent faults will increase. Existing algorithms to detect permanent faults could not be effective for the detection of intermittent faults due to the tim e-varying spectrum characteristics of the last ones. The intelligent electronic devices (IED) in substations should include new algorithms able to effectively detect intermittent faults. With the insulated neutral regime transient voltage peaks that could be harmful for the power grid could occur regularly during intermittent faults. For this reason, the insulated neutral regime characterized by a high neutral-to-Earth impedance, is considered as a first approach in the study of algorithms for intermittent fault detection. The power grid topology influences the natural frequency of oscillation. The case study of a distribution grid topology with one primary power line connected with a distribution transformer to aggregated secondary feeder lines is considered. The time interval and duration of intermittent faults varies in time, being characterized by non-stationary spectrum. This paper evaluates the effectiveness of two combined time-frequency algorithms for detection of intermittent faults.