Originally Posted by Colm
Not true. A properly design lightning protection system with appropriately located air terminals, appropriate downleads and grounding will do wonders. But it sure isn't what we think of as a surge protective system.
In any case, I don't think Tanner was referring to a direct strike. He would have a lot more to worry about than failed HDMI ports after a direct strike.
More precisely properly bonded. Even with a good grounding electrode system, the ground voltage can rise hundreds or thousands of volts. Effective bonding ensures the the other conductors rise with it so that the voltage difference between the conductors remains more or less nominal.
Proper bonding and grounding does not eliminate the possibility of damage from surges. It is only part of the solution. It won't do a thing for a L-N surge that comes in on the AC. Nor will it do anything for a surge that comes in on the center conductor of coax. You need a surge protective device to shunt the surge to ground,
FWIW surges do not magically disappear into the earth through the grounding electrode system. The surge has to return to its source. The earth is a crummy conductor. Often there is an easier return path for the surge.
Lightning strikes do not go through electrical lines or communication lines normally. What they will do is find the shortest return path to ground, and that can be anything from a tree root that has bumped against the house, buried low voltage lighting wiring, sprinkler wiring, outdoor receptacles, Copper water lines or Copper propane lines, Black iron piping.
There have been stories of people seeing during a lighting strike ball lightning or blue colored Plasma glow around the perimeter of a structure that has Copper sheeting between the foundation and wood framing, while the lightning strike is attempting to find a way to find a return path out of the structure.
Majority of the problems found with blown electronics or even telephones, comes down to improperly bonded or grounded communications or video circuits at the structure. That is why it is beaten to death, that any line coming into a structure needs to be bonded to a proper ground, whether it is a ground rod, or Ufer, or structural framing member rated for bonding for ground.
There have been many transmitters for tv & radio, along with radar stations taken out by direct lightning strikes, even though they were so well grounded, the Gas discharge system and ring ground system failed, or ground/bonding system was corroded, that the lightning surge went down the tower through the equipment taking everything out with it.
What is even better, is when you get lighting strikes at outdoor catv or telephone enclosures, which in turn look like a melted mass after the fire goes out, due to the bond to ground failed. Here is one pic of a direct lightning strike to a radio antenna http://ayellowspringsblog.blogspot.com/2011/07/like-bolt-out-of-blue.html
Go to the paragraph labeled "...And no one noticed!", it is an example of a direct lightning strike to a incoming power line (480V Service Entrance) http://www.copper.org/applications/electrical/pq/casestudy/suncoast.html
The TVSS shunted the strike on the last example, so no damage, but on the first one with the radio transmitter, it took out everything in the transmitter (boards, equipment, antennas, wiring).
Lightning on its own, will do weird things, It will either not do any damage, and destroy something else nearby, or will continue on its path regardless of whatever measures you have taken to properly bond your communications lines and electrical lines, and find stuff to destroy. That is why there is always a push to install TVSS systems for both communications lines (catv, satellite, telephone, Internet (dsl, T1, Catv, Satellite, Ethernet)) and power service to a structure, along with making sure that it is also properly bonded to a good Earth ground, not just some bracket on a water pipe, meter pan, or some rod or wire just stuck in the ground.
Only way that stuff is getting blown through the HDMI lines, is that people are not going back and making sure that proper protection is in place for their incoming communication lines. Never trust the tech just going and thinking they know what they are doing when it comes to protecting the incoming communication lines, make sure that it is protected with the above stated.