| I've run my own cable because the electric company wanted me to cut a 20' | easement of trees to put up poles and run the electric service.
Those bastards! Always wanting to cut down trees.
| I opted to have my meter base on a pole (similar to a mobile home setup) | with a 200 AMP service box that is being used as the meter base and | disconnect. It is grounded to a copper rod sunk 8' deep into the earth. | | From that service box(on the pole) I've run two 4/0 HOT conductors and one | 2/0 neutral underground. I have not run a separate grounding conductor.
That lack of separate grounding conductor will make it more difficult.
| On the cabin, there is another 200 AMP service box. At the moment only the | to hots and the neutral are connected to it (The power is not one by the | way) | | My question was: Do I ground the service panel on the cabin and if so do I | isolate the ground from the neutral.
This would be similar to a building to building feed. In this case the pole is the main location, and the cabin is the subfeed location. If you had fed this with the extra ground wire, you would need to keep the neutral and ground separate. But since there is no ground wire, you need to drive a couple grounding electrodes, ground a new grounding wire to them, and bond the neutral to that.
But, there is one more issue. Any other metallic runs of anything, be it water pipe, cable TV, or telephone, must stay AWAY from that pole. Any current imbalance on the neutral will attempt do flow in parallel over anything grounded at both ends near each point the power is grounded.
| I'm clear on the fact that I require a secondary ground, what I'm not clear | on is wheather or not I isolate it from the ground.
You need to ground the neutral at both ends due to lack of grounding wire in order to protect against extreme voltages induced by weather.
But that said, I also know this is not that great a protection. By grounding the neutral on each end, it will ground out these voltage differences. But the hot wires are still poorly protected by that.
An alternative that I feel is safer, although more expensive, is to use a transformer to derive a neutral at the cabin, and just power it with the two hots only. Then the 3rd wire can be used as a true ground (but do not connect it to the neutral supplied by the power company in this case). This could be an auto-transformer, which would provide a DC path to ground for any static charge buildup.
| Also, I'm guessing I will have to use a much larger conductor than a #6 for | the ground. Do I use the same size throughout the grounding system?
It's best to have the grounding wire be the same size as current conductors anywhere they are. The code allows smaller grounding wire in certain cases, but you should be fine with the same size everywhere.