Dspark, what is it that you are not understanding?
Think of it this way. Place one end of your voltmeter probe in the ground(not ground rod), place the other probe on the neutral buss of an electrical system that has a broken neutral. What is the reading on the voltmeter? 120V? 100V? Now consider yourself in place of the voltmeter. How much current is going thru you?
Say for instance the ground rod is in tact and working perfectly. Take a load reading on the ground wire. Lets say its 10A. Now remove the ground wire from the ground rod. This would simulate a non existent ground rod or a rod that has baked out earth surrounding it. By my saying baked out , what I mean is that the earth in contact with the rod has crystalized(probably from a lightning strike or from carrying load for a period of time). When current is introduced into the ground for periods of time the earth at the point of contact becomes insulated(turns into glass). Now if that rod is not making contact then it is useless. Everthng that is bonded to the neutral buss becomes an extension to that buss. And if that buss is isolated from its source anything that tries to create a path to ground will become energized.
I wish my scanner was working because a picture is worth a thousand words.
