olemus
pinge püsimine nimipingest kuni 10% madalamana üle 60 sekundi
= a condition where the applied voltage drops to 90% of rated voltage, or less, for at least 60 seconds

ülevaateid
https://www.mes.com.sg/2019/09/19/overvoltage-undervoltage-all-you-need-to-know/
https://www.etechnog.com/2021/10/undervoltage-protection-devices.html
https://en.wikipedia.org/wiki/Undervoltage-lockout