My hotel is a three-phase four-wire system. When an electrician installs electrical equipment in the kitchen, connect the ground wire and zero wire on the equipment to the zero wire of the power supply. Does it play a protective role? This is inappropriate! Once the neutral wire is disconnected, all electrical enclosures may be charged. It is suggested that the electrical enclosure must be connected to a specially designed grounding grid to prevent electric shock accidents caused by insulation damage of electrical equipment and ensure the safety of electricity use. Now we advocate the use of "three-phase five-wire system" power supply mode.