Neutral line fault detector NFP-1801?

[nardev]

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

[f4eru]

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 fact
3) not sure if protected/safe from a few aspects, would like to see the inside
4) Would probably have false positives in situation like lightning
5) does not protect downstream (3-phase home only)

[nardev]

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?

[f4eru]

hmm.. No CE marking. does not look good yet for compliance, but they will probably improve that over time.

[nardev]

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. 

[f4eru]

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.

[mikeselectricstuff]

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 fault

This is a similar device : https://matt-e.co.uk/

[excrucio]

No review?
Device is certified for EU.
CE is there.

[uer166]

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)

Which 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..

[uer166]

No review?
Device is certified for EU.
CE is there.

I 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".

[max_torque]

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)

Which 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..

Added 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........

[richard.cs]

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.

[dietert1]

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

[Siwastaja]

it may be useful in countries with bad electrical infrastructure, where shoddy neutral connection is a real risk.

For example, Finland. We take pride of our "good" grid infrastructure, yet N fault (or PEN fault) is something that does happen 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-fault

Yet, realistically, I don't think anyone has actually died due to neutral fault in decades.

[Alti]

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.

Indeed, 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.

And the advice is nearly hilarious.

A neutral fault in the electricity network is usually caused by a tree falling on a power line, disconnecting the rope that supports the bundle assembled aerial cables of the low voltage network, known as the PEN conductor, which is a metal cable that supports the phase conductors between poles.

I have to visit Finland. Crazy, can you show some photos how this Finnish PEN looks like?

[uer166]

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?

No, the way PEN fault protection devices work, is they disconnect 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.

[uer166]

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.

[Siwastaja]

I have to visit Finland. Crazy, can you show some photos how this Finnish PEN looks like?

Maybe 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.

[dmills]

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.

The 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. 

[gf]

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.

The 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.

Foundation 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.

[Siwastaja]

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 for detecting fault 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.

[themadhippy]

An alternative approach is to convert the property to TT earthing

no need to convert the property,just the  circuit going outside the equipotential zone.

[uer166]

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.

it'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.

[dmills]

no need to convert the property,just the  circuit going outside the equipotential zone.

True, 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. 

[Alti]

I have to visit Finland. Crazy, can you show some photos how this Finnish PEN looks like?

Maybe the phrasing on that website is odd, but here's nothing weird about it

There 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?

the PEN conductor, which is a metal cable that supports the phase conductors between poles.

[Siwastaja]

I have to visit Finland. Crazy, can you show some photos how this Finnish PEN looks like?

Maybe the phrasing on that website is odd, but here's nothing weird about it

There 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?

the PEN conductor, which is a metal cable that supports the phase conductors between poles.

https://mycourses.aalto.fi/pluginfile.php/1473286/mod_resource/content/3/S%C3%84HK%C3%96ENERGIAJ%C3%84RJESTELM%C3%84N%20RAKENNE%20JA%20OSAT.pdf
See page 9 for images

This is for low-voltage distribution, on countryside. More densely populated areas have been converted to underground cabling of course.

[Alti]

This is for low-voltage distribution, on countryside.

AMKA cables. Or Aerial 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 of PEN.

And some bigclivedotcom YT:

[Siwastaja]

AMKA cables. Or Aerial Bundled Cable.

Looking at a datasheet for a cable used here, it says the conductors are just aluminum, but the supporting bare wire is aluminum alloy. 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.

[okaro]

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.

EVs 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).