Is there a standardized way of calculating load bearing of beams with connections notching the beam?
All loads on beams / columns matter. So, if you are adding beams (loads) to existing beams, you are right to worry about its affect. However, there are three things in your favor: 1) everything is designed with a "safety factor", 2) residential design is way-over designed, and 3) beams are designed to fail in tension. 

1) Structural design has "Working Stress" and "Ultimate Stress". Ultimate stress (failure) is about 150-180% more than working stress (what we design beams, columns, etc. to).

2) Residential design is largely done by non-professionals (architects and structural engineers). So, "what is commonly used" in residential construction is grossly over sized. 

3) Beams are designed (design formulas used) to fail in tension. That way, we'll see cracks and presumably investigate, rather than fail by compression, which will fail with a bang...and have a disaster. 

So, back to your question, yes, there is a way to determine how much weight can be added to a beam, how big holes (and how many holes) can safely be drilled into a beam, etc.  However, unless you're "doubling the load" or excessively drilling an existing beam (1 connector is not excessive), then I think your safe. 

You can destroy a concrete beam quicker than steel or wood beams. When drilling the concrete beam, you'll know quickly if it's a poured-in-place beam or a steel beam encased in concrete. In fact, you may not be able to drill through the steel/concrete beam. So, rather than "mess with the concrete beam", why not design a "saddle" to fit over the beam and support your new added beam and lights. 

If you decide to proceed with drilling the concrete beam, I'd recommend you contact an architect or structural engineer (not a CIVIL engineer.)