In order to determine the lightning impulse withstand level of substation connection section equipment reasonably, a transmission linesubstation connection section model considering the power frequency voltage and induced voltage is established in EMTP. Then the characteristics of shielding failure invasion wave and back striking invasion wave are calculated, and the influence of lightning current model, induced voltage and insulator string flashover model on substation connection section are studied. The simulation results show that the severe overvoltage under maximum shielding failure lightning current should be taken into consideration when checking the insulation withstand level of equipment, and the equipment withstand voltage level should be improved. Considering the resistance at typical frequency of lightning current, the amplitude deviation of invasion wave, which is caused by some unreasonable oscillations while modelling, can be effectively eliminated. The lightning current mode, induced voltage and insulator strings flashover model have significant influence on overvoltage simulation results. Reasonable simulation models should be selected strictly when checking the insulator withstand level of equipment. The research results can provide reference to the substation engineering.