Övervoltage

Övervoltage, or overvoltage, is a condition in electrical systems where the voltage exceeds the normal operating level or the insulation rating of equipment. It is commonly categorized as transient overvoltage, which lasts a very short time, and sustained overvoltage, which persists due to faults or abnormal supply conditions.

Causes include lightning strikes and switching transients from power networks, short circuits, faults in equipment, resonance or harmonic activities, and operational events such as capacitor switching or transformer energization. External events such as weather or grid disturbances can also induce overvoltage.

The effects depend on magnitude and duration but can include insulation stress and breakdown, accelerated aging of insulation, damage to electronic components, nuisance tripping of protective devices, malfunctions, and, in extreme cases, fires.

Protection and mitigation rely on proper engineering and protective devices. Surge protection devices such as metal-oxide varistors (MOVs), transient voltage suppression diodes (TVS diodes), gas discharge tubes, and protection relays are commonly used. Adequate insulation margins, grounding and bonding, isolation between subsystems, and appropriate voltage regulation reduce vulnerability. Design practices may include selecting equipment with adequate withstand voltage, using filtering and damping, and applying coordinated protection.

Measurement and standards define acceptable levels of overvoltage and response times. Standards from IEC, EN, and IEEE provide definitions for transient and sustained overvoltages and specify test methods and protection requirements for equipment and installations.