26 mm 2 (10 AWG) ground wire must be used, and in all other markets a 6 mm 2 must be used. On the US market, a 5. Each DISTRIBUTION BOX and controller must be grounded. Grounding of the units: Attach a ground wire from one of. Grounding is a mechanism to protect distribution equipment and people under normal operating conditions, abnormal operational (overcurrent and overvoltage) responses, and hazardous conditions such as shocks. The neutral line (N line) is the neutral line. When the three-phase load is symmetrical, the. The three-phase five-wire system includes three phase wires (A, B, C wires), neutral wire (N wire), and ground wire (PE wire) of three-phase electricity.