Power surge question

[gr8gr8]

Hello,

I have a question about power surges. We have a pc that is on a protected circuit (backup power) and is connected to a monitor which is not protected. Can a power surge migrate to the pc via the video card? A user brought it up to my attention and I'm thinking this is ridiculous... there's no way that could happen. Thanks for any replies.

 

[Skogsgurra]

That depends what you mean with a "surge". You are right that a surge in the classical meaning cannot propagate through the monitor to the PC. No problems there.

But, some HF pollution or fast transients (ESD) could perhaps sneak in that way. But that shouldn't be a problem either. And a UPS wouldn't prevent it. Most of these "but, have you considered" (this and that?) are mostly someone showning off.

 

[advidana]

yes your computer is not protected place the monitor on the ups or use a surge protected power strip on the monitor. even with the surge protection a lightning strike will get thru. The surge protection will give you a lot of protection but not total protection. it depends where the lightining strike hits your power line ( how close to your equipment). I usually disconnect my equipment when there is a lot of lightning strikes near by.

 

[dangnm]

I agree with advidana on this one, although mine is just an opinion based on no hard data. It is my understanding that a lightning strike will follow any conductor, and jump across non-conductors if that is easier. If the monitor gets zapped by lightning then I would expect the pc to get fried as well.

The occasional kilovolt transient that you get on ordinary mains supply should not be a problem though.

 

[logbook]

This new automatic logoff "feature" is beginning to annoy me. That is my post above.

 

[BrianR]

As advidana said, you are not protected. At least use a good mains filter on the monitor. There are a number of ways that power surges can slip by through an unprotected channel but one of the more interesting is this one.

When a piece of equipment faults to ground, for a brief time until fuses blow or power supplies shut down, there is a large current in the earth wire back to the fuse/junction box and the gound pin at ALL power outlets on that loop circuit can rise momentarily to full mains voltage. Subsequently any other piece of equipment connected to that circuit will be subject to a capacitive current from the chassis ground into the circuit boards and they may be damaged. This occurrs more frequently than you'd think.

This is going beyond your question but for interest the protection againdst this is to use MOVS (A-N, A-G, N-G) at each equipment and insert an earth choke of about 1uH in series with the ground wire. The choke must be capable of carrying full fault current.

 

[robertjo]

It has been my experience, (unfortunate and costly experience), that any unprotected device in a system affects the entire system. I have had equipment that was “protected” destroyed by transients coming from seemingly insignificant peripherals.
I don’t think that there is any real protection from a direct strike taken on the incoming power; you can only lesson the severity with protection devices. Surge protection power strips are a great “first line” of defense for most general users. For systems requiring more protection, add high frequency filtering as well as surge protection on the incoming power lines into your main power distribution system. The great thing about a UPS system is that it often offers filtering and some level of surge protection. If you add filtering and surge protection before a UPS system you gain even more.
Extra protection only seems like a waste of money if you have never experienced a devastating surge event.
The old adage “an ounce of prevention…” says allot for surge/transient protection.

Best of luck.

 

[Bung]

All the surge (transient over-voltage) protection in the world won't protect you if the real problem is a "brownout" or "dip", which is often what is meant by the non-electrical man-in-the-street when he talks of a "surge".

Bung
Life is non-linear...

 

[BrianR]

I think the issue is an affordable amount of protection and assess risk or inconvenience against cost. Eg, on a PC network if you can tolerate an interruption to work but not an accompanying loss of data when there is a power surge/outage/brownout then a UPS on the server and optionally the workstations will save the data. Work will stop if the workstations go down but as long as all other equipment is protected against damaging surges, not only for their own benefit but also to stop them being the conduit for surges into the UPS powered boxes you have a good level of protection.

 

[peebee]

Beware that, contrary to some of the above posts, surge suppressors will NOT protect against lightning. That's what lightning arrestors are for.

A lightning stroke on either of your systems could take your PC out unless both systems are provided with both lightning arrestors and surge suppression.

But outside of lightning stroke, I would not be concerned about other surges propogating through the video cable from the monitor to the PC.