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Transformer Tails Sizing

fiftyhertz
Hi All,


I am trying to nail down sizing the tails from the TX into a switchpanel.


I have reviewed the the information in GN1 and understand the methods of installing to get the best current sharing capabilities. 


The issue is getting reasonbly sized AWA singles.


Example: 1500KVA TX - FLC 2165A.


Using Table 4D3 (to run to 70C) I cannot even get Trefoil 3 sets of 4 x 630mm2 (809A) cables to work, due to a grouping factor of 0.54?


How is the dealt with practically?
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  • 0
    The length is only 6m straight from the TX into the Switch panel within an internal trench. The proposed conductor is copper but with an AWA. I would say that 3 x 3 x 1C 630mm2 + Neutrals is a reasonable size for a 2500A ACB turned down to 2125A as long as the vented trench metholody 117 mentioned above is used to allow the 2DE spacing, although not strictly an installation method to BS 7671 if used in trefoil.


    There must be a standard-ish arrangement for TX tails for transformers sizes 1MVA, 1.25MVA and 1.5MVA


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  • 0
    The length is only 6m straight from the TX into the Switch panel within an internal trench. The proposed conductor is copper but with an AWA. I would say that 3 x 3 x 1C 630mm2 + Neutrals is a reasonable size for a 2500A ACB turned down to 2125A as long as the vented trench metholody 117 mentioned above is used to allow the 2DE spacing, although not strictly an installation method to BS 7671 if used in trefoil.


    There must be a standard-ish arrangement for TX tails for transformers sizes 1MVA, 1.25MVA and 1.5MVA


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