Abstract: To prevent bush fires caused by single-phase grounding faults in distribution networks crossing high fire-risk forest areas, the ignition conditions for forest fires caused by single-phase grounding is described. The relationship between zero-sequence voltage and system capacitive current during single-phase grounding is analyzed. An approach to prevent forest fires caused by single-phase grounding in distribution networks for isolated neutral systems, arc suppression coil grounding systems as well as small resistance grounding systems is proposed, which involves using an isolation transformer to isolate the capacitive current of the distribution feeder segment crossing fire-risk areas from the system's capacitive current, and configuring an automated intelligent switch downstream of the isolation transformer. This reduces the capacitive current in the feeder section crossing fire-risk areas, thereby enhancing the ability of single-phase grounding detection to withstand high transition resistance and preventing bush fires caused by single-phase grounding faults. Technical issues such as differentiated configuration strategies for isolation transformers and intelligent switches, relay protection coordination, and circuit broken down handling are discussed. Experiment results of full scale test and typical case demonstration show its feasibility.

Key words: distribution networks, isolated neutral system, single phase grounding, zero sequence voltage, bush fire