I'm looking at helping someone with putting up solar and it seems that in the area they have a secondary power network which does not allow power to be fed back into the grid. Is there an easy way to determine if an address is on a secondary network instead of a radial network? I've looked online already and it doesn't show exactly. This is for PG&E. I figured someone here might know. There is no map online that I can find.
How do you know if you are on a secondary power network or not?
- Thread starter frasere2
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zanydroid
Solar Wizard
I don’t know the answer but residential interconnection application is only $195 or so and they will do this as part of the engineering. I don’t know at which phase though. Hopefully at the stage that comes before PTO, which is when I purchased my equipment
400bird
Solar Wizard
I called PGE and they told me if my house could apply. They checked the transformer rating and availability right there. This was in 2018, so it might not be applicable any more. But a call is free.
Ampster
Renewable Energy Hobbyist
I have never heard of a secondary power network. A quick Google search revealed a PG&E page that says it is more reliable because power can flow in both directions. So it does not make sense why backfeed would not be allowed.
400bird
Solar Wizard
Glad I'm not the only one, I was just going to gloss over that part...
zanydroid
Solar Wizard
The problem with calling PG&E is you need to know which part to call. Some parts will give you an answer even if they don’t know
hwy17
Anti-Solar Enthusiast
I had heard of these being called Downtown grids or something before.
No export rule is like the 120% rule for panels I'd imagine, they already have multiple sources and loads mixed in on their conductors and the engineering is complicated, so adding in more sources would create risks of overload.
No export rule is like the 120% rule for panels I'd imagine, they already have multiple sources and loads mixed in on their conductors and the engineering is complicated, so adding in more sources would create risks of overload.
Hedges
I See Electromagnetic Fields!
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"In a secondary network, electricity is delivered through a highly integrated system of transformers and underground cables. Each cable is connected and operates in parallel. Power can flow in either direction on lower voltage service delivery lines, typically called secondary distribution lines."
"In secondary networks, devices called network protectors prevent power from "back-feeding" from one transformer through another. Network protectors are designed to break the circuit quickly when they detect back-feeding. Any power exported by a generator into this system is recognized as back-feeding by the network protectors.
Most network protectors in service are not designed or tested to function as switching or isolation devices for operating electric generators. This concern prevents PG&E from allowing energy generator installation within the areas served by secondary networks."
Shared secondaries in a loop network.
It’s very robust for URD networks, no single failure will cause a power outage for all. Maintenance can be done with zero customer interruption.
Looped transformers high sides and looped transformer low sides.
The only down side is during cable faults all customer see the blips as protective devices operate and isolate a fault, but still way better than a power outage.
Ampster
Renewable Energy Hobbyist
That would be my guess as well. Rather short sighted of them to not consider distributed generation from other sources given the industry trends. I do not know how long ago these were planned so that may be their excuse. Most transformers are bidirectional so my understanding is the limitation at substations is that the control mechanisms were only designed for one way flow.
It would require substantial protection upgrades. Relays look for fault current in predefined direction.
I’m sure the redesign of the entire network protection is possible but at what costs borne by one developer?
I think the only thing that could fly would be a zero export interconnection, and even then I’m sure they’d be nervous.
Ampster
Renewable Energy Hobbyist
Thanks for your insights. Other than secondary networks, I believe, based on what I hear about substation issues in Hawaii, it that the grid could be enhanced by accomoding more distributed generation. VPPs and other distributed ESSs have proven to be valuable to support the grid and avoid brownouts, for example.
