灵活接地系统接地故障分析与保护原理

灵活接地（消弧线圈并联小电阻接地）方式是我国中压配电网近年应用的热点，具有快速扩张趋势。由于故障持续期间中性点并联小电阻投切，其接地故障暂稳态特征同时受制于故障点状态与系统零模阻抗突变，明显区别于谐振接地系统和小电阻接地系统。相应的，已有接地保护原理适应性存疑，专用保护原理缺乏。.针对不同类型（瞬时性与永久性、低阻与高阻、稳定性与间歇性）接地故障，建立灵活接地系统接地故障等值电路，分析全故障周期各阶段（小电阻投入前、后及退出后）系统零模阻抗变化特征，定量计算各阶段稳态与暂态电气量，分析其时空分布特征及变化规律；分析已有小电阻接地、小电流接地系统接地故障保护方法的适应性，并给出可用方法的改进及定值修订方案；提出综合利用不同阶段电气量变化特征、适应不同类型故障的专用保护原理；利用数字仿真和实际故障数据进行验证。.成果将填补灵活接地系统接地故障分析与保护原理空白，解决灵活接地方式应用的关键问题。

Flexible grounding (arc suppression coil in parallel with small resistance grounding) mode has been a hot topic in China's medium-voltage distribution network in recent years. Due to the small resistance switching during the duration of the fault, its transient fault characteristics are limited by the state of fault point and the sudden change of zero mode impedance of the system, which is obviously different from the resonant grounding system and the small resistance grounding system. Correspondingly, there are doubts about the adaptability of the existing grounding protection principles, while the dedicated protection principles are still insufficient..For different types of grounding faults (transient and permanent, low resistance and high resistance, stability and intermittent), a flexible grounding system grounding fault equivalent circuit is established. The zero-mode impedance change characteristics of the full fault cycle (before, after and withdrawing of the small resistance) is analyzed. The steady-state and transient electrical quantities at each stage is quantitatively calculate. Its temporal and spatial distribution and change characteristics are analyzed. The adaptability of existing ground fault protection methods for small resistance grounding and small current grounding systems is analyzed. An improvement method of available methods and a fixed value revision plan are proposed. A special protection principle that comprehensively utilizes the characteristics of electrical quantity changes at different stages and adapts to different types of faults is proposed. Verification is performed using numerical simulation and actual fault data..The results will fill the gap in the grounding fault analysis and protection principles of flexible grounding systems, and also provide theoretical support for the analysis and protection of grounding faults in other active intervention systems.