A DESIGN GUIDE TO NEUTRAL GROUNDING OF INDUSTRIAL POWER SYSTEMS

Neutral grounding of indvohial power systems has always been a controversial topic. Historically, systems with an 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 lending 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 a grounded neutral. With a myriad of grounding methods the question is: "which is the most appropriate method to use?" Each method has it pros and cons, making the choice of the appropriate grounding method application dependant. This paper presents a brief description of each grounding method, a selection criterion to evaluate each grounding method, and the pros and cons of each method.