Have a very brief & slight flickering of incandescent lights (on different circuits) every 45 seconds. Just started doing this during last week. Can't tell if the lights get brighter or dimmer - it happens so fast. No other electrical devices turned on that might cause flickering. Have an old house with some old wiring and a 60 amp fuse box. Fuse and light bulb changes made no difference. Electrician found no shorts or problem with fuse box or wiring but did suggest upgrading to 100 or 200 amp breaker box. He suggested I have power company check out power line in. Power company could not detect a problem - although squirrels had been chewing on line. He fixed that spot on the line and will have line replaced in future. He also said power company will do a more sensitive check of voltage coming into house by installing device by meter sometime after the holidays. Any ideas?

Since you have some pros on site they will give you a much better answer than we can from reading symptons. I do not think it's a short at all but more like a loose neutral in your panel or your feed. Let the power company do their job, they would not appreciate hearing advice from outsiders

Since you only have a 60 Amp service, any load upline could affect your power. It may be in the house next door. If you have a computer online, it could be the automatic memory update although 45 secs seems fast.

Thanks for suggestions. Problem turned out to be a malfunctioning low voltage transformer on the circuit.