Published: 23 June 2014
Category: Q&A
Steve asks this question about the type of cable connection required to a UKPN transformer, and what solution to use. It has been answered by ABB (Theme – Power):
This Q & A is one of thousands posted in our Technical Expertise area, and answered on a daily basis by our Voltimum Experts.
Question: I have a problem – UK Power Networks (UKPN) cannot accommodate connecting main supply cable into its transformer because of the following: the existing cable provided are 12 no singles to equate 800kVA supply (4 no each for each of the phase and neutral).
The people at UKPN are saying that they require 630mm2 single cable only.
This is baffling to me, as the calculation carried was not recommending 630mm2, where distance between the substation and the LV switch room is over 100m.
My question, therefore, is this: is it possible to locally terminate into an un-fused switch isolator and then take singles to the substation, or can I request UKPN for a better solution using the existing cables?
Answer: We would not recommend using a switch as a terminal box to convert your four conductors/phase to singles, since there will be no protection to the switch in case of an overload or short circuit occurring between the load terminals of the switch and the incoming side of the low voltage switchboard (if I have interpreted your circuit correctly).
I would request a better solution from UKPN, such as extended bushings or a 'joggle box' solution. This will be an added cost to you I suspect.
To see many more Q & A in Voltimum UK's Experts Area, please click on the link. Experts from leading organisations provide online answers to your technical questions on a broad range of subjects. Our searchable database of existing Q & As now contains over 3,500 entries; you can browse through them here.