Distributed single phase generation

[HamburgerHelper]

How do utilities handle a bunch of distibuted single phase generation feeding back onto the grid? Is it managable? What problems does it cause?

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If you can't explain it to a six year old, you don't understand it yourself.

 

[Desrod2]

Not a problem for networks in North America since part of the distribution network is single phase. Some challenges for high DG penetration area regarding voltage regulation and protection coordination but it is under control.

 

[waross]

I don't believe that single phase generation can get very large before three phase becomes more economical.
Diesel generators go to three phase at about 25 KVA. If you purchase a single phase DG rated at 30 KVA, it most often will be a three phase, 45 KVA set with a double delta connection to provide 30 KVA of true single phase power.

Bill
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"Why not the best?"
Jimmy Carter

 

[davidbeach]

Think non-rotating generation... ;-)

 

[waross]

I hear you David. I did think about non-rotational. My thought was that invertors of any size (above 15 or 25 KVA) would be about the same price or cheaper in a three phase configuration.
I am under the impression that there are few single phase services greater than 200 Amps. That's about 50 KVA and the invertor would not be a full 50 KVA on a 200 Amp service.
So we are back to about 25 KVA or less, similar to DG sets.
But there is a lot of new information coming forward with small distributed generation.
Am I about to learn something new?
Respectfully
Bill


Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[FreddyNurk]

There has been a trend with certain sizes of inverter units to provide 3 phase generation via 3 separate single phase units, and communications between the units to balance things out in terms of output. Above a certain size it appears easier to design the whole thing as 3 phase from the start. I've seen some systems that indicate 3-phase capabilities up to 63kVA by multiple banks of single phase inverters (e.g. 3 banks of 3 by 7kVA single phase inverters).

As I understand it, the generation on single phases causes voltage balance issues for the utilities (e.g. all the inverters on a street are on phase 1) and also voltage rise issues in LV distribution.

EDMS Australia

 

[davidbeach]

10kVA here and 5kVA there pretty soon you have some real numbers. A single phase tap with good exposure... Real world weird stuff happens.

 

[xnuke]

I work more in generation, not distribution, but if I remember correctly, here in Oregon a Tier 1 net metering interconnect application is pretty much rubber stamped approved if it's a maximum of 25 kVA, connected via an approved inverter, and the total DG on the feeder is less than 10% of the maximum connected load on the feeder (15% if it's solar PV), etc. Might be missing a couple of small items there, but I think the last part of my sentence is key. If it would exceed the percentage of load limit, I think trying to add new DG to the feeder triggers an engineering study as part of the Tier 2 interconnect application. I bet no homeowner will want to pay that added cost and will bail on the idea, therefore the unbalance on the single-phase feeder phases is likely limited by both requirements, probably to an amount that can be handled by nearby voltage regulators.

xnuke
"Live and act within the limit of your knowledge and keep expanding it to the limit of your life." Ayn Rand, Atlas Shrugged.
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[Desrod2]

IN some legislations in North America, Utilities must provide general public with how much generation could be connected at every location on the distribution network (both single and multi phase networks). In California, there are now so many small units on residential rooftop that in a sunny day, more and more feeders are backfeeding into the HV/MV substations. Search for the "duck curve" reference showing the issue for the network operator in California. Household size units don't require engineering impact studies to be able to connect to the grid for as long they don't exceed the hosting capacity provided by the utility.
Luckely for us, we provide the tools to support the utilities managing the DER challenge.