Medium Voltage Power Cables Catalogue - AEC Online

Where;
P : Sidewall pressure in N/m (lbf/ft)
T o : Tension leaving the bend in N (lbf)
r : Inside radius of conduit in m (ft)
The normal maximum sidewall pressure per meter (feet) of radius is as given below. However, in order to minimize cable
damage because of excessive sidewall pressure, the installer should check the proper recommendations for each type of
cables to be installed.
Cable Type
Maximum sidewall pressure
( N/m ) ( lbf/ft )
6 to 15 kV Power cables
20 and 30 kV Power cables
Armoured cables (all voltage grades)
7300
4400
4400
500
300
300
B.7 Laying methods
The best method of laying a cable depends on the type of cable and working conditions. The following are generally
applied as the most common cable laying methods:
B.7.1 Direct in the ground
This method is shown in the figure below, and is employed in following cases;
1. Where road is narrow so the construction of conduit under the
road is not permitted.
2. Where the number of cables is few and no future increase is
expected.
3. Where the road digging is easy.
B.7.2 Underground tunnels or ducts
This method is shown in the figures below, and is employed in following cases;
1. It is the main underground transmission line where the number
of cables is many or expected to be increased in near future.
2. Where there is hard pavement or where hard pavement will be
constructed in future.
3. Where digging is difficult due to heavy traffic.