[BC] AM transmitter lightning sensitivity issue

[dynotherm at earthlink.net]

As I said, I'm on the road and without access to my archives.
When I return in about a week I'll be happy to forward some
instances of ESE protection failure.

When methods of standard setting are abused, I see the term
"abused" as a fully reasonable adjective.

BTW, DR. Mousa generally makes a reasonable SCIENTIFIC argument
for his case, as do others in the Lightning Protection and
Power Quality (Yahoo) forum. It is generally the pieces posted
as examples of submissions by those submitting ESE - for want
of a better word, propaganda - who are often less than forthright
and generally somewhat convoluted in their representations.

The bottom line is that the NFPA is in business to reduce fire
insurance rates by preventing fires and other structural
catastrophic events. 

Regardless of recent testing, or lack thereof, it is clear
that Franklin rods, when spaced according to modern practice do
serve to channel and mitigate lightning damage.

The problem with ESE "protection" is that although it MIGHT work
IF INSTALLED TO THE SAME STANDARDS would be prohibitively expensive;
and if installed to the manufacturer's standards DOES NOT PROVIDE
THE SAME PROTECTION AS A GROUP OF FRANKLIN RODS in the case of an
actual HEAVY STRIKE. The difference for safety of life and property
in quite significant.

Broadcasting is nearly unique in that it can make good use of ESE
equipment for lessening the frequency of strikes to towers and is
not at greater risk as it is one of the few applications where the
NUMBER of rods needed is essentially the same.

However, in the general market, the principal reason for ESE equipment
seems to be the enrichment of those manufacturing it without regard 
for the hazards created by the mis-statements by some promoters of its
use.

Regardless, with the actions of the NFPA during the past year, there
seems to be no further argument for changing the Franklin rod standard
until someone presses it during a subsequent cycle.

See further comments interspersed below.

Phil Alexander, CSRE, AMD


-----Original Message-----
>From: Ron Nott <ron at nottltd.com>
>Sent: May 25, 2008 8:23 PM
>To: Broadcasters' Mailing List <broadcast at radiolists.net>
>Subject: Re: [BC] AM transmitter lightning sensitivity issue
>
>To reiterate one more time, here is a quotation from an NFPA official 
>report: "It appears to the Panel that the NFPA 780 document does not 
>meet the NFPA criteria for a standard since the recommended lightning 
>protection system has never been scientifically or technically 
>validated and the Franklin rod air terminals have not been validated 
>in field tests under thunderstorm conditions".  This says simply that 
>neither system has been scientifically tested.  However, NFPA 
>continues to list the lightning rod system.

Exactly! The Franklin rod remains THE standard for protection when
properly installed because it has worked since Ben invented it.

>Discussions found on the web become highly emotional with the term 
>"abused" appearing frequently.  Check out the "International 
>Lightning Protection Association" site for some colorful rhetoric on 
>Mr. Mousa and others. However, if any of these devices are to be 
>tested truly scientifically, then insults, ridicule and derogatory 
>comments have no place in the discussion. They have nothing to do 
>with true scientific testing.

Careful reading may show these are responses to outright falsehoods
represented as truths by the promoters of ESE equipment.

>Now lets define exactly what an ESE (Early Streamer Emission) device 
>is and how it works.  

There is no proven SCIENTIFICALLY VALID explanation that I have seen
for enlargement of the area of protection beyond the 30 meter rolling
sphere method prescribed for Franklin rods.

Comparing the costs of protection for a 400,000 sq. ft. warehouse with
ESE rods vs. Franklin rods, both spaced according to the 30M rolling 
sphere method would be quite interesting and, I believe, shed much light
on the true motive for trying to get the ESE manufacturers' standards
approved. 

>An excellent example may be found by Googling 
>INDELEC and then looking at their "Prevectron" products.  These 
>devices look like an inverted cone with electrodes near the 
>tip.  They function by initiating an upward streamer during the onset 
>of a thunderstorm.  The streamer goes up and attaches to a downward 
>streamer from a cloud at which time a lightning discharge 
>occurs.  The idea is to discharge part of the electrical energy 
>contained in the field between earth and a storm cloud.  They 
>function by repeating this process over and over, hoping to control 
>the lightning strikes by providing a target, rather than allowing 
>them to strike at random.

Who, in the SCIENTIFIC COMMUNITY supports this idea? Recent failures
indicate the theory is UNSOUND.

>Charge dissipation works on an entirely different theory.  An array 
>of grounded multiple sharp points is placed at a relatively elevated 
>location. Prior to the arrival of a thunderstorm, the electric field 
>slowly begins to build between the cloud and the earth or tall 
>structure thereon.  A small current begins to flow from each of the 
>points due to air ionization.  Ben Franklin described a "silent 
>current" that flows from a sharp point into the air during these 
>conditions.  It is analogous to a bleeder resistor in the HV supply 
>of a transmitter.  When a transmitter is shut down, the bleeder 
>discharges the power supply capacitors in order to make it safe for a 
>person to work inside the transmitter.  Yes, I know that the caps 
>should be discharged using the "sissy stick", but capacitors can 
>build up a charge even after they have been discharged this way.  The 
>bleeder resistor continuously drains the charge to make it safe.

If I had a dollar for every open bleeder resistor I've see ... Ah well.
The problem here is FALSE ANALOGY. The theory works MOST of the time.
However, when it does not work (when the charge is too great) the
downstroke attaches, and if there is inadequate conduction to earth,
there will be damage, sometimes catastrophic damage. Fortunately, a
broadcast tower is inherently well protected when this happens, thus
the addition of either CD or ESE to it does not INCREASE the risk as
it does in buildings without rods installed according to the 30M
rolling sphere method.

>The only thing wrong with a single sharp pointed rod is that it has a 
>limited capacity of current.  Placing many of them in parallel is 
>analogous to placing many high value resistors in parallel to provide 
>a lower resistance discharge path.  If enough sharp points are placed 
>in the proper geometry, the electric field voltage will be decreased 
>below the point where lightning strike will occur.  

That is true if, and only if, the discharge potential is not exceptionally
large.

>This field is 
>measured in volts per meter from ground upward toward the 
>cloud.  When it exceeds 10 KV/meter of elevation, a strike may occur.
>
>There are in fact three methods of attempting lightning protection:
>
>1. The Franklin rod (an array of them for a large building is not cheap).

But far cheaper than ESE rods placed on the PROVEN Franklin rod pattern.

>2. ESE (Early Streamer Emission) which intentionally causes strikes.

>3. Charge dissipation in which the field voltage is diminished by 
>controlled discharge.

>They are not the same.  Charge dissipation products do not use the 
>principle of ESE.

This rather depends on the PROMOTER, does it not?

>Ron Nott
>