angle de garde

Hello!
I'm working on thyristor bridges in the context of power electronics, specifically the operating area in a plane PQ, and part of the area is marked "angle de garde" - it seems to be some kind of inaccessible area, but I haven't been able to find an exact translation. Does anyone with experience in the field have any ideas?
Thanks!

In one search, "angle de garde" came up with "clearance" - that didn't specify the context.


In another search, it translated into German as "der Böschungswinkel".
And in English, this was:-


angle of rest
natural angle of incline
slope angle
angle of driving slope [autom.]
angle of repose [tech.]
angle of slope [engin.]
natural slope
angle of repose [tech.]


Do any of these terms help?

Thanks. I think I'm going to go with "buffer angle" for now - it gets the meaning across, and there doesn't seem to be one generally accepted translation.