IT earthing system: FOR or AGAINST?

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  • #12828
    Spir Georges GHALI

    michaelt said:

    can anyone advise what would be best set up to use with a delta delta 690/480v transformer being used to supply two 15kw vsd with emc filter to ground . insulation metering versus imedance relay and ground monitoring , i take it ground monitoring equipment for a delta/star set up will not work with the former it system unless with impediance relay, or am i missing something ,this is for offshore situation . and a retro fit .



    For ” IT ” system :

    – If the transformer's secondary is with Neutral : the Neutral point can be either connected to the Earth point by ” Impedance ” or not connected ( completely opened ).

    – If the transformer's secondary is without Neutral : one phase ( any one ) can
    be either connected to the Earth point by ” Impedance ” or not
    connected ( completely opened ).

    – Some of ” Insulation Monitoring ” are internally equipped by ” Impedance “, so, we don't need it. Noting that we can know from the schematic diagram of intallation if we need an impedance or not.


    The new range is fully compatible with the existing Salamandre system, and its popular marking jig measuring tool.


    Hi, I was wondering if anyone could please advise on the following.
    Which of the two following earth connections should always be done without intentional impedance?
    a) System (functional) earthing
    b) Protective earthing
    What is the purpose of doing so?


    IS any body help to clarify below,

    We are using an IT system with IMD in a 480v 60hz Motor control Center , which is feeding 15 motor circuits.
    1. when a fault occurs on a One feeder which will trip total MCC?
    2.Is each maotor feeder required any RCD in IT system, or IMD will fuction thsi protection.
    3.Is IMD will monitor each feeder or only main circuit.


    Continuation of above,

    Due to IMD used in iT network,
    Is the each feeder require seprate fault idetifier like RCD to avoid tripping of the total circuit.

    My customer does not require main feeder should not trip due to one feeder fault in a IT system.Is there any solution.


    bro… use Bender products…
    Isolation moniters and insulation fault locaters..
    A-Isometer and EDS products your problem will be solved
    for details contact Bender , on


    I am new this forum and hope I enjoy being here and resolve issues as and when they occur.

    Hoping your humble support!



    Its good to earthing your installation,for example a house is near me but that house has earthing.but i don’t have consumer control unit and so i connect LIVE and NEUTRAL only but no earth wire.and asking you it good do that.


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