Typically, AC-powered electromechanical equipment can handle —13% to +6% line-voltage variation or “excursions”. They won’t necessarily operate efficiently, but they’re not supposed go up in smoke, either. An AC voltage-range ‘treaty’ settled upon by utilities and appliance manufacturers has been around since about 1954.
With semiconductors and other electronics being shoehorned into just about everything with a cord, the game changed a bit with the eventual realization that electronics was far more susceptible to transient-voltage changes, and may not only misoperate, but fail, and in some cases, become dangerous {and/or very expensive} in the process.
Enter the CBEMA-ITIC curve summarized at
www.itic.org/technical/iticurv.pdf Voltage Tolerance Envelope Applicable to Single-Phase 120-Volt EquipmentAnother reference is IEEE Std 1100-1199 {Emerald Book}
Powering and Grounding Electronic Equipment Short article
www.ecmweb.com/ar/electric_overview_ieee_emerald/ A “surge” is a subset of overvoltage. {It’s mostly all a matter of timing.} Poorly-designed power supplies can be agonizing to deal with.
