Neutral line fault detector NFP-1801? - Page 1
Forum section: electronics / general

author: nardev
author_rank: Unknown
timestamp: April 27, 2021, 03:14:59 am
content: Hey guys,I'm just curious what do you think about this device "NFP-1801" by "Elektronska industrija Niš".I can't find anything similar by any other manufacturer. Is it something that you would install in your fuse box?Essentially in case of N line cutoff it shuts down the FID/Safety switch in fuse box.There is a video demonstration but it's not in English, though the demonstration is pretty clear.https://youtu.be/50DNhf6F0CY

author: f4eru
author_rank: Super Contributor
timestamp: April 27, 2021, 11:18:44 am
content: Clever device.But:1) It is not certified for any EU country. Probably not allowed in a lot of them. Won't recommend.2) neutral fault is extremely uncommon in most countries, it's not needed in fact3) not sure if protected/safe from a few aspects, would like to see the inside4) Would probably have false positives in situation like lightning5) does not protect downstream (3-phase home only)

author: nardev
author_rank: Unknown
timestamp: April 27, 2021, 12:15:28 pm
content: In regards to certification, the guy have mentioned that they have got all required certs for Serbia, which actually since JUS (Jugoslavia Standards) is actually pretty strictly following EU standards. So i would not be surprised if they make all required testings and get certified.It's pretty new product, i might get one if someone is willing to make a proper review video?

author: f4eru
author_rank: Super Contributor
timestamp: April 27, 2021, 01:58:17 pm
content: hmm.. No CE marking. does not look good yet for compliance, but they will probably improve that over time.

author: nardev
author_rank: Unknown
timestamp: April 27, 2021, 02:04:44 pm
content: Certifications aside, i was primarily wondering how useful such protection could be.I guessing as nobody made it already, for all those years, so is it something worthy of installing.

author: f4eru
author_rank: Super Contributor
timestamp: April 27, 2021, 04:24:44 pm
content: it may be useful in countries with bad electrical infrastructure, where shoddy neutral connection is a real risk.Elsewhere, it's just not worth the trouble.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: April 27, 2021, 05:14:33 pm
content: In the UK, the wiring regs stipulate than an external EV chargepoint on an installation with TN-C-S earthing must have either a ground rod or a device that isolates all 3 conductors in the case of a neutral fault (PEN fault)This is to prevent the body of a plugged-in EV becoming live in the event of a neutral faultThis is a similar device :https://matt-e.co.uk/

author: excrucio
author_rank: Newbie
timestamp: January 19, 2023, 03:07:49 pm
content: No review?Device is certified for EU.CE is there.

author: uer166
author_rank: Super Contributor
timestamp: January 19, 2023, 08:40:59 pm
content: Quote from: mikeselectricstuff on April 27, 2021, 05:14:33 pmWhich is absolute bollocks. Most regs stipulate that you need the PE bonded to car, not going through any switching, so it's a fundamental regulatory incompatibility..Not to mention that in a PEN fault, every chassis-bonded device in a house becomes live, not just your car, so singling out EVs specifically seems a bit weird..

author: uer166
author_rank: Super Contributor
timestamp: January 19, 2023, 08:45:04 pm
content: Quote from: excrucio on January 19, 2023, 03:07:49 pmI don't see any certification marks to any known standard. There are no 3rd party cert marks, and the CE means nothing here. CE mark in EU is like policemen in the US, "we have investigated ourselves and found nothing wrong".

author: max_torque
author_rank: Super Contributor
timestamp: January 24, 2023, 09:14:55 pm
content: Quote from: uer166 on January 19, 2023, 08:40:59 pmAdded to which, go and try to actually touch a bare metal bit of a modern car? Go on, you'll be surprised how difficult that is! You are absolutely going to touch a tap or metal domestic device like a toaster or kettle well before you get a shock off your car (which is painted, plated and increasingly, plastic and hence non conductive!) My BEV is actually a carbon plastic composite chassis and has entirely plastic body panels, to there is no "live chassis" to touch any way ;-)That reg is simpy a backdoor to making installing a charge point more expensive and complex and hence keeping electrical labours in buisness........

author: richard.cs
author_rank: Super Contributor
timestamp: January 25, 2023, 09:20:04 am
content: Shunt tripping RCDs is usually discouraged in most EU safety standards. I skimmed the video, but isn't this just a MOV in a box connected between post-RCD-neutral and some true earth pulled from somewhere (rod?) such that when they deviate by too many volts the RCD trips?Also opening the RCD won't actually mitigate the main TNC-S lost neutral risk, it'll only prevent equipment damage.

author: dietert1
author_rank: Super Contributor
timestamp: January 25, 2023, 01:06:18 pm
content: Faulty N connections will most likely happen downstream of the installation box, i mean somewhere in the building. For example, here in Sao Paulo it is common practice for electricists to connect wires by twisting the bare copper ends of cables and wrapping the knot with tape. After some years the copper develops oxide layers and contact resistance. When checking i have seen 10 Ohms or the like in the N net. The device won't detect this kind of problem.Regards, Dieter

author: Siwastaja
author_rank: Super Contributor
timestamp: January 25, 2023, 02:31:02 pm
content: Quote from: f4eru on April 27, 2021, 04:24:44 pmFor example, Finland. We take pride of our "good" grid infrastructure, yet N fault (or PEN fault) is something thatdoeshappen to the point of having utilities and mass media regularly remind us how to recognize N fault and what to do with it.And the advice is nearly hilarious. When you see some of the lights being extra bright and others dim, use leather gloves and some wood/plastic broom/etc. to turn off the main switch, remembering that the metal enclosure of the fuse box is now potentially lethal to touch. I mean, who really remembers this advice when your electronics are emitting smoke, while part of the house is in brown-out?https://caruna.fi/en/power-cuts/neutral-faultYet, realistically, I don't think anyone has actually died due to neutral fault in decades.

author: Alti
author_rank: Frequent Contributor
timestamp: January 25, 2023, 08:00:37 pm
content: Quote from: richard.cs on January 25, 2023, 09:20:04 amIndeed, seems like it is causing a residual current to flow and trip RCCB when voltage exceeds some threshold values. Varistor, zener or some crowbar. As mentioned, this is only going to save equipment, maybe prevent fire but has nothing to do with alleviating risks when damage is made to PEN.Quote from: Siwastaja on January 25, 2023, 02:31:02 pmQuote from: Caruna.fiI have to visit Finland. Crazy, can you show some photos how this Finnish PEN looks like?

author: uer166
author_rank: Super Contributor
timestamp: January 25, 2023, 08:54:33 pm
content: Quote from: richard.cs on January 25, 2023, 09:20:04 amNo, the way PEN fault protection devices work, is theydisconnect the PE conductor, as well as all the live conductors from the load. Of course that works okay to protect humans from downstream loads' enclosures being live.The stupid thing about it when it comes to EVSE regulation, is it's required in UK for single phase EVSEs, which disconnects the cars' chassis from PE. Of course that doesn't help with any devices in the house where suddenly PE became essentially a phase/live. If you were to put such a device in the panel for the entire house/unit, that would make more sense. There is added risk due to much crappier PE bonding now, since it goes through a relay back to the supply.

author: uer166
author_rank: Super Contributor
timestamp: January 25, 2023, 08:57:57 pm
content: I just re-watched the video, it seems that it's not a PEN fault protection device but something else entirely. It does seem that they trip the RCCB using induced leakage current. This is explicitly disallowed (the intentional injection of leakage to trip an upstream device) by most national standards. On top of that, I don't see how the device disconnects the PE. If it doesn't, then this is basically a scam device.

author: Siwastaja
author_rank: Super Contributor
timestamp: January 26, 2023, 09:52:26 am
content: Quote from: Alti on January 25, 2023, 08:00:37 pmMaybe the phrasing on that website is odd, but here's nothing weird about it, anywhere where the physical Earth is not very conductive (for example, granite bedrock), one fully relies on having an explicit PEN conductor. This conductor isn't supernaturally tough, so it can be damaged like any of the other wires (out of total 4). But while cutting a phase only cuts the loads connected to that phase, while not affecting phase-to-neutral voltages of the other phases, Neutral is special in such way that if you cut neutral, then the line-to-neutral voltage will vary, up to line-to-line voltage, based on loads connected.This is the inherent design flaw of:* Using TN-C, TN-S, or TN-C-S earthing system,* Having highly resistive soil type* Using 3-phase system where line-to-neutral voltages are being used to power loads (wye configuration).* Using overhead distribution (countrysides)Finland is not the only place on Earth to have this, I guess.But if I recall correctly, Norway uses delta connection in distribution, so loads are always connected between phases, and voltage can't get any higher if you cut any of the three wires.

author: dmills
author_rank: Super Contributor
timestamp: January 26, 2023, 11:07:37 am
content: Quote from: uer166 on January 25, 2023, 08:54:33 pmThe difference is that a EV is one of the only places you will see a PE conductor exported from the "equipotential zone". Assuming TN-C-S supply (Normal in the UK), inside the house all the metalwork (Taps, pipes, and such) that might bring in a 'earth' at a different potential to the PE conductor are bonded together and to the PE. This means that in the event of a neutral fault the PE might rise up, but everything in the house will be at the same potential relative to ground so no shock. You cannot practically do this with a heavy power line run out onto the drive way.If you look at garden tools you will discover that most of them have 2 core supply cables and double insulation to get around the need to export a ground.Arguably the easy way would have been to make an EV a ground free device and just feed it with phase(s) and neutral, but I can see squabbling about EMC issues if going there.An alternative approach is to convert the property to TT earthing with a mess of ground rods to try and get the impedance low enough, but while sometimes done by radio hams it is rather more of an invasive change then just adding an extra little box in the wall box doings.

author: gf
author_rank: Super Contributor
timestamp: January 26, 2023, 12:12:50 pm
content: Quote from: dmills on January 26, 2023, 11:07:37 amFoundation earthing, and having the "equipotential zone" and PE connected to earth is state of the art today. At least in the country where I live. Old buildings/installations are an exception, though, they may not have local earthing at all.

author: Siwastaja
author_rank: Super Contributor
timestamp: January 26, 2023, 12:20:55 pm
content: Let's say your house is build on granite bedrock directly. How do you ground anything to the actual ground? Even if you drill holes, granite is still insulator.Actual ground is pretty good fordetectingfault currents - i.e., to provide high-resistance path to current, enough to trip RCDs (either for human protection (<30mA) or fire protection (>30mA)). But to provide reliable return path for actual load currents - this is not an option everywhere.

author: themadhippy
author_rank: Super Contributor
timestamp: January 26, 2023, 02:04:50 pm
content: Quoteno need to convert the property,just the circuit going outside the equipotential zone.

author: uer166
author_rank: Super Contributor
timestamp: January 26, 2023, 07:02:48 pm
content: Quote from: dmills on January 26, 2023, 11:07:37 amit's a safety issue for US and other regions that rely on PE bonding for safety. AFAIK most EV's traction systems have basic insulation to the chassis (and maybe also basic from mains input of OBC to chassis? I don't remember), and in some of these instances, an insulation failure is mitigated via a bonded chassis and PE conductor that can carry the full fault current of a few thousand amps.

author: dmills
author_rank: Super Contributor
timestamp: January 26, 2023, 09:57:05 pm
content: Quote from: themadhippy on January 26, 2023, 02:04:50 pmTrue, but can be much trickier then it at first appears, played that game with an outbuilding once because I wanted to use it as a radio room and had all sorts of aerials and metal structure connected to it.Even finding a sparks who was comfortable with it was harder then you would expect, and I can see an argument for making a charging point easy to install by a hot very skilled electrician.

author: Alti
author_rank: Frequent Contributor
timestamp: January 26, 2023, 10:05:12 pm
content: Quote from: Siwastaja on January 26, 2023, 09:52:26 amThere is. You live in Finland and you see that every day but believe me - we do not have such overhead designs elsewhere. I meant: How does such overhead line with phase conductors supported by PEN cable look like? Could you post an example photo?Quote from: Caruna.fi

author: Siwastaja
author_rank: Super Contributor
timestamp: January 27, 2023, 12:14:15 pm
content: Quote from: Alti on January 26, 2023, 10:05:12 pmhttps://mycourses.aalto.fi/pluginfile.php/1473286/mod_resource/content/3/S%C3%84HK%C3%96ENERGIAJ%C3%84RJESTELM%C3%84N%20RAKENNE%20JA%20OSAT.pdfSee page 9 for imagesThis is for low-voltage distribution, on countryside. More densely populated areas have been converted to underground cabling of course.

author: Alti
author_rank: Frequent Contributor
timestamp: January 27, 2023, 04:48:39 pm
content: Quote from: Siwastaja on January 27, 2023, 12:14:15 pmAMKA cables. OrAerial Bundled Cable.Overhead lines are popular of course but it is the first time I see a bare PEN conductor that serves as mechanical support for phase conductors.. I thought such cables have an additional steel strand that serves as mechanical support.An AL+FE version ofPEN.And some bigclivedotcom YT:

author: Siwastaja
author_rank: Super Contributor
timestamp: January 28, 2023, 07:40:16 am
content: Quote from: Alti on January 27, 2023, 04:48:39 pmLooking at a datasheet for a cable used here, it says the conductors are just aluminum, but the supporting bare wire is aluminumalloy. So probably some alloy with better mechanical strength. Not going to beat steel, of course.I would assume such bundle almost always breaks as a whole, making neutral faults rare (or last for only some milliseconds). But it's impossible to completely eliminate neutral wire from breaking as long as the wire exists.

author: okaro
author_rank: Newbie
timestamp: January 11, 2024, 09:11:28 pm
content: Quote from: uer166 on January 25, 2023, 08:54:33 pmEVs are a large grounded item that is straight on the ground so the risk is seen as high. Also they are a new thing. It is easier to make requirements when people install new things than to to regulate afterwards. When you are inside bonding protects you from shocks between grounded items and metallic surfaces like taps. There are some 400 PEN-faults in the UK annually with some 40 injuries (electric shocks).

author: excrucio
author_rank: Newbie
timestamp: January 01, 2025, 11:42:01 pm
content: So, this is inside of ithttps://youtu.be/kBxAjbUnYos?si=SDFH6r0xE856L2yl&t=440Inductor...What is principle behind it?

author: f4eru
author_rank: Super Contributor
timestamp: January 07, 2025, 07:16:40 pm
content: Seems like an LC network, i.e defined impedance that is connected between neutral and PE ?then it triggers an RCD if the neutral deviates from PE.Works only of course if the defect is after the bonding point, or if the PE comes from a separate earth rod...Could it be that the LC is tuned to 50Hz, so that normal sine does not pass, but HF/harmonics of DC will trigger the RCD ?I would have expected more like a 25V VDR or so.In any case, it's probably not nice, because injecting currents into the RCD can make it inefficient against it's original purpose....

author: excrucio
author_rank: Newbie
timestamp: January 07, 2025, 09:41:27 pm
content: Quote from: f4eru on January 07, 2025, 07:16:40 pmthere is no current until it is N fault, and when it is it is not big. so rcd works as it is intended

author: f4eru
author_rank: Super Contributor
timestamp: January 09, 2025, 07:18:39 am
content: not really. There are often a few volts between PE and N.If it would trigger suddently, and then connect a resistor between L and PE, having the same effect as the RCD "Test" button, then I would agree that it does not affect the RCD.

author: themadhippy
author_rank: Super Contributor
timestamp: January 09, 2025, 10:50:29 am
content: Quotethats not how the test button is wired as the PE rarely goes anywhere near the rcd,its wired across the incoming side and the output side

author: uer166
author_rank: Super Contributor
timestamp: January 09, 2025, 09:29:50 pm
content: Quote from: f4eru on January 09, 2025, 07:18:39 amAnd to be clear: triggering a upstream RCCB/RCBO via leakage to PE as a safety function is specifically prohibited by most product and installation standards both in EU and NA, it's a janky and dangerous way to go about it.If you need a remote trip, use a shunt trip attached to a breaker or something, don't be cheap about it.