Using Four-poles Switch with Caution in Power Supply and Distribution System with TN Earthing

Based on the calculation of the voltage and the current of three-phase and four-line unbalance circuit,it analyzes the change of electrical properties because of neural line cut.Combined with the characteristics of TN earthing system and bonding inside structure and four-poles switch,it puts forward that the use of four-poles switch should be cautious in TN earthing system.