Surge Protector

What Does Surge Protector Mean?

A surge protector is an electrical device that is used to protect equipment against power surges and voltage spikes while blocking voltage over a safe threshold (approximately 120 V). When a threshold is over 120V, a surge protector shorts to ground voltage or blocks the voltage. Without a surge protector, anything higher than 120V can create component issues, such as permanent damage, reduced lifespan of internal devices, burned wires and data loss.


A surge protector is usually installed in communications structures, process control systems, power distribution panels or other substantial industrialized systems. Smaller versions are typically installed in electrical service entrances located office buildings and residences.

Techopedia Explains Surge Protector

A voltage spike is a short upsurge of voltage intensity that occurs when a surge sustains longer voltage intensity. A power strip, which is sometimes mistaken for a surge protector, uses a male electrical plug outlet and may or may not have a built-in surge protector. Most power strips are clearly labeled.

A common misconception is that surge protectors always protect against lightning, which can create sudden and increased electrical pressure (thousands of volts or greater). Generally, a surge protector has a slight operational delay, but a surge protector fuse can blow during a lightning surge and cut off all current.

Surge protector components and features include:

  • An iron core transformer transfers alternating current (AC) power but cannot absorb sudden surges.
  • A zener diode protects against common circuit spikes and is sometimes combined with a transient voltage suppression diode.
  • If a circuit breaker is out or blows a fuse, a surge protector provides internal protection and protects against device and exterior surges.
  • Uninterruptible power supply takes in spikes using a low pass filter and allows external power beyond the battery, which supplies uninterrupted power.
  • A metal oxide varistor (MOV) is thermal fused and limits voltage three to four times that of a regular current. Parallel MOV connections expand life expectancy and increase current capacity. If exposed to many large transients or numerous small transients, MOVs can self-destruct.

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Margaret Rouse
Technology Expert

Margaret is an award-winning technical writer and teacher known for her ability to explain complex technical subjects to a non-technical business audience. Over the past twenty years, her IT definitions have been published by Que in an encyclopedia of technology terms and cited in articles by the New York Times, Time Magazine, USA Today, ZDNet, PC Magazine, and Discovery Magazine. She joined Techopedia in 2011. Margaret's idea of a fun day is helping IT and business professionals learn to speak each other’s highly specialized languages.