The flickering coincides on 2 separate circuits that I know of.
This is not the brief interruption of electricity that occurs when a
major appliance starts up.
A licensed electrician inspected the circuit breakers for ground,
broken buss bars, signs of arcing and loose connections, but found
nothing. He also inspected the utility company's electric meter for
loose connections and signs of arcing.
One of the circuits has a refrigerator and microwave oven connected to
it (2 separate electrical outlets on same circuit). I notice the
clock on the microwave oven dim and hear the refrigerator cut off at
the same time. Also, a fluorescent lamp flickers at the same time the
electricity to a modem is cut off on a different circuit (2 separate
electrical outlets on same circuit).
What could affect 2 separate circuits and cause this flickering?