earth leakage

[Exfarmer]

Anyone had issues with earth leakage on the DC side. Not sure if this really possible due to the nature of DC. However we have recently installed two new Fronius inverters and both are consistently tripping out error State 475 Earth leakage, whenever it rains

 

[Servac]

If one side of the DC circuit is grounded then I cant see why you couldnt have earth leakage in a DC system, and I cant see why the fault couldnt be traced with an insulation resistance tester on a rainy day, just in the same way as you would in an AC system.

 

[Exfarmer]

If one side of the DC circuit is grounded then I cant see why you couldnt have earth leakage in a DC system, and I cant see why the fault couldnt be traced with an insulation resistance tester on a rainy day, just in the same way as you would in an AC system.

Can be a bit difficult on a big roof covered in panels, but should one side be grounded?

 

[Servac]

I dont know, never done anything with renewables tbh.

Edit. Quick look on google seems to suggest so.

 

[Servac]

 

[f0ster]

you might find one of the mc4 connectors shorting out when it gets wet, they are supposed to be water proof but water can get in if they are continually immersed, always best to tie up the mc4 connectors behind the panel, there are usually holes on the back of the panel edges for this purpose

 

[rogeriko]

During startup and every now and then the inverter tests the resistance between the panels and ground and if it is less than 8 megaohms it flags up this fault. The resistance value can be changed or disabled on most inverters and they will work fine. ABB recommend changing it to 2 megaohms to stop their inverters tripping out. You will never find the ground fault on a roof of panels because it could be several panels with a tiny short to the frame on each one. Find out from the installers/manufacturers how to change the setting. SMA inverters you can completely disable this feature.

 

[Exfarmer]

Interesting how these inverters are set up.
I have virtually all Fronius. The range of Resistance settings is from 33K Ohms through 100K to 500K ohms And I can see no reason why one should be safer than another.
Problem I have is that these new ones are set at 100K ohms, the ones they replaced have no resistance trips and the damp resistance drops to 40 depending on how many strings are attached. The earth leakage is widely spread, I do wonder if the others on this array are actually wired in, hoping to have another dig tomorrow.
The Fronius inverters do not appear to accept changes below the factory preset although they accept up 99M ohm if wanted

 

[rogeriko]

You probably need a code to change them below their current settings. Have you called fronius to ask them.

 

[Exfarmer]

You probably need a code to change them below their current settings. Have you called fronius to ask them.

Have spoken to Fronius and they have sent me four pages of waffle. Fairly certain it needs a man with a laptop to adjust it, but not sure Fronius would do that.
you may be right though if we can get deeper into the system via the touchpad. I am aware these controls systems have many levels. Will keep working on it

 

[Exfarmer]

Have finally got to the bottom of the issue.
All previous Fronius models flashed up a warning when they detected low resistance in the PV insulation
This warning could be adjusted to the differing levels considered correct for the size of array
So the small ones were set at 500K ohms
The largest model was set at 30K ohms
The industry standard for a 20 Kw array is a minimum resistance of 30K ohms
it seems Fronius in their wisdom for the UK and probably the rest of Europe have set a trip into their latest machines at 100K ohms
This is a trip rather than a warning message.
So anyone considering replacing an inverter needs to take great care on this issue.
All PV arrays will have a level of leakage, for a 500 kw array 1K ohms is accepted. There is any number of ways the damp can affect a system no matter how carefully the wiring is done.
I am in the situation where we specified Fronius on an upgrade after an issue because we believed that they offered the best service.
It seems to have back fired badly.
This is not a safety issue unless warning messages are ignored totally
The power is still being generated by the panels whether the inverters feed it into the grid or not
There may be 2 Fronius Sumo inverters up for sale soon very little work done! Hopefully Fronius will adjust the settings though
I will keep posting