7.13.1 - Overhead wiring
types
Most overhead wiring is carried out by
the Electricity Supply Companies, and is not in the domain
of the electrician. However, wiring between buildings is
often necessary, and can be carried out using one or more
of the following methods:
1. - rubber or p.v.c. insulated
cables bound to a separate catenary wire,
2. - specialist cables with an integral
catenary wire,
3. - p.v.c. Insulated and sheathed,
or rubber insulated with an oil-resisting and flame retardant
sheath, provided that precautions are taken to prevent chafing
of the insulation or undue strain on the conductors,
4. and 5. bare or p.v.c.
Insulated conductors on insulators. In this case, the height
of the cables and their positions must ensure that protection
against direct contact is prevented,
6. - cable sheathed and insulated
as in 3) above enclosed in a single unjointed length of
heavy-gauge steel conduit of at least 20 mm diameter.
Table 7.8 - Maximum
span and minimum height for
----------------- overhead
wiring between buildings |
|
Type of system
|
Max. length
of span
|
Minimum height above ground
|
|
-
|
(m)
|
At road crossings (m)
|
Accessible to vehicles (m)
|
Not accessible to vehicles (m)
|
|
1
|
No limit
|
5.8
|
5.2
|
3.5
|
|
2
|
Consult manufacturer
|
5.8
|
5.2
|
3.5
|
|
3
|
3
|
5.8
|
5.2
|
3.5
|
|
4
|
30
|
5.8
|
5.2
|
3.5
|
|
5
|
Consult manufacturer
|
5.8
|
5.2
|
3.5
|
|
6
|
3
|
5.8
|
5.2
|
3.0
|
|