7
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.
4. Single Point Grounding System.
If grounding network A and grounding network B is without overhead line, and doesn
’
t connect together on
the ground, then grounding network A and grounding network B can regard as standalone single point grounding
connection. Detector cannot test single point grounding system
’
s grounding resistance directly. This moment it
needs adding one or more auxiliary grounding electrode, to form multipoint return circuit, then to install Detector.
In the small range, if there are two or more single point grounding system, it can use metallic conductor to connect
all single point grounding system
’
s grounding down lead together on the ground, to form a return circuit, then
install the Detector to monitor.
5. 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.
illustration:R1 is predicted grounding resistance, R0 is the equivalent resistance of all the other pole
’
s
grounding resistance parallel connection, that is R
0
=R
2
∥
R
3
∥
R
4
∥
…
∥
R
n
, if the greater n is (the more grounded
junction), the closer R
0
gets to 0,far smaller than R
1
, from engineering point of view, R
0
=0,so, the data Detector
receives should be R
1
’
s value.
(2). Underground Mine Power Transformation Ground Connection.
respectively
，
primary grounding electrode R,R
1
～
R
3
…
R
n
is a independent grounding body under the ground,
don
’
t connect together, are multipoint grounding system, convenient to test. Detector is installed on the primary
grounding electrode, the Detector
’
s indication is R
r
=R+R
1
∥
R
2
∥
R
3
∥…∥
R
n
. If the more part grounded
junctions are, so R
1
∥
R
2
∥
R
3
∥…∥
R
n
≈
0,then R
r
=R. It
’
s the four-code cable in the picture, one code is ground
lead among it, all the devices and part grounding connection are connected to be a network by cable grounding
connection, dotted line is bare copper wire of grounding connection.