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ground connection and so on, they are all an integral large-scale
grounding grid under the ground, meanwhile there are many
grounding down lead extends to the ground, and connects the other
on the ground, as the following picture. To such large-scale ground-
ing grid, its grounding grid’s maximum diagonal distance is about a
few hundred meters to thousands of meters, testing its grounding
resistance is very difficult and troublesome. If it exist unqualified
grounding resistance, that problem is appearing at the connection
position of grounding down lead and grounding grid (direction of
arrow of the welding position in the picture), engineering reform is
to excavate grounding down lead’s position, then again weld
grounding down lead. Actually it’s impossible to reform the whole
grounding grid, or the whole grounding grid and surface facilities
need to pull down and rebuild, this is impossible.
Therefore, for the large-scale grounding grid, we can install Detector
on the primary grounding down lead and secondary grounding down
lead to monitor connection status between the grounding down lead
and the grounding grid, judge the grounding down lead’s grounding
conditions by testing metal return circuit connection resistance.