Ground the wire.
There are three terminals on the back of the USB socket, respectively, L, N and E. When wiring, directly connect the red wire to the L end, the blue wire to the N end, the yellow and green wires are connected to the E end, if you do not know much about the letters, then you can remember the law of wiring, that is, the left wire, the right wire, the ground line.
The USb socket must be grounded. Without grounding cables, security cannot be ensured