High Voltages Causing Inverter Trip-Out

We fitted a solar system some 2 years ago which has been working fine iuntil about 3-4 months ago when the customer reports his inverter keeeps cutting out. Cuase of this is the grid supply which keeps hitting 250V (max allowed 253v) not leaving any room for inverter to operate under G83 requirements. NOw we have contacted Western Power to go investigate, but I'm half expecting WP to say 'it's in tolerance, tough titty'. I am therefore after a potential solution to problem should that occur. I have considered something like a v-phase, but apparently that's not suitable. Only real answer that I can think of is getting WP to sort out their system, or setting voltage parameters higher which contravenes G83 requirements.

To be fair I would expecting the dno to say the same. It's hard enough to get them to do something with their voltage when it's not in tolerance let alone when it is actually within tolerances! 

Bit of a discrepancy between inverters, the voltage in this country and G83 to a laymen like me. Was voltage checked before installation could it be that customers with voltages at the higher end of the scale are not suitable for pv? 

Has the voltage changed dramatically? Must admit I've never seen voltage to change at a customers by more than a coupe, of volts (unless they have a low voltage problem). 

Sorry for more questions than answers. 

yer, try a massive massive big cable,

is it a long run?

whats the inverter cut-off?  263v?

the problem is volt drop from inverter back to the head.

I'd hazard a guess its wired in 2.5 T&E, 4mm might solve the issue.

A company I sub to i stalling solar pv has installed Marshall tuflex voltage optimisers on jobs where the incoming supply has been to high. They have done a few of the 100a units & havnt had any problems after a couple of years.

Voltages around here are normally around 245V, which inverters can handle. The inverter is a Fronius IG35, which displays 250V then cuts out - i watched it do this a few times, should have taken test gear and measured exactly what it went upto.

have looked at several VO units, and they all say PV needs to fed into unit on mains side, defeating the object, plus it won't feed back into grid anyway, plus capacitors can effect shut down to grid.

Can't remember what we wired that rig in Steps, think it 2.5 flex from memory, (might have been 4mm) - looks neater when clipped to wall in garage and feeds through glands straight into inverter. Cable run is only about 5m to cut out on TT system

manual unfortunately doesn't say what upper grid voltage is tolerated, no doubt G83 settings - I'll have to look these up - its been a while since the course lol.

R1+R2 for circuit 0.5 hms Rod 209 hms

wozz said:

... could it be that customers with voltages at the higher end of the scale are not suitable for pv? 

Click to expand...

this certainly has lead to arguments, but usually countryside locations at end of overhead power lines.

could there be an issue with regard to the resistance to earth?

is the inverter simply shutting down, or is it taking out the RCD?

I dont have a IG35 manual here, only IGxxTL manuals, and they dont allow 30mA protection on them, most SMA are the same, and with SMA the Ze needs to be a lot, LOT lower than 209 ohms

rcd fine - weve had rpblems with TL range and fitted type s rcd for this installation. Soon as voltage drops, inverter is straight back on-line - its doing exactly what it needs to do.  I think the only way around this is to re-set some upper voltage parameters,  not increasing the voltage, but resetting time it takes to trip out ie lengthen it. Something has changed in local area, customer reports £300 down on same time last year

manual too lrge to post on here, link is to Fronius website - if you fancy a read look at operating manual.

http://www.fronius.com/cps/rde/xchg/fronius_international/hs.xsl/83_13017_ENG_HTML.htm

inverter is set for 262V max allowed 264V

you need to check the voltage at the inverter,

remember the one I went to a while back?

it was reading bang on 263 at inverter when it tripped.

Sunnyboy on a TT

yep sounds about right Steps, but must be some Volt spikes to take out inverter set for 10V higher than top limit of grid. Would suspect it must be hitting 255V at least.

Think it might be worth fitting simple surge suppressor if WP decide to do nothing??? Certainly easy enough to throw bigger cable in if you really think that would improve situation. I have to say I now fit 4mm as standard, mostly becuse my local Denmans has large stock at good price they bought to service a competitor. Will also contact Fronius service dept, see what they have to say.

I dont think bigger cable will help such a short run in any great way.

for that run I take it you never calc'd VD, I wouldnt have,

I wonder just how much higher the Fronius needs to put out to 'push it back'  ?

the one I looked at was a stupidly long run, and the source was never over 253 the whole time I measured for, over an hour, but the inverter tripped on quite a few occasions,

this was cutting out, restarting, cutting out, restarting etc never got more than a few minutes, voltage would drop to 245/248 then creep back up to 250 (as shown on inverter display) then cut out again. Really annoying.

Did you do a Z L-N when you did the install?

Is the "Ze" still around where it was when you installed the job?

Does this happen when the house is consuming a lot of power?

quick update, Western Power have installed data logger to monitor voltages.

Anyone know of a good supplier of surge suppressors - I'm thinking if necessary we stabilise voltages to take out spikes.