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Topic Title: HV transformer
Topic Summary: Power transfer
Created On: 02 July 2013 04:38 PM
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 02 July 2013 04:38 PM
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Clivebird

Posts: 7
Joined: 01 March 2011

I have a client who is proposing a 200Kw PV system.
Their incoming supply is 11KV and is metered at the incomer. They have their own HV distribution with two local 500KVA 11Kv/400v transformers. My question is will the HV transformer allow the power to be exported back to the HV network when the PV is generating more than his demand? Cheers Clive
 02 July 2013 06:01 PM
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alancapon

Posts: 5768
Joined: 27 December 2005

It will do, and they need to contact their DNO before the connection is made. They may well need to fit G.59 protection to the installation.

Regards,

Alan.
 02 July 2013 06:15 PM
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OMS

Posts: 19668
Joined: 23 March 2004

Theoretically yes - -but you would need to look at the protection system to see if it's fitted with reverse power protection etc - and you'll need to consider all the implications of the G59 protection system, location of point of common coupling and emergency EPO system.

Regards

OMS

-------------------------
Failure is always an option
 02 July 2013 09:17 PM
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statter

Posts: 126
Joined: 06 February 2013

..... he'll need export HH metering too.

The location of the G59 protection is worth giving serious thought to. Much cheaper and easier if installed at LV on one of the transformers but may not be possible.
 03 July 2013 07:13 AM
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Clivebird

Posts: 7
Joined: 01 March 2011

Thanks all, I was aware that g59 protection would be required, I was not so sure that the local HV transformer would allow the power to be exported back up my clients HV system and hence slow down/stop the consumption meter. Cheers Clive
 03 July 2013 11:08 AM
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broadgage

Posts: 1293
Joined: 07 August 2007

Yes the transformer itself will work fine in feeding energy back into the grid.

The issues are likely to be g59 protection, metering, and protection, not the transformer itself.

Enough small PV systems on one one substation can result in a net backfeeding, and that normally works just fine.
The transformer does not "know" if it belongs to the DNO or to a consumer.

Another possible issue is what is the actual voltage at the transformer terminals ?
If it is actually 400 volts then it should be fine.
Many such transformers are about 433 volts actual to allow for voltage drop. Large scale backfeeding can then push the voltage over the limit for inverter operation, and over the limit for appliances.
If the actual voltage is about 433 then the transformer taps may need altering to say 415.
 03 July 2013 05:22 PM
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Clivebird

Posts: 7
Joined: 01 March 2011

Originally posted by: broadgage

Yes the transformer itself will work fine in feeding energy back into the grid.



The issues are likely to be g59 protection, metering, and protection, not the transformer itself.



Enough small PV systems on one one substation can result in a net backfeeding, and that normally works just fine.

The transformer does not "know" if it belongs to the DNO or to a consumer.



Another possible issue is what is the actual voltage at the transformer terminals ?

If it is actually 400 volts then it should be fine.

Many such transformers are about 433 volts actual to allow for voltage drop. Large scale backfeeding can then push the voltage over the limit for inverter operation, and over the limit for appliances.

If the actual voltage is about 433 then the transformer taps may need altering to say 415.


Thanks, for you help.
Cheers
Clive
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