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Converting a TT earthing system to TNS System

Akhil Vinayak Gopimohanan Shubha

Hi

I am a control systems engineer who dabbles in the electrical side of the job now and then as the job demands. I have come across an issue which I cant find much help online. 

One of clients is located in Japan and they have informed very late into the build that they have TT earthing system on site, instead of TNS system as they have previously told us.

Our product is designed for TNS earthing system and therefore a significant amount modification will be needed to make the product work safely with a TT system. Since it was too late and expensive to make the changes to our system, the client has agreed to look in the possibility of providing our system with a TNS supply by converting the existing TT supply on site.

They have transformer on site which they are using to supply to our system. The proposal is essentially to connect earthing of the secondary of the transformer to our system and use that as PE. Is that a viable solution? I cant believe that it can be this simple.   

Can you please advise any other considerations to be made while making the decision.

Thank you very much

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  • 0

    In Japan, IEC 60364 series are introduced into Section 218 of Interpretation of Technical Standards for Electrical Equipment which is published by Agency for Natural Resources and Energy. So if the design firm and the construction company are well aware of the regulation and technically competent, it is possible that they can build TN-S earthing system.

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  • 0

    In Japan, IEC 60364 series are introduced into Section 218 of Interpretation of Technical Standards for Electrical Equipment which is published by Agency for Natural Resources and Energy. So if the design firm and the construction company are well aware of the regulation and technically competent, it is possible that they can build TN-S earthing system.

Children
  • 0 in reply to eizo

    Do you happen also to know what approach is commonly taken  in Japan to lightning electrodes and bonding to the building earthing ? I can imagine that if TT is standard for commercial supplies,  then it may not be quite the same as someone more used to TNx may expect.

    My knowledge of Japanese wiring is theoretical only- I have only even been briefly to Japan as a visitor, but just looking up I was impressed (as I was in the US actually) by the amount of overhead combined MV/LV and how different it looked, especially  the rarity 3 phase compared to Europe.

    Mike.

  • 0 in reply to mapj1

    Maybe I mentioned  the  Japanese regulation about  IEC 60364 series misleadingly. In Japan traditinal earthing system is still TT system.  In adition to the earthing system, Japanese contracactor can now build TN-S system because Agency for Natural Resources and Energy took in IEC 60364 series almost entirely into Interpretation of Technical Standards for Electrical Equipment in 1999. But I entertain misgiving that most of elecatrical contractor in Japan might not know the existence of IEC 60364 series･･･. I hope this is not irrelevant answer.

  • 0 in reply to eizo

    Thanks eizo for the reply..

    I am in the process of creating a check list for the engineers, who proposed the solution, based on the information I got from here to make sure that the final arrangement is safe and up to the standard.

    Hopefully this will lead to some useful discussions with the client and a proper solution.

  • 0 in reply to Akhil Vinayak Gopimohanan Shubha

    I expect that protective devices in your recieivd proposal are circuit breakers. In that case and when protective condutor’s sizes are to decide using calculation, manufacture’s data are needed to decide whether sizes of protective conductors are adeqate for these breaker’s let through energy or not. I would like to know if the manufacture could provide these data, (if the manufacture is Japanese one), form my personal feelings.

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