Is it possible to break down the VrayRawLighting Render Element?
I was not able to find the Underlying Compositing Equation.
thanks for any little info!
No, since the VRayRawLighting is the direct lighting data itself.
If you wish to break the pass in terms of separating the effect of individual lights, you can use the VRayLightSelect render element with its mode set to ‘direct raw’.
is there any use you can make of the element VrayLightSelect?
Why would you use Raw elements in the first place? Any specific reason to not use the standard ones?
This is a good source to start from.
Know you can divide the standard REs by their corresponding filter ones (f.e. VRayLighting by the diffuseFilter, VRayReflection by the reflectionFilter, and so on) to get their raw counterparts, minus the edge issues. 
is there any use you can make of the element VrayLightSelect?
It can be plussed with other lightSelect REs, or subtracted from the beauty.