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Thread: Generator Connection

  1. #1
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    Generator Connection


    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.

    Ian Franken

  2. #2
    Site Caretaker Dave A's Avatar
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    Hi Ian,

    Based on edition 2.0 of SANS 10142-1, 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

    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.

  3. #3
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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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