cable distance transformer to switchgear
cable distance transformer to switchgear
(OP)
Hi,
Can anyone tell me if there is a minimum allowable cable distance from the LV output terminals of a MV/LV transformer, say 1MVA, 11kV/433V to the CB, and what regulations/standards will apply in the UK.
Thankyou.
Can anyone tell me if there is a minimum allowable cable distance from the LV output terminals of a MV/LV transformer, say 1MVA, 11kV/433V to the CB, and what regulations/standards will apply in the UK.
Thankyou.






RE: cable distance transformer to switchgear
that should be "maximum alllowable cable distance......"
Regards, and thanks in advance.
RE: cable distance transformer to switchgear
Regards
Marmite
RE: cable distance transformer to switchgear
David Castor
www.cvoes.com
RE: cable distance transformer to switchgear
What's the reason for the question?
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If we learn from our mistakes I'm getting a great education!
RE: cable distance transformer to switchgear
The reason I ask is that a couple of years ago I was involved in a scheme where the 11kv/433V Dyn11 Tx (No onboard isolator) was installed and the ACB was some 40-50m distance away. The DNO made us install a local ACB within 15m (cable length) of the Transformer LV terminal box. I cant remember the reason why, but am thinking that there must be some standard/reg/code that states the limits for the length of the LV cables in such circumstances.
Or is just down to upstream protection settings etc..
I am currently at the start of a similar scheme and would have liked to have clarified the need (or not) for a local isolation point as above.
Your views much appreciated.
Many thanks.
RE: cable distance transformer to switchgear
- Protection: there are limitations for cable lenght depending on neutral system earthing
- Voltage drop which increases with cable lenght and so leads to oversizing cables. A big number of cables is a bad issue considering limitation in connection possibilities for both sides (transformer secondary and ACB terminals)
For economic side: i think it's better to extend MV cable than to add more LV cables.
**for 1MVA for exemple:
Primary current: 52.5 Amps --> 1 cable 3x35mm.sq Copper(assumption)
Secondary current: 1333.4 Amps --> ~ 9 cables 240mm.sq (3c/phase) (assumption)
For erection, it's very difficult to lay and to connect such a number of cables.
BEN.
RE: cable distance transformer to switchgear
If there was no electricity there would be no internet. Good point, don´t you? :D
RE: cable distance transformer to switchgear
NEC does permit limited (10 feet or 25 feet) unprotected secondary lengths for practical reasons and with some other restrictions.
In general NEC requires conductor overcurrent protection at its source. I would think rules elsewhere would be very similar.
Rafiq Bulsara
http://www.srengineersct.com
RE: cable distance transformer to switchgear
RE: cable distance transformer to switchgear
Rafiq Bulsara
http://www.srengineersct.com