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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
    Okay, after further looking. 


    For cables installed as per Installation method 117, with a ventilated trough. Which i would expect from an internal trough with an opening each end for connections to the TX and Switch panel, I can also specify a GRP ventilated lid. A 630mm cable from 4D3 can carry 771A horizontal flat spaced. This is the same figure if the cable was installed ladder horizontal flat spaced, I think therefore we can use the Trefoil method of the cable ladder as a reasonable substitute as there is no trefoil option in Installation method 117, this can then be combined with the grouping omission of 2De with neutrals in between.

Reply
  • 0
    Okay, after further looking. 


    For cables installed as per Installation method 117, with a ventilated trough. Which i would expect from an internal trough with an opening each end for connections to the TX and Switch panel, I can also specify a GRP ventilated lid. A 630mm cable from 4D3 can carry 771A horizontal flat spaced. This is the same figure if the cable was installed ladder horizontal flat spaced, I think therefore we can use the Trefoil method of the cable ladder as a reasonable substitute as there is no trefoil option in Installation method 117, this can then be combined with the grouping omission of 2De with neutrals in between.

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