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Topic Title: Connection Between Busbar and Functional Unit
Topic Summary: Switchboard Construction
Created On: 27 February 2014 03:47 AM
Status: Post and Reply
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 27 February 2014 03:47 AM
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LIAW

Posts: 3
Joined: 01 April 2011

Can anyone help to clarify if there is any known (IEC or BS) standards that allows or prohibits the use of PVC insulated cables to connect the busbars and MCCBs within a switchboard construction ?
 27 February 2014 09:08 AM
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broadgage

Posts: 1300
Joined: 07 August 2007

I am not aware of any regulation that specificly prohibits PVC insulated cables used as you describe.

On the other hand, some bus bars and switchgear operate at suprisingly high temperaures, and regulations DO require that cables and other equipment be suitable for the conditions, including temperature.
IF the operating temperature is likely to exceed the limit for PVC insulation, then yes it would be excluded and either a different type of cable should be used, or suitable heat resistant sleeving be used.

In some situations, standard PVC cables are prohibited throughout, not just for bus bar and switchgear connections.
This is due to the very toxic smoke produced in case of fire and would be a building regs or insurance requirement, not part of the IET regs.
 27 February 2014 02:43 PM
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LIAW

Posts: 3
Joined: 01 April 2011

Hi broadgage. Thanks for your prompt response, although it wasn't quite what I was looking for.

OK, this may sound a bit embarrassing as I seem to have found at least part of the answer to my own question in IEC 60439-1 (2004) clause 7.5.5.1.2 and Table 5 under clause 7.5.5.3 implies that use of pvc insulated cables to IEC 60227-3 (unsheathed pvc insulated cables for fixed internal wiring) can be used as active wiring between busbars and the supply side of any functional unit. There is also a note in Table 5 which states that this cable may only be up to 3m long. Note also that clause 7.5.5.1.2 states that active conductors using "solid rigid manufacture" are preferred.

So, any clarification which prohibits the use of pvc cables for the above purpose is welcome too.
 27 February 2014 05:25 PM
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iie63674

Posts: 78
Joined: 17 May 2006

IEC 60439-1 has been superseded by IEC 61439-1, some years ago.
 27 February 2014 07:32 PM
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Avatar for OMS.
OMS

Posts: 19695
Joined: 23 March 2004

BS EN 61439 still allows the use of cable as connections between busbars and functional units however, basically, the commentary is the same - particularly in relation to temperature, short circuit forces and clearance/creepage distances

Regards

OMS

-------------------------
Failure is always an option
 28 February 2014 02:44 AM
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LIAW

Posts: 3
Joined: 01 April 2011

Thanks all. I take it that the use of pvc insulated cables as active connection between busbar and supply side of functional unit can be permitted within a switchboard construction, provided certain requirements can be met as laid down in the respective standards.
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