[BC] Dealing with Lightning

[Dave Hultsman]

In a message dated 5/11/05 12:01:32 A.M. Central Daylight Time, 
broadcast-request at radiolists.net writes:
 >My issue in this message is to open a debate on the merits of CTS 
(protection / avoidance) technology.  Lightning is an issue that most 
broadcast must deal with and how you deal with it will determine the safety 
and reliability issues of your broadcast site.  I do not believe that the 
claims made by CTS vendors is clearly understood in our broadcast 
community, and I would like to open this issue up for discussion.  I invite 
all interest parties to participate.  I encourage you to read the messages 
below to understand with who you are dealing.

 >Bruce

*******************************

Bruce:

You are certainly well aware of lightning and its effect on broadcasting if 
you have equipment on a tower.  Especially since the strongest lightning 
area in the nation is the line from just South of Tampa to near Daytona 
Bch, FL..

I remember the CE of WTSP used to tell me that they would, on days of 
predicted storms, go to generator at 3 PM in the afternoon and operate till 
9 PM or later just to have the entire site off FP&L.  He said they had less 
problems with induced transients from the power line if lightning hit their 
big tower, North of Clearwater, while they were on generator.  The cost of 
the fuel was offset by the lack of failures, man power and replacement parts.

However I have also heard many accounts that the so called "spreaders" or 
"feeler" type dissipators of leaders have reduced strikes at many facilities.

Again what is good in one area of the country may not work in another area 
of the country.  Too many variables when it comes to lightning.   What 
works for the goose may not work for the gander.Years ago I was amazed to 
watch lightning strikes in the dry west Texas mountains during storms which 
produce little or no rain but really illuminated the sky and would hit the 
high tension power lines going up the mountains.  The amount of energy in 
those strikes would be clearly visible in the size of the leader and you 
could smell the Ozone for miles. One can only imagine the amount of current 
in that fraction of a second that the bolt equalized the charges.

The same goes for Chem rods, ground screens,  three inch copper casings in 
a well and etc.  What ever works in your case do it.  I have also heard 
comments about a company in Florida that manufactured MOV transient 
absorbers/clamps and the flack they took when a station had a strike on the 
AC power line and the device started a minor fire at a station.  I can also 
recall another guy the also had something similar happen but claimed that 
he didn't lose any equipment except his MOV suppressor box which was burned 
up. After repairs his transmitter and all associate equipment worked 
normally.  The result was the device worked and was destroyed.

I guess this will always be one of the great discussion topics,  lightning 
along with grounding. One thing I remember, an elderly engineer telling me 
years ago,  lightning is like a big elephant  IT goes wherever IT wants to, 
usually taking multiple paths to ground.  Your job is to try to see that 
the path is easier for IT the next time.

Dave