The effect of metal layer surround the lightning rod on lightning electromagnetic field distribution

To reduce the electromagnetic radiation, we set a metal layer to surround lightning rod for shielding. Then we use the finite-difference time-domain (FDTD) method to analyze the field distribution laws of this situation. Moreover, we also calculate the corresponding field distribution without metal layer for comparison. It is shown that the metal layer affects the electromagnetic field distribution laws, especially for the vertical electric field Ez above the ground. The field value decrease as the distance from the lightning channel increases and the extent reduces except the Ez above the ground with metal layer exists. No matter the metal layer existing or not, the field distribution laws below the ground are the same. In addition, there exist many differences between electromagnetic fields obtained above and below the ground with metal layer exists, including wave shape and value. The finite conductivity of metal layer and discharge occurring between the rod and the coaxial metal layer should be considered.