Re: pole bases once and for all
Charlie and Dereck, Tell me how a ground rod at a lighting pole protects you interior electrical system?
Lightning is an "arc" that temporarily neutralizes the positive and negative charges between objects.(A negative charged cloud to a positive charged earth surface, or vise-versa)
When a negative charged cloud approaches the area of a positive charged earth surface(A tree, light pole, radio antenna,house,ect)the arc ensues.The arc is at a very high fequency for a short duration of time,often obtaing voltages over 30,000V with 60,000 ampers of current.
Light poles are conductive and therfore low resistivity and thus as the electrons flow the neutralization doesn't produce a heat intense enough to create a fire. On the other hand a tree or house is made of wood and has a high resistivity, when electrons flow to neutralization through this medium, heat ensues, which can lead to fire.
Lightning is not looking for a conductive path, that is why trees get struck. You are no more likely to be struck by lightning if your holding a 6-foot golf club in the middle of an open field than if you were holding a 6-foot wood 2x4 in the same location. Because lighting strikes proximity.
Grounding Electrodes(GE) are utilized to connect metal parts of electrical equipment to the earth to LIMIT the voltage from lightning by providing a conductive, low resistant path for the disipation of the neutralizing current flow between the earth and the cloud. If the system is not connected to earth the elevated voltage that enters the system will travel through the system via metal raceways or cables, seeking a path to earth. The high voltage on the metal parts from lightning can result is electric shock and fires, as well as the destruction of electrical equipment.
So if lightning striks your exterior pole light and it does NOT have a ground rod, than your contention is that the lightning will travel UNDERGROUND through the branch circuit,(ignoring the bolted connection to the concrete base not to mention the rebar in the concrete base,6-feet under ground,) enter your building system to find your building systems Electrode system to dissipate the energy into the earth.
Lets say that is true, and we decide to put a ground rod at each pole. Does this ground rod ensure all the lightning is shunted to ground and no current will travel into the building via the branch circuit conductors?
The answer is NO, even if you ground rod dissipated 90%(which it doesn't) of the lightning into the earth and 10% went into your building via the branch conductor your still allowing 3,000V at 6,000ampers of current to enter your system. HOW IS THAT PROTECTING YOUR SYSTEM?
To limit and protect your building from the entrance of lightning, you must utilize Transient Voltage Surge Suppression (TVSS)to shunt the lightning to the earth before it ever has the chance to enter your system. You do this by providing isolation transformers for your exterior lighting circuit and installing TVSS on the Branch panel that feeds your Exterior lighting.
To conclude, to say that a ground rod at your pole lights protects your interior electrical from lightning is false. It doesn't protect any thing. 3,000V or 30,000V what is the difference when you electrical system is only rated at 208 or 480 volts.
If there is a puplication that proves this wrong, and actually shows that ground rods at exterior pole lights PROTECT your internal electrical system, Quote me chapter and verse of the article and I will be happy to review it. The problem is I do not beleive it exists.