A Design Guide to Neutral Grounding of Industrial Power Systems: The Pros and Cons of Various Methods

Abstract

Neutral grounding of industrial power systems has always been a controversial topic. Historically, systems with ungrounded neutral were dominant because of the service continuity with a ground fault on the system. This resulted in high system availability because there was no need to trip after the first ground-fault inception. However, as industrial power systems became more complex, transient overvoltage during a ground fault became more severe, making ungrounded-neutral systems less attractive. On the contrary, the ability of grounded-neutral systems to limit overvoltages made them more popular. Over time, ungrounded systems in North America started to disappear, except legacy systems, and almost all new industrial systems are designed with grounded neutral. With myriad grounding methods, the question is which is the most appropriate method to use? Each method has its pros and cons, making the choice of the appropriate one dependent on the application. For each grounding method, this article presents a brief description of selection criteria used for evaluation and their pros and cons.