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logic28 avatar image
logic28 asked

Ground Mount Grounding

I have built an adjustable galvanized steel frame for my ground mount with four steel posts embedded in 1 cubic metre of concerte each at around 4' of depth.

Since I also have a solar shed 20m away containing all the Victron equipment with its own 8' copper-electrolyzed grounding bar, I was wondering if the 4 posts would provide sufficient grounding to the 15 ground mount solar modules but, most importantly, should I connect the two grounds together in a TN-C-S configuration? I have read different opinions on that.

My concern is that if some excess current should hit the ground mount such as lightning and the two are connected, it would spread the fault to the shed and the equipment as well.

I am using 4 jumper cables between the posts and the fixed part of the frame in order to avoid any resistance that could be created by the hefty supporting bearings.

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Grounding
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mvas answered ·

What country do you live in? You are worried about a lightning strike coming in on the Ground Wire? What about the PV (+) and PV (-) wires bringing in high voltage? Is this 100% off-grid? Will this be permitted and inspected by a local authority?

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logic28 avatar image
logic28 answered ·

Hi, it is totally off grid for a second unit next to the house in the UK. No, it won't be inspected as it is a didactical experiment on my part. Yes, I have thought about other conductors also potentially been able to migrate the problem through to the equipment, hence my question to those who have done this before.

I read somewhere (cannot remember where) that there are situations where it is best to keep the two grounds isolated from each other presumably as the neutral from the PV is not linked to ground Unless one does so)

My thinking is that if a high voltage should strike the framework it would not necessarily involve the +/- conductors but just the framework and use the local earthing point as a quicker path to reach the ground.

Yes, it would also reach the ground through the second earthing rod but I have no idea what Victron connects/disconnects to ground in different states of operation.

Finally, I am not worried about what the local authorities decide to be appropriate, I am mostly concern in the best scientific solution having a vary sandy substrate after the first two meters of soil with a water table that can reach as high as 40cm from the surface at time with the sea only a few miles away.

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seb71 avatar image seb71 commented ·

If there is a direct lightning strike to the panels, I don't think that it will matter how you made the panel frames grounding.


In the schematics I seen, the panels ground is connected to the house ground. Or just a wire connecting the panels frame to the house ground (such as when the panels are on the house roof). In this case, run the PE wire in a different conduit than the PV + and - wires.

Also use SPDs both on the AC side (at the connection to the grid) and on the DC side.

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logic28 avatar image
logic28 answered ·

Thank you, yes I have laid an earth cable between the solar shed and the PV Ground system (20m away) but unfortunately, since it is running underground, I was forced to use the same 75mm ducting shared by the 6 lines of the 3 strings with the idea in my mind to perhaps introduce a "ground lift`" so that I could decide at the time.

For the same reason, I am combining at the shed end rather than at the ground mount where instead I have 3 isolators, 3 breakers 6 fuses and 6 DPDs.

However, at the solar shed combiner box, I only have 3 isolators and I see your good point of introducing 6 more DPDs at the end of the 23m cable run.

Something still tells me inside that I should not connect the internal grd with the external PV grd and let the potential excessive/spike voltage find its own way through the shortest route.

Also, I might consider having a pair of "MidNite solar surge protectors" (1 for AC and 1 for DC) as I don't trust these Chinese gadgets that much.

What is your thinking about that, please?

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Ground, earth and electrical safety


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