I only have a small amount of experience in this but I'd say that the
loop-in, loop-out should have a higher reliability and lower lifecycle cost
due to the fact that underground joints do create a weak point which can
(and does) fail later in the life of the cable system.
yes I also agree, however cable jointing has become more advanced than it
was a few years ago, with some very sturdy jointing kits availible.
Also, there is a possibility of course, that on long runs of cable (along a
highway for example) the main cable will be of a large CSA (e.g. 120mmsq)
providing a low impedance earth loop impedance return path and therefore a
relatively high fault current.
The joint spur cable into the lighting column will only need to be of small
CSA.
The concern is that should an earth fault occur in the column, the spur
cable would carry the burden of the fault current and could overheat or
completely fail.
Of course, it would not be possible to use the same CSA as the main cable
run because it would be impossible to terminate such a large conductor into
the column. the answer would be to add fuse or circuit breaker protection
to the smaller cable, but joints do not allow this facility.
In the UK it is common to use loop-in / loop-out wiring. what is the norm
in other countries??
Any comments welcomed, as i am putting a project proposal together soon.
