busbar s.c. rating

busbar could overheat and melt.

Also, large currents create magnetic forces that can bend the bus bars if they are not properly braced.

Fault current has two-fold effect on busbars:

i) Thermal stresses - proportional to I2Rt - which would melt the bus bars.

ii) Electrodynamic stresses - proportional to i2 - which would deform the bus bars

For detail of the mechanical stress that the bus experiences due to fault current, see this thread:

http://cr4.globalspec.com/comment/553378

-MS