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  • 4MW Solar

    The latest here, there are zoning requests for 4 different sites of 4MW or 2MW (AC) each. My neighbor is in
    the zoning process, looks like I might get involved too. A couple sites are just a road or 2 south of me.
    They propose to feed a 12.5KV single phase line, same one my transformer is connected to. I don't believe
    that line can begin to handle that power level, maybe the 33KV 3 phase circuits nearby could do it (barely).

    Perhaps my biggest concern is what will happen to the neighborhood line voltage when these arrays turn
    on and off. There is a MAJOR sub station very close, it runs several miles to the Byron Nuke. Seems to
    me these systems need their own dedicated connections to the sub, to avoid disturbing the locals too much.

    I went through that before, don't want to play again. Bruce Roe
    Last edited by bcroe; 05-11-2018, 12:25 PM.

  • #2
    Originally posted by bcroe View Post
    The latest here, there are zoning requests for 4 different sites of 4MW or 2MW (AC) each. My neighbor is in
    the zoning process, looks like I might get involved too. A couple sites are just a road or 2 south of me.
    They propose to feed a 12.5KV single phase line, same one my transformer is connected to. I don't believe
    that line can begin to handle that power level, maybe the 33KV 3 phase circuits nearby could do it (barely).

    Perhaps my biggest concern is what will happen to the neighborhood line voltage when these arrays turn
    on and off. There is a MAJOR sub station very close, it runs several miles to the Byron Nuke. Seems to
    me these systems need their own dedicated connections to the sub, to avoid disturbing the locals too much.

    I went through that before, don't to play again. Bruce Roe
    Your concern is very real.

    I worked on a problem at a high school out in Nevada that had installed a 1MW solar pv system with 2 x 500 kW inverters. They were on the same power feed as a sewage treatment plant down the road. Every time a large HP motor started up the feeder would experience voltage transients causing the 2 inverters to briefly shut down until the system settled down.

    Keep us informed on that status of those pv projects Bruce.

    Comment


    • #3
      4Mw, that should keep my batteries charged even in the cloudy winter.
      Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
      || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
      || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

      solar: http://tinyurl.com/LMR-Solar
      gen: http://tinyurl.com/LMR-Lister

      Comment


      • #4
        Originally posted by Mike90250 View Post
        4Mw, that should keep my batteries charged even in the cloudy winter.
        Heck with that size of an array you could build a solar canopy and shield your home from snow, rain or anything else that drops down from the sky.

        Comment


        • #5
          Another outfit seems to be touring the neighborhood, already sold a modest rooftop system
          to a neighbor. Now another neighbor is asking me about being offered a 10KW for his shop
          roof. Made noises like its practically free after rebates, will look into this. Bruce Roe

          Comment


          • #6
            Originally posted by SunEagle View Post
            I worked on a problem at a high school out in Nevada that had installed a 1MW solar pv system with 2 x 500 kW inverters. They were on the same power feed as a sewage treatment plant down the road. Every time a large HP motor started up the feeder would experience voltage transients causing the 2 inverters to briefly shut down until the system settled down.
            Rule 21 compliant inverters should make that issue significantly less troublesome.

            Comment


            • #7
              Originally posted by jflorey2 View Post
              Rule 21 compliant inverters should make that issue significantly less troublesome.
              I agree. The new standards will help keep inverters connected to the grid and let them ride through transients that use to shut them down.

              Comment


              • #8
                Originally posted by SunEagle
                The new standards will help keep inverters connected to the grid and let them
                ride through transients that use to shut them down.
                What is Rule 21? Bruce Roe

                Comment


                • #9
                  Originally posted by bcroe View Post

                  What is Rule 21? Bruce Roe
                  CA decided the existing inverter compliance software was too sensitive to "changes" on the grid. To eliminate false shut downs a group of experts, that jflorey2 is familiar with, worked on a new set of rules to change the software so that the grid would not see swings of pv systems turning on and off too quickly for minor influences which is something that happened to the 2 x 500kw inverters installed at the High School project I worked on in Nevada.

                  As far as I know those changes to inverter software have been introduced into the newest versions.

                  Here is an article on Smart Inverters that mentions Rule 21.
                  Last edited by SunEagle; 05-15-2018, 01:09 PM. Reason: added link to Rule 21 article.

                  Comment


                  • #10
                    Originally posted by bcroe View Post
                    What is Rule 21? Bruce Roe
                    Rule 21 came out of the smart inverters working group (SIWG) which is a group within the CPUC. This group started because utilities noticed that residential solar PV sometimes caused problems during grid instability. When frequency or voltage dropped, the solar inverters out there initially were a stabilizing influence; their contributions of power tended to reduce the amplitude of the excursion. But since UL 1741 calls out fairly narrow limits on voltage and frequency (to ensure that the inverters did not 'island' or run when they're not supposed to) once the disturbance got beyond a certain point, the inverters would trip off-line - and suddenly that part of the grid would lose a few megawatts of generation, and that would make the problem worse. Voltage and frequency would drop further, sometimes leading to service interruptions.

                    So the SIWG came out with new guidelines on frequency and voltage limits, as well as a host of other features that help support unstable grids (like controlled ramp rates, voltage regulation capability and remote monitoring and control.) There are three phases to this.

                    Phase one is already in place; new inverters sold after 2017 need to support Rule 21 phase 1 and must meet UL 1741-SA, which contains the new ramp rates, voltage regulation and voltage/frequency limit changes.

                    Phase two will require the ability to communicate with the outside world, although the ability to communicate back to the utility will not yet be required. (In other words, the inverter has to support communication, the customer does not.) This is pending.

                    Phase three will require the ability to communicate with the utility, set power limits (to prevent overgeneration) and support remotely-commanded grid stability functionality. This is still a work in progress.

                    Comment


                    • #11
                      Originally posted by jflorey2 View Post

                      Rule 21 came out of the smart inverters working group (SIWG) which is a group within the CPUC. This group started because utilities noticed that residential solar PV sometimes caused problems during grid instability. When frequency or voltage dropped, the solar inverters out there initially were a stabilizing influence; their contributions of power tended to reduce the amplitude of the excursion. But since UL 1741 calls out fairly narrow limits on voltage and frequency (to ensure that the inverters did not 'island' or run when they're not supposed to) once the disturbance got beyond a certain point, the inverters would trip off-line - and suddenly that part of the grid would lose a few megawatts of generation, and that would make the problem worse. Voltage and frequency would drop further, sometimes leading to service interruptions.

                      So the SIWG came out with new guidelines on frequency and voltage limits, as well as a host of other features that help support unstable grids (like controlled ramp rates, voltage regulation capability and remote monitoring and control.) There are three phases to this.

                      Phase one is already in place; new inverters sold after 2017 need to support Rule 21 phase 1 and must meet UL 1741-SA, which contains the new ramp rates, voltage regulation and voltage/frequency limit changes.

                      Phase two will require the ability to communicate with the outside world, although the ability to communicate back to the utility will not yet be required. (In other words, the inverter has to support communication, the customer does not.) This is pending.

                      Phase three will require the ability to communicate with the utility, set power limits (to prevent overgeneration) and support remotely-commanded grid stability functionality. This is still a work in progress.
                      Sounds like CA Social Engineering to me.

                      MSEE, PE

                      Comment


                      • #12
                        Originally posted by Sunking View Post

                        Sounds like CA Social Engineering to me.
                        Actually the original inverter standards were too rigid to protect it from frequency and voltage changes on the grid. Being too sensitive cause many inverters to disconnect and then reconnect 5 minutes later for no real reason at all.

                        I fully support the actions of Rule 21 because they improve the inverter's ability as well as makes them smarter.

                        Comment


                        • #13
                          Originally posted by SunEagle View Post
                          I fully support the actions of Rule 21 because they improve the inverter's ability as well as makes them smarter.
                          I support them because they will result in inverters that work better, have more standardized interfaces and don't trip off-line at the drop of a hat. Real engineering improvements, rather than social improvements. (Although I imagine such changes will give more time for installers to partake in more social activities . . . )

                          Comment


                          • #14
                            Originally posted by jflorey2 View Post
                            (Although I imagine such changes will give more time for installers to partake in more social activities . . . )
                            Just what I need: More installers calling/hanging around the house boing social, asking questions or giving me hassle about HOA requirements in their spare time.

                            Comment


                            • #15
                              We had the first of several meetings for a zoning special permit on 2 sites very close to me, each
                              4 MW solar. Farming neighbors were there, not happy. The conclusion was recommendations to
                              approve one, not the other. Nothing concrete in this, more fact finding. I mentioned the need for
                              a proper PoCo line, not the tiny single phase (same one I am on with 0.015 MW PV) on the original
                              drawings. And possible issues with electrical noise, voltage regulation in the area.

                              Hope everyone understands, this is industrial, not agricultural. On to the next meeting. Bruce Roe

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