MV design guide - Schneider Electric

Design rules
Busbar calculation
Mechanical strength of the busbars
Assuming that the ends of the bars are sealed, they are
subjected to a bending moment whose resultant strain is:
F1• l v
η = •
12 I
with
η : is the resultant strain in daN/cm 2
l : distance between insulators
in the same phase
70
cm
I /v : is the modulus of inertia of a busbar
or of a set of busbars 14.45 cm 3
(value chosen in the table below)
η =
482.3 • 70
12
1
•
14.45
η = 195 daN / cm 2
The calculated resultant strain (η = 195 daN / cm 2 )
is less than the permissible strain for the copper busbars
1/4 hard (1200 daN / cm 2 ) :
Busbar dimensions (mm)
The solution is OK
100 x 10
S cm 2 10
Arrangement m Cu 0.089
daN/cm A5/L 0.027
x
I cm 4 0,83
x'
x
x'
x
x'
x
x'
x
x'
x
x'
I/v cm 3 1.66
I cm 4 83.33
I/v cm 3 16.66
I cm 4 21.66
I/v cm 3 14.45
I cm 4 166.66
I/v cm 3 33.33
I cm 4 82.5
I/v cm 3 33
I cm 4 250
I/v cm 3 50
36 Merlin Gerin MV design guide Schneider Electric