I need educating here. I thought that with TN-C-S the neutral and earth started off being combined ('C') at source, and then subsequently separated ('S') somwehere, usually on entry to the building. In what we're seeing here, it looks as if the earth comes in separate, and then is combined (TN-S-C !!). What am I missing?TNC-S as the neutral is connected to the earth.
It is.TNC-S as the neutral is connected to the earth.
I thought that with TN-C-S the neutral and earth started off being combined
But should it be?
YEDL do exactly this where the TN-S earth has failed on PILC.
Fair enough - but if it were a bog-standard TN-S supply as far as the consumer's premises, but some joker then joined L and N at the service head, you wouldn't then call it TN-C-S, would you? Or maybe you would? (thereby shattering what I thought TN-C-S meant - as I said before, in terms of my understanding of the nomenclature, that would actually be "TN-S-C" - or, ultimately, TN-S-C-S!).Ah well, erm, in reality on a network, be it PME or not the neutral and the earth are in most cases combined at the substation anyway!!I thought that with TN-C-S the neutral and earth started off being combined
I thought substations were star TXs, so N comes from the star point, which is earthed whether the type of supply is TN-C-S, TN-S or TT?Ah well, erm, in reality on a network, be it PME or not the neutral and the earth are in most cases combined at the substation anyway!
That was also my understanding. I took westie's comment to mean not only that but also that what appeared at the customer end as a TN-S supply sometimes had a bit (perhaps only a small bit) of cable without a separate earth (i.e. TN-C) at the substation end, before splitting into TN-S for distribution to customers. I must confess that I didn't think that happened, rather that the E of a TN-S supply always came all the way from the star point, earth rod, or somewhere between the two.I thought substations were star TXs, so N comes from the star point, which is earthed whether the type of supply is TN-C-S, TN-S or TT? i.e. at the substation N & E are always combined, no matter how the earth is, or is not, delivered to the consumer?
Hope you dont mind the pics, heres a Delta/Star configured 500Kva 11000/415v Transformer with the LV star point/Neutral fixed to earth at the Distribution board(lower pic). Its covered by the Electricity supply regs if i remember correctly.
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