Eversolar 4000TL inverter issue

[STEL]

Hi,

Problem arisen with a solar pv system installed in December 2011.

Eversolar 4000TL connected to 16 250W Suntech panels (1x string)

Worked fine until 3 weeks ago where a problem has developed in bright sunshine, inverter makes a loud clonk and cuts out.

Reads error code: UAC failure, reconnection pac = 0.0w

Inverter datasheet states: max DC current 680 and MPPT voltage range: 115 - 550.

suntech panels datasheet: optimum operating voltage 30.7, Open circuit voltage: 37.4.

Suppliers have said that it should have been one String as the max MPPT is 550 and the voltage running through one string could be over 600V (not sure where they're getting that number from)


Are they correct, should it have been one string? I find that hard to believe usually if that's the case the inverter has an error message immediately, not 18 months down the line. Second question, is the inverter now damaged, or will switching it to two string fix the problem?

Thank you in advance for your help!

 

[infinity]

2 strings

 

[dansk]

We do these in two strings. it will work as one string but its too close to call/for comfort - hence the cut out.

Having said UAC - Utility AC? over voltage on the AC side? i checked the manual but didnt see that exact problem.

 

[Gavin A]

yeah looks like grid over voltage, with the high output pushing the voltage over the limit.

 

[STEL]

Ok we're going to switch it to two strings, i figure the inverter is switching off to prevent damage so it'll run 2 strings fine. Bit odd it took 18 months to decide it doesn't like the high voltage though.

 

[dansk]

it could be high voltage on the AC side not DC side.

 

[STEL]

So is that not an inverter issue? But a problem on the grid side, ie voltage problem within the house?

 

[STEL]

Hmm ok, any tests we can do to confirm this?

 

[Earthstore]

If it says VAC too high, would that be the panels DC causing it?

And it is strange that it took 18 months to show too.
Have you checked the incoming AC voltage, is there more PV installed locally, could there be a bad connection somewhere on you AC cable causing a resistance as that may push the inverter AC voltage up.

Just some thoughts..

 

[STEL]

It's a very long ac run, perhaps the cable is undersized?

 

[Earthstore]

What size is the cable, what is the length of it, have you done your VD calcs? and how come it has worked for 18 months???

 

[Worcester]

As more local PV is added , it will push up the local voltage as it all tries to backfeed the grid, so if that is the case , it makes sense that it could have taken 18 months to get to that point and only now is the voltage on the AC side to high. the DC side will have no effect on it. An undersized AC cable (it really should be 6mm2 minimum) will have an effect on the voltage drop / rise between the grid connection and inverter, dependin upon how long the cable run is.

Q: -
1) What size cable? and
2)what length between grid connection and the inverter?

 

[STEL]

6mm cable with an armoured section as its a ground mount array. 35m cable run.

 

[Worcester]

For one your cable is undersized, you have a voltage drop of about 1.35% whereas the limit is 1%, it should be a minimum of 10mm2
@ 1.35% you are adding 3.1 volts to the incoming.

Next thing to do is to accurately measure the Vrms at the point of connection to the grid. That way you'll either prove or otherwise the Overvoltage issue.

 

[STEL]

We're going to the installation tomorrow to run some tests. The owner says there's been only one additional solar pv installation in the area (it's pretty remote). Thanks for your suggestions, all are welcome!