In accordance with the fault that the power port of intelligent components often fails to work or is destroyed in th process of lightning impulse tests

the electromagnetic disturbance characteristics of power port were researched by experiments and measurements. According to the circuit connection of a test hall

the reason of the ground potential rise（GPR） was analyzed by measuring the loop currents. Results show that the high frequency capacitive current flows into ground will result in GPR

and the inductive impedance of ground wire leads to the difference in large ground potentials. To accurately measure in the complex measuring environment in testing hall and substation

the measure system was developed

which is able to avoid the space electromagnetic disturbance and circuit conduction disturbance. The voltages of power port were acquired and analyzed in time-domain and frequency-domain. Results show that

in the absence of surge protection device（SPD）

the common-mode disturbance is more than 20 kV

which is much higher than specified value（4 kV） in IEC61000-4-5. When SPD is connected

the common-mode disturbance can be restrained to 4 kV and the difference mode disturbance can be restrained to 2 kV. The conclusion in this paper can provide a reference to resist electromagnetic disturbance for intelligent components.