ABSTRACT
Grounding is one of the main defenses against hazardous electric shocks and hazardous overvoltages. Most North American distribution systems have effective grounding; they have a neutral that acts as a return conductor and as an equipment safety ground. There are several grounding configurations for three-phase power distribution systems. Four-wire multigrounded systems have several advantages over three-wire systems. Four-wire systems provide low cost for serving single-phase loads: single cables for underground single-phase load; and single-phase overhead lines are less expensive. Other types of grounding such as high-resistance grounding or high-reactance grounding are rarely used on distribution circuits. The five-wire design is a new approach that may reduce stray voltage and magnetic fields and also make high-impedance faults more easily detectable. The system grounding configuration determines the overvoltages that can occur during a line-to-ground fault. Urban underground circuits feeding predominantly network load can have overvoltages from neutral shifts during faults.
