high voltages and spikes

Thread Starter


Joined Dec 22, 2019

Thank you for pressing my post.

I would like to know,

What type of circuitry is usually used to protect electronic and electrical equipment from voltage spikes and high voltages for both AC and DC applications?

In addition, how can one classify high voltage?

For example, if a system requires 120V AC what would be the acceptable voltage percentage error that the system can operate safely and correctly. Would it be approximately 2% ?

Help would be much appreciated


Joined Aug 7, 2020
To answer your last question first - 10%.
There are all sorts of definitions of "high voltage" depending on the context. For example, if you are the power company, then 230V AC is called "low voltage". In your context, I think a suitable definition would be a voltage that can damage your product.
There are statistics available which will tell you for a given level of over-voltage how often it is likely to occur.
You have several lines of defence: capacitors, varistors, spark-gaps, sidacs (and other zener-diode type things), trisils (and other diac-type things), and simple LC and RC filters.
"Protection of Electronic Circuits from Overvoltages" by Ronald B Standler (ISBN 0-486-42552-5) is a good text on the subject .
It's not a exciting read.