220 kV Pantograph Disconnector Terminals

[Power0020]

I am currently doing a design for a 220 kV double bus single breaker SS, the design uses pantograph disconnector.

Manufacturer drawing shows that the terminal permissible loading differs greatly from horizontal and transverse horizontal directions, making life a bit hard for pipe connection with the other disconnector due to high short circuit forces.

I don't know why the equipment terminals have different values for Fa horizontal(straight)and Fb transverse horizontal (cross/lateral) loads despite the fact that both forces act horizontally (with the same cantiliver moment on the post insultors!!)

any clues?

 

[7anoter4]

In my opinion, it is according to:
lEC 62271-102 Standard HIGH VOLTAGE SWITCHGEAR AND CONTROLLER
PART 102 ALTERNATING CURRENT DISCONNECTORS AND EARTHING SWITCHES
Table 3- Recommended static mechanical terminal loads[ for 245 kV 2000 A rated]