Quote from: DavidM on April 21, 2017, 11:15:38 AMThe National Electric Code requires one and only one ground located at the power source, which in your case is the power company supplied power panel. You will not be in compliance if you install another ground rod downstream of that one.
Close! What you're thinking of is NEC 250.24(A)(1) where only one neutral to ground bond is allowed. You indeed can have multiple ground rods or GEC's in a system per that section and NEC 250.32 which outlines requirements for a grounding electrode system and bonding of grounding electrodes.
Ground loops cause hell for low voltage systems like paging amplifiers, but the point of a ground is strictly for safety of life and property when something goes wrong.
It's absolutely OK to install a ground rod at an RV pedestal, an automatic standby generator (if neutral is bonded to frame, check installation guide), a telco demarc, hot tub - anything like that. Give that fault current a short path ground.
Then also remember the amount of current flowing through the line leg should equal the amount of current flowing through the neutral wire for your load (true for line to line but let's focus on N and G) - this is where the single Neutral to Ground bond rule comes into play. If that current finds another path in your system to flow, best case you have weird problems, worst case a fire.
There's a fantastic video on Youtube from Dave Gordon called Open Neutral that helps visualize where the current is going in a two leg + neutral system. The video ID is LJvyb_WujZg.
Also countless Youtube videos about the N-G bong and why it's important, what is a loaded neutral, etc.