In my solar system i do have 2 axpert kings 5 kva in parallel. When the grid is not connected to the inverters i measure between live line and nul line 230V, and also between live and ground 230V,  and between nul line and ground 0V. Result RCD's on load side working fine.

When i connect the grid towards both inverters i measure bewteen live and nul 230V, between live and ground 138V, between nul and ground 92V. Result RCD's on load side not working!

Does anyone recognize this problem and is there a solution?

In my system there is no where any connection between output inverters and grid, these are fully seperated.

Yes the inverter is isolated from the grid.  Those readings you are getting between live and ground are likely leakage current from X capacitors, so there is no current behind it.

Why on earth would you want continuity between your grid and inverter?

It sounds like your utility neutral is at fault. When in line mode, the Axpert relies on the neutral to earth connection at the utility.

What do you measure utility neutral to earth with the inverter not connected?

Thanks for your answers. When inverter not connected i measure between neutral and earth 2.4V. Would this be to high? Should i make a connection beween neutral and earth on the grid side? Or could this be a earth problem?

I try to find a solution to have a solar system turning worry free fully automatically, which is not the case till now. AC in two inverters in parallel, i have a little but to high leakage current sometimes which is tripping rcd grid to inverters. So i mounted a isolation transformer to solve this problem.  Sometimes, let's say once a two weeks, the grid is unstable. Result tripping interrupters ac in duy to low voltage. So in summer time enough energy, no grid connection. In winter time i want to leave grid connection on, when battery low automatically grid connection will be established. Not to charge the battery but just for the loads. When at home no problem, a reset is easily done. When away it would be nice to have a system 100% reliable

 

 

On 2022/02/13 at 2:13 AM, Pieke said:

When i connect the grid towards both inverters i measure bewteen live and nul 230V, between live and ground 138V, between nul and ground 92V. Result RCD's on load side not working!

I assume that these measurements are at the output of the inverter. Is it in line or battery mode when you get these measurements?

Neutral should be tied to earth either by a relay contact inside the inverter when in battery mode, or by the utility's neutral to earth connection when in line mode.

1 hour ago, Pieke said:

When inverter not connected i measure between neutral and earth 2.4V. Would this be to high?

It sounds a little on the high side, but it should not be causing any problems.

1 hour ago, Pieke said:

Should i make a connection between neutral and earth on the grid side? Or could this be a earth problem?

You have to be careful to make only one connection ("bonding") between neutral and earth at any one time in your premises. So yes, adding one could cause problems. But your premises should have one already. If it doesn't, then I'd suggest that you do add one, but I'm in Australia where regulations are different.

These measurements i get in line mode when grid is attached. Even when grid is not used but attached i get the same measurements. In battery mode without grid connection everything is fine. 

As i understood in France the bonding between neutral and earth is made by the electricity company, before electricity entering the premises. And like many other countries it is forbidden to bond the neutral and earth.

On 2022/02/15 at 9:36 PM, Pieke said:

Even when grid is not used but attached i get the same measurements.

My only guess is that your neutral "safety" relay (AC-in to AC-out) is open circuit. The only reason that the King could operate in line mode with that fault would be that it has the double conversion. Perhaps you find that it won't power loads in bypass mode (different to line mode in the King). I'm not familiar enough with King operation to know if this makes sense.

When you get these strange measurements, I assume that you would read significant voltage between the output and input neutrals; is that the case?

Edited February 17, 20223 yr by Coulomb

@Pieke

I made a quick check on my system as it is also a King (single one) and I found the following values.

Grid side (connected to the grid input on the King):

- Phase to neutral: 230v

- Neutral to earth: 1.2v

- Phase to earth: 230v

King output side;

- Phase to neutral: 230v

- Neutral to earth: 0.5v

- Neutral grid to neutral King; 0.5V

This was done on SBU working mode.

I hope it will be useful for you to figure out what's going on.

Thanks all for your answers, could not respons earlier. @coulomb is right, i measure between output and input neutrals 89V.

Could this be a malfunction between both inverters in parallel. I noticed also that when i only connect one inverter to the grid the input voltage is around 110V, and therefore no current taken from the grid!

What would happen if you take out the parallel sytem and seperate them in two different output systems?

 

4 hours ago, Pieke said:

Could this be a malfunction between both inverters in parallel.

I can't see how.

4 hours ago, Pieke said:

I noticed also that when i only connect one inverter to the grid the input voltage is around 110V, and therefore no current taken from the grid!

? I don't follow. You're not on 120 V utility are you?

in france utility is 230V, so rather strange when one inverter is connected to the grid and the other not, the grid voltage on the inverter is indicated as 110V. With both inverters connected 230V indicated, but neutral not 0V. Still don't know why this happens? The worrying thing is that the rcd's are not working on the load side when inverters connected to the grid because this. 

 

9 minutes ago, Pieke said:

in france utility is 230V,

I'm with you so far.

9 minutes ago, Pieke said:

so rather strange when one inverter is connected to the grid and the other not, the grid voltage on the inverter is indicated as 110V.

Which one indicates 110 V? The one connected to the grid or the one not connected?

Also, is this as I assume on the front panel of the inverter, or perhaps from monitoring software? Or from a multimeter? If so, connected where?

On an inverter that's not powered at all, can you measure connectivity (less than one ohm, using a multimeter on ohms range) between neutral AC-out and earth? If not, that's a faulty inverter, as far as I understand it. This would cause your symptoms.

To have two faulty ones would be very unusual, I would think, unless some sort of weird wiring fault is blowing PCB tracks or some such.

Your right, the monitor software says 110V and on the panel is indicated 230v of the inverter connected to the grid.

So i measured between ac in neutral and ac out neutral  of the inverter which is only one connected to grid. There i measure around 5V. Same value when i connect the other inverter to the grid and disconnect the first one. But now the stange part when i connect both inverters to the grid i measure a value of 95V? With both inverters disconnected from the grid the value measured is 3.3V, this should be 0V i guess.  

16 hours ago, Pieke said:

when i connect both inverters to the grid i measure a value of 95V?

There are two things that change when you parallel most Voltronic inverters but neither of these applies to the Axpert King.

Presuming that yours are genuine Voltronic King models, one King specific feature changes when units are paralleled. It is ECO mode, which is marketing speak for bypass mode, where AC-in is connected to AC out. That saves the losses inherent in double conversion, hence the ECO name. Are your inverters perhaps in ECO mode? That might explain why the connection between AC-in neutral and AC-out neutral goes away in parallel mode. 

Both inverters, axpert king, are not in eco mode. I do this in a different way, that is the inverters are switched off the load automatically when batteries are to low, the grid takes over till batteries are at least 50%. This switch between solar and grid has a delay of 2 seconds and is commanded by a raspberry pi with home assistant. 

I only need the ac in in case i have to charge the batteries due to a long period without sun!

I'm confused about when the King activates its AC-in to AC-out relays. Regardless, the AC-out neutral should connect to either earth or AC-in neutral, and both of those should show a low neutral-out to earth voltage.

I'd still like to know the resistance from AC-out neutral to earth on one of your Kings when completely powered down. I realise that this may not be convenient, so don't go to any trouble.

After a lot of research i found some answers?

When inverters are connected in battery mode without ac in connected the inverters are bounding neutral to earth, so everything is working ok. Ac out acts normal, result rcd's on my mains working fine.

If i connect ac in somehow the bond between neutral and earth disappears and i get these strange voltages. And the rcd's on my mains are not working due to these strange voltages, this is a dangerous situation. So is there a way to establish this connecting between neutral and earth automatically only when ac in is activated? Is this a solution to my problem? What would happen if the inverters are going into line mode?

 

34 minutes ago, Pieke said:

If i connect ac in somehow the bond between neutral and earth disappears and i get these strange voltages.

My guess is that you have output source priority set to utility before battery, so when you enable AC-in, it goes to line mode. Can you confirm this with your monitoring software, or via the front panel?

In line mode, the neutral to earth bond comes from the utility. It sounds like your utility's neutral to earth connection is weak or not present at all.

System is running in solar/battery/utility mode. Line mode only is used if batteries are lower then 30% at 8H in the morning. Batteries are never charged by grid. If battery state of charge is below 20% whole system changes automatically to grid, just as safety measure.

Even in SBU with ac in connected, although not used, i get these strange measurements.  Disconnecting ac in everything is fine. So connecting ac in regardless of using it, changes the behaviour of earth and neutral.  Using the grid only with no connection to solar system earth is ok, resistance is below 30 ohm, measuments made by digital earth tester. 

I can't see how the mere presence of AC-in could affect the neutral to earth voltage unless it actually goes to line mode. You haven't ruled that out completely, as far as I can see. Obviously in SBU output source priority, AC-in presence should not cause a switch to line mode, but a bug causing this is the only way I can understand your situation. 

Edit: getting late here. Perhaps you are saying that you confirmed (from monitoring software? Display?) that it is not entering line mode, except in the conditions you mention. If so, it must be turning on the grid relays in battery mode, ready for blending, and I didn't think it would do that. 

Edited March 17, 20223 yr by Coulomb