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IT Earthing System Testing

Les Spiteri

What is the accepatble/understood method of testing an electrical panel where during test the building has a standard TN earthing system however when it gets to final destination it will be using an IT Earthing system?

For example testing the insulation monitors that are required on IT systems to indicate shorts to earth (on 3ph system) that would not trip protection devices or indeed testing that the protection devices do not trip on shorts to earth.

I have had suggested to use a 3ph isolating transformer, however I would suggest that addtional safety measures would be required for testing?

Thanks for any comments, much appreciated.

  • +1

    I suspect that you will need to understand and perhaps involve the designers of the system,  Unlike TN systems where test methods and limits are pretty much standardized, IT systems are rarer, and application specific.  If you know which insulation monitoring and protective devices are used and how they are configured, then the makers may be able to advise.

    That said, before the wiring is made off, insulation can be verified in the normal way and earthing up to the last point that needs it can be verified by R2 wander lead.

    Mike.

  • +1
    Les Spiteri said:
    What is the accepatble/understood method of testing an electrical panel where during test the building has a standard TN earthing system however when it gets to final destination it will be using an IT Earthing system?

    The accepted methods should conform to BS EN 50191.

    The issue is really one for the product standard, that is the test requirements of the relevant parts of the BS EN IEC 61439-series, and how the verification clauses are assessed using BS EN 50191.

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