Based on a low resistance grounded distribution network, according to the control strategy of IIDG combining symmetrical component method, establish IIDG grid after its upstream and downstream side of single-phase earth fault analysis model, the IIDG interconnection transformer fault point current under different grounding method, main side and IIDG side of each sequence and each phase current are analyzed respectively, and finally using PSCAD/EMTDC builds the fault simulation model, verify the validity of the analysis, for the interconnection transformer grounding method provides the basis for selection and configuration of protection.