Rigid bus simplified short-circuit calculation 1

[b_gibb]

I'm trying to follow the IEEE 605 example for calculating the cantilever force on a rigid bus insulator due to short-circuit. I understand the example with the exception of how they determined the equivalent forces (F1, F2, F3 in Figure F.2) from the Fsc.

Example:
F3 = 3 x Fsc_corrected * L / 16. Where did the constant 3 and 16 come from? Same for F2 (where did constants 5 and 8 come from?). See pictures.

ben
bengibb.ca
powerdesignerpro.com

 

[cuky2000]

The table 18 is to determine the maximum span length between insulator supports.
The reactions on the bus supports insulator are determine by other structural calculations based on a uniform beam load with selected support (boundary) conditions P, F, C.
The 3/16 and 5/8 come from structural calc and loading diagrams similar to the one shown below.

 

[7anoter4]

Although the calculation -in IEEE 605-e is done for the cantilever
the explanation for the beam supported at two ends can be considered. Thank you, cuky.