The Victron SmartSolar manual says, “The positive and negative of the PV array should not be grounded.
“Ground the frame of the PV panels to reduce the impact of lightning.”
So should I connect my PV mounting frames to my electrical ground or lightning ground?
I was assuming electrical ground and then I saw the reference to lightning. Forgive me if I’m using the wrong terminology.
I currently have my PV frames connected to electrical ground but I’m wondering if they should, in fact, be connected to lightning ground? I have both but they are deliberately separated.
Here’s another risky topic for public discussion, everyone’s chasing one-size-fits-all solutions without factoring in the specific technical conditions.
The frames of photovoltaic panels must be connected via a separate grounding loop (lightning down-conductor) sized to the correct cross-sectional area. If your home is situated in an exposed location, you should install a capture loop on dielectric insulators of the correct rating on the roof, along with a 1.5-2 metre mast.
Lightning currents typically reach around 50 kA and voltages of 1-1.5 MV, although they can spike to several hundred kA and tens of megavolts. So, consider what conductor cross-section will safely road those currents to earth?
Designing, sourcing, and installing a lightning protection system is costly. There’s also the age-old debate over whether to link the two earthing systems (AC earthing and lightning down-conductor) for equipotential bonding. If everything is based on engineering calculations, equipment specifications, and local regulations support it, the short answer is YES, they should be combined!
That said, there are scenarios where it’s better to keep both loops independent, provided the equipment’s schematic allows for galvanic isolation.
ESS and PV installations aren’t just kettles or microwaves in terms of load, they’re full-scale energy systems subject to stringent safety standards.
To sum up, based on the above, think carefully before making any decisions…
I appreciate the subject is complex. I have a sort of lightning protection (a rod, a conductor and some equipment in the ground) on my house installed by an “expert”. I have since added PV panels to the roof.
I don’t trust so-called experts here because they don’t do any assessment and can’t explain what they’re doing. Forget local regulations, they don’t exist. The only real options are to educate and do it yourself, leave it to so-called experts and hope for the best or simply do nothing.
If I understand you, the practical option is for the PV to have their own lighting protection. What about electrical ground?
The reason I keep the two separate is that I don’t want to introduce the big lightning currents into my electrical system. This is what is advised by some readings and that seems logical to me.
You cannot make an assessment of something you don’t understand, nor do you have the equipment for performing control measurements. In this case, you should hire a licensed engineer who specialises in grounding systems and lightning protection. They will check everything you have in place and tell you if anything needs correcting. As part of their work, in addition to issuing an invoice for their services, they are obligated to provide you with a certified test report, signed by them, detailing the measurement values for the grounding system.
You just haven’t encountered this yet!
I’m not offering any practical advice along the lines of “how it works…” or “how it’s done…” precisely because I strongly oppose discussing grounding with non-professionals, as this involves life-threatening risks and places significant responsibility on those giving such advice!
I’ve merely tried to explain to you the complexity of making such decisions.
Moreover, others, when reading such topics, may try to use them as a template for their own purposes, which is absolutely unacceptable!
There are no identical installations, and there are no uniform technical conditions!
These decisions should only be made by an electrical engineer on location, taking into account all the factors I’ve mentioned above!
In my opinion, the topic has been exhausted and should be considered closed!
Thanks for attention.
In Germany we need to have surge protection where the cable enters the building. If the distance from entering the building to the inverter/charger is long, e.g. 15 meters, we need a second surge protection. Reason are possible parallel cables, water or gas tubes charged by induction.
The cable must be 20 or 16qmm depending on some conditions.
There three different sensitivity classes from 1 rough to 3 “electronic protection”. You cannot have 3 without 1+2.
Depending on your network type (TNC, TN-C-S, IT…), you need different devices and cascades.
Depending on your roof and PV size, you need several down streams or even diagonal streams for the mounting rails. In any case, the mounting railed shall be connected with at least 10qmm non oxidizing rods.
The company “Dehn” is specialized on surge protection and also offers information. The devices are expensive with 500+ RUR list price.
I have them on DC-PV, AC-PV and grid connection.
You need proper grounding, which is another topic where a certified electrician needs to measure resistance with a special device in 20m distance. Those measurement instruments cost thousands of EUR. Grounding is done with a several meter long spike (3-12m) deep into the ground depending on water or full area below the building. If you have a high steel mast, like a radio tower additional measurements have to be considered.
Just to give you some first ideas and yes, I agree with @Diessel pls get a real expert on this topic.
This is exactly the kind of engineering design work and technical oversight I do on a regular basis, but not remotely, I’m on location.
So, I know what I’m talking about and don’t dish out “one-size-fits-all” = silly advice
Here’s an example of today’s Monday :
Series “How do they do it?”
3 X 9m stainless steel in earth
@Fideri Just to answer that remaining question about “electrical ground” which I guess refers to the “protective conductor” used in AC installations.
This type grounding is required for PV systems to equalize voltage potentials across the building in order to protect people and also PV panels+inverter electronics from static electric discharge shocks and - in case of an inverter without galvanic insulation on DC side and one of the DC cables getting faulty and touching the frame - also to protect from AC leakage currents.
But as the others already said, it will not protect against high currents that come from lightning strikes.
If you have a proper lightning protection system and the mounting frames of the PV panels are properly connected to it, then that “lightning ground” will also serve the purpose of voltage potential equalization and an additional connection to electrical ground / protective conductor is not required and it can even be argued that it is counter-productive / hazardous in case of a lightning strike as it will carry a certain fraction of the lightning current into the building.
And because you stated that you already have lightning protection on your roof, in proximity to your PV panels I assume, then it’s very crucial to properly integrate the PV mounting frames into that system.
Disclaimer: I’m not a professional, just sharing my opinion and half-baked knowledge here - exactly what you can expect from a public discussion forum
This can only be done in one case, if the MPPT schematic has galvanic isolation between the PV input and the DC output. At the same time, it is also necessary to ensure overvoltage protection for the PV system right on the roof. Before opening the road for lightning, you need to understand where it will go.
The important is not to open Pandora’s box.
It’s already been opened by existence of this discussion I’m afraid
How about proximity for instance - i.e. the distance between existing lightning protection rods and conductors vs. the pv mounting frame. If it’s too close, lightning will enter the house via arking.
I wish we could close the thread at this point and leave all further discussion to local experts, because many details cannot be figured out without local inspection. Unfortunately, many electricians and solar companies are not experts when it comes to lightning protection. That’s exactly why I started to dig into that topic myself and finally found someone with enough expertise to gain my trust.
Thank you @BjoernK and @HansDampf for your thoughts. I fully agree with everybody that such matters are best left to people with the right knowledge and experience. I’m only adding that in a place where such experts do not exist, it is kind of difficult to defer to them. I appreciate that it is difficult for some people who live in organized societies to imagine that such a place can exist. I’m talking about a place, for example, where nine people routinely squeeze in car meant for five people in full view of the traffic police.
But it’s not all doom and gloom. The weather is excellent throughout the year. The coldest it gets is 16 degrees, the hottest is 27 degrees, the average is 20 degrees, all Celsius; great for solar. The schools are (still) OK. Most resources are cheap.
It is some sort of wild west but personally, I follow UK or South African standards. This is not a regulatory requirement; it’s purely voluntary. (Fun fact: most people here use UK-type sockets, but you can find and use any socket you fancy). Nevertheless, @BjoernK reference is very helpful in clarifying my understanding of grounding concepts and approaches.
@HansDampf you have hit the nail on the head. Presently, my building has lightning protection with its pit in the ground (though lightning is extremely rare); the grid has its own grounding point to which all my sockets and electronics terminate; and my internal electrical wiring has SPDs (surge protection device) at various places. According to Denh and other multiple sources, such systems can be integrated or separate, depending largely on the type of equipment used.
I have my PV frames linked by 25mm sq. wire to my grid grounding point. This is what I was referring to as “electrical grounding” but I now realize that phrase can be ambiguous. I was wondering whether my frames should not be linked to the lightning grounding point instead. My thinking was exactly the same as that of @HansDampf Nothing I have read so far contradicts that, so I will go with the said approach.
Hm, ok - then lets add some info to the pot…. 25mm² is what is usually required for conductors that are to carry lightning current (for aluminium, for copper it’s only 16), but for lightning it’s very important that the wire is not stranded, otherwise it will just bust…. and for the mere purpose of voltage potential equalization, less cross section (usually 4mm², depending on some other parameters that I don’t want to into detail here) is sufficient and stranded wire is allowed. So you see, it all depends on the purpose.
In my installation, the lightning protection system is connected to the electrical ground with 16mm2 stranded wire (because that’s the cross section of the incoming wires from the public power grid. it’s very few thick strands, but surely not capable to carry lightning current, only discharge currents from grid transients / overvoltage spikes, and currents from possible faults / short circuits of course until the fuses or RCDs kick in). This is basically to improve the effect of my surge protection device - which otherwise could direct any overvoltages only to the ground coming from the public grid which is not the best destination for that - and that setup is following official requirements of my local electric grid provider. With this comes also the requirement that the lightning protection system is grounded to earth in a proper way, verified with earth resistance measurements - like Diessel is displaying in one of his photos.
