Fault classification for medium voltage networks connected with conventional and renewable resources

The integration of renewables is increasing to overcome the climate crisis and to achieve net zero emissions. The renewables are connected to the grid through converters, which alters fault characteristics. These challenges affect the fault classification methods, which is crucial for correct operation of distance protection and single pole tripping. To overcome above challenges, we developed a solution which comprises of adaptive switching between modified-voltage-angle and apparent-power and voltage-angle based fault classification method which is independent of system grounding and type of source. The proposed modified-voltage angle-based method classifies the fault by checking the ratio of negative to zero sequence voltage angle and negative to superimposed positive sequence voltage angle within the defined fault classification zones. The proposed apparent-power and voltage-angle based method classifies the fault by checking the change in apparent power and the ratio of negative to superimposed positive sequence voltage angle. As a final solution we combined both the methods which exploits the combined advantages of both the methods to classify faults. The solution is verified with both HV and MV networks connected with different types of sources and the performance of the solution is found to be accurate. The solution is implemented in relay platform and prototype is validated with the field records; the performance is matched with the laboratory experimental results.