Abstract: Cables will become the main effector of coupling when high altitude electromagnetic pulse（HEMP）is coupled to the interior of substation. Based on the typical substation layout,three typical control cables connected with the secondary equipment are selected,and the three-dimensional TLM algorithm is selected to simulate and analyze the typical cables for HEMP coupling. The results show that cable ends that are not grounded at both ends can generate voltage signals up to 49 kV. Analog transmission cables can sense current signals of the order of hundreds of amperes on the ground core wire and shielding layer.The cables transmitting the switching quantity senses current signals of the order of hundreds of amperes in the shielding layer. The signal on the core does not exceed0.23mA. Finally,a horizontally polarized radiated wave simulator is used to conduct field tests,compared with the comparison with the simulation results,the equivalence of the algorithm and the validity of the coupling calculation results are verified.