This paper research on the disadvantages of arc suppression coil grounding

small resistance grounding and arc suppression coil combined with small resistance grounding in distribution power network at present. The adaptive grounding system based on controllable resistor and extinction coil is developed. The criterion based on overvoltage of arc light is developed

and it is extracted that the per unit value of zero sequence voltage by morphological filter. And protection configuration of this system is improved

this system is effective for avoiding the disadvantages of original system. When permanent earth happens

the system blows out of arc automatically then finds singlephase earth fault

the system cuts off the line then finds permanent faults.This method is testified to have advantage of improving power supply reliability

and to have good effect on equipment safety.