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Thread: photovoltaic 101

  1. #1
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    photovoltaic 101

    Anyone have any suggestions for photovoltaic installations learning.....readings... cliff notes... I know it's in the book (and maybe what I'm looking for as now I've seen little today)but looking for simple one line diagrams and layouts..
    Basic protection and layout out.. and design

    I've never needed to know it (and kinda still don't) but there is a company installing a system for the church. They are putting pv panels and inverters on/in one building then feeding that building and two others from those panels and inverters in that one building..

    The mechanic was kind enough to walk through some things which I found interesting...


    They will power the inverter from the building they want to supply, and the inverter uses those conductors to back feed that building..... WOW...

    My questioning would be as far as them tapping from each buildings mains (length of taps and ocp), labelling ..., disconnect locations (as it seems that they may be entering the building below grade and its questionable if they should install a disconnect before entering the building...

    Seems like they are putting inverters together to handle the loads and he will be paralleling smaller conductors between them and I'm curious in his design should have these conductors protected...

    How the wires (dc) are protect (ocp) as they attach to the pv panel (is array the word) and go the the inverter???

    I will see more as the next couple of weeks go by, but would like to know for my own head and to also see that it is kinda right..
    " I'm at a crucial part of my painting "...........Monika Danneman

  2. #2
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    I moved your thread here. It seemed to fit better.
    If you don't think too good, don't think too much.

  3. #3
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    I didn't learn from any books. I took a couple classes and then started working in it. I think Dunlop's book is considered a kinda classic but it's probably pretty out of date. You're probably better off using Google to find a most recent publication. Something that covers microinverters and optimizers which are prevalent these days.

    As far as overcurrent protection, PV power sources can't really overload their own circuits. So protection, when it's required, is there against parallel sources. On the DC side that would be other PV panels or sometimes batteries. On the AC side it's the grid. On the AC side the utility is usually going to provide essentially all the fault current, so generally an inverter is not wired any different than a load. Where you connect it matters though, see article 705.

  4. #4
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    You should ask you see a plan drawing set (construction documents). Should outline a lot of your concerns.

  5. #5
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    was thinking and watching some Mike Holt videos on you tube...
    he talks about several different types of systems and in one type a breaker from the load side of the main feeds the pv system... he talks about oc protection and possible doubling up of current on feeds to sub panels....
    has me thinking of the system this company is putting in........
    From what I understand of it they are tapping onto the LINE side of the service.
    building 1 is a ct cab 3 phase that has a line/load meter on it (no ct's) and it feeds a 225 amp main breaker....
    he will be tapping onto the line before the main breaker.
    building 2 is a ct cabinet with ct's he will not touch the cabinet but will tap on before the main breaker enclosure...
    building 3 is a house... guessing he's tapping on before the main breaker...
    I'm guessing his disconnects at the tap point are going to be breakers or fused disconnects??


    In all those cases, I'm guessing the main breakers will protect the existing service wire to the main breaker.. but was wondering theory..

    the utility power feeds the service main, it will be tapped to feed the inverter, power comes back on those same conductors to the existing utility wiring feeding the same main breaker.

    When the system is on, how does the building know which power source to take power from? The utility or the PV..... they are the same wire with two different power sources on it...

    WOW
    " I'm at a crucial part of my painting "...........Monika Danneman

  6. #6
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    PV101, light collected by the array is converted to electrical energy. End of class.

    You maybe looking for PV 102 and 103?
    I live for today, I'm just a day behind.

  7. #7
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    Quote Originally Posted by kwired View Post
    PV101, light collected by the array is converted to electrical energy. End of class.

    You maybe looking for PV 102 and 103?
    OK...... I'm smiling, that was funny
    " I'm at a crucial part of my painting "...........Monika Danneman

  8. #8
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    Quote Originally Posted by ritelec View Post
    was thinking and watching some Mike Holt videos on you tube...
    he talks about several different types of systems and in one type a breaker from the load side of the main feeds the pv system... he talks about oc protection and possible doubling up of current on feeds to sub panels....
    has me thinking of the system this company is putting in........
    From what I understand of it they are tapping onto the LINE side of the service.
    building 1 is a ct cab 3 phase that has a line/load meter on it (no ct's) and it feeds a 225 amp main breaker....
    he will be tapping onto the line before the main breaker.
    building 2 is a ct cabinet with ct's he will not touch the cabinet but will tap on before the main breaker enclosure...
    building 3 is a house... guessing he's tapping on before the main breaker...
    I'm guessing his disconnects at the tap point are going to be breakers or fused disconnects??


    In all those cases, I'm guessing the main breakers will protect the existing service wire to the main breaker.. but was wondering theory..

    the utility power feeds the service main, it will be tapped to feed the inverter, power comes back on those same conductors to the existing utility wiring feeding the same main breaker.

    When the system is on, how does the building know which power source to take power from? The utility or the PV..... they are the same wire with two different power sources on it...

    WOW
    It's all in 705.12(B) in the 2017 NEC and in 705.12(D) in earlier editions. Read and understand it. I agree with kwired, though; it's a little above the basics.

  9. #9
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    Quote Originally Posted by ggunn View Post
    It's all in 705.12(B) in the 2017 NEC and in 705.12(D) in earlier editions. Read and understand it. I agree with kwired, though; it's a little above the basics.
    Read through the 2014....... evelyn wood....... suggested reading and 685, 690

    picked up some of what I was asking, will look into it deeper..... BUT, nowhere did I see the theory of how two power sources use the same conductors to the main and the main magically knows which one to use ???
    " I'm at a crucial part of my painting "...........Monika Danneman

  10. #10
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    Quote Originally Posted by ritelec View Post
    ...

    When the system is on, how does the building know which power source to take power from? The utility or the PV..... they are the same wire with two different power sources on it...

    WOW
    Didn't we already answer that?
    Oh, right, that was this thread.

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