Why do the lights on the top of the elevator car use 36v or 220v plus residual current to operate the protector?

Because the car is made of metal, it is easy to leak electricity and get an electric shock. 36V is not dangerous.

The protection period of residual current action is to automatically cut off the power supply when leakage occurs. The principle is to compare the currents of the neutral line and the live line, and if they are inconsistent, the power will be cut off automatically. When people get an electric shock, they usually touch a live wire, and then the current passes through the human body and leads to the ground wire. At this time, the currents of the neutral line and the live line will be inconsistent, and the protector will cut off the power supply.