Interesting, on a side note do you have a link to the one in current use for Brazil/south America? Their voltage ranges have moved up, they now use a 220Y127 volt nominal system as and phased out 208V. But I dont think they did that at other commercial/industrial voltages like 480Y277.https://www.pge.com/includes/docs/p...ergystatus/powerquality/voltage_tolerance.pdf
All you could ever wanted to know about voltage range. But 291 is a hair above, or right at the very edge of the sustained utility voltage limit.
Still, LED ballasts that can not handle +/- 10% sustained are inadequate ballasts.
Looking again at his first pic, my guess is the phase conductors attach on the right, with the ECG on the lower right.Other than exceeding voltage limit (such as those caused by loose neutral), electronic ballasts are rather sensitive to surge and even the integral ballast on some disposable LED lamps have an MOV to protect its ballast from small line transients that can harm semiconductor parts. MOVs look similar to a capacitor, but they're not marked "C" on the board. https://www.edn.com/teardown-a19-led-bulb/ see figure 5.
Now, if you find a cooked MOV, that is often caused by over-voltage. So that's something to check on the fried LED ballast. A normal "surge failure don't usually cause the MOV to visibly cook.
Thread starter, you didn't post the other side of the failed board. Did you take pictures of the component side?
what burned appears to be a bank of 4 resistors in paralell, that perhaps connect to a trace of the ECG?
My guess is the MOV's would be really close to where the large pads are for the line conductors.
Would be cool to get an update on this.