Accurate　modeling　of　high-impedance　arc　fault　(HIAF)　is　of　great　significance　for　studying　the　characteristics　of　arc　fault　and　suppressing　its　harm.　In　traditional　arc　models,　the　arc　column　is　usually　considered　a　cylindrical　channel　with　constant　length　and　diameter.　However,　the　arc-burning　process　is　susceptible　to　the　environment.　The　changes　in　arc　length　and　diameter　present　complex　characteristics.　Therefore,　this　study　proposes　a　new　HIAF　model　for　distribution　networks　based　on　the　arc＇s　dynamic　geometry　dimension　(DGD).　First,　the　arc　length,　diameter,　and　field　strength　expressions　are　improved　based　on　the　classical　cybernetic　model.　Next,　an　automatic　parameter　optimization　method　for　the　DGD　model　is　proposed,　and　then　this　model　is　compared　with　existing　advanced　models.　After　that,　the　effects　of　the　variable　parameters　of　this　model　on　arc　characteristics　are　analyzed.　Finally,　the　practical　application　effect　of　this　model　is　tested.　The　experimental　results　show　that　the　DGD　model　can　accurately　describe　the　dynamic　arc　development　process,　approximate　the　given　arc　waveform　closely,　and　generate　high-quality　samples,　which　has　certain　advantages.