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If I construct my own solar powerplant to add my output to the power grid how is it done technically ?

What are all the steps I need to go through ? (Not regulatory procedures.. But would still be interesting to know)

For example, If I filter water at my water treatment plant I can connect my pipeline to the water network of the city. I'm guessing it might not be so simple with electricity ?

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  • \$\begingroup\$ Is this a technical only question or both regulatory (legal?) and technical? \$\endgroup\$ – user3528438 Aug 18 '17 at 19:54
  • \$\begingroup\$ Just updated my question. Would be very interesting to know about regulatory procedures for any one country. But not necesaary for this specific question. \$\endgroup\$ – RHLK Aug 18 '17 at 19:56
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    \$\begingroup\$ With the water analogy, consider how you will keep the pressure in the city water pipes from pushing water back in to your treatment plant? How will you do that if the pressure in the city pipes fluctuates? --- There are similar considerations for the electrical grid. \$\endgroup\$ – The Photon Aug 18 '17 at 21:06
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I have a solar installation on my roof that produces up to 4kW.

It's connected to the grid through an imaginitively-named device called a "grid tie inverter". This does two things:

  • it detects the phase of the existing grid supply and refuses to turn on otherwise ("anti islanding"). This allows sections of the grid to be turned off safely and is a regulatory requirement.

  • it supplies AC power to its terminals (converted from the ~320VDC of the panels) in phase with the grid supply. Necessarily this is at a voltage fractionally higher than the grid supply, enough to overcome the voltage drop on the wires between the substation and my house.

Because I got the system supplied through an approved installer, I'm eligible for feed-in tariffs and have a second electricity meter which pays me £0.13 for every kWh of energy generated.

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  • \$\begingroup\$ Forgive me if I'm going off-topic, but does the "anti-islanding" requirement mean that you personally can't have power, even when the sun is out, if your section of the grid is down? From your brief description, it sounds like it might, especially if the law is carelessly worded. \$\endgroup\$ – AaronD Aug 18 '17 at 20:51
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    \$\begingroup\$ @AaronD I think it is to prevent pjc50 from supplying power to anyone nearby. In my location, for example, there are two homes attached to a shared pole-mount transformer. If the grid were shut down but I were to still supply power through my meter, then my neighbor would be directly connected -- and -- I suspect the primary of the pole-mount transformer would be rather dangerous for workers on the pole, too. \$\endgroup\$ – jonk Aug 18 '17 at 21:35
  • \$\begingroup\$ @jonk So far, that makes perfect sense. In fact, I just finished adding an automatic generator controller and transfer switch to an RV, which would have the same problem if done naively. I'm just thinking about all the alternative energy installations that automatically shut down when Fukushima blew up, much to the annoyance of their users who thought they had a backup. \$\endgroup\$ – AaronD Aug 18 '17 at 21:45
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    \$\begingroup\$ @AaronD I think that may be a different case. At least here in the US (pdj50 isn't here, I think), installations I've seen continue to work just fine if the grid shuts down. It's just the "gate-keeper" cuts off access to the grid (or neighbors) when the grid itself appears to be non-functional (intentionally or otherwise.) This means you may have excess capacity then. Which can be used if you have local energy storage for that, too. \$\endgroup\$ – jonk Aug 18 '17 at 21:48
  • \$\begingroup\$ @AaronD -- there are "multimode" or "hybrid" inverters that contain an internal transfer switch and downstream AC bus that is backup-powered from batteries/renewables when the upstream AC source dies. \$\endgroup\$ – ThreePhaseEel Aug 18 '17 at 22:14
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To add power to the grid, you approximately match the amplitude, and then lead the phasing of the external grid.

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