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Topic Title: wind turbine inverter cutting out when grid voltage hits 253v
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Created On: 19 February 2012 06:47 PM
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 19 February 2012 06:47 PM
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hertzal123

Posts: 503
Joined: 26 August 2007

A customer has contacted me about the above problem with his inverter.
This problem has appeared since the board did some work on the local network(according to him).This is a remote farm fed from a pole mounted tx (1 phase).I assume the problem is that the inverter has to put out a higher voltage than the grid voltage in order to feed back into the grid.
Are there different tappings on the tx or is the problem elsewhere?
Thanks for any help,
Hz
 19 February 2012 07:20 PM
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perspicacious

Posts: 8055
Joined: 18 April 2006

There will need to be a PD to export

There could be an element of self cause as to get the maximum return from the PV, you need to use it yourself and say this is by an immersion heater that you wouldn't normally use, when the output drops the immersion is still in circuit and then causes additional load on the supply that wasn't there before

Just as or even more likely, loads have been shed in the area raising the HV or the HV has been reinforced to cater for additional load.

Just because you have a 25 kVA PMTx, don't assume that the DNO will allow you to connect 2 x 4 kW of PV............I know of cases where large PV installs apparently less than 50% of the Tx rating have triggered the installation of a larger Tx at the PV owner's expense before the DNO will allow connection. I've heard that the same can apply to basic domestic installs where several houses with PV on the same Tx or feeder have had to have Tx upgrades.

This is topical as my voltage recorder is out this week with a contractor whose own PV cuts out when the supply is above 253 V and he wanted to make sure before he complains to the DNO and they send him a box to plug in and return.

Regards

BOD
 19 February 2012 07:27 PM
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ArthurHall

Posts: 754
Joined: 25 July 2008

I had a similar problem last year. A farm and a cottage fed from a pole mounted transformer. The incoming voltage was above the limit and the wind turbine invertors kept tripping out.
Measure the voltage at the cutout on light load if it is above 230/400 +10% notify the DNO in writing and note the date, they have to rectify the problem within 12 months.
The invertors usually have an overvoltage setting, sometimes this can be tweeked up but this may break some of the supply agreements, on the other hand it may allow some cash income.
The senario above is not that un-common. Back in the 50's and 60's the evening peak on farms often brought the voltage down, (milking machines, cookers etc) the low voltage affected the televisions. The easy solution for the DNO was to tapp up the voltage at the transformer, few people complained of slightly high voltage in those days.
The local DNO responded fairly quickly in the above case and fitted a new transformer within a couple of months.
 19 February 2012 07:33 PM
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bajb

Posts: 593
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You need to find out a bit more about your customer's connection:

- If a G83/1 connection (the norm for <=16A per phase) then the cut out voltage for the inverter is 264V. If the inverter is cutting out at 253V then it is set up wrongly (typically to a continental standard).

- if a G59/2 connection (the norm for >16A per phase) then the cut out voltage for the inverter is indeed 253V. If it is regularly hitting that then the network voltage will need to be reduced or it may be that there are voltage drops (actually rises) within the consumer pv installation that could be reduced by increasing the cable size to the inverter.

Regards
Bruce
 19 February 2012 07:37 PM
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alancapon

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. . . A farm and a cottage fed from a pole mounted transformer. The incoming voltage was above the limit and the wind turbine invertors kept tripping out.

Measure the voltage at the cutout on light load if it is above 230/400 +10% notify the DNO in writing and note the date, they have to rectify the problem within 12 months. . .

It can also be the fault of the inverter as well. Has the customer notified the DNO of the connection? Connecting solar PV or wind generation to the end of a line can cause unexpected voltage rises in the wrong places on the feeder. It may well be that the tranformer needs to be changed for a larger unit, the network reinforced, or it could be as simple as tapping the existing transformer down to reduce its voltage.

. . . The invertors usually have an overvoltage setting, sometimes this can be tweeked up but this may break some of the supply agreements, on the other hand it may allow some cash income. . .

That is an easy way of breaking the supply agreement and possibly getting the installation banned from connection if the changes mean that it no longer complies with its G.83 or G.59 test certification!

Regards,

Alan.
 19 February 2012 08:25 PM
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hertzal123

Posts: 503
Joined: 26 August 2007

Originally posted by: bajb

You need to find out a bit more about your customer's connection:



- If a G83/1 connection (the norm for <=16A per phase) then the cut out voltage for the inverter is 264V. If the inverter is cutting out at 253V then it is set up wrongly (typically to a continental standard).



- if a G59/2 connection (the norm for >16A per phase) then the cut out voltage for the inverter is indeed 253V. If it is regularly hitting that then the network voltage will need to be reduced or it may be that there are voltage drops (actually rises) within the consumer pv installation that could be reduced by increasing the cable size to the inverter.



Regards

Bruce

Do,nt know what type of connection,but turbine is 5kw,feeding 2 inverters.
Regards hz
 19 February 2012 08:56 PM
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Fm

Posts: 2032
Joined: 24 August 2011

You need to check the commissioning sheet for the inverter.
Sounds like it is reaching the max cut off
Get the make and model and google ie sma windy boy.
Its probably not your problem
 19 February 2012 09:05 PM
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alancapon

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Originally posted by: hertzal123
. . . turbine is 5kw,feeding 2 inverters. . .

In that case, it won't be G.83, as 5kW is 20A. I am not sure how you would organise G.59/2 settings across two inverters, but I guess it is possible. I assume that the DNO is aware of the connection and the size of the turbine. As Bruce correctly says, the cutoff voltage for G.59/2 is indeed 253v.

Regards,

Alan.
 19 February 2012 11:49 PM
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bajb

Posts: 593
Joined: 20 November 2002

We are all guessing a bit. There is no substitute for seeing the commissioning paperwork.

Alan is right that in principle it would today at that size be connected under G59. But inverters the size you are talking about are most likely to be G83 out of the box. Many DNOs I understand were allowing G83 compliant units to be used up to 17kW over the last few years under G83/1-1 Stage 2 connection arrangements, albeit they are becoming more reticent now since the widespread deployment of solar pv installations.

You really need to get the detail from the commissioning paperwork.

Regards
Bruce
 19 February 2012 11:57 PM
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sparkingchip

Posts: 11682
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Surely you describe the problem in this sentence:

"Do,nt know what type of connection,but turbine is 5kw,feeding 2 inverters. "

That easily resolved if the cause of the problem is there

Andy
 20 February 2012 10:15 AM
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ArthurHall

Posts: 754
Joined: 25 July 2008

. . . The invertors usually have an overvoltage setting, sometimes this can be tweeked up but this may break some of the supply agreements, on the other hand it may allow some cash income. . .

That is an easy way of breaking the supply agreement and possibly getting the installation banned from connection if the changes mean that it no longer complies with its G.83 or G.59 test certification

Unless it is with the agreement of the DNO as a temporary measure until they get the voltage back within the statutory limits.
 20 February 2012 10:23 AM
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AJJewsbury

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Originally posted by: alancapon

Originally posted by: hertzal123

. . . turbine is 5kw,feeding 2 inverters. . .


In that case, it won't be G.83, as 5kW is 20A. I am not sure how you would organise G.59/2 settings across two inverters, but I guess it is possible. I assume that the DNO is aware of the connection and the size of the turbine. As Bruce correctly says, the cutoff voltage for G.59/2 is indeed 253v.



Regards,



Alan.


Couldn't it still be G83/1 if the two inverters were connected to different phases (<16A per phase)? Might be a split-phase supply?
- Andy.
 20 February 2012 01:57 PM
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sparkingchip

Posts: 11682
Joined: 18 January 2003

This is all pure guess work!!!

Single phase Tx, remote farm so probably the only load on the Tx is that farm.

So two inverters in parallel both feeding into the installation at the same point, both trying to up the voltage above mains and its adjoining inverter. So particularly when the loads are off on the farm the two inverters up the voltage to the point where they cut out as the voltage is too high.

So move a inverter connection to where there is less voltage in the system due to cable lengths and loads, with the other inverter at the intake.

Or install a multiphase Tx.

Or install one big inverter to replace the two smaller ones

or stick a dump load in like Bod suggested such as a immersion heater, to drag the voltage down.

Go on rip me to pieces

Andy
 21 February 2012 05:55 PM
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sparkingchip

Posts: 11682
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It doesn't seem right when no one is pointing out my errors!!
 21 February 2012 06:15 PM
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jcm256

Posts: 2327
Joined: 01 April 2006

Stick one of these on the mains supply, not sure, if it would like the supply from the wind turbine coming in from another direction via an inverter.

http://www.reuk.co.uk/VPhase-Voltage-Optimiser.htm
 21 February 2012 06:32 PM
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bajb

Posts: 593
Joined: 20 November 2002

No, you cannot put a generator on the output terminals.
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