ECN Forum Forums Technical Discussion Electrical Theory and Applications surge vs. overvoltage

Can anyone explain to me the technical difference between protection from overvoltage (as in a line conditioner) and surge protection. What is the difference between an overvoltage situation and a surge (is it a voltage threshold or a phase characteristic?)

When protecting something like a fire alarm panel shouldn't I be considering both?

Thanks

Typically, AC-powered electromechanical equipment can handle —13% to +6% line-voltage variation or “excursions”. They won’t necessarily operate efficiently, but they’re not supposed go up in smoke, either. An AC voltage-range ‘treaty’ settled upon by utilities and appliance manufacturers has been around since about 1954.

With semiconductors and other electronics being shoehorned into just about everything with a cord, the game changed a bit with the eventual realization that electronics was far more susceptible to transient-voltage changes, and may not only misoperate, but fail, and in some cases, become dangerous {and/or very expensive} in the process.

Enter the CBEMA-ITIC curve summarized at www.itic.org/technical/iticurv.pdf Voltage Tolerance Envelope Applicable to Single-Phase 120-Volt Equipment

Another reference is IEEE Std 1100-1199 {Emerald Book} Powering and Grounding Electronic Equipment Short article www.ecmweb.com/ar/electric_overview_ieee_emerald/

A “surge” is a subset of overvoltage. {It’s mostly all a matter of timing.} Poorly-designed power supplies can be agonizing to deal with.

As is my understanding a "transient" is when the voltage rises at least 10% above nominal for a period no longer than 8.3 microseconds. Any duration from 8.3uS to 1 minute is a "surge" and anything longer than 1 minute is an "overvoltage".

Don't hold me to that absolutely, I couldn't find a recognized source to verify it.

-John

Thanks guys.

Good stuff, Bjarney. I can't seem to locate a copy of Emeralds book. Not on Amazon or IEEE website. I was only curious about the cost and availablity, but now I wonder why it's not available.

Thanks again.

IEEE Std 1100 is shown available in hardback book and PDF vesions, for a fee. [PDF is ~2.9MB]

{...Dead Link}




[This message has been edited by Bjarney (edited 04-06-2004).]

Go to http://shop.ieee.org/store/default.asp?tabtype=stand
and type “ 1100-1999 “ [no quotes] in the search field.