A rapid method for calculating short-circuit currents in distribution networks with high renewable energy penetration

Calculating short-circuit currents in active distribution networks by treating renewable energy as a constant current source tends to overestimate its impact on overcurrent protection, while refined methods such as iterative calculations are difficult to promote and apply in real engineering scenarios. This research first analyzes the voltage and current relationships of renewable energy sources in a 10 kV neutral-point-ungrounded system under both symmetrical and asymmetrical faults, with a focus on engineering feasibility. Next, the study examines the voltage increase and its increment ratio at the fault point and renewable energy connection point, with and without the presence of renewable energy sources. It is found that the voltage increment ratio at the fault point is consistent with that at the renewable energy connection point. Based on this observation, a fast calculation method for short-circuit current in networks with renewable energy integration is proposed, utilizing voltage increments. Finally, a fault simulation model for a distribution network with high renewable energy penetration is developed in PSCAD/EMTDC, and a short-circuit experiment is conducted in an actual distribution network. The results from both the software simulation and real-world experiment demonstrate that the proposed short-circuit current calculation method offers high accuracy, and can satisfy the required accuracy for protection settings.