Lightning Effect on Computer CRT's

[Shazam]

Is it possible that a nearby lightning strike can effect the operation of CRT computer monitors? An office I support recently reported that they may have been struck by lightning and immediately afterwards ALL their CRT computer monitors went dim or displayed distorted images. There are no signs of a lightning strike to the building and an electrician has confirmed that there is no damage to the power distribution in the building. The building does not contain a lightning protection system or TVSS. There were no other reports of problems in the building. No tripped breakers, loss of power, or lighting issues. All CRT's have been replaced with LCD's so I may never find out what caused this problem. Most everyone in the office does not have a technical background and they think they took a direct lightning strike. I think there is a more logical explanation to this event.

 

[grich]

I think there is a more logical explanation to this event.

I think the staff conspired to get new LCD monitors!:wink:

I may be wrong, but if a lightning strike hit close enough to affect CRT's, the EMP would have roasted SOMETHING else. One of my clients had a strike hit the ground just outside the building. Computers were hard-hit-every NIC and every occupied network switch port fried, most of the phones fried, audio consoles had input or output op-amps fried, but only four power supplies out of 25 computers, and no other damage to 120/240V devices (and there is a TVSS at the meter).

Was there a brown-out in the office?

 

[Shazam]

Thanks for the response. There wasn't a brown-out. From what we can tell, those in the office saw the flash and felt the building shake from thunder. One fax machine had a problem, but they replaced the phone cord and it was fine. The lights never went out and everything continued to operate with no problem. There were approximately 40 monitors that were replaced. No surrounding buildings appear to have any damage or issues from this event. The office LAN equipment did not experience any outages or problems. It appears that the only affected components were the CRT monitors.

 

[LarryFine]

Is it possible that a nearby lightning strike can effect the operation of CRT computer monitors?

It appears that the only affected components were the CRT monitors.

It seems the thing speaks for itself. Unless it's a conspiracy, what else could it have been?

 

[petersonra]

I suppose it is possible.

Could also have been a magnetic event. Did they try the degaussing function on their monitors?

 

[steve66]

It is possible that the lightning strike magenitized the monitor screens.

The earth's magnetic field is even strong enough to do this to a TV or a monitor. (Don't ever leave a TV on its side or upside down overnight - unless you like seeing green and purple people.)

The monitors have a degaussing coil that fires when the monitor is first turned on. The distortion might be eliminated after several on-off cycles of the monitor.

Steve

 

[catchtwentytwo]

Were "the former" monitors (now boat anchors) a single brand and/or model or were several manufacturers involved?

 

[wirenut1980]

I think the staff conspired to get new LCD monitors!:wink:

I may be wrong, but if a lightning strike hit close enough to affect CRT's, the EMP would have roasted SOMETHING else. One of my clients had a strike hit the ground just outside the building. Computers were hard-hit-every NIC and every occupied network switch port fried, most of the phones fried, audio consoles had input or output op-amps fried, but only four power supplies out of 25 computers, and no other damage to 120/240V devices (and there is a TVSS at the meter).

Was there a brown-out in the office?

This sounds more like ground potential difference from having all grounds not bonded together than EMP.

Only CRT monitors affected would suggest some kind of magnetic interference.

Or a conspiracy.

 

[Shazam]

All good suggestions! By the time I was made aware of the problem, most of the monitors were replaced with LCD screens. Not sure where all the screens came from! It appears that the CRT's were all Dell monitors. I agree that several on/off operations of the monitors may have degaussed the screens and corrected the condition. I think the office panicked and thought the problem was more serious then it was. All computers are connected to an Isolated Ground panelboard. No other components are having problems from this panel.

 

[catchtwentytwo]

Sound like your customer should have an expert look at the whole picture. The monitor issue looks like a wakeup call.

The lightning protection contractor I've worked with once gave me something to think about that I want to share:

"Remind IT people that lightning strokes go in two directions ...cloud to ground or ground to cloud".

Once we had a "protected" microwave antenna. A network guy carefully took the coax and neatly tie-wrapped it along the lightning leader for a good 50 feet before entering the building. When the antenna was removed, the coax stayed "as is" and eventually got hit by a ground to cloud discharge, bringing it into the building to a LAN closet. You can guess the rest!

 

[oceanaradio]

Sound like your customer should have an expert look at the whole picture. The monitor issue looks like a wakeup call.

The lightning protection contractor I've worked with once gave me something to think about that I want to share:

"Remind IT people that lightning strokes go in two directions ...cloud to ground or ground to cloud".

Once we had a "protected" microwave antenna. A network guy carefully took the coax and neatly tie-wrapped it along the lightning leader for a good 50 feet before entering the building. When the antenna was removed, the coax stayed "as is" and eventually got hit by a ground to cloud discharge, bringing it into the building to a LAN closet. You can guess the rest!

Hello "Wrangler" John,

While it's a good call that something could be seriously amiss, there is however no such thing as "ground to cloud lightning".

There are the less-common positive-charged cloud to ground strikes (most are negative charged), and cloud-to-cloud lightning. What comes "up" from objects on or near the earth are positively-charged ion streamers. They are emitted from all objects in advance of the arrival of a thunderstorm. Some of these upward-flowing streamers will reach high enough to form a connection to a downward-flowing step-leader from the cloud. That connection "snaps" everyone to attention in the nearby area, and the upward-flowing streamer momentarily intensifies enough to ionize a vivid colored current path visible to the eye and certainly to cameras. Hence the misnomer that lightning stikes from the ground-up. Not really, the downward-flowing step-leader already traveled miles to make a last-second choice from among hundreds of upward-flowing streamers. It makes it's choices between 50-150' above ground.

Then the first of several possible "return strokes" follow the original connection. Thousands of times the energy is expressed in these return strokes than even the step-leaders carrry. The low-energy upward-flowing streamers are what makes hair stand up on people who witness them such as golfers who are about to be struck, or run a dangerous risk of being struck anyway.

A CRT should be able to actually emit a positive-charged upward flowing streamer while it was operating without any ill effects. Of course anything that is part of the final connection from a stepped leader is another story.

Best regards,
Jack
Virginia Beach VA

 

[catchtwentytwo]

As a follow up on the existence of "ground to cloud lightning", I asked about it on Yahoo's LightningProtection ? Lightning Safety & Power Quality Issues Group. Here's a response from Dr. Abdul Mousa:

Upward lightning discharges do occur from tall objects when lightning strikes a ground object in their vicinity. This is because the transient electric field at tip of the tall object exceeds the breakdowm gradient of the air. Most upward lightning discharges are harmless as their vertical reach is limited and the related current is small. In some cases, however, they may reach the base of the cloud and attract subsequent downwatd strokes. High currents would then flow into the ground objects. The median value for these is about 12 kA.

Upward lightning discharges do not require special protection as the measures intended to protect against the typical downard lightning discharges will also protect against upward discharges. However, in case of some communication towers, the frequency of the encountered transients will be significantly increased.

Regarding safety of personnel, upward lightning discharges is the cause of many of the shocks which some people encounter when a close lightning flash occurs. People often confuse the trauma as being a consequence of a direct lightning strike and feel happy that they survived a lightning strike. The real cause of the minimal injury, on the other hand, is that they were subjected to an induced upward discharge rather than a direct lightning strike.

Thank you.

Abdul Mousa, Ph.D., P. Eng., Fellow IEEE
Lightning Protection Consultant
Vancouver, Canada


Removed email by request, Bob

 

[oceanaradio]

While I follow the work of Dr Abdul and others on the Yahoo Group also, what he described is not a ground to cloud lightning strike, it is a very small continuation of a cloud to ground strike. It is rare in and of itself to have enough energy left to cause a secondary breakdown in the transient voltage level of the air above a tower, and as he commented if it does there is not enough energy left in it to go any appreciable distance. Reading the same research that NASA provides from thousands of rocket-triggered strikes, I recall no such mention of ever measuring a single strike reaching ground and then observed making it all the way back to a cloud from a tall tower. Perhaps that tower reached the clouds. While that doesn't mean it can't be modeled, postulated or observed, it is very rare. Nonetheless it remains a continuation of a cloud to ground strike. No strike ever originates on the ground, and it appeared that was the story John related second hand from someone else. Further to Dr Abdul's coments, the effect of feeling electrical shock from a nearby strike is hardly comparable to the rare phenomenon of a secondary air-breakdown in a reverse-direction. The ground potential return up and through nearby objects (or people) is a common and secondary effect of the original strike, but it is not a separate event.

What confuses many readers of lighting research is the term "return stroke". Perhaps half the readers who see that phrase assume it means from the ground up to the cloud. This is not the case, the return stroke is the powerful follow-on from cloud to ground of an original connection betwwen a downward-flowing step-leader and an upward flowing streamer.

Hope this helps.
Jack