I think reliability should be divided up in different ways.
Their is "how well the moving bits are moving" which is different than "lines getting knocked down by acts of nature".
So, for example, I live in Seattle. Our power generation is quite reliable, but trees falling down during wind storms and knocking out power lines is also reliable, gravity being what it is.
I don't consider the Seattle grid to be unreliable, though I do acknowledge that digging up the entire city and burying power lines would, at great expense, prevent nearly all power outages.
But that sort of unreliability feels different than brown outs.
My utility concluded that between underground animals chewing wires, idiots with backhoes not locating before digging, and the extra time effort to repair burred lines: overall overhead wires are more reliable than underground. Note that they put a lot of effort into tree trimming near their overhead wires, which made trees falling on them was a rare problem.
Their is "how well the moving bits are moving" which is different than "lines getting knocked down by acts of nature".
So, for example, I live in Seattle. Our power generation is quite reliable, but trees falling down during wind storms and knocking out power lines is also reliable, gravity being what it is.
I don't consider the Seattle grid to be unreliable, though I do acknowledge that digging up the entire city and burying power lines would, at great expense, prevent nearly all power outages.
But that sort of unreliability feels different than brown outs.