基于余弦相似度的新能源场站T接型送出线路纵联保护

新能源场站T接型线路保护受新能源电源短路电流幅值受限、畸变的故障特征以及T接型线路拓扑影响，传统电流相量差动保护不能同时满足区外故障可靠性与区内故障灵敏性，存在误、拒动风险。因此，在分析T接型线路对基于余弦相似度纵联保护主判据影响的基础上，提出了基于余弦相似度特征判据的T接型线路纵联保护。综合考虑了电流互感器饱和、发展性故障与电流互感器二次侧断线的影响，研究了相应辅助判据。仿真结果表明，所提保护原理能够在新能源场站T接型线路中可靠识别区内外故障，并应对电流互感器饱和与发展性故障场景，且在常规采样频率下动作性能良好，适应不同类型新能源场站的故障特征。现场数据验证了所提新原理保护的有效性。

Cosine Similarity Based Pilot Protection of Teed Transmission Line Connected to Renewable Energy Power Plants

The protection of teed line connected to the renewable energy power plants is affected by the limited and distorted short-circuit current of the renewable energy sources and the topology of the teed transmission line. The traditional current phasor differential protection cannot simultaneously meet the reliability of external faults and the sensitivity of internal faults, which has the risk of maloperation and false operation. Therefore, by analyzing the influence of teed transmission line on the main criterion of pilot protection based on cosine similarity, the pilot protection of teed transmission line based on the characteristic criterion of cosine similarity is proposed. The influences of the saturation of current transformer(CT), the developing fault and the secondary side disconnection of CT are considered, and the corresponding auxiliary criterion is researched. Simulation results show that the proposed protection principle can reliably identify faults inside and outside the region in the practical scenarios of teed transmission line, and the principle can cope with the fault scenes of CT saturation and developing faults. The proposed principle has good performance with conventional sampling frequency, and it is suitable for all kinds of renewable energy power plants. Practical data validate the effectiveness of the proposed protection principle.