The Grounding of Power Systems above 600 Volts: a Practical View Point

This paper discusses grounding practices used on electric distribution systems above 600 Volts. In particular, the paper concentrates on the three-phase fourwire, multi-grounded neutral system that is extensively used in North America. The paper addresses the benefits of the multi-grounded power system and makes comparisons with other grounding system designs including ungrounded; three-wire single-point grounded; three-phase, four-wire single point grounded neutral; and the three-phase, five-wire systems. Advantages and disadvantages of each system will be discussed. Some criticism regarding stray currents and stray voltages has been made of the multi-grounded neutrals on electric distribution systems and this will be discussed. Technical responses will be made to these comments including a discussion on reasonable solutions, alternative designs, and “acceptable risks.” Index Terms – Acceptable risk, multi-grounded system, resistance grounding, reactance grounding, single point grounded systems, solidly grounded systems, stray current and stray voltage.