-10-
Three-point method has another advantage: Due to auxiliary ground
pole B and C is parallel to the tested ground pole A, so that the actu-
al grounding resistance will be less than RA to improve the tested
grounding pole. RA
∥
RB
∥
RC
＜
RA. At the actual construction, the
grounding resistance of auxiliary ground pole B and C must less
than 10 times of the grounding systems engineering standard value.
If the engineering requirements of the grounding resistance value
cannot exceed 4
Ω
,then RC
＜
40
Ω
,RB
＜
40
Ω
. RB, RC as small as
possible, more can improve measured grounding system.
6. Application.
(1). Power Transmission System Pole Ground Connection.
It forms multipoint grounding system through overhead ground wire
connection; test conveniently, its equivalent circuit as the following
picture on the right.