[TowerTalk] Grounding for lightning protection

[Red]

Hi, TTs;

Ground resistance and ground impedance are not nearly as important for 
lightning protection as is preventing differences among the several 
grounds involved and preventing excessive surges on all ungrounded 
connections. All the stations grounds may be at very high voltage as 
long as they are all the same and all the antenna, control lines, power, 
telephone, and other utilities are clamped with respect to that ground. 
It is very important to tie all the utility grounds to the station 
grounds with as little impedance as possible and to employ lightning or 
surge arrestors, each tied to that common ground, to limit surges on 
every feedline, power line, computer connection, etc. Other conductors, 
like water pipes, should be close enough to that ground potential that 
there is no danger of a spark between them and the ground system and is 
no danger of an injurious voltage difference that might affect a person 
who may contact both. The whole system must be grounded well enough to 
prevent reaching a voltage that initiates a discharge to the air, but 
that is thousands of volts and shouldn't be a problem if things are 
grounded at all.

The emphasis must be on limiting potential differences among ALL the 
conductors connected to the station.

I recommend these references:

Lightning: Physics and Effects, Dr. Vladimir A. Rakov and Dr. Martin A. 
Uman. 2003. Cambridge University Press. This is an undergraduate text, 
not too technical, that provides useful explanations of why lightning 
does what it does as well as the latest findings and data from lightning 
research and information regarding lightning protection. It is not 
commonly available at local public libraries. I borrowed a copy via 
inter-library loan from U of MN.

All About Lightning, Prof. Dr. Martin A. Uman. U of Fl, Gainesville. 
1971, reprint 1984 with revisions. Layman’s level describing some of the 
attributes of lightning. Some of the information is superseded by 
information in Lightning Protection and Physics.

Protection of Electronic Circuits from Overvoltages, by Ronald B. 
Standler, 1989; John Wiley & Sons, Inc., particularly Part 2, Chapters 7 
through 15, for information about gas tubes, varistors, avalanche and 
Zener Diodes, semiconducor diodes and rectifiers, thyristors, impedances 
and current limiters, filters, isolation devices, and parasitic 
inductance and how these devices may be used to protect electronic 
equipment from overvoltage stresses such as those associated with 
lightning. This book may not be available in many public libraries but 
is available on inter-library loan from college and university libraries.

The Lightning Book, Peter E. Viemeister. Doubleday & Company. 1961. 
Layman’s level. Not up to date but very readable and still informative.

Lightning Protection and Grounding Solutions for Communication Sites, by 
Ken R. Rand; 1st ed., 2000, Polyphaser Corporation. Available by request 
to Polyphaser. Some of the information in it is not up to date and I 
disagree with the diagram for deploying ground rods.

Lightning Protection for the Amateur Station, Parts 1, 2, and 3, by Ron 
Block, KB2UYT, QST, June, July and August of 2002. Ron Block is a 
brother of Roger Block, founder of PolyPhaser. In my opinion, the 
recommended grounding diagram uses ground rods ineffectively and does 
not adequately address the utility grounds.

There is lots of other information available, including many items from 
ICE and PolyPhaser. Read them critically. They are not totally unbiased 
and up to date.

73 de WOØW