Transient Voltage Surge Suppressors (TVSS) and nearby lightning strikes

[WB2CAU]

I'm hoping to get input from folks who have experienced nearby lightning strikes as Bruce W1UJR experienced last week.

Over the years, I've experienced many nearby strikes that took out various pieces of electronic equipment and left others unscathed.  Based upon personel experiences with close strikes, what DID survive?  Did you have transient voltage surge suppressors (TVSS) on any devices that survived?  Or perhaps I should ask, did anything directly connected to a TVSS crap out? 

Personally, I've only started taking an interest in these devices after having experienced nearby strikes in 1997, 2000, and 2003.  All 3 strikes resulted in some damage, and no TVSS devices were used at all.  We are in the middle of lightning season now and W1UJR's recent hit reminded me of methods to protect what I have.

Since I can't necessarily be around to disconnect everything when those unexpected T-storms arrive, I think it might be prudent to embark on a program to buy TVSS power strips for ALL sensitive household devices.  And these days that includes basic appliances with microprocessor controllers and switching power supplies that might be sensitive to sudden impulses.  But I'd like to know the track record of TVSS in real-world conditions, not just lab conditions. 

Anybody care to comment on their own experiences with TVSS? This question includes TVSS with provisions for 75 ohm coax and modular jacks for telephone and CAT-5 connections. 

Thanks,
Eric - WB2CAU

[WA1GFZ]

Eric,
We use a lot of them at work and they are a fine part. I've done some testing and find a 10 volt 3 KW unit will clip at 15 volts with a 45 amp 70 us. pulse going through it.
We use a lot of 15 KW units on out products. Higher voltage parts handle less current.

[N9NEO]

They have Joule ratings.  Larger parts = more joules.  There used to be a guy at GE in NY(GE either invented them or perfected the marketing of them.) Named Sebald Korn.  His co-workers called him Mister Varistor.  He was a pretty good resource as far as they go, but I'm not sure he is still there.... and there I go rambling on.  Anyway, if you can find an old GE varistor data book they have done quite a bit of research on power lines to determine probabilities of various overvoltage events.  I think that is what you are looking for.  I will look for the data books in the company library, but I don't remember seeing the book recently.

You can probably buy a couple of big ones (MOVs) and stick em on your lines coming into your house.  If you have a lot of connected capacitance to your line you may find they will eat up a lot of joules as well.  If you leave your computer plugged in or other types of gear that have a diode bridge and bus caps then this will help.  You have in effect created an LC filter with the power line impedance and the bus capacitance.  Also, a capacitor will act like a large zener diode and clamp some extreamly large currents when the voltage gets to 120% or so.  If lightning strike a mile down the road and has to go thru a transformer or two to get to you then that is good.  If it strikes your line into your house you probably don't have much of a chance no matter what you have for protection.  So the MOV will probably protect for a limited set of overvoltage events.

[WA1GFZ]

Nothing beats an isolation transformer on an AC line. It just goes into saturation and passes limited power. Also gives common mode isolation. MOVs work great but they explode at end of life. We can't use them in aircraft.

[WBear2GCR]

The biggest problem is the differential in ground potential.

If you keep your computer plugged in, it's likely to get fried.
The main reason is the differential between the power supply ground  and the phone or the cable ground.
I unplug both the computer and the data line everytime.
Before that, it fried.

The TVSS won't help you if the grounds are moving.

I'd use them, though... just not rely upon them vs. an unplug...

              _-_-WBear2GCR

[K3ZS]

Most newer PC computers are powered on all of the time.  That is why you can press a button and start it up.  I have repaired many computers that the only problem was the power supply voltage source that is on all the time.  This source is prone to failure with power surges also.  Best insurance is using a plug strip with a surge protector and a power switch you can actually use to turn off the power.