#1 Feb. 4, 2014 09:54:00

Britta
Registered: 2014-01-09
Posts: 33
Reputation: +  0  -
Profile   Send e-mail  

Inverter outages?


Hi


I have been reading in the 2006 DTI PV trial Good Practice guide, and come across this issue of inverter outages a result of high voltages in the grid, and I'm curious about whether this has long since been sorted or if it is something anybody recognises?


Here's the blurb from the guide:


A high grid voltage can also lead to the suspension of
inverter operation if it is above the maximum allowable value for the inverter. Since the grid voltage varies with load level, the inverter can turn on and off regularly under some
conditions and operate continuously at other times.
This behaviour is characterised by repeated short-term stoppages in inverter operation, with normal behaviour at all other times. These stoppages can extend for a few minutes or a few hours depending on grid conditions. They are
often not connected with any obvious change in operating conditions, since they depend solely on the grid voltage at the inverter connection. However, they do often occur in good weather conditions when the PV output is high and
the load levels are low. As such, the stoppages are more
common in the summer and can reduce overall system output by a substantial amount.

Britta



Edited Britta (Feb. 4, 2014 09:54:00)

Offline

#2 Feb. 4, 2014 16:44:00

martint123
Registered: 2013-01-09
Posts: 23
Reputation: +  0  -
Profile   Send e-mail  

Inverter outages?


Glancing at the spec of my inverter it would appear to support mains voltages between 180 and 280 volts.


I haven't noticed any droputs in the coupld of years installed.





Edited martint123 (Feb. 4, 2014 16:44:00)

Offline

#3 Feb. 5, 2014 10:28:00

rogerhoward
From: Southend
Registered: 2012-08-01
Posts: 273
Reputation: +  0  -
Profile   E-mail  

Inverter outages?


But is the DTI report referring to our domestic inverters? Isn't the voltage in our homes - far from being high - limited to 240V?










Economy 10 tariff provides 6.9p/kWh off-peak import between 12am-5am, 1pm-4pm and 8pm-10pm; http://www.pvoutput.org/aggregate.jsp?id=21047&sid=18934&v=2&t=m on approx. 63% off-peak usage, 22% solar usage, and 15% peak-rate usage.
1,900kWh annually is exported, mostly in summer, on approx. 3,200kWh generation. Approx. 4,500kWh/year is imported, mostly for (a) winter and springtime off-peak Storage Heaters, and (b) off-peak hot water Immersion heating (which is “dumb”, i.e. not linked to the solar PV).
PV array is split East-West. Income is from Phase II 21p/kWh Feed-in-Tariff plus smart metered 3.2p/kWh Export Tariff.

Edited rogerhoward (Feb. 5, 2014 10:28:00)

Offline

#4 Feb. 5, 2014 11:09:00

Britta
Registered: 2014-01-09
Posts: 33
Reputation: +  0  -
Profile   Send e-mail  

Inverter outages?


yes, DTIs Domestic Field Trial from 2006. I'm quoting the Good Practice Guide they produced as a result of it (http://www.bre.co.uk/filelibrary/pdf/rpts/DFT_GoodPracticeGuidePart2_DTI.pdf if you are curious), but obviously there aren't many numbers in there, so I don't know what the extent of this was in the trial (you can download the entire report of course, but is is long…)


I can't remember how much voltages are allowed to fluctuate, I seem to remember figures of 6-10% ? but that is completely off the top of my head. I'm pretty sure they won't go up to 280v though, so I'm guessing it's a teething thing and that inverters are all made to cope with it. It was just one of those things that made me stop as I was reading it, but I have not put much effort into taking it apart.


Britta





Edited Britta (Feb. 5, 2014 11:09:00)

Offline

#5 Feb. 5, 2014 11:24:00

rogerhoward
From: Southend
Registered: 2012-08-01
Posts: 273
Reputation: +  0  -
Profile   E-mail  

Inverter outages?


I'm not sure if the wiring in this 1925-built place can cope with 280V - you're worrying me now!










Economy 10 tariff provides 6.9p/kWh off-peak import between 12am-5am, 1pm-4pm and 8pm-10pm; http://www.pvoutput.org/aggregate.jsp?id=21047&sid=18934&v=2&t=m on approx. 63% off-peak usage, 22% solar usage, and 15% peak-rate usage.
1,900kWh annually is exported, mostly in summer, on approx. 3,200kWh generation. Approx. 4,500kWh/year is imported, mostly for (a) winter and springtime off-peak Storage Heaters, and (b) off-peak hot water Immersion heating (which is “dumb”, i.e. not linked to the solar PV).
PV array is split East-West. Income is from Phase II 21p/kWh Feed-in-Tariff plus smart metered 3.2p/kWh Export Tariff.

Edited rogerhoward (Feb. 5, 2014 11:24:00)

Offline

#6 Feb. 5, 2014 11:43:00

Britta
Registered: 2014-01-09
Posts: 33
Reputation: +  0  -
Profile   Send e-mail  

Inverter outages?


:-D good thing I couldn't help myself and had a quick search and I can (- well, I'll have to admit this came from wikipedia…) now reassure you: " The declared electricity supply in the United Kingdom is now, as a result of European Harmonisation in 1995, 230V with a tolerance of +10% to -6%. This means that supply voltage can theoretically be anywhere between 216.2V and 253V depending on local conditions"


But what has now got me going, is what would happen if your neighbor had one of those voltage optimisation devices?….


I am sorry.. I'll get on with some work now…


Britta





Edited Britta (Feb. 5, 2014 11:43:00)

Offline

#7 Feb. 5, 2014 13:39:00

Britta
Registered: 2014-01-09
Posts: 33
Reputation: +  0  -
Profile   Send e-mail  

Inverter outages?


btw I have also just found out that if you upload to PVoutput, then you should be able to see your voltage in the live production





Edited Britta (Feb. 5, 2014 13:39:00)

Offline

#8 Feb. 5, 2014 16:20:00

rogerhoward
From: Southend
Registered: 2012-08-01
Posts: 273
Reputation: +  0  -
Profile   E-mail  

Inverter outages?


Case Study 6.2 states;


"Grid voltage varies with load level. High grid voltage can lead to the suspension of inverter operation if it is above the maximum allowable value for the inverter.


Repeated short-term stoppages in inverter operation can occur, with normal behaviour at all other times. These stoppages can extend for a few minutes or a few hours depending on grid conditions. This can occur in summer good weather conditions when PV output is high and the (local domestic) load levels are low … and can reduce overall system output by a substantial amount.


System A (in the observed pair of systems on the same grid feed) operated continuously with an output matched to the sunlight profile for that day. System B, however, only showed very short periods of operation with the inverter being off for the majority of the day.


The susceptibility of a system to this behaviour depends on the local grid voltage and load conditions, the settings of the inverter, and the position of the system on the supply feeder (systems close to the local transformer are the most vulnerable)."


A recurring theme of the report seems to be the need for a realtime data monitoring facility to pick up on faults (and they aren't referring to some inverter display or other in a loft). It is in this context that they quote this example of a theoretical fault in more remote rural areas with limited grid carrying capacity.


I'm a townie. But for this example we'd at least notice balmy summer days recurring of such poor generation as that wouldn't we?







Economy 10 tariff provides 6.9p/kWh off-peak import between 12am-5am, 1pm-4pm and 8pm-10pm; http://www.pvoutput.org/aggregate.jsp?id=21047&sid=18934&v=2&t=m on approx. 63% off-peak usage, 22% solar usage, and 15% peak-rate usage.
1,900kWh annually is exported, mostly in summer, on approx. 3,200kWh generation. Approx. 4,500kWh/year is imported, mostly for (a) winter and springtime off-peak Storage Heaters, and (b) off-peak hot water Immersion heating (which is “dumb”, i.e. not linked to the solar PV).
PV array is split East-West. Income is from Phase II 21p/kWh Feed-in-Tariff plus smart metered 3.2p/kWh Export Tariff.

Edited rogerhoward (Feb. 5, 2014 16:20:00)

Offline

#9 Feb. 5, 2014 16:51:00

rogerhoward
From: Southend
Registered: 2012-08-01
Posts: 273
Reputation: +  0  -
Profile   E-mail  

Inverter outages?


As regards your original enquiry, Britta, see the recent thread on 'System Tripping'.







Economy 10 tariff provides 6.9p/kWh off-peak import between 12am-5am, 1pm-4pm and 8pm-10pm; http://www.pvoutput.org/aggregate.jsp?id=21047&sid=18934&v=2&t=m on approx. 63% off-peak usage, 22% solar usage, and 15% peak-rate usage.
1,900kWh annually is exported, mostly in summer, on approx. 3,200kWh generation. Approx. 4,500kWh/year is imported, mostly for (a) winter and springtime off-peak Storage Heaters, and (b) off-peak hot water Immersion heating (which is “dumb”, i.e. not linked to the solar PV).
PV array is split East-West. Income is from Phase II 21p/kWh Feed-in-Tariff plus smart metered 3.2p/kWh Export Tariff.

Edited rogerhoward (Feb. 5, 2014 16:51:00)

Offline

#10 Feb. 6, 2014 10:22:00

Britta
Registered: 2014-01-09
Posts: 33
Reputation: +  0  -
Profile   Send e-mail  

Inverter outages?


That's it! Thanks rogerhoward, I hadn't read far enough down that thread. A quick visit to the electricians forum and it seems Thackie's comment that this is not unusual, is probably just about the size of it.








Edited Britta (Feb. 6, 2014 10:22:00)

Offline

Board footer

Moderator control

Powered by DjangoBB

Lo-Fi Version