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11kV/400V TX with no LV protection

amlec2021

I am working on a project where we have been asked to install a new LV cable from the outgoing side of a transformer to a new Panel board however the outgoing side of the transformer does not have any protection. We have raised this with the client however they have advised this is not an issue. I am looking for some guidance to back up our argument that the LV cable does not have any protection.

Parents

  • An output short circuit WILL blow something, and the best thing is the HV protection.  If not this then one of the cables may blow open circcuit but this may not remove the short. You are talking fault powers of many 10's if not 100s of MWA here for a 1MVA TX.  You probably shouldn't be anywhere near this, because you have a complete misconception of "Fault Protection". What are you attempting to protect, because it certainly isn't the TX or the cables? This is exactly why we have HV circuit breakers and fuses at each transformer, you are thinking BS7671 all the way, which at higher powers simply doesn't work.

Reply

  • An output short circuit WILL blow something, and the best thing is the HV protection.  If not this then one of the cables may blow open circcuit but this may not remove the short. You are talking fault powers of many 10's if not 100s of MWA here for a 1MVA TX.  You probably shouldn't be anywhere near this, because you have a complete misconception of "Fault Protection". What are you attempting to protect, because it certainly isn't the TX or the cables? This is exactly why we have HV circuit breakers and fuses at each transformer, you are thinking BS7671 all the way, which at higher powers simply doesn't work.

Children
  • in reply to David Stone

    David,

    I am unsure why you don't think BS 7671 is not relevant here. I am talking about the output side of a transformer which is 400V and completely relevant under BS 7671

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