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Thread: Generator Connection

  1. #1
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    Generator Connection

    Hi,

    We have a 350KVA generator connected directly to our factory. The generator operates automatically when the Eskom power is lost.

    The generator has been in situ for a number of years and during a recent routine service, I was informed by the technicians that the generator has been installed illegally. We are also having major issues where the contactors are falling out dropping power to the factory even though there is still Eskom power.

    The electrical contractor is being very evasive and not very helpful. Is there a Electrical Board that I can contact to assist me as if the below is true, then I have a serious issue to deal with.

    Findings from the generator people:
    Die Contactors is nie meganies geinterlock nie wat n probleem is sou die mains relay op die gen brand en die gen start en sy relay die ander contactor intrek dan maak die mains en gen contactor saam toe wat katastrofies sal wees.
    Die mains contactor word ingehaou deur n 24 V / 220V AC 14 pin relay wat in die generator sit . Hy word deur die batterye en charger ge energize en oor die afstand (dit is 220v wat geen vlotdrop het nie) van gen na contactor en onstabiele voltage van die Munisipaliteit val die contactor in en uit . Die generator panel is nie ge design vir dit nie en dit verkort ook die leeftyd van die batterye. Ons gebruik daarom n 4 pole ATS wat in een posisie bly of Mains of Gen soos wat daar in was . Nuwe wet vereis ook dat ons die neutral breek . In die geval is al die Neutrals gebunch


    Reply from electrical contractor that installed the generator:
    Die contactors is elektries ge-interlock en daar is nie n manier wat hulle saam kan inkom nie. Selfs al stuur jou generator albei signals sal dit net een van die twee contactors laat inkom. So daar is geen gevaar hier nie.

    Regards
    Ian Franken

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    Hi Ian,

    Based on edition 2.0 of SANS 10142-1, 7.12.6.1 requires that precautions are taken to ensure the alternate supply cannot unintentionally operate in parallel with the main supply. Then there is a note that advises that "suitable precautions can include an electrical, mechanical or electromechanical interlock between the operating mechanisms or control circuits of the changeover switching devices, or"... (let's not get into the rest as the point is covered already).

    So based on SANS 10142-1, it seems electrical or mechanical interlocking is compliant. That said, having a mechanical interlock between the relays in addition to the electrical interlock is definitely good practice if that is a practical option.

    Unfortunately that does not seem to be the end of the story for you.

    Quote Originally Posted by infranken View Post
    Nuwe wet vereis ook dat ons die neutral breek . In die geval is al die Neutrals gebunch
    Actually this has been true for some time already.
    (For those wondering, take a close look at 7.12.3.1.3).

    Seems you're in for a change anyway. May as well make sure you cover the drop-out problem while you're about it.

    One last thing to cover - one also has to pay attention to the requirements of the electricity supply authority of the installation as they may have additional requirements.

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    Thought I would resurrect this thread rather then start new .

    I cannot believe that so far down the line we still have generator so called specialist suppliers and manufacturers selling generators with 3 pole switches and then trying to convince the client that the Electrician does not know what he is doing when we insist on a 4 pole switch.

    We have an irate client this afternoon complaining because we refuse to connect.

    We originally priced to included the generator and stipulated 4 pole change over - They argued that they could get cheaper and we said fine but ensure that it has 4 pole switch .

    There must be numerous contractors still connecting 3 pole change overs up to part installations that this problem stills crops up.

    If you don't own the supply transformer - you cannot use a 3 pole changeover
    If you only connecting part of the installation - you cannot use a 3 pole changeover

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    Hi

    Decided to add to the thread -
    I have yet again come across consultants insisting on 3 pole change overs even though the shop is not taking the full load of the minisub and generator will be remote from the minisub.
    Because the entire store , being one store in a shopping complex, has a generator suppling the full store they feel that annex P1 allows the store to be changed on 3 pole.
    When reading Annex P we need to read in conjunction with the regulation that it was derived from.

    I am pasting the relevant reg's from ED3 below to see if anybody has a different view

    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).
    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).
    NOTE Where four pole switching is implemented, consideration should be given to use
    overlapping neutral switching devices.
    7.12.3.1.4 Where only part of an installation is switched to the alternative
    supply in the same distribution board, the neutral bar shall be split (see
    figures P.2 and P.3).

    6.1.6 The neutral conductor shall not be connected direct to earth or to the
    earth continuity conductor on the load side of the point of control except as
    allowed in 7.16.4

    7.16.4 Neutral earthing
    7.16.4.1 Whereas TN-C systems may be implemented along the distribution
    system backbone, the individual service connections at every distribution
    kiosk shall be TN-S.
    7.16.4.2 From the point of supply to each user or part of a communal
    installation, the neutral and earth conductors shall be separate conductors.
    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”.
    7.16.4.4 A clear notice shall be fitted at the combined neutral-earth
    connection inside each distribution kiosk in the distribution system, that
    prohibits the removal of this connection while the supply is alive, or might
    become alive.
    7.16.4.5 The neutral shall not be earthed beyond any earth leakage unit.
    7.16.4.6 A TN-S system shall not be converted to a TN-C system.

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    I need to read and understand this ... if an inverter is fed from and earth leakage (inout of the inverter) you dont have to ground the neutral on the output ... this would makes sense because thwe majority of free standing plug in inverters are genrally fed from and earht leakage.

    If I build a mobile 5 kva unit and plug it into the wall ... I dont have to earth the neutral so long as it is fed from circuit with earth leakage protection.

    However if I mount the 5 kva unit against the wall and feed it directly from a circuit breaker in the DB not on earth leakage ... then I must earth the neutral and fit and earth leakage after the neutral earth link.


    7.16.4.5 The neutral shall not be earthed beyond any earth leakage unit.
    7.16.4.6 A TN-S system shall not be converted to a TN-C system.
    Comments are based on opinion...not always facts....that's why people use an alias.

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    Hi Ians

    It would depend on the inverter

    Some inverters the input and output are isolated from each other and you would need to bridge earth neutral.

    When an inverter feed str through while power is on then you shall not earth the neutral - when the power drops and you feed off batteries you shall earth the neutral

    It is very much dependent on the make and set up of the inverter

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