TT testing.

johnboy6083 · Feb 9, 2012

if you click on the link that ruston posted, then they list common distances that can be followed, in order to produce reliable results. thats where i got my distances from, and i remember the 60% (61.8% exactly i seem to remember) from when i was taught in the royal school of military engineering. I agree that it is a specialised field, and only substations, comms grids ect would require such accuracy.

Engineer54 · Feb 9, 2012

johnboy6083 said:
if you click on the link that ruston posted, then they list common distances that can be followed, in order to produce reliable results. thats where i got my distances from, and i remember the 60% (61.8% exactly i seem to remember) from when i was taught in the royal school of military engineering. I agree that it is a specialised field, and only substations, comms grids ect would require such accuracy.

Your right 61.8% is the correct figure, but is normally rounded up to 62%. Most manufactures (including Megger), when supplying and/or selling the spike and cable earth kits will generally provide 1 X 50m , 2 or 3 X 30m cable reels. So you would be unable to follow any distances over that unless you extend using your own cable. As i said above, for single or even a twin rod system this set-up would more than suffice/

Being in the Military, you would have maybe had more cause to do quite a bit of earth rod/electrode testing in the field than most here. Did you lot, still use that insane 200 ohm maximum Ra value too?