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Hi guys I hope somebody can shed some light on this problem.
We have installed (as a subby) 10 sharp 235s on a SB 2500 initially got an error which was a replacement inverter job.
new inverter same problem.
Changed inverter to 2000HF a nice bit of kit and really what i would have specced if it were my job.
this inverter is slightly easier to communicated with via bluetooth and sunny explorer.
what occurs is as the inverter starts to feed the grid the voltage rises to 264V and trips the inverter as it should.
The grid voltage at origin is 248V a bit high but nothing out of the ordinary in rural Cornwall.
I changed the upper voltage threshhold settings for a bit of a test and the inverter was peaking at 275V while generating 1kW what is going on?
Things I have checked: cable size 4mm from inverter to garage board length 1.2 m (SMA in Germany said this is perfect)
All AC testing giving great readings insulation resistance etc all as they should be no anomalies checked all connections all good!!
I have visited this job 5 times trying to sort this, i and the customer are going mental


Thanks :cry_smile:
 
This is not my area, however if you check some of the older threads this has been covered many times.
It sounds like the inverter is not set for the UK, there are 2 dials inside, one needs to be set to 5 and the other to 8.
If the inverter has run for more than 10 hours you then need a code from SMA and a laptop to reset the inverter.
Please check the threads though, as the experts on this have answered it before.
Hope this helps.

On page 6. Changing sunnyboy 3000.
 
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When you say 'garage board', is this the main board connected to the incoming mains?

264v sounds right for G83 settings so I think the chances are that it is set up correctly.
 
Check the voltage at the service head (or as close as you can get) when the inverter is outputting 275V at 1kW. If the voltage is also 275V or thereabouts it means the voltage rise/drop is external to the property which could happen if the property is on the end of a very long, thin bit of wire, which could happen in the country. That could be the case because you said the voltage has been set at 248V, which is high but within spec, perhaps with the expectation of it dropping to 230/240 once a few amps is being drawn.

If this is the situation, then the only long term solution will be to get the DNO to re-cable from the transformer with something thicker.

You need a bit more testing to be sure before you speak to the DNO.

DNO then likely to put voltage monitoring equipment in place for a bit and you would need to ensure sufficiently low and sufficiently high currents being drawn to take the voltage excursions out of spec. Subtle co-ordination with neighbours to help could be in order.

Regards
Bruce
 
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Thanks Bruce testing at origin is a good idea there is a transformer about 5 m from the property I have assumed it is feeding the property but it may not be. Which would work with your theory ie wet piece of string posing as a distribution network
 
It does happen. I had one a couple of months ago on a long country lane where there was a pole transformer on the end of a 11kV line outside a property but it was not energised because a landowner had not let the electricity company onto their land to cut trees away from the 11kV line because his wife thought the trees looked nice. WPD could not be ärsed to fight the person so just connected my customer and another dozen houses to an already loaded transformer half a mile away, with predictable consequences.
 
Just before I get too excited is there the possibility that a circuit with a very high resistance within the property could also cause this?
 
Yes, of course. One high resistance joint somewhere between the inverter output terminals and service head.
 
the main incomer comes in from an outside enclosure containing the wpd fused cutout on 16mm tails into henley blocks which in turn feed the consumer units. It is these henley blocks which the 10mm tails feeding the 2way garage consumer unit are connected to we have checked these connections and they are in sound condition
 
the main incomer comes in from an outside enclosure containing the wpd fused cutout on 16mm tails into henley blocks which in turn feed the consumer units. It is these henley blocks which the 10mm tails feeding the 2way garage consumer unit are connected to we have checked these connections and they are in sound condition

Assuming you have tested the voltage at the service head is sensible (and therefore not the DNO's problem) you could while you are generating use this point as a reference and then probe along the circuit to the inverter with a voltmeter. Test successively along the line connections and separately along the neutral, this will tell you where the excessive drop/rise is occurring. It will reveal poor connections with more certainty than any resistance testing on a dead circuit.
 
Your supply voltage is 248v, and rising to 275v when pushing in 1Kw. Voltage rise of 27v.
1Kw = 3.64A at 275v.
R=V/I so 27v/3.64A = 7.42 ohms grid impedance between your intake and the supply transformer.
Assuming the 11kV/0.4kV transformer has a nominal impedance of 0.05 ohms, there is a 7.37 ohm resistance in the overhead supply lines.
This is unusually high, and would suggest a high resistance joint in the LV supply line, so approach the DNO asap with your calculations. They need to send an engineer out to do a site survey, and possibly use a TDR to locate the distance to the fault.
If they try to fob you off, remember that a 1Kw load could cause you a volt drop of 29.7V, giving supply voltage of 218v, the lower acceptable limit being 216.2v (230 +10% - 6%), so imagine what a 3Kw load could do the supply voltage.
 

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