On a related topic, John Rumm wrote:
There are also requirements for segregation of high and low voltage
circuits (or provision of adequate earthed screening. See 528-01-01,
and 02

Is SWA cable considered "adequate earthed screening" in this context?

I'd appreciate comments on a plan to run an SWA mains cable to an
outbuilding, along with several other cables, using a broad trough
covered by 600x600 flagstones to make a path.

The cables would simply be laid in the open trough, on a bed of pea
gravel to prevent stone cuts, running the SWA along one side and keeping
all the other cables as far away as possible. Then the flagstones would
bridge over the whole lot, resting on two parallel runs of block edging
(heavy load bearing is not a problem in this particular location).

Hopefully the SWA itself would be deemed to meet the requirement for
"earthed screening". In addition there will typically be at least 1ft of
physical separation plus four layers of insulation between mains and
signal conductors.

Conventional deep burial of the SWA is not a practical option here,
because we're on rock - even the proposed shallow trough will be very
hard work. Overhead conduit is not an option either. The flagstones
would seem to meet the requirement to prevent anyone from accidentally
digging into the SWA, at least as well as deep burial could.

All in all, I think this method would be more than adequate in technical
terms, but I'd very much appreciate comments from the regulatory
experts.



--
Ian White

Hopefully the SWA itself would be deemed to meet the requirement for
"earthed screening". In addition there will typically be at least 1ft of
physical separation plus four layers of insulation between mains and
signal conductors.

When you say "high voltage", are you sure you mean that? 230V mains
electricity counts as "low voltage". What are the other cables? If they are
comms or suchlike, then they are likely to be "extra low voltage". This
requires separation either by the provision of physical separation (5cm),
running through a separate conduit channel or run through cables insulated
to the same spec as the low voltage cables. Note that direct buried cables
are likely to need such insulation anyway. It is likely that your system
would comply using all 3 methods, let alone 1.

Conventional deep burial of the SWA is not a practical option here,
because we're on rock - even the proposed shallow trough will be very
hard work. Overhead conduit is not an option either.

Could you surface mount on a wall?

Christian.

If SWA cable is connected properly at both ends earthing is
automatically bonded.
SWA can be run in a trough sunk on a bed of sand.
Any other cabling must be run in conduit, plastic is ok. this can then
be laid alongside the SWA.

Christian McArdle wrote:
Conventional deep burial of the SWA is not a practical option here,
because we're on rock - even the proposed shallow trough will be very
hard work. Overhead conduit is not an option either.

Could you surface mount on a wall?

Thanks for thinking of that... but again, it isn't an option here.


--
Ian White

"Ian White" wrote in message
...

On a related topic, John Rumm wrote:
There are also requirements for segregation of high and low voltage
circuits (or provision of adequate earthed screening. See 528-01-01,
and 02

Is SWA cable considered "adequate earthed screening" in this context?

I'd appreciate comments on a plan to run an SWA mains cable to an
outbuilding, along with several other cables, using a broad trough
covered by 600x600 flagstones to make a path.

The cables would simply be laid in the open trough, on a bed of pea
gravel to prevent stone cuts, running the SWA along one side and keeping
all the other cables as far away as possible. Then the flagstones would
bridge over the whole lot, resting on two parallel runs of block edging
(heavy load bearing is not a problem in this particular location).

Hopefully the SWA itself would be deemed to meet the requirement for
"earthed screening". In addition there will typically be at least 1ft of
physical separation plus four layers of insulation between mains and
signal conductors.

Conventional deep burial of the SWA is not a practical option here,
because we're on rock - even the proposed shallow trough will be very
hard work. Overhead conduit is not an option either. The flagstones
would seem to meet the requirement to prevent anyone from accidentally
digging into the SWA, at least as well as deep burial could.

All in all, I think this method would be more than adequate in technical
terms, but I'd very much appreciate comments from the regulatory
experts.



--
Ian White

Segragation doesn't seem to be an issue here since there will be EMC
protection due to the cable armour. I am assuming the highest voltage is LV
i.e. 230 Volts.

If there is no option to run the cable on the surface, clipped to a
substantial fence or wall, it would be preferable to use an angle grinder or
jack hammer, (hired if necessary), to cut a channel in the rock as deep and
as wide as possible. Sifted soil or sand, at least 50mm compacted thickness,
is used as a bedding; both below and as a top cover to the cable, pebbles
are certainly not to be used for this purpose. In addition a warning tape,
as available from electrical wholesalers, should be laid on top of the cable
along its total length, under your flag stones. For record purposes, a
layout plan should be made, marking the route of the cable as accurately as
possible; a copy of this should be left at the DB. Route markers should be
considered at the start and end of the cable run, these can simply be
painted arrows on a fence or wall.

There is no mention of the type of supply that this installation applies to,
is it TT, TN-C-S or TN-S? This has a bearing on what is possible with the
bonding of the cable armouring, the selection of materials and methods of
installation. Where is the RCD installed, at the cable start or end
location?

This work probably requires notification to the LBA, unless you are in
Scotland.

Jaymack