Gradient Characteristics of Fault Impedance in Distribution Network of Vegetation High-Impedance Fault

Vegetation high-impedance faults in medium voltage distribution networks pose risks to forest fires and cause serious safety accidents. Therefore, it is particularly crucial to develop an effective detection method. The existing methods overlook the non-linear characteristics of the tree impedance, thus, this study establishes a branch circuit model from the perspective of fault impedance based on the physical process of vegetation high-impedance fault. This study finds the majority of trees exhibit a similar process when subjected to the high-voltage conductor. Subsequently, a bi-exponential model based on the early research to accurately capture the initial fault impedance is proposed. The proposed model can better respond to the initial tree impedance gradient decay process, which offers a promising direction for the detection of the vegetation high-impedance fault.