Help with lights flickering at weird regular interval

Question

Lights flicker for ~17 seconds at 1 flash/sec, then normal for ~23 seconds. This cycle repeats itself continuously.

The video starts with the 23 second "normal" period, followed by 17 seconds of flickering, and shows 2 cycles. May need to turn screen brightness up, but if you watch closely the flashes are evident.

Context about my home's electrical system:

• video is of ceiling light
• flickering is not isolated to a single circuit. Occurs in bedroom circuit, bathroom circuit, kitchen circuit (fridge light), outside garage light, and floor lamps plugged into outlets
• 1950's house, copper wiring, no ground on most circuits except for kitchen. Location is in Indiana, USA
• In Jan 2018, recently after purchasing house, I:
  • installed GFCI outlets at the head of each circuit to conform with NEC code for having 3-prong (grounded) outlets on wiring with no ground.
  • replaced all other normal receptacles and switches
  • replaced all lights with LEDs
  • flickering phenomenon only started about 4 months ago, well after I made above changes
• I have a single dimmer switch for kitchen ceiling light, which is LED. Both dimmer switch and LED claim compatibility with dimming functionality. Oddly enough, this light doesn't flicker, at least not strongly enough that I can perceive it
• 100 amp service

Things I've tried already:

• Had utility company replace connections to weather-head due to imbalance on legs of main coming into panel. Flickering was occurring before this, and this did not solve.
• Asked utility company if transformer was sized appropriately/working correctly. Technician said yes, but also didn't climb pole to inspect transformer.
• Inspected breakers on all circuits. Replaced some that I thought could have poor connection, but flickering continued.
• Inspected panel for any loose connections at bus bar, tightened a few, but found nothing suspect

I'm fairly handy, an engineer, and confident in my ability to troubleshoot without getting myself electrocuted, but I'm out of ideas. Any thoughts?

Link to video

Panel model info:

Answer 1

I had strange flickering in the past (but not quite with the strange periodicity you are), and this is how I found the device(s) that was dirtying up the power for my whole house:

1. Go to the breaker and shutoff all but one of the flickering circuits

Did the flickering stop?

if yes:

2. One by one turn each circuit back on until the flickering returns
3. Once flicking returns you now know which circuit contains the device causing the problem (the last one you turned on). One by one, unplug/unscrew each device/bulb from the circuit until the flickering stops

if no:

• Turn off the circuit, and switch on a different one that you had noticed flickering on

  • If the flickering is gone, it was due to a device in your home, proceed to step 3 to isolate the device.
  • If you are still experiencing flickering, it is likely due to a problem your electrical carriers equipment. Call them and let them know you've isolated the problem to something on their end.

Answer 2

It's the toaster oven cycling. My Breville does that, whole house has LED bulbs that only flicker when oven is on.

Answer 3

I had the same problem it turned out to be the preheater in my ninja coffee maker. Now i turn the coffee maker off till im ready to use it. Problem Solved.

Answer 4

I have this problem, it seems that power fluctuations can be common. This can be caused by a central heating system turning on or off, or an oven or something else. Unfortunately with LED bulbs in particular they are incredibly sensitive to slight variations in power / voltages.

If this isn't a wiring problem and the flickering is once every minute or so - like mine, just swap the LED bulb for a dimmable LED bulb.

In my case I am suspicious that it's something going on with the meter.