What Are the Causes of Overvoltage?

Overvoltage is an electrical event that can occur for various reasons, many of which can be destructive for facilities. With the increase of electronic components today, understanding the causes of overvoltage and providing solutions has become even more important. Perhaps the most well-known overvoltage impulse is the lightning strike. This impulse, with a 10/350 waveform, is the most destructive for facilities. Internal overvoltages, on the other hand, with a 8/20 waveform, are often neglected impulses that cause most of the damage.

Why Does Overvoltage Occur?

1-Voltage Sag

Temporary reductions in AC voltage are called sags. Temporary sags last between 0.5 and 2 seconds and usually occur due to short circuits. Longer-lasting sags are permanent sags.

2-Voltage Swell

Voltage swell, the opposite of sag, can be another cause of sudden overvoltage. Temporary voltage swells last between 0.5 and 2 seconds and usually occur due to short circuits. Longer-lasting swells are permanent and dangerous.

3-Impulses

Impulses usually have high destructive power and can damage systems if proper protection is not provided. While lightning is the best-known electrical impulse, large motors, transformer switching, inductive and capacitive effects are other important impulse causes.

Sudden voltage increase and resulting impulse

Impulse peak caused by a lightning strike

Other sudden overvoltage causes include:

• Harmonics
• Switching operations (8/20 waveform)
• Inductive or capacitive coupling

A factory burned due to a lightning impulse