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Lightning Choke Coil - Optimum Value - Dimensions?

This application is for a small shed or radio-equipment room in a lighting intensive area. The goal is to prevent a lightning surge from entering the boundary of the shed over the power lines by using a coil and a lighting arrester to divert the surge to ground.

Incoming power is split-phase 240/120 (2 hot wires and a neutral) to a

100 amp panelboard.

There are many commercial surge protectors/lightning arresters to choose from and one of these will be installed at the service entrance panelboard.

I am thinking of providing extra protection by having the incoming lines routed through coils to provide a high reactance path to the short, massive DC pulses typical of a lighting strike. A similar arrangement is used to protect electric fences in lighting intensive areas.

The question is what values should the coils be in mH, H, and the approximate physical dimensions? Can/should the neutral be routed through a reactor coil in addition to the hot wires?

Anyone have any information on this? Am I missing any obvious problems?

Thanks! Beachcomber

Reply to
Beachcomber
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Polyphaser has a lot of information on this. Google will get you there.

Reply to
ehsjr

With any luck you have a ground wire as well from your service. The way I learned lightning/surge protection is you need to cover at least 2 of the 3 zones of coverage. The zones are distribution, service and point of use. I use a panel mounted surge protector for the whole service. Then I add plug strip surges in at point of use. I studied the level of protection of each and tried to get the one at the service to withstand enough that the strips would handle the rest. An grounding/earthing copper strip around the room will help get the all the equipment at equal potential. Does not have to be 1/4 inch or anything a good copper foil will do the job. Verify by testing your ground connection. Add ground rods properly until you achieve less than 5 ohms. You will need a decent meter to do the testing. Check with Amecc or AVO. Amecc is available from WW Grainer for about $2k.

Are your service conductors overhead? If so won't the chokes force the strike back to the main house? Or is this a separate service. If your conductors are underground it would help a bunch. I volunteer with a man here in AZ that is studying the effects of lightning and the proximity to the strike. Pretty much if you get hit pray your lightning rods were installed correctly. There will be damage. If the strike is as close as a half mile you might be able to mitigate the problem. A UPS would give you some protection from the feeders. But you doing radio, so what about the antennas? Can you put optic isolators in the antenna leads? Happy dodging

Reply to
SQLit

Reply to
w_tom

It is possible that something like the induction neutralizing-transformer concept could be applied at the building 60Hz entrance.

References describe ?Longitudinal voltage surges and ground potential rise? seem to accurately describe the lightning problem. A ?longitudinal choke? might be fabricated at a reasonable expense.

See description at

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under header ?Lightning Destroys 17 KSUs, Park Phone System Damaged by Lightning?. Also

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Truly kelvin-connected {series- not ?T?-connected} MOV protectors may be effective in overvoltage protection in 60Hz feeders.

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--s falke

Reply to
s falke

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