TVS protects against voltage spikes that can damage modern locomotive electronic boards and fragile wires. A voltage spike won't trip a breaker or blow a fuse, overcurrent surge does that. Fuses,and breakers protect your transformers.
I read an article in a wood working magazine about the dangers of high static charges that can build up in us using a shop vac. After cleaning up his wood shop with a shop vac, a man entered his kitchen where his wife was cooking at the stove. She offered him a taste of what she was making with a fork while her other hand was touching the stove. When he opened his mouth to accept, a bolt of static rushed to ground through his fillings in his teeth. It knocked him to the floor and also caused several fillings to come out. It made me wander, if we ourselves were statically charged, would it be possible to damage any electronics on a layout if we touched the tracks while trains were running and discharged.
@Dave Zucal, what you are speaking of is ESD, or electro static discharge. When I serviced computers and their hardware, we always use a static mat and a wrist grounding strap to prevent a static buildup on our bodies from damaging electronics. This is applicable not just to computers, but anything with sensitive electronic components, including our toy/model trains.
Here is a video about ESD:
ESD Mat and Wristband:
So to get back to your main question, yes, it is possible (but not a certainty) for a static buildup on your body to damage your train equipment.
Thanks BMORAN4, I use that same mat when I do upgrades that's in your picture. Got it at Radio Shack. The air traveling through a plastic shop vac hose, does create a lot of static that enters the body. It's so bad that all dust collection system's plumbing must be grounded to prevent a dust explosion internally. I have received a pretty good shock once when I was vacuuming under the layout and reached up and touched a track when I pulled myself up. Just made me wonder, if the trains were running, if that charge could have traveled through a board and damage it.
Where can one buy the TVS diodes recommended by Gunrunnerjohn?
Arnold
@gunrunnerjohn posted:I actually recommend a higher value for the clamping voltage for O-gauge model train use, the 1500W 36V TVS at Digikey. The 27V model can clamp at too low a voltage for O-gauge use. Peak voltage for 18V RMS is 25.45 volts, very close to the minimum breakdown voltage of the 27V TVS.
@Arnold D. Cribari, you can see that @gunrunnerjohn provided a direct link to DigiKey as a source. Mouser, Newark and many other electronic suppliers will have them.
Thanks bmoran4.
I actually reviewed this thread again and figured out that Digikey Electronics from Minnesota carried the TVS diodes. I just placed the order, the cost was very modest, and I am very pleased with Digikey's service.
Incidentally, Digikey had the particular TVS diode that Gunrunnerjohn recommended (commonly used for automotive), but not the similar one for general purpose use. I think the part number given for the latter one may have been slightly off.
Arnold
Seemingly minor differences in part numbers could completely change the suitability - you may want to post your exact part number for your order here for review just to be sure you are getting the protection you expect and not going to cause damage to any of your equipment.
@bmoran4 posted:Seemingly minor differences in part numbers could completely change the suitability - you may want to post your exact part number for your order here for review just to be sure you are getting the protection you expect and not going to cause damage to any of your equipment.
Thanks for that suggestion, bmoran4.
What I ordered today was Digikey part # F7614CT-ND, as recommended above in this thread by Gunrunnerjohn. Arnold
That DigiKey number is a 1.5KE36CA so looks like you are spot on!
This 1.5KE36CA TVS diode from Micro Commercial Components seems to be the lowest-priced version on Digikey at ¢48/diode.
@Matt_GNo27 posted:This 1.5KE36CA TVS diode from Micro Commercial Components seems to be the lowest-priced version on Digikey at ¢48/diode.
Just over 41 cents/ea if you buy at least ten. 
