Study on the Mechanism and Electrical Characterization of the Tree-Contact Incipient Fault in the Non-Effectively Grounded System

The tree-contact incipient fault (TCIF) is caused by a temporary contact between a distribution feeder conductor and a tree branch driven by the wind. Compared with permanent vegetation contact faults, TCIFs can easily escape notice due to their self-cleaning properties. But a branch can cause multiple TCIFs over significant periods of time, and also carries the risk of vegetation ignition. This paper analyzes the generation and development mechanism of TCIF and divides the fault into three stages: approach, contact, and separation. The model of equivalent grounding resistance in each stage is established, and its features in different stages are analyzed. The features of TCIF were further analyzed by field experiments. The influences of varying types of tree branches, different moving speeds, and neutral grounding modes on the fault grounding current waveform are analyzed. The results discussed in this paper establish a basis for the detection of TCIF.