EL
BG
DE
ES
FR
ITGlossary · Power quality
Overvoltage
A voltage above normal that lasts from seconds to hours and can stress or damage connected equipment.
Technical level:Intermediate
Overvoltage occurs when the mains voltage rises above its tolerance limits. It can be sustained, caused by poor grid regulation, light loading on the line or a lost neutral in a three-phase supply, or transient, such as surges from lightning and switching operations on the grid.
Sustained overvoltage overheats power supplies, motors and lamps and can destroy electronics within minutes. An AVR stabilizer or a line-interactive UPS corrects it within a certain range, while a double-conversion UPS delivers a stable output across its whole input range and switches to battery beyond it.
A common mistake is assuming that a power strip with surge protection also covers sustained overvoltage; its varistors are designed only for brief spikes.
Questions that mention it
All frequently asked questionsWhat does a UPS protect against?
Depending on its type, a UPS protects your loads from: loss of power (power outage), overvoltage (short- or long-term), frequency variation, switching transients (momentary interruption), harmonic distortion, and noise (electromagnetic interference).
Related terms
- Voltage SpikeA momentary, very high voltage rise lasting microseconds, e.g. from lightning or load switching, that can damage equipment.
- Automatic Voltage Regulator (AVR)A device that automatically maintains a constant voltage level to protect electrical equipment from fluctuations.
- BlackoutA complete and sudden loss of grid power, lasting anywhere from seconds to several hours.
- RFI — Radio Frequency InterferenceA subset of EMI: high-frequency noise from electronic equipment that can disturb radio, Wi-Fi and other devices.
- Surge ProtectorA device that limits brief voltage spikes from lightning or grid switching by diverting the excess energy to earth.
- UndervoltageA sustained drop of mains voltage below normal that can cause malfunctions or overheat motors.