The following is from a web site that describes the experiences of a real world broadcaster who has to deal with lightning, big time. Most of the folks on this site are very practical types and I'm posting this for any comments. The NEC requires a single bonding of the neutral/ground, generally at the service entrance. I think this fellow is talking about multiple point bonding of the neutral/ground versus a single point bond as required. I'm not aware of anything that allows complete isolation of the neutral/ground in most systems.

=================================================

GROUNDING SYSTEMS THAT WORK IN THIS AREA

This area of Florida receives some of the strongest and most frequent lightning strikes of anywhere in the United States. This system of grounding seems to be the best so far for this area (proven over time). I am not quite sure why or how it works, but on the stations where this type of system has been installed we have cut the downtime and equipment losses almost to zero. We have installed this system on new and existing towers up to 500 ft. in the last ten + years with very good results.


We have had many DISCUSSIONS on this subject with other "engineers", that prefer the "single point" grounding systems without any "ground loops", which I'm sure
works well somewhere,(but not here). So we pretty much have done everything as "wrong" as possible and it has been working 100% better than before...


Some of the local electrical codes require the neutral and ground buss to be isolated from each other?? I tie them both to the ground system after inspection. I guess "they" will come and get me someday.....


A few examples.....

WXCV had a single point ground (installed by the tower mfg.)with 6 in copper strap tied to a long ground rod and to the tower. From 1983 until 1994 I have replaced everything from the plate transformer to the top beacon (lost the top half). Since installing this system in 1994 we have not even blown a fuse in any equipment on that site. We have had breakers trip but that is what they're supposed to do.

WGUL FM We constructed this station in the May of 1995 and to date we have not had any lightning damage on that site.

WRGO FM We constructed this station in July of 1996 and to date we have not had any lightning damage on that site.

WXOF FM This site was built in the summer of 1996 by a well known tower mfg. It also uses a single point ground, they almost had a good idea, they ran a #6 copper strand around the inside of the building connected to four ground rods in each corner. The only problem was the rods were drilled into the floor INSIDE of the building!! and only connected to the transmitter ground strap that ran outside to the single point ground. This station has been off the air more than it's been on. The wall where the 6 in copper strap goes through is black and burned from lightning. This site will have our system installed by the middle of September. This will be a very good test for this type of grounding system. Installed ground 02.1998, lightning problem solved to date... 2005.

WYKE DT We constructed this DTV station 03-05. We installed our grounding system during construction as normal. Well... It was hit every time a little storm passed over !!!
Needless to say I thought the Devil was out to get me. After a few days of pondering the installation and could not find anything out of order in the plant I decided to look elsewhere. I walked out to where our burried power left the pole and everything looked OK. I then continued down the power line feed and found the transformer pole ground rod sticking out of the ground about 4 feet. I contacted our local power company, and quite a few weeks later they showed up. We checked nine spans and none of the power poles had ground rods. I'm sure all of you guys realize that most of the time they plant a power pole the ground wire that runs from the top of the pole is just wrapped around the base of the pole and stuck in the ground. This is not a good thing in Florida or anywhere else for that matter. We determined that the tower and building had such a good ground system that all the surges from the lightning on the power grid was ending up at our ground grid. After driving a truck load of ground rods on the power poles leading into our site the the Devil has left the building. We also have phone lines into the building, and thats another story.... we have B-1s T-1s and a T-3. The interface boxes were usually found on the floor after a storm along with the Optilator boxes. Since there is no way to properly ground phone lines at the terminals we decided to seperate the telco ground from our plant ground. That has worked very well so far.... So just when you think you know it
all.... it can still bite you in the butt.......


Update 11.02.2005 ..... Still Going Strong...
The only lightning problems to date is connected to phone lines.. Optilator does the trick most of the time with 4 inches of fiber optic isolation. We are using their new T1 boxes and are working great.