About 3 months ago, our dining room lights started to flicker on and off for about 15-20 seconds at the same time every night-- between 7:05-7:15. They only do it once, then not again until the next night.
It started when we switched to LED bulbs. Nothing else is coming on or off in our home at that time. Any ideas??
Some sort of periodic (evidently once per day at that time, or perhaps that's the only point it happens when you'd have those lights on to see it) EMI/RFI event that the LED bulbs are sensitive to, which went unnoticed by the previous bulb type.
Could be industrial (heavy equipment shutting down or starting up) could be some type of radio/radar event (military base or airfield nearby?)
The "Australia?" comment brings up the possibility that it might be a Utility signal on the line to activate "off-peak" devices. They are not the only place that uses that sort of system, but they certainly are one that does.
In our house, LED lamps with dimmers would do this, every time the power went off and the supply switched to solar. Strangely, it does the same thing when the batteries run out and we are on the Generator. The only thing I found was that the grid is 220V but the Solar and the Generator are 240V.
So, I would suggest that it's either the lowering or raising of voltage that may be causing it. Also, note @Ecnerwal's good suggestion that you only notice it when they are turned on at night. It could be turning on or turning off of appliances that may be causing this. Examples of events that may cause this
This could be a neighbor that's been supplied on the same phase. If you are in Australia, they are most probably wired the same as here in New Zealand. The grid supply from the local transformer is 3 phase. This is crudely balanced by supplying every third house with the same phase.
A local pet shop had this problem where the computers would restart at 10 am every morning. I finally discovered that the mechanic down the road was turning on heavy equipment such as Air compressors and welders at that time.
If they are just bulbs (as compared to light fittings), then try putting them in another room. It will give you more information.
