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Forum Index : Solar : earthing
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| brucedownunder2 Guru  Joined: 14/09/2005 Location: AustraliaPosts: 1548 |
I'm posting this ,so as not to interfere with Glenn's post.. I think it would be a nice help if we got discussion on the proper earthing of inverters ,solar panels, inter-connections between out -sheds and the house,ETC. Not only for the safety of everybody , but for the safety of the inverter. It's been a bit confusing to me to follow the posts about this ,lots of different ideas. When posting , a circuit diagram ,hand drawn will do , would be a nice help . Lets start it off with what Glenn and many of us have -- A shed out near the solar panels ,batteries, windgennie. Then a trench ,, then a distribution box under or inside the house .. with existing mains feed and WITHOUT existing mains feed . Or,, how to correctly (Sparkies welcome) go about this .. Glenn mainly started his post off with a question on steel conduit , let that discussion continue . But this post is important for the safety aspect.. Thank you Bruce. Bushboy |
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sPuDd Senior Member  Joined: 10/07/2007 Location: AustraliaPosts: 251 |
Bruce, problem with asking an individuals (sparky or otherwise) is you get a different interpretation of what they think is right. Might I suggest extracts from the relevant AS3000 (electrical) and all the other solar, battery, grid connect, stand alone Australian Standards of which there are many. This will ensure that forum readers are getting the correct information from which they may adopt their interpretation to suit their unique setup, or at the very least provide a guide when speaking to sparky/electrical/solar engineer. sPuDd.. It should work ...in theory |
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mac46 Guru Joined: 07/02/2008 Location: United StatesPosts: 412 |
Lightning... will do as it pleases, so don't kid you'rself into thinking it can be totally prevented. I agree, take all measures to stay safe and try to protect the equipment. I have witnessed a location where the lightning rods and ground rods drew in the lightning strikes and have prevented electrical damage for a period of years and then a storm came along and lightning fried most of the equipment, why, don't know. When you are dealing with A million volts or so anything can happen. Mac46 I'm just a farmer |
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| brucedownunder2 Guru Joined: 14/09/2005 Location: AustraliaPosts: 1548 |
Thanks Spud.. OK, Who's got an AS 3000 book out there --would you mind if we ask you questions from it ?. ( I had one or two editions years ago to refer to ,but they are not cheap) I'm more worried in blowing up a fully installed expensive Inverter ,by just having an earth wire connected to it's own earth stake or not ? . I'm about to connect mine (sort of same as Glenn) but petrified about the magic smoke escaping.. I'll ask the first question -- Battery negative post ,, do I connect this to the inverter's Earth point-manual says yes. Now the Important part-- do I now drive an individual seperate Earth stake in and connect inverter,battery to this .. Now ,I have two earths --one at the house mains board tied to the house neutral and one tied to the inverter ,battery . then this inverter/battery earth is 'stand-alone". Now from the inverter e-n-a to the breaker distribution box (a 6 breaker box installed purposely for the outlet of the inverter, the earth from the inverter is tied to the neutral common link . So now we have a similar situation to the house distribution breaker cabinet.but seperate, electrically. This must be an isolated stand-alone system.., completly isolated from the house wiring . Otherwise we will have linesman being eletrocuted from an active solar /inverter system. Anyone have a safe way this can be intergrated into the house system?? Bruce Bushboy |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
One other thing to think about is electrolysis and corrosion. Not such a big problem with ac, but with dc where there may be small leakage currents to ground from dampness and moisture, it can rot away metal parts with alarming speed. Grounding one side of an ac circuit is very good from the safety point of view, it prevents the whole circuit floating up to very high and possibly dangerous voltages. Grounding dc circuits can create some unexpected long term problems, especially if buried cables are involved. Telephone systems always ground the positive side of the dc supply for exactly this reason. That may seem like a very odd thing to do, because most people are used to working with positive dc voltages with respect to ground. But if you have buried cables, grounding the positive side can be very worthwhile. Cheers, Tony. |
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| Privatteer Newbie  Joined: 09/06/2012 Location: AustraliaPosts: 39 |
I'll throw 2 clauses at you. 5.5.3.1 (vi) The combined protective earthing and neutral conductor supplying the distribution board in an outbuilding should not be connected in parallel, by means of earthing or equipotential bonding conductors, with conductive pipes or structural metal within the electrical installation. 7.3.8.1.1 a)The neutral-earth connection (MEN) shall be made within the installation at the switchboard to which the electrical generation system is connected. c) Neutral and earth conductors shall not operate in parallel. So my interpretation is the second you create an Earth/neutral link in the outbuilding, ie MEN, you must land the earth from the main building cable on an isolated terminal and not use it. Then install a separate earth electrode and comply with the relevant clauses to do so. This makes senses to me given if you have a broken/high resistance neutral between buildings you don't want an alternative path via the earth. Just the earthing/MEN section is over a 100 pages in AS3000, and that's not referring to various other standards that are referred to as well eg electrical generation systems/solar. I strongly advise that anyone doing electrical gets a local sparky on board to check/help stand alone or not. |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
Yes indeed. Some of these seemingly nonsensical and difficult to interpret wiring regulations have a very sound technical basis and should be strictly followed. There can be all kinds of weird failure modes that can unsuspectingly create a hazardous situation. The mains wiring regulations are the result of a great deal of historical experience (and Coroners inquests). Cheers, Tony. |
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| brucedownunder2 Guru Joined: 14/09/2005 Location: AustraliaPosts: 1548 |
Thanks Privateer and Warpspeed,, I agree 100% about getting a Sparkie on board.. Thats really not what i started the discussion about , even though it's the most important part.. Why I started it --well, the moment we pick a F&P motor up from th tp ,we're fiddling with dangerous voltages.. We've spelt this out frequently ,so far good. Those that have no clue at all must stay away from these voltages .. But in reality, most of the members are intelligent enough to take advice and heed the warnings by the time they get to testing . It's when they get to using the power , that these "hobbyist's" might get confused and need a helping answer. Once we hook up an inveter ,things can get dangerous if we intend to use that power in the house ,caravan,Etc. Thats the reason I thought ,as an extension, I'd get expressions of correct advice from forum members. it's sort of an extension after they have the panels,wind-gennie working.( We talk a lot about building windgennies and installing solar and inverters,,but I don't feel enough is discussed concerning the magic smoke and lethal aspects of our "Hobby". Yep, get a Sparkie ,Oh, a Sparkie is a Licenced Electrical Trades Person - Bruce. Bushboy |
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| windlight Guru Joined: 03/03/2007 Location: AustraliaPosts: 331 |
Of my installs by licensed contractors, only one earth point. For the safety of your inverter do not use a walk around phone during thunderstorm season, phone lines love lightening so unplug them (from the phone line) for that season. jungle Jim "I like this place and willingly could waste my time in it" - (Act II, Scene IV). |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
Where you have something like a high voltage wind machine, it should certainly be ground referenced at some point, simply to avoid the buildup of destructive voltages. Lightning strike is an extreme case, but what may not be realised is that a fully floating well insulated system can accumulate electrostatic charges big enough to cause insulation breakdown. If you have a 300 volt system ground referenced, the highest voltage it will ever see is 300 volts. If it is fully floating, it can rise to thousands, or tens of thousands of volts very easily. The resulting flash over can puncture insulation and permanently damage or degrade parts of your system. Cheers, Tony. |
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Yes thats good advise, but finding a good one can be difficult. When I started this project I contacted a few electricians and told them I was planning to go off grid, and needed someone to connect up the power board, check a few things, etc. The response I got from all of them ( after the first 3 I gave up ) was they dont do off-grid systems and to contact company X ( I wont mention any business names here ), who specialize in off grid systems. I contacted company X, and told them I had the inverter, solar panels etc, but they were not interested in using my gear, and wanted to do a clean install using their own equipment. They then estimated it would cost close to $40,000! So what could I do? What I should have done is asked the questions here on the forum earlier, the answers posted here have been more informative than any I've had dealing with local companies. Luckily I have found a sparkie who will help with the powerboard work and install a mains powered fire alarm ( one of the requirements of a new home ), but he knows nothing about the inverter side of things, so I explained it's just like a mains connection from the street. Bruce I've read if you earth the -ve battery connection, it can affect the inverters standy switching, so I've not earthed mine. I do have some gass arrestors in there though. My solar panel frames are bolted to the shed roof, as is the little battery shed. The shed is steel construction, and earthed at 3 corners. The house is also on a steel frame thats earthed, and there is a earth wire from the steel roof to the frame. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| Privatteer Newbie Joined: 09/06/2012 Location: AustraliaPosts: 39 |
Glenn, you did see my post about the Brooks 12v detector in the smoke detector thread? I'll agree that find a good sparky can be hard which is why I am willing to provide some info within the areas I know. Many have never read the rule book since getting their licence and do things by routine. Anything outside the box is scary! Even for myself even though I am a sparky I paid some beer for a specialist to help do my grid connect system since I don't install them. As an industrial sparky I can't justify the cost of the solar standard for just interest. While I would have got the basics right, I could have been caught on some petty thing like labeling quite easily. |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Yeah I did see the post on the smoke detector, thanks for that. Also, the two regulations... 5.5.3.1 (vi) The combined protective earthing and neutral conductor supplying the distribution board in an outbuilding should not be connected in parallel, by means of earthing or equipotential bonding conductors, with conductive pipes or structural metal within the electrical installation. 7.3.8.1.1 a)The neutral-earth connection (MEN) shall be made within the installation at the switchboard to which the electrical generation system is connected. c) Neutral and earth conductors shall not operate in parallel. ... now make perfect sense, I didn't think what could happen if I get a bad neutral connection. The earth and neutral should only be connected at one point. Multible earths between the two buildings cant be helped, there are two many paths, like the dog fence, water mains, etc, but the way I read it, thats ok, so long as the neutral is only connected to earth at one place, in my case, just after the 2 pole mains switch, fed from the inverter. I know what you mean by keeping up with changing regulations. I'm ex Telecom and once had a restricted electrical ticket, so I have the tool skills, but I also know my knowledge is very out of date. With regards to windmill towers, I've always earthed the tower, but not the power. I've had a lightning strike to a tower, the electrics survived, except for a garden light. It was a 12v system and floating with repect to earth. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904 |
This subject is of interest to me too so I'll post my particular situation below. Firstly, I am a licenced electrician, now retired, but one who has not worked as what you call a 'sparkie' for many years. The last 29 years working as an electronics technician repairing fancy research equipment. My copy of AS3000 is at least that old  .
Anyway, my RE installation is as follows: I have two stand alone sine wave inverters connected to my 24V battery bank. I started up with just one that fed the light circuit only of my small house via a 2 pole isolation switch so I could select to have the lights powered either from the grid or from my inverter. Then more batteries were added to the bank and another inverter purchased, this one powering selected GPO's via a similar isolating switch arrangement. There is no way that my inverters could feed power into the grid, they can't be synchronised to it anyway. This setup works fine for me, I can shed power demand from the battery bank if the solar input is low. Certain loads in my house (such as the stove) will always rely on the grid for power. I did rewire my entire house, I'm licenced to do that, to acommodate the above, not an easy job BTW. What I would value now is your input as to the consequences, if any, if I connect the neutrals (only) from each individual inverter together as well as to the grid neutral (only). Presently they are completely separate. Doing this certainly would make the earthing situation simpler. My gut feeling is that nothing would happen as its electrically similar to the neutral of a 3 phase supply where all the phases are out of sync but I might be wrong... All the earth wiring is connected together at the house switch board and hence to the ground stake. Only the grid neutral connects to that earth at present. The inverter cases are grounded to their own earth stake, none of the 24V wires are grounded. Klaus |
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| Privatteer Newbie Joined: 09/06/2012 Location: AustraliaPosts: 39 |
Glenn, Actually I think the listing of structural metal would cover things like the dog fence. I thinking this over today. I also got a draft copy of the solar AS/NZS 5033 to try to get some ideas. While there are a number of clauses that cover outbuildings and so forth the 5.5.3.1 makes things very difficult if you have metal water pipes etc. It sounds silly but the safest method I can think of is to actually run the supply from the inverter direct back to the main switchboard and have one MEN only. The issue then is a second cable being required for the lights/gpo in the shed if needed. I might ask the question on a different forum to see if there has been any clarifications on the matter given to solar installers. I am assuming you do have mains power, don't think thats been mentioned? A full standalone would be easy. Just put the MEN in the shed and not have one at the house. Tinker, That sort of scenario is really getting into some of the other standards I don't use. The below pic is the best answer I could give. 
In regards to towers I have done a lot with microwave/wireless and the tower was always direct earthed to ground. Then depending on the area lightning arrestors may or may not be used on the electrical side. |
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Downwind Guru Joined: 09/09/2009 Location: AustraliaPosts: 2333 |
As per the diagram above that is correct to my understanding as well, it might be said that BOTH earth and neutral from the inverter should share ONE common connection each, and when you factor in using one or more RCD's within the wiring circuits then the neutral will need to be via a common supply. Only the active should be switched (this might be different in the US where 2 phases are used (VAC 220) and no neutral) I see no problem with a separate earth from the chassis of the inverter to its own earth stake as long as the chassis is not connected to the mains earth, this is actually requested in some inverter manuals. With solar panels IF the inverter is transformer-less than the EACH panel must have a earth wire attached to it, a single earth to the panel mounting rail is not permitted unless the rail system is pre approved as a earthing system. Panel earthing is not currently law in all Aussie states, but due to the fact it is in most then its a worthwhile practice to do. I found when i installed my workshop roof full of panels the cordless phone simply would not work in the workshop any more, huge static noise on the line, once all panels were earthed the phone returned to normal in the workshop. (figure that one out) Sometimes it just works |
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| brucedownunder2 Guru Joined: 14/09/2005 Location: AustraliaPosts: 1548 |
Thanks for the very informative discussion fellas. In a nutshell,, I'm treating my solar/windgennie power as a completly seperate electrical/power system all together isolated from the grid supply .(there's no other way you can do it ,actually .) (Earthing might be another thing). So, it will be power points and light points from the grid , untouched. Power and lights from the RE inverter standing alone --allmost exactly as the grid installation ,but completly isolated. Bruce Bushboy |
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| windlight Guru Joined: 03/03/2007 Location: AustraliaPosts: 331 |
This should open up a copy of electricians newsletter.....http://www.google.com.au/url?sa=t&rct=j&q=men +connection&source=web&cd=1&ved=0CCEQFjAA&url=http%3A%2F%2Fw ww.commerce.wa.gov.au%2FEnergySafety%2FPDF%2FNewsletters%2Fe lectricians_newslet.pdf&ei=veFDUOW2Gu6TiAf4t4HIBQ&usg=AFQjCN FxfjwPF3qR7MSxlLoUdWeXbKOOIQ An earth connection is necessary to ensure a reference point (one) so protective devices will operate. Think if you will about power line repair crews........http://laughingsquid.com/repairing-a-live-high- voltage-wire-by-helicopter/ On the point of lightening, it goes from ground to sky and sky to ground, meeting somewhere in the middle, think about it. Go out and squirt the garden hose into the air, what happens. "I like this place and willingly could waste my time in it" - (Act II, Scene IV). |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
Safe grounding of the 240 volt side is fairly straightforward, apart from the already discussed single earth/neutral link back at the main power board. What may complicate things is the dc side, sometimes very high voltage dc. And does your inverter have total (galvanic) isolation between the dc input and ac output? That may be an issue if more than one inverter is being used, or if the loads are a mixture of low voltage dc and 240 volt inverter power. Some of these systems tend to grow over time, and some compatibility issues can complicate the grounding. Cheers, Tony. |
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yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
This is all very timely, there are amendments to the safety requirements for PV's AS 5033 on the 16 of October 2012. energy council guidelines to amendments There is some clarification on grounding panel frames. downwind, your interference was due to the anodised aluminium acting like a capacitor. check this for an explanation energy matters earthing PV frames There is also mention of the expected 24 month transition of changes to the earth fault interrupter (EFI) standards for Low Volt panels that are functionally earthed. I will be interested to see how this is applied (or not ) to off-grid systems. I have fitted them to the American standard before, but a fault indicator and alarm is something new. I'm confused, no wait... maybe I'm not... |
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