Abstract:The penetration rate of distributed new energy in the distribution network is increasing, the traditional three-section current protection is difficult to meet the protection needs. Pilot protection is a crucial strategy to meet the protection requirements of distribution networks with high new energy penetration, but it requires strong communication conditions and its protection sensitivity is sensitive to the effect of unmeasurable branch lines within the distribution network. This study considers the influence of undetectable branch lines, based on the analysis of the phase relationship between negative sequence currents on both sides of distribution network lines, obtains the ratio difference between the dq-axis components of negative sequence currents on both sides of the lines under internal faults and external faults, and then proposes a pilot protection method based on the dq-axis components of negative sequence currents. The method can adapt to the complex and changing operating conditions in distribution networks, and doesn"t require high communication conditions, has good application prospects in active distribution networks. By building an active distribution network model using PSCAD/EMTDC software, the proposed method was validated. The results showed that it can effectively identify asymmetric internal faults and external faults of the distribution network line.