Diehl AKO Platinum 3800S dropping out

[Markc]

Hi All,

We have a problem on an installation that is getting worse and I haven't any joy with the supplier.

The system is 16 x Sanyo HIT250, South facing 30 degree (ground mount) zero shading. The system was installed in May this year and worked very well for the first month. Then it started to drop out once or twice a day from midday to 3pm. Now it starts dropping out at about 10am to 4pm and can be over 100times a day.

When I talked to Deihl Germany and gave the fault code they said high grid voltage is the problem. So DNO in to monitor the voltage. One week later and this proved not to be the case and voltage is within guide lines. So back to site and checked resistance and voltage again.

The array is 52mts from the sub main. Underground cable in duct. 10mm 3c SWA. The sub main is wired back to incoming supply 10mm T&E and 6mm T&E. No load on this submain as is now only doing PV system. Possible length of this is 40mts.

When the PV kicks in the AC voltage goes high to 255-257 before dropping out.

We have swapped the inverter for the same model but again it happens on this also so swapped it back again.

We are now looking to install as a temporary trial a 10mm T&E direct off the incomer to the inverter a length of approximately 70mts straight line. Just to see if this helps.

The supply to the property is TNCS and all the incomer is good etc. Tested well and under 0.35 Ze

Anyone any other ideas or things to try.

Thanks

Mark C

 

[malcolmsanford]

Would a volt drop affect it Mark

 

[Markc]

I had considered VD on design and hence the 10mm SWA supply cable. Now seeing the installation in place and measuring the voltage on TRMS I'm more concerned it could be over voltage?

The grid voltage at the inverter is anything form 244 to 252. Once the inverter kicks in this rises to 257 to 259 before the inverter drops out. Once dropped out the voltage appears to be 244 (ish)

The display to the inverter gives us this info but I am concerned now as of today that there seems to be a greater difference between the DC V,A & W to the AC from what we have seen of other installations of the same design. One of the biggest differences between this system and other is the length of run from inverter to point of incomer. So yes VD is a concern but it isn't what is being displayed.

I have a thought the overall resistance of the supply is a concern? And causing the output voltage of the inverter to rise to produce the "push" required?

Thoughts?

 

[SolarCity]

I agree that volt drop appears to be the most likely issue.

 

[SolarCity]

Have you tested the voltage at the AC isolator (with the inverter switched off) and checked the voltage at the incomer?

 

[Markc]

Yep. Around 244 at incomer and Isolator.

I've thought no different than what you are all suggesting. With our metrel meters at the origin and isolator (simultaneously) we get about 1 to 1.3V difference with the inverter isolated. Have not done it when in generation but it's a thought for Monday.

The grid voltage can sit at around 244 until the inverter kicks in then it rockets to 250+ within seconds. Once it reached anything between 257 and 259 according to the display on the inverter and it then drops out but then instantly changes back to 244. Our metrels show about the same at the inverter.

I am planning come Monday to throw some 10mm T&E in as a trial to see if this relieves the problem. We can get a cable a much shorter route if we lay it straight across the garden.

Cable calc at 1% showed 10mm SWA was fine (and that's at 70 degree C) but I must admit I didn't consider the sub main supply! My fault if it is the case.

 

[daytona600]

try a eltek theia 3.8het if you need a transformer inverter for hybrids , higher effciency as well with webserver

 

[Markc]

You may need to send me more info on that please.

 

[Markc]

Further news on the problems.

Today was spent on site again all day.

We installed a 10mm T&E as I said across the garden and into the plant room to ensure we are on our own healthy supply. Once the inverter got close to max output the inverter dropped out. The display voltage was around 255V, 15A.

We have now moved the inverter into the plant room. Converting the 52mts of 10mm 3c SWA into a DC cable and keeping the 10mm T&E (50mts) as a clean supply. Loosing time today meant we lost the best part of the day for generation so no drop out on this, however the voltage readings seem to indicate it will (around the same wattage output to similar voltage) So AC side is 50mts 10mm T&E and DC is 52mts 10mm 3c SWA.

The system was commissioned on 2nd June 2011. Ran with NO problems until 9th July. Since then it has dropped out almost every day. Anything from 10 to 60 times.

Looking at the clients detailed recording of drop outs and generation we can see a drop from around 30kWh per day to about 6kWh. Average about 10 or 12kWh per day. Yesterday 21st August the system did NOT drop out at all and the generation level maxed at 3500kW So why didn't it drop out yesterday? Same supply, voltage etc.

The property is an overhead supply, 60amp, TNCS. DNO are going to upgrade overhead cable to property. Don't know why. The DNO have monitored the |TX and point of origin within the property for a week. The graph shows the maximum voltage of 252.5V only half a volt under the max!

The array is 16 x Sanyo HIT250 and inverter is Diehl AKO Platinum 3800S, just to refresh. A similar system all be it roof mounted works fine and I have checked this also.

Still scratching our heads here and need to act fast to keep the client happy.

Again gents, your thoughts?

 

[SolarCity]

I still think it may be volt drop. This may sound drastic but it's definitely what I would do - get hold of some 32mm cable and run it in temporarily directly to the supply. If it doesn't solve it then just keep the cable in the store.

Sounds like a nightmare, Mark, and I wish I could help out more.

 

[Markc]

I still think it may be volt drop. This may sound drastic but it's definitely what I would do - get hold of some 32mm cable and run it in temporarily directly to the supply. If it doesn't solve it then just keep the cable in the store.

Sounds like a nightmare, Mark, and I wish I could help out more.

Inverter is now 50mts away from incomer and 50mts away from array. 50mts AC - 50mts DC. Today hasn't been great generation due to weather so keeping an eye on it. 1% VD comes in at 16mm but this is 70C and 0.35Ze.

Considering the Vphase unit now as well but I will need to find the reason why this is happening.

I agree to the VD however it doesn't answer why we got the first months generation with no problems? All of June was reasonable weather and longest day also so how come the problem only started around 9th July. If it is down to VD how come it didn't show its head in June? We had lighting storm on 8th July but that might be coincidence.

 

[SolarCity]

I wonder if the grid voltage is now slightly higher than it was previous to 9th July. If this was the case then the volt drop may not have been such an issue in the past but the inverter is now not capable of producing a voltage high enough to negate the VD and fall within grid parameters?

 

[BruceB]

Considering the Vphase unit now as well but I will need to find the reason why this is happening.

How will that help? You cannot connect PV through them.
Regards
Bruce

 

[Markc]

How will that help? You cannot connect PV through them.
Regards
Bruce

I don't agree this is the best course of action. It isn't a cure it's a solution. I need to know whats happened to cause the problem so I can avoid it in the future. The client is keen to explore the Vphase option so I have to look into it.

 

[Markc]

How will that help? You cannot connect PV through them.
Regards
Bruce

OK VPhase not an option!