3 Phase earth test - Page 1
Forum section: electronics / beginners

author: gildasd
author_rank: Frequent Contributor
timestamp: August 25, 2015, 04:35:22 pm
content: Hello,Just discovered that my new house has 380V...It's contracted to be 240V, but the old 380V stuff was left. And is still live!Two phases are combined to make a false neutral 240/250V mains (depends on circuit, 16A=250V, 40A=240V)This is done via an innocent looking module on the electrical panel.Apart from the inconvenience of the phase tester lighting up on phase and neutral, the normal earthing test gives a weird result.Normally, when testing earth, one side should read 1V or less and the other the nominal voltage.Here I get about 130V on each side...Is this normal or should I call the Ghostbusters because ball lighting is going to fly out of the outlets?CHeers!

author: nihilism
author_rank: Regular Contributor
timestamp: August 25, 2015, 04:42:35 pm
content: My advice on this one is, if you don't happen to be a ghostbuster yourself, i'd call one in.AFAIK earth should be close if not the same to the neutral potential. May be different for a split phase system in your particular country though, i'm not sure.

author: gildasd
author_rank: Frequent Contributor
timestamp: August 25, 2015, 05:48:25 pm
content: Quote from: nihilism on August 25, 2015, 04:42:35 pmA yes I forgot a detail. There was no earth post. 380V and no earth, what could go wrong? 1950's men were scared of nothin'!So I've sunk a by the rules post to the exact specs to be legal, that's why I was testing the earth...Did some more checks and it's pretty near to split phase potential. It get much nearer with just a small load (40W bulb).I did have a ghostbuster over for two days just making the whole thing safe, but he had never done 380V in the residential context, so he was not 100% sure of everything right off the bat.There is no way that I can pay a ghostbuster to do all the work, the electricals in this house are too crazy, real "stick a wet finger and see if it tingles" crazy, it would cost a literal fortune to get someone to do it all.So I have made little to no attempt at fixing, I'm simply replacing line after line starting from the fuse box making fresh furrows with new legal wiring each time.

author: SeanB
author_rank: Super Contributor
timestamp: August 25, 2015, 06:20:03 pm
content: Good to do that, and rip out the old wiring asyou go. that way you can spend a weekend or a few nights with a stanley knife and get a lot od copper to sell as scrap. Might help defray the costs a little.

author: gildasd
author_rank: Frequent Contributor
timestamp: August 25, 2015, 06:54:48 pm
content: Quote from: SeanB on August 25, 2015, 06:20:03 pmThe old wiring is not pure copper, it's kinda orange when freshly cut but turns to a stainless steel colour after a while. The gauge is also about 65% of what's legal today.Another weird thing is that the insulation has two layers: an off-white centre and a coloured PVC outer. Any humidity makes this last layer crumble.If there was any value, I would stick it in the burn off oven at work - too easy.

author: SeanB
author_rank: Super Contributor
timestamp: August 25, 2015, 07:07:05 pm
content: So it is tinned copper wire with a PCB filled PVC outer insulation. Put the lot in the burn off oven ( here they just light a fire next to the road somewhere to burn off copper wire) and then wash it, it will be pure copper wire inside.

author: TheElectricChicken
author_rank: Frequent Contributor
timestamp: August 25, 2015, 11:49:26 pm
content: Quote from: gildasd on August 25, 2015, 06:54:48 pmQuote from: SeanB on August 25, 2015, 07:07:05 pmThe wiring may not be as old as you think, there are places with even older kinds of wiring than pvc...Burning off the cable is the worst idea ever.It creates and then distributes all over the places you walk around and live and eat, the worst poisons you can imagine ! It all comes back down and gets all over peoples gardens including yours, or as a dust throughout the neighbourhood. Please guys, just use a knife and do it in front of the TV and you won't even notice the effort at all.

author: Delta
author_rank: Super Contributor
timestamp: August 25, 2015, 11:59:22 pm
content: I am struggling to get an idea of your 3 phase installation, could you post some photos please? Do you have 3 phases AND A NEUTRAL coming in?A line voltage of 380v (phase to phase) gives a phase voltage of 220 (phase to neutral), not 240.Connecting two phases together cannot "create a neutral", it creates a short!Some photos could really help here! 😃

author: JacquesBBB
author_rank: Frequent Contributor
timestamp: August 26, 2015, 08:31:54 am
content: Normally, from what I know, you should have 230V between a phase and neutral, and about 400 V between two phases.If you have no Earth, the neutral may be floating. You should have an Earth pole installed and the neutral connected to Earth at theelectric board.Another inconvenient may exist in old installations, which is common neutral.In modern installation, each circuit has three wires starting from the electric main board.: Phase, Netral and Earth.In old installations, there may be just a Phase from the main board, and the neutral is taken from any circuit.The problem is that if you cut the circuit at the main electric board, there may still be power coming from the neutral through another circuit.Is your installation of this kind ?If it is, I would suggest to gradually replace these circuits by modern circuits starting from the main electric board.

author: vk6zgo
author_rank: Super Contributor
timestamp: August 26, 2015, 11:16:47 am
content: Quote from: JacquesBBB on August 26, 2015, 08:31:54 am3 Phase&a Neutral is very common in "all-electric" homes in Western Australia (I'm not sure about the other States).Kitchen stoves are often operated on two Phases,and some Electric Hotwater systems use all three Phases.I have a "honking big" 3 Phase socket in the carport---I have no idea what the previous owner operated off it!

author: gildasd
author_rank: Frequent Contributor
timestamp: August 26, 2015, 02:16:36 pm
content: Quote from: Delta on August 25, 2015, 11:59:22 pmThe first pic is an idea of what I find here and there... Blue and Brown for 240 mixed with Grey+Grey and black of 380. In the same box...The four black boxes (starting from top right) are; day meter, general cut off, night meter, 380V thing.This is a detail of the 380V box.The electrical panel.The magic box that converts 380 into 240...An idea of how I'm installing the new circuit.

author: M. András
author_rank: Super Contributor
timestamp: August 26, 2015, 05:26:10 pm
content: that "electrical board" is a mess where are the incoming wires? the 5 core cable have only the phases connected no earth and neutal where the hell is that going?

author: gildasd
author_rank: Frequent Contributor
timestamp: August 26, 2015, 05:49:06 pm
content: Quote from: M. András on August 26, 2015, 05:26:10 pmThe incoming wires are in the lower left.The neutral and the ground are connected to nothing.If you think this is a mess, you should have seen it when I arrived; "bombed out multicolored spaghetti factory" would be fair description.All the earthing you see is mine, there was NO earth at all...

author: 128er
author_rank: Regular Contributor
timestamp: August 26, 2015, 05:53:00 pm
content: What an electrical nightmareQuote from: gildasd on August 26, 2015, 02:16:36 pmThat's an RCCB. But it's totaly useless in your case. It's hard to see it from the pictures. But it seems, that there is a separate Earth conductor going to the PE bar at the top right of your panel, maybe 16mm². You practicaly have a TN-C configuration. If you had a real separate Neutral, it should be passed through the RCCB, to protect you from electrical shocks.Edit:Quote from: gildasd on August 26, 2015, 05:49:06 pmWhere does the thick (16mm² ?) PE wire comes from? Grounding electrode? Water pipe?

author: gildasd
author_rank: Frequent Contributor
timestamp: August 26, 2015, 06:04:17 pm
content: Quote from: 128er on August 26, 2015, 05:53:00 pmI put that ground connector, it's 20 or 24mm² - it's over spec't.Edit: 1.5m earthing spike 0.6 m below surface, moree than 1.5m from the house and the neighbour. It so legal I could offer it a drink.Edit3: Using the water pipes is about as legal as a suitcase of Colombian marching powder.There was NOTHING connected to the earth at all when I started...There are 13 "spaces" in this house. So far I've made 3 100% up to norm, 4 partially. It's a battle.With an electrician we cleared out the biggest piece of spaghetti (things that were connected to two differentials, 75% of the house supplied via a single 0.75mm² wire etc).This triphase is a nuisance, but I can work around it for the time being.Edit 2; I'm using the regulation guides from Vinçotte and Belor. I use those as a base line.

author: SeanB
author_rank: Super Contributor
timestamp: August 26, 2015, 06:27:57 pm
content: I want to meet that electrician, I think I have seen his work over here in the Metro side where anything goes. At a minimum that box should have everything stripped out and it should be redone from the meter outlet onwards to some code. Try to do to BS spec aside from the ring mains, it is pretty safe.

author: 128er
author_rank: Regular Contributor
timestamp: August 26, 2015, 06:38:16 pm
content: Quote from: SeanB on August 26, 2015, 06:27:57 pm

author: gildasd
author_rank: Frequent Contributor
timestamp: August 26, 2015, 06:39:58 pm
content: Quote from: SeanB on August 26, 2015, 06:27:57 pmThat's the plan. But I need all the lines installed to do that.The box is by far not the worst or the most dangerous electrical mess.He untangled the mess that somehow allowed for about 75% or the house to run from a single wire that is only legal for a single light.I can now continue removing things from the old and getting new wires in.When I have that done, I'll run over the box with my car before taking it to the recycling centre, and put a all new one in."Getting it done" would cost 5 to 6000€, mostly pulling wire.Getting the electricity supplier to come rewire the meters and supply (that I or an electrician can't touch) would also be costly, so they are coming when it's ready within the general inspection - they are not coming twice.I also fitted 3 good quality (German) fire alarms.

author: cs.dk
author_rank: Unknown
timestamp: August 26, 2015, 06:40:03 pm
content: Quote from: JacquesBBB on August 26, 2015, 08:31:54 amI don't know how many european "standards" there is..Our system seems like yours, but the neutral wouldneverbe floating - It is actually the starpoint in the nearest transformer-station, which is grounded safely - And the generators starpoint at the plant to. (TT)Measuring between a phase and neutral should give the same reading as between a phase and ground (PE). = ~230VTN-C and TN-S is not very populated here.Belgium must be must like the rest of the EU - But again, differences appears.

author: gildasd
author_rank: Frequent Contributor
timestamp: August 26, 2015, 06:47:35 pm
content: Quote from: cs.dk on August 26, 2015, 06:40:03 pmThat's what I've seen in commercial installations.My system was barely legal in 1954 and totally illegal now. I can't even connect the neutral because it's in a box with seals...

author: Delta
author_rank: Super Contributor
timestamp: August 27, 2015, 12:10:47 am
content: Wow, what a mess!But you CANNOT get 240v from a 380v three phase supply! Phase voltage = line voltage / 1.73220v 1p from 380v 3p230v 1p from 400v 3p240v 1p from 415v 3pWhat is the nominal single phase supply voltage in your area? (can you measure it at a friends house maybe?)Where do the three cores supplying the consumer unit (breaker panel) connect to at the meter board?Is that a jumper connected on the top of each RCCB?Is there an unused terminal (marked N maybe) on each RCCB?Could you get some photos of the incoming cable and first termination into the house?What you have sounds more like a split phase supply.....

author: gildasd
author_rank: Frequent Contributor
timestamp: August 27, 2015, 08:05:57 pm
content: I will measure all that tomorrow... I'll go to the neighbour's to read the mains there.

author: M. András
author_rank: Super Contributor
timestamp: August 27, 2015, 08:08:42 pm
content: Quote from: gildasd on August 26, 2015, 06:39:58 pmjesus christ... how big is that property? thats an insane amount of wire to be 6k euros or is it mostly cost of the workmanship?btw three phases, its simple you have single phase to everything with 3 core cables, phase/neutral/earth, for 380/400 2 or 3 phase loads motors, stoves, heaters, you need atleast 2 phase wires neutral and earth, for 3 phase stuffs 3 phase wires and earth

author: gildasd
author_rank: Frequent Contributor
timestamp: August 28, 2015, 04:17:36 am
content: 200m2 (of which170m2 are living spaces).It's hard to get an electrician for 32€ an hour, a good one costs about 50€... So I'm rewiring myself, this is a lot of cutting up brick walls (no wood structures here) because the old tubes are too thin and the old wires break if I try to pull anything bigger than lights wiring.Thusly, I only call the cavalry when I get stuck or for the final check before inspection.

author: bills
author_rank: Frequent Contributor
timestamp: August 28, 2015, 04:42:11 am
content: Wow I did not know that 3 phase was used in a home? Is this common in your country?In the US industrial plants we would use a transformer to convert 3 phase to 120/240v for the offices low voltage.and use 277volt for lighting as long as the load is balanced.is this a 4 wire system? and where does the neutral come from? It is not common to have a 4 wire system here (just 3 hots and a common ground 480v.) no neutral. Each leg of the 480v to ground is 277v.I wish I could be more helpful but after reading this thread I am confused. (that is easy to do with me)I have seen some industrial setups with a separate single phase service 120/240v.

author: MarkF
author_rank: Super Contributor
timestamp: August 28, 2015, 05:12:44 am
content: I don't pretend to understand the 3-phase configuration used in your country. Here in the states are delta-wye and a delta-delta configurations I captured about 2014 NEC - Transformer Electrical Code. Maybe it will help understand what you have.

author: vk6zgo
author_rank: Super Contributor
timestamp: August 28, 2015, 05:50:41 am
content: In Australia,the 3 phase house wiring is "Wye" or as commonly said here, "Star" configuration.The 230v (nominal) supply to the wall power sockets is connected between Neutral & Phase.The Phase to Phase voltage is "the square root of 3"(or approx. 1.732) times 230v.(my calculator has "gone walkies",& I am too lazy to work out the exact value on paper.)

author: Towger
author_rank: Super Contributor
timestamp: August 28, 2015, 07:14:48 am
content: Quote from: vk6zgo on August 28, 2015, 05:50:41 amSo that's were the the phase to phase 220 is coming from, I think most of us assumed it was delta.Many of the older houses in Dublin city have 3 phase, dating back to when they were first converted from gas lighting 100+ years ago. Not that common in a more modern house, unless it is huge or you have a particular reason to want it. Electricity is distributed in (most areas) as 3 phase. The conected phase alternating between every few houses along a road. If you want 3 phase you fill up the paperwork and pay cost to connect up the other 2 phases.

author: German_EE
author_rank: Super Contributor
timestamp: August 28, 2015, 03:44:41 pm
content: We have three phase here in deepest Germany. The reason for that is the cooker and that's the only three phase connector in the apartment however I also know that the lights are on one phase and the sockets are on another. The incoming cables to the apartment are as thick as my thumb, the incoming cable to the building is thicker than my arm.Chunky German electrical engineering

author: gildasd
author_rank: Frequent Contributor
timestamp: August 28, 2015, 04:29:12 pm
content: The neighbours house is exactly 230V.My house has 229v.Measured at a plug: phase to ground is 113.5 and 113.8.But another plug is 227.8 but the phases are 131 and 133And there is 50V between the "unconnected" earth and the "unconnected" neutral... WTF?Also 30V between either of these two "unconnected" wires and my new earth...There is 50 amp limit, but that's still a shitboat full of energy.The installation and wiring is from 1954 but the box and the differentials are 10 years old max.I'll look around for the name of the electrician of the previous owner and report him, this is ridiculous."Angrier than this emoticon;"I will now switch off the electricity and go cap those faaaackin' wires.

author: M. András
author_rank: Super Contributor
timestamp: August 28, 2015, 04:52:49 pm
content: pull everything out of the walls cos thats a whole lot off broken or burnt trough cables in those walls if you measure that insanity, get a wall chaser hilti makes good ones and i guess you can rent them too in your country to cut up the walls for the plastic tubing for the cables you dont need anything more then the chaser and a good industrial vacuum for it then you can use even a srewdriver to break out the the brick from the cut channel

author: gildasd
author_rank: Frequent Contributor
timestamp: August 28, 2015, 05:47:37 pm
content: Quote from: M. András on August 28, 2015, 04:52:49 pmThe old system is disconnected at the room and the fuse box.Straight lines are drawn with the wiring as per regulation. If I find old wires I rip them out, but I don't go out of my way to find them.The old PVC tubing is macerated cow excrement in material and disposition, so it's not worth pulling new wires in them.I'm only concerned in not cutting water pipes with the 350mm grinder/wall cutter while laughing maniacally.

author: M. András
author_rank: Super Contributor
timestamp: August 28, 2015, 05:56:02 pm
content: Quote from: gildasd on August 28, 2015, 05:47:37 pmget a wall scanner or some kind of metal/wire detector that can work over 10cm to find the water pipes.if those are measured with new wiring from the distribution panel something is oddly wrong still. and i highly doubt you have a split phase system

author: gildasd
author_rank: Frequent Contributor
timestamp: August 28, 2015, 06:13:09 pm
content: Quote from: M. András on August 28, 2015, 05:56:02 pmThe pipes are connected to nothing, no earth, nothing.I follow the pipes (they are in steel 5cm deep max, a magnet is sufficient) and mark them with a red spray.The position of the now wiring is in green.The old wiring, well, I don't care about the old wiring when I'm sure there is no juice in it.

author: Delta
author_rank: Super Contributor
timestamp: August 28, 2015, 09:35:52 pm
content: Your supply is seriously fucked up mate!From your figures, the first set of measurements indicate a split phase supply on that circuit, but the second set indicate two phases of three phase star connected supply (with the star point earthed).I can only guess that the distribution network uses some form of high leg delta (high leg star?), but I've only ever heard of the Yanks using such a daft system.

author: vk6zgo
author_rank: Super Contributor
timestamp: August 29, 2015, 02:15:13 am
content: Quote from: gildasd on August 28, 2015, 04:29:12 pmIf you are measuring at a normal domestic power socket,(what we call a General Purpose Outlet,or"GPO"in Oz),229 volts between the two"non-Earth" pins is about right for a European system.(you are usually on the low side of "nominal"--we are on the high side).Remember,those pins of aGPOare not "Phase to Phase"------they are "One Phase & Neutral"."Phase to Phase" would be around 400v.It is not common in Domestic situations in Australia to bring 3Ph out to any sockets,it is usually used for stoves,hotwater systems,etc.or to feed two or more runs of GPOs,or light circuits.I would suggest normal practice in your country would be similar.It looks like you do not have a connection between Neutral & Earth at your Entry PointMany of your funny results are because of this,AND the fact your DMM has a 11MegOhm input impedance-------------Google "Phantom Voltages",,