A strong electromagnetic pulse (EMP) has a short rise time and high peak field strength, propagating to electrical equipment through strong coupling with cables, thereby causing damage. To investigate the coupling effect of strong EMPs on primary equipment, a conductive EMP environment is established, and equivalent circuit models for zinc oxide surge arresters, glass insulators, and distribution transformers are constructed. Through simulation, the port voltages and currents of each device under strong EMP conditions are obtained. The results indicate that when the terminal voltage waveform generated by the coupling of strong EMPs with overhead lines enters typical primary equipment, the voltages and currents of the surge arrester, insulator, and transformer remain as pulse waveforms when a protective resistor is connected at the port. However, the leading edge becomes slower, and the pulse width increases. Without a protective resistor, streamers form on the surface of the insulator string after flashover, causing the equivalent impedance to shift from capacitive to inductive, leading to sustained oscillations in the ground current. During flashover, the voltage and current amplitudes rapidly decrease. The transformer′s port voltage and ground current without a protective resistor both exhibit oscillatory waveforms, gradually decaying to zero.