V2L Earthing - how?

[1Pawn]

Thank you for your well considered comment that contributes so much to the discussion on this thread. But before I invest £7000 (according to the Energy Saving Trust) on a solar PV system - and that doesn't include battery storage - please would you answer a couple of questions:
1) In the event of a power cut by what magical process could the 218V generated by my V2L bridge an open RCBO, RCD, MCB or main breaker?
2) Assuming the fairies were playing tricks, how many millivolts could my V2L deliver to the load presented by 25+ properties sharing the same phase between here and the nearest substation?

Zero volt, since the breaker will immediately trip (too much current).

The back feeding wouldn't last a second

 

[Staffex]

Zero volt, since the breaker will immediately trip (too much current).

The back feeding wouldn't last a second

 

[Tim Green]

Do breakers trip with the current flowing backwards?

 

[1Pawn]

Do breakers trip with the current flowing backwards?

Sorry what is backwards?
Do you see the marking "input and output" on it?
Do you see a left or right on a fuse?

 

[Staffex]

Sorry what is backwards?
Do you see the marking "input and output" on it?
Do you see a left or right on a fuse?

The official line is that bi-directional RCBOs etc. have a different arc quenching arrangement. Really? Perhaps someone on this forum with a background in plasma physics could give us an explanation. Or maybe it's just a marketing ploy - a bit like those special 'digital' tv aerials that appeared when Freeview was introduced.

 

[Tim Green]

I accept it's not my field, but most breakers have an accepted input and output, and they are not fuses, which are obviously bi-directional. I have never examined how breakers work so would take the conservative route.

 

[Coulomb]

Most of the breakers will be experiencing power flow in the normal direction, towards the loads. The main breaker to the grid will be carrying no load. It's only the breaker on the circuit with the suicide outlet that will be running backwards. If you power the house via a generator input switch (i.e. do it properly), then no breakers will be operating under non-zero load in the wrong direction.

 

[blippy]

The house breaker will never trip on overcurrent because the short circuit current will be whatever the V2L output maximum is, which generally will be nowhere near enough for an overcurrent device to trip except perhaps if there a 1 or 3A circuits in the installation. RCDs will not function because there is no parallel return path unless the car N is bonded to house earth (and a local rod present).

JD and others have some good videos about IT based generators and their use as supplies to fixed installations and I would suggest anyone attempting this (in my view, very ill-advised) exercise watch them.

 

[1Pawn]

The house breaker will never trip on overcurrent because the short circuit current will be whatever the V2L output maximum is, which generally will be nowhere near enough for an overcurrent device to trip except perhaps if there a 1 or 3A circuits in the installation. RCDs will not function because there is no parallel return path unless the car N is bonded to house earth (and a local rod present).

JD and others have some good videos about IT based generators and their use as supplies to fixed installations and I would suggest anyone attempting this (in my view, very ill-advised) exercise watch them.

The breaker of the plug that he is using to backfeed will trip.
The car itself will limit the output as well.
And the RCDs will work: I agree neutral of the car need to be bonded with the ground of the house.

Not sure what is ill-advised? I understand pessimism and critics. I understand recommendations about how to safely to things. But would you please allow me and others to fully benefit from features of our (well paid) cars?

A car parked in front of the house serve no purpose. If instead is acting as storage, I see it being much more useful.
What's the real reason why you are against this?

 

[blippy]

The clue really is in the name - it is not vehicle to grid. It is not tested nor approved for connection to a fixed installation. Who knows how it would perform under the full spectrum of fault conditions, for example a power cut could be a loss of PEN (or just N upstream). Does that leave the car bodywork itself live? It might do, due to the combined resistive load of other dwellings I suppose. The very connection of it depends on multiple manual steps, error or omission of which could easily be fatal. And errors made in the process the other way could conceivably damage the vehicle itself, maybe even causing a fire.

Still, several contributors to this thread have warned against doing this. It is most definitely against the wiring regulations and by extension could lead to criminal proceedings in the event that something horrible were to happen.

 

[aserraric]

V2L is intended to supply a single load directly from the car. It was designed for this purpose and this usage is safe.

To attempt to run your entire house off the car is ill-advised in several ways:

• You cannot convert an IT supply into a TN-S network simply by grounding. About the only safe way to do this would be to galvanically separate the two with a transformer (or a separate rectifier/inverter, but that increases losses way too much)
• And that's not even taking into account houses with 3-phase supply.
• You have to ensure to never connect the car and the grid in any way. A single mistake can lead to danger to human life and damage/destroy involved devices (i.e. the car and all infrastructure in your house).
• In turn, this means every time you want to switch between car and grid, everything will be unpowered for a second or longer. Aside from the inconvenience of losing clocks and settings all the time, this will shorten the lifespan of electronic devices exposed to those short outages regularly.
• Again, all this is way out of the design specifications for the car. Solar inverters and switches that allow for gridless and grid-connected operation are expensive because they were designed to do this safely and reliably.

Would I use this in a emergency (prolonged power outage) to connect some essential loads like a freezer, heater etc while they are disconnected from the house network? Absolutely, with the knowledge that running more than one load is a calculated risk I would be willing to take, because of emergency. Would I connect it to my entire house as a power storage? You couldn't pay me to do that.

 

[1Pawn]

Assuming one is using an automated transfer switch, like with any generator, I don't see any meaning in your doubts.
Once the transfer happened, the house is just a bunch of loads. Nobody is talking about V2G here, since the vehicle and the grid have nothing to do with each other.
What manual actions are you talking about?
Who cares about the PEN from the grid. if the grid is completely disconnected by the transfer switch, and the grounding rod of the house is connected to the neutral of the car?
Why would the same RCDs inside the house fail to work, if they are doing exactly the same job as before?
No worries, nobody will pay you to do anything, and you'll not be responsible about the fires deaths and explosions in and around my house (lol).
I have already the exact same setup: IT inverter hooked up to a transfer switch that feeds the house.
If you feed the switch with a car, a petrol generator or a windmill doesn't change a thing.
The RCDs are perfectly working, neutral and ground are connected, and I don't see any difference between the grid and the generator.

Doom' s day will happen anyway regardless of the above: I suggest you try to live with limited fear until then

 

[aserraric]

I don't know why you feel you have to condescend to people who disagree with you.
You asked why people say this is a bad idea, I told you my opinion. I'm not going to lose a minute of sleep over what you do or do not do. You do you.

 

[Staffex]

V2L is intended to supply a single load directly from the car. It was designed for this purpose and this usage is safe.

To attempt to run your entire house off the car is ill-advised in several ways:

• You cannot convert an IT supply into a TN-S network simply by grounding. About the only safe way to do this would be to galvanically separate the two with a transformer (or a separate rectifier/inverter, but that increases losses way too much)
• And that's not even taking into account houses with 3-phase supply.
• You have to ensure to never connect the car and the grid in any way. A single mistake can lead to danger to human life and damage/destroy involved devices (i.e. the car and all infrastructure in your house).
• In turn, this means every time you want to switch between car and grid, everything will be unpowered for a second or longer. Aside from the inconvenience of losing clocks and settings all the time, this will shorten the lifespan of electronic devices exposed to those short outages regularly.
• Again, all this is way out of the design specifications for the car. Solar inverters and switches that allow for gridless and grid-connected operation are expensive because they were designed to do this safely and reliably.

Would I use this in a emergency (prolonged power outage) to connect some essential loads like a freezer, heater etc while they are disconnected from the house network? Absolutely, with the knowledge that running more than one load is a calculated risk I would be willing to take, because of emergency. Would I connect it to my entire house as a power storage? You couldn't pay me to do that.

IET On-Site Guide: 2.4.3 “Where there are extraneous conductive parts…from other electrical systems present, generator reference earthing, by means of an earth electrode…should be installed…the system will be TN-S in form from the generator…”

 

[blippy]

The need for an earth electrode was also mentioned earlier.

Just a thought - if the floating neutral is referenced to true earth, and not bonded to the car chassis - where does that leave the car chassis?

 

[Staffex]

The need for an earth electrode was also mentioned earlier.

Just a thought - if the floating neutral is referenced to true earth, and not bonded to the car chassis - where does that leave the car chassis?

It leaves the car's chassis 83V above earth! So MG's V2L implementation doesn't comply with the IET regulations for portable generators. The only mitigating factor is that an earth leakage of just 1.2mA is sufficient to halt the discharge.

 

[Coulomb]

It leaves the car's chassis 83V above earth!

How did you arrive at that figure? It sounds like small EMI capacitors to earth are involved. These can essentially be ignored, i.e. you can safely earth the neutral by other means and only small EMI pulse current will flow in the earth wiring.

 

[Staffex]

How did you arrive at that figure? It sounds like small EMI capacitors to earth are involved. These can essentially be ignored, i.e. you can safely earth the neutral by other means and only small EMI pulse current will flow in the earth wiring.

See post #87. It also explains why a simple socket tester raises an earth fault warning when plugged into the V2L lead.

 

[Jomarkh]

This might be of interest to some of you guys.

 

[Staffex]

This might be of interest to some of you guys.

Wow, quite depressing isn't it? John's impeccable logic leads him to conclude that on non-TT supplies (the majority of those in the UK) outdoor charging points should only be installed in conjunction with a 10-20 square metre earth mat!

Or perhaps a cheaper alternative would be a 7kW continuous-rated isolating transformer combined with a simple earth stake... Victron Isolation Transformer 7000W 230V