When single － phase grounding fault occurs in distribution network with ungrounded neutral point，grounding technology of neutral point through arc suppression coil is the key technology for reducing fault current and realizing fast arc extinguishing at grounding point． At present，a large number of pre － adjustable arc suppression coil tuning devices have been used in 10 kV system in China． However，its operation status and commissioning methods cause some misunderstandings to the opration and maintenance staffs． The calculation methods of capacitive current under various operation modes of the system are analyzed，and a better control strategy for arc suppression coils in parallel operation is provided． Combining with the commissioning and operation experiences of different types of arc suppression coil tuning devices，the judgement methods for the operating conditions of automatic adjustment，automatic tracking and manual shifting are put forward． It has a certain guiding significance for the theoretical research and engineering practice of arc suppression coil technology．