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Thread: COC for PV Systems

  1. #11
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    Quote Originally Posted by Pieter00 View Post
    here she is
    That looks like it is a proposal - I have not seen or heard of such a report

    It looks like it is linked to the SANS 10142-1-2 that was withdrawn - The test report that appeared in that document is different and withdrawn so not in use

    Will go through the report and original question and paste some of the answers later on when I get a chance

    They are making it complicated by putting a document out there that is not actually linked to a set of regulations with definitions so that you actually know what they want.

  2. #12
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    Quote Originally Posted by Pieter00 View Post
    Hi guys, I need to do a coc on an inverter system and there is some questions I have arising from the test report. Can you please tell me what this stuff refers to as I've never heard of it before.
    I honestly think that it is a draft wish list from somebody and does not match anything I have seen in draft format to date -

    I have pasted , in Italics, snips from NRS 097 and a version of SANS 10142-1-2 that was withdrawn and put down some of my thoughts in normal type.
    Hopefully it helps explain some of the points and if some are still unclear let me know.
    Personally , I would not use that test report until somebody can tell me where it is published.
    It is maybe a useful check list


    Closing on dead bus protection and control function tested
    A dead bus verification event shall be simulated to ensure that it is not possible, whilst the grid is
    dead, for the EGI to energize the utility’s point of supply (point of utility coupling).


    Anti-islanding protection and control function tested
    islanding
    condition in which a portion of an electric grid, containing both load and generation, is isolated from
    the remainder of the electric power grid

    You would need to test that the inverter actually disconnects from the grid and does not feed back into a grid that has lost supply or that the supply is not to grid compliance , in other words frequency and/or voltage is above or below what is deemed acceptable , normally +/-10%

    what single line diagram are they talking about that must be displayed in the DB?
    It would appear that they want you to indicate the position of isolators and c/breaker protection , or fuse protection , in relation to the equipment that you install. The PV panels must be able to be isolated from the Inverter and batteries from inverter , ac connection point isolator and ac protection breaker size.

    Additional Utility requirements for EGIs are identified and addressed
    It is recommended that the EGI designer does basic power quality measurements (such as power
    factor, harmonic content and load balancing in cases of three-phase supply) of the present utility
    power supply prior to the installation. Identified issues can then be addressed and / or measurements
    can be compared during the realisation and operation of the EGI.
    NOTE NRS 048 covers the reporting requirements.


    The above test and requirements are linked to the stipulations that PV may not exceed 25% of supply C/Breaker size on residential and no more than 4,6Kw imbalance between phases along with not exceeding 75% of minisub size and no more than 15% of MV line load
    Also if you go with a system that generates more than 350Kw AC than you will be required to carry out a utility network assessment

    Islanding condition - time to disconnect
    Almost a repeat of the previous question

    Size of embedded generation installation ___kVA A1 / A2 / A3 (what is meant with this A1 or A2 or A3?)
    From NRS-097-2-1 Ed2.1 2017
    4.1.1.11 In line with the current Renewable Power Plant Grid Code, embedded generators smaller than 1000 kVA connected to low-voltage form part of Category A generators, with the following sub-categories:
    a) Category A1: 0 – 13,8 kVA;
    This sub-category includes RPPs of Category A with rated power in the range from 0 to 13,8 kVA, inclusive of 13,8 kVA.
    b) Category A2: 13,8 kVA – 100 kVA; and
    This sub-category includes RPPs of Category A with rated power in the range greater than 13,8 kVA but less than 100 kVA.
    c) Category A3: 100 kVA – 1 MVA.
    This sub-category includes RPPs of Category A with rated power in the range from 100 kVA but less than 1 MVA.



    and then the Tests:
    How do you do a earth and neutral loop test if the supplier says the test can be done but not through the inverter? and the Prospective short circuit current at point of isolation of the storage system? how do you guys do these tests?
    Remember this code is also for bigger units like a 120KWH battery system - You could have a massive PSCC at the connection point to the batteries and your fuse/ CB would need to be rated accordingly - The supplier would be able to give you the PSCC.
    If you take a smaller system like 5KWH battery , the PSCC is going to be no more than the maximum discharge current of the battery - On lithium but will be different on lead acid , the fault level will climb

    With regards to the earth neutral loop test on the output of the unit - You will need to verify that the earth neutral is bridge when the grid drops out and when grid is on that the earth neutral is not bridged - Think that loop test would be incorrect

    Max calculated gas build-up?
    A bank of lead acid batteries emits gas and in an enclosed space can be a problem and could be a hazardous area - If you have 2 batteries there will not be an issue but install 37 batteries and you would need to ensure that the calculations are done according to SANS - SANS 10142-1 clause 7.14.3(h) will direct you to SANS 10086-1 and 10089-2 to deal with battery charging areas
    On Lithium this would not come into play , on smaller units anyway , not sure about 100KWH systems , again supplier can help.

    Ambient temperature during commissioning
    Would have an effect on the voltage from the PV panels and to check that you have taken that into account when working out the string voltages
    Maximum expected temperature
    Same answer as above
    specific gravity of each cell
    Suppose to make sure that you actually check the batteries - On Lithium this will be N/A

    It's my first time seeing this test report as I'm used to the traditional COC pages. Is there an institution that offers training on the above mentioned points perhaps?
    AS far as I am aware and what I see of the test report you have put out here, I do believe that it is still a draft format and until the regulations are actually published I would not start paying somebody to teach me something that may not come about.
    Last edited by GCE; 15-Jun-22 at 05:10 AM.

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  4. #13
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    where exactly would you put your test leads for a earth loop impedance test/neutral loop impedance test/ prospective short circuit current and would you do all 3 these tests on a hybrid as well as an off-grid inverter and axpert inverter?
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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  5. #14
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    Quote Originally Posted by Pieter00 View Post
    where exactly would you put your test leads for a earth loop impedance test/neutral loop impedance test/ prospective short circuit current and would you do all 3 these tests on a hybrid as well as an off-grid inverter and axpert inverter?
    I have never done a Loop and PSCC test on the output of an inverter as I am nervous of damaging components - Would like to know if somebody has done so

    The loop you could verify with a multi meter as the earth neutral reading when Eskom falls away should be zero .

    The PSCC you can get from the rating plate of the inverter - It is the Prospective short circuit current or in simply terms the maximum current that could flow if there was a dead short on the output terminals.
    The rating plates of all inverters give the maximum current before the electronics will trip it.
    On small 5kw type inverters it will more than likely be a maximum of double rated output current which will keep the PSCC low at 0.04KA
    On bigger units like 100Kw inverters it could be as high as 1KA which is still next to nothing.

    On the battery side it will be different especially lead acid and if memory serves me correctly , rule of thumb would be 12 times Amp hour rating

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    Should the neutral earth bridge not be done externally in an inspection type box as it's not allowed in a DB according to SANS 10142:1?Click image for larger version. 

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  8. #16
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    Quote Originally Posted by Pieter00 View Post
    Should the neutral earth bridge not be done externally in an inspection type box as it's not allowed in a DB according to SANS 10142:1?Click image for larger version. 

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    I assume they are using 7.12.3.1.3 to make that statement, that it is not allowed in the DB ? It is not so much as not allowed , just that it should be at the unit

    On bigger systems where the transformer is owned by the client , it would need to be done in the transformer room or close to it , and could be the main D/Board for the installation if that is where the main neutral earth bar is



    7.12.3.1.2 In an installation that is supplied from a combination of
    transformers and alternative supplies located near to each other, the neutral
    points of each of these items shall be connected to a single earthed neutral
    bar (see P.1 and figure P.1). This earthed neutral bar shall be the only point
    at which the neutral of the installation is earthed.
    Any earth leakage device
    shall be positioned in such a way as to avoid incorrect operation due to the
    existence of any parallel neutral/earth path.


    7.12.3.1.3 Where alternative supplies are installed remotely from the
    installation, or from one another, and where it is not possible to make use of
    a single neutral bar or neutral conductor which is earthed, the neutral of each
    unit shall be earthed at the unit
    and these points shall be bonded to the
    consumer's earth terminal (see 6.12.4). The supply from each unit which
    supplies the installation or part of the installation, shall be switched by means
    of a switch that breaks all live conductors operating substantially together
    (see figures P.2 and P.4), to disconnect the earthed neutral point from the
    installation neutral when the alternative supply is not connected (see also
    6.1.6).


    7.16.4.3 Wherever the neutral is connected to the earth, a warning notice
    shall be fitted to the outside of each distribution kiosk in the distribution
    system, indicating "Neutral earthed inside".

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