This paper describes the accident analysis by modelling the current transformer mounting in a metal-clad switchgear at 22.9kV. In analyzing the accident, the reconstruction at the current transformer mounting(VCB connecting guide) has to be taken into account. The accident was modelled as a 3-phase ground fault occurring between the end plate of 22.9kV lines and the safety shutter at the current transformer mounting of the VCB inside the metal clad switchgear. Since the outside maintenance of the metal clad switchgear is restricted by the enclosed compartments, Its circumference has to be kept clean. Through the reconstruction results, it was confirmed that the fault of the enclosed switchboard could be reduced when the shutter made of Fe material was chanted into an insulation.