Hi All,
Instead of trying to get rid of the fluctuations from a mains
perspective, perhaps you can get rid of them via using filtering on your
recording gear.

The formula for capacitive reactance is Xc = 1 / 2 x pi x f x c

pi = 3.141592654.......

f = frequency

c = capacitance

Xc = Capacitive Reactance

You will have to look up more info on your own, this is just a guideline

Paul