Bill, I haven't been and won't be able to participate in the forums for a while as I am working out of town and zillion hours a week. A few weeks ago I posted a topic about a silver soldered ground strap. I thought some of you might be interested in some pictures.
Picture one: Rolling off the reel.
Picture two: Turning a corner. The PVC is there two maintain a wide radius and keep the back hoe from crushing it flat. Later this week we will be auguring the chemical ground rods and making the silver solder connections at the corners. I'll post pictures of this when I get a chance.
mamills The reason for not letting it crushed flat is that is it designed to carry stray currents in the giggaHZ range. It flows better with more surface area and it doesn't like sharp bends. (Kind of like lightning) The other option is to cut and splice at the corners but there are two down falls. 1) The fewer splices there are the more integrity the system has. 2) A 12" to 12" bolted and silver soldered splice takes a man that is experienced an hour to one and one half hours to make. Quite a bit longer than mearly rounding the corner!
elektrikguy, This is a TV station/Studio with tons of digital television equipment. The strap is a reference for that equipment and is a spec for this particular client. This is the second installation I have done for them like this. The first was the national master control center for the USA network. I was disappointed to find out that 2 years after we completed the project Telemundo bought them out and cleaned the place out. What do ya do?! I can send more PICS of other aspects of the project if the people here are interested. Just let me know.
Wow, that looks weird, but sounds like the designer has specific ideas on how he wants it done. Copper coil stock and silver solder—sounds like armed-guard duty. Hopefully a few yards of ready mix is on the way.
Interesting photoes. I've never saw anything like that before. I did work at a power house once where we laid copper wires in the ground to form a grounding grid. I think they call it cathodic grounding.
I have tons of pics of regular construction stuff but rather than bore everyone with that I am waiting till we do some of the unusual stuff. I did think you might enjoy these.
Picture one: One (of two) 300KVA Mirus harmonic canceling duel output transformer. This transformer has two 180KVA outputs phase shifted 30Deg from each other. One is 15 degrees out from the primary the other is 45 degrees out. The concept here is that the two outputs create a common mode rejection point to cancel 3rd 5th 7th etc. harmonic currents rather than allowing them to circulate in the primary delta winding as a normal transformer would. This eliminates the need for a high K rated transformer and filters noise out of the grounding system. Notice all the secondary terminals!
Picture two: The point where the 12" ground strap emerges from outside into the building. You can see one of the four rows of seismic rack bases for this room. At each one we will bolt and silver solder a 12" tap run down the inside of the bases. Each rack has a ground bus in it with a 2" copper strap silver soldered to it which we will silver solder to the 12" under the bases. Pics will follow.
PS: The silver solder we are using costs $32.00 per pound!