On Thu, 19 Jan 2006 22:19:04 -0800, Richard Clark
wrote:


I found a much more compelling report in:
UNITED STATES DEPARTMENT OF AGRICULTURE
Rural Electrification Administration
REA BULLETIN 1751F-802
SUBJECT: Electrical Protection Grounding Fundamentals
Which is vastly more comprehensive and directly answers these
questions when viewed in the terms of the resistivity of the earth
connection.

Thanks Richard, I have read the document quickly overall, and a bit
more detailed in some key areas.

It covers similar material to documents I collected when studying
power earthing and lighting protections in years past, but it is a bit
more comprehensive... so a good read and a good reference document.

One good pickup was the functions for predicting the low frequency
resistance of shallow buried radials (which is relevant when radial
wires are required to provide a level of power / lightning protection.
I created a graph to add to an existing web page from the functions
for 3mm (bare) wires buried 0.1m, the graph is at
http://www.vk1od.net/post/earth02a.gif . (For avoidance of doubt, this
graph does not predicting the RF characteristics of the radials.)

Tks...

Owen

PS apologies for the delay in responding, I have been up to the big
smoke (the city... Sydney) over the weekend... reminds me of why I
left there thirty something years ago.
--