Question about possible induced currents from large overhead transmission lines

[dr_ed@swbell.net]

More questions Sunking..if you have time.

I was thinking about the grounding issue. I live in an area with solid limestone rock just below the surface...sometimes it IS the surface. I assume the power company drills deep holes with a rock drill to place ground rods for the transmission poles. Is that correct?. Or is the pole itself the ground? I have a rock drill that will drill to about 4 ft. Sounds like I will need to have someone drill holes for the grounds. Is this the case, you think? They would need to be more than 4 ft, right? I doubt I could get the utility to do it. I guess I could ask.

I was planning on a custom welded steel fixed mount. Maybe eight uprights set in the ground (in concrete). Could you tell me how many ground rods I'd be likely to need? Would it be one for each pipe set in the ground? Can you give me an idea of exactly what kind of ground it would take to work in this situation? The plans I was following only called for one small ground rod for the array, built under normal circumstances.

I looked closely and I'm not going to be directly under the line. I have about 30 ft of clearance from a point directly below the transmission line. That does fall within the "no-build" safety zone, I think. It's close. I'm going to present it as a temporary structure..because they do permit things like fences and gates, which they refer to as temporary.

I can see that I need to present a really good set of plans if I have a chance at getting them to let me do it at all.

I hope I'm not overstepping my welcome by asking so many questions. I really want to understand this.

[Sunking]

I have lived with those lines over my land for nearly twenty years...

Well then the threat to you is the family Jewels.

EMI effects are debatable with respect to health issues. Not going there. As for electrical it can cause problems when signals are involved like a computer, telephone, or video display. But for DC Sources of power, Not even a remote problem. FWIW I bet you know what a Power & Protection Engineer is working for a Telco. Been doing it for 33 years for all the big players like ATT. SW Bell does not exist anymore. Land line is DOA.

[dr_ed@swbell.net]

Thank you!

I appreciate the excellent advice! Understood on the professional help part. I have lived with those lines over my land for nearly twenty years...would guess the likelihood of a line falling is fairly infinitesimal. I'd be happy to sign a waiver. I just wasn't sure the function of the panels would be unaffected. You cleared my confusion up nicely.

[Sunking]

Goggle EMI. The big issue for you is a fairly significant ground electrode system in the event when and if the high voltage lines fall on your array. Otherwise no concerns. But if the lines fall on your array, even with a significant GES would likely blow up all you equipment and set it on fire. Basically 13.2 Kv to 750 Kv would be applied to all your conductors for the duration of the fault until the utility line switches off from a ground fault. They are set to about 1 to 2 seconds to burn the fault clear like a tree limb or big bird with large wing span.

They will likely make you sign a Wavier to release them from any damage or injury, and inspect the system before they allow you to proceed. You are going to need professional help.

[dr_ed@swbell.net]

I was wondering whether anyone could give me some guidance. I am planning to build a 600 sq. ft ground mounted solar array on my property. The best available site extends at least partially into a utility easement near some huge overhead transmission lines.

Are there issues of induced currents in panels mounted below high voltage transmission lines? I'd appreciate input from anyone knowledgeable in this area. There doesn't seem to be much information on the net about it.

I have to submit a plan to the utility before I build anything in the easement, and I'd like to be able to address this sort of question. I expect them to be resistant to my project in any case...so I'm trying to arm myself with the correct information ahead of time.

Thanks in advance

Eddie