Why petrochemical plants and refineries exceed minimum NEC requirements when it comes to burying copper wire and ground rods.
Ever wonder why petrochemical plants and refineries bury so much copper wire and ground rods throughout the process units when it isn’t required by the NEC? The NEC establishes the minimum requirements considered necessary for safety. Most industrial installations go over and above what the Code requires, since performance and safety is usually more important than the overall costs.
While process units typically don’t have a complete copper grid like that installed at high-voltage substations (see IEEE Std. 80), they are concerned about touch and step potentials during large faults or lightning strikes. Also, during maintenance inspections, the inspector can visually see that each piece of equipment has a grounding conductor attached to it and doesn’t have to be concerned if the equipment is adequately grounded. Each tap to equipment above ground can also be used to test the grounding system to ensure it is intact and functional.
There is one caveat though. When installing large amounts of copper in contact with the earth, a cathodic protection study should be performed. Copper will act as a cathode and any anodic material in the earth in the vicinity of the copper, such as iron or steel, will sacrifice itself to the copper because a corrosion cell could be formed. Underground piping/rebar may need to have a cathodic protection system installed to protect it from the copper.
© 2014 Fluor Corporation. All Rights Reserved.