Question PC shutsdown when another appliance is turned on

[Harsun]

I bought a pc last year, i didnt have this problem at first after several months my pc started to shutdown randomly without a warning and restarts. This happened 2 or 3 times a day then i realised it does this when i turn on too many lights at once in my room or when there is a power flux so i bought a standby ups which still didnt help. I checked the ram , ssd, gpu, everything. It happens even when the pc is not under heavy load like only chrome and discord. I checked event viewer it says critical error kernal power id 41. Its been a 6 months and i still dont know whats wrong pls help

intel i5 9600k, 2x8gb adata ram, gtx 1660 super, asus stirx h 370 f motherboard, corsair mp510 nvme

 

[Brian Boru]

I checked the ram , ssd, gpu, everything

Did you take all cards out and reseat them? Same with all cables & connections, especially PSU & drives.
If you have 2 RAM sticks, try with one only.

What's the wattage on your PSU?
Look carefully around the motherboard with a flashlight, check for burn marks or blown capacitors—typically a little 'dome' on their top, they should be flat top.

Have a look at your power settings, especially when computer sleeps. If your hard drives are set to turn off after a time, change that to never turn off.

Is it possible your CPU heatsink has become clogged with dust? If it's been a while, give the insides a general blow out to clear dust—and check all fans are working.

If Fast Start is enabled, turn it off.

So you plug the PC power cord into a UPS, but this still happens when you switch on extra lights. That's odd.

Can you recall installing any new hardware or software shortly before this started?