[fainpul]

So the assumption is that the electricity you get is not "clean". You could check if your energy provider publishes some data on their website (like frequency and voltage stability). If not, or if the issue is within your house installation, you could use a multimeter to measure voltage and frequency at the outlet during such an event. Disclaimer: be careful – this can kill you if you make a mistake. Only use a multimeter and probes which are properly rated to measure electrical outlets in your house. Read the manual / make sure you understand the risks involved.