A Guide to High Resistance Grounding

Part 4 of 4: Sizing the Neutral Grounding Resistor

 

We are now offering as a free download the final part of I-Gard’s four-part treatment of high-impedance ground protection as permitted by NEC 2005 under certain condition enumerated in Article 250.36. Please note that seven provisions of Article 250.36 must be complied with. They are laid out in (A) through (G). For example, (B) stipulates among other things that the neutral conductor from the neutral point of the transformer or generator to the grounding impedance must be fully insulated. If you think about it, this requirement is logical since under fault conditions there could be voltage to ground on this conductor due to the impedance.

 

I-Gard concludes its treatment of impedance grounding in Part Four, Sizing the Neutral Grounding Resistor, with a discussion of the practical aspects of applying high-resistance grounding, including sizing the resistance, how to connect the neutral grounding resistor when no neutral terminal is available, and other informative tips.

 

I-Gard’s Guide is conveniently organized into four parts. Over the last 3 months we sent Parts 1 - 3, and now here is the final Part 4.

 

• Part 1 covers Power System Grounding Basics
• Part 2 covers the Disadvantages of Delta Ungrounded Power Systems
• Part 3 covers High Resistance Grounding Basics
• Part 4 covers Sizing of the Neutral Grounding Resistor

 

Click here or on the image above to download Part 4 (170KB), but be advised that this download may take a few minutes to download depending on your internet connection speed. If you encounter a problem opening this file, be sure you have the latest version of Adobe Acrobat installed on your system (click here).