中文摘要：

对于小电流接地故障，暂态等值电路是故障暂态分析的主要工具，可定量计算暂态电气量，为接地故障保护、过电压防护、接地补偿及配电网中性点接地方式选择等提供理论依据。针对传统暂态等值电路忽略了线模分量且缺乏明确的参数计算方法的问题，提出一种工频等效阻抗与首谐振频率相等、首谐振频段内等效阻抗综合误差最小的模型简化原则；针对中性点不接地系统，建立了基于线路分布参数、包含故障点两侧网络的小电流接地故障复合网络模型；依据模型简化原则将复合网络模型逐级简化。最终得到一个包含线模和零模分量的等效电阻、等效电感与系统对地分布电容构成的Γ型暂态等值电路，以及模型参数的准确计算方法。相比于传统暂态等值电路，所提出的暂态等值电路具有更高的模拟精度和更强的适用性。

英文摘要：

Transient equivalent circuit is very important for the analysis and calculation of transient electrical quantities of single-phase earth fault in non-solidly earthed networks, which provides basis for the investigation of fault detection, over-voltage phenomenon, earthing current compensation and the selection of neutral earthing mode. The effect of aerial model parameters is neglected in the traditional transient equivalent circuit and the derivation of the circuit parameters is not clearly given. A model simplification principle, which ensured the calculated power-frequency equivalent impedances, the first resonant frequency were closest to the actual values and comprehensive error of equivalent reactance within the lowest frequency band was minimum, was proposed. Taking the neutral isolated system as an example, a complex network of single-phase earth fault based on the distributed parameters of feeders was established which covered both sides of the fault point. According to the simplification principle, the network was simplified into a lumped-Γ circuit composed by aerial modal and zero modal equivalent resistance, inductance and the distributed capacitance of feeders step by step. Meanwhile, an accurate calculation method of model parameters was presented. Simulation results show the new transient equivalent circuit has higher accuracy and stronger adaptability compared with the traditional one.