Totally agree in the majority, but with years in the fire department.... Lightning strikes tree next to house. Single point ground is 80 feet away on far side of house. Lightning does not go to ground, and jumps from trunk of tree to side of house leaving extensive burn mark on trunk and side of house. Sets house on fire where it goes through wall, follows wiring to bathroom where it jumps to copper water piping and finally goes out the front. Destroyed power meter, toasted most appliances, obviously water damage in bedroom end where "hot" sheet rock had to be pulled down to get at fire in walls. Of the conductors that were followed, only the copper pipe survived. Mostly charred holes where the romex was pulled through the walls.
OR, Lightning strikes power pole in area of very thin soil cover over what is basically a miles wide rock ledge underneath. Lightning follows a phone line into the house, ignores "grounds". Jumps from a telephone jack across an open room, frying radio and computer equipment setting on a table in the middle of the room with no cords of any sort connected anywhere. Jumped from there to an inside power outlet, emerged from a power outlet in the hallway, dissipating in a ball of fire that chased owner down the hall and out the front door. There's more...all conductors from top of pole to house, including power company ground conductor to bottom of pole simply gone...etc...but entertainment value aside... So yes there ARE throw up your hands cases. In the above seriously doubt anything could have been done. These are the folklore strikes. BUT, BUT... These kinds of things are way, way the tiny minority of events by comparison, and seem to be more common because the grapevine propagates and amplifies the gorilla and T Rex strikes for their entertainment value. The great majority of events in the gray area can be seriously reduced by attention as specified below, and allow one to dodge altogether, or mostly or partly dodge, lesser events. One does oneself a great service by careful planning for the lessor events. At my house the lightning events that damaged something, mostly the electronics in my HVA outside units, were strikes out in the woods somewhere and all was an induced strike. HVA guys insist that my units were 100% code-wired and I was lucky to have damage confined to a single circuit board. My misfortune is to have them nearly 100' from the SPG with long copper coolant pipes to the air handlers. And no, wife will not hear of relocating them to front side of house near SPG. Strategically, the error was not routing power to the west end of the house. This happened because the original owner who was also the builder, built the house in stages, middle first, east end, then west end. The most recent lightning event on my property involved a gorgeous 120' poplar tree where lightning literally turned the top half of the tree into toothpicks in an explosion that scattered leftover poplar all over a hundred foot radius. The base of the tree was near where my driveway goes over the creek, and so also where where phone lines cross the creek (54 inch drainage pipe under driveway). The lightning fused conductors in the 4 and 6 pair cables enough that they had to pick single conductors at the end of the cables to find two undamaged. The lightning did NOT make it past the single point ground and the telco gas tube protectors and did NOT damage the PILE of stuff connected inside the house. MAYBE, just MAYBE a DSL modem that failed a year later was related. But probably not. The little Motorola beastie was one of a model which were failing of heat related problems by the thousands, with which the repair guy was well acquainted. Learn how to do grounds and protection right and just do it. In the end, FAR less trouble to do it right. Only a hand's count or so of the readers on this reflector will ever in their lifetimes have to deal with the gorilla or T Rex strike that swamps protections blowing up everything in its path. 73, Guy. On Thu, Aug 12, 2010 at 10:32 AM, Tom W8JI <[email protected]> wrote: > I'm going to disagree with the popular but misplaced notion that when > lightning hits nothing can be done to prevent damage other than a complete > disconnect. > > The real problem is almost always that people pepper the station with > protection devices but use poor wiring layouts or poor entrance schemes. 99% > of the protection is in the layout and bonding, not in the protection > devices we throw into the system. > > I'm not saying you should not use protection devices, just that they are not > anywhere near the solution. > > We have got to start thinking in terms of ground loops or common mode paths > through the gear, and not depending on devices that let 700 volts in or out > to protect solid state devices. It's the poor lead routing and ground > bonding that really kills our gear. Especially when the power mains ground > and the shack ground have any significant impedance between them. > > 73 Tom ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
