Why use metal casings for distribution boxes, etc.?

two reasons
1. When there is a strong electric field outside the casing (such as lightning), the positive and negative charges on the conductor casing are rearranged on both sides of the casing under the action of the electric field, and the built-in electric field formed can just balance with the external strong electric field, and The equipment inside the casing is not affected by the external strong electric field, which can prevent lightning
2. The chassis can be grounded. The ungrounded chassis will induce charges on the chassis due to the action of the internal strong electric field, making the chassis electrified. After the chassis is grounded, the charges induced on the chassis can be quickly discharged. , to protect the safety of operators. | metal electrical box