Principle Of Operation - Megger DET10C Manual Del Usuario

PRINCIPLE OF OPERATION

Below is a simplified typical ground distribution system. The equivalent circuit is shown in Figure A. If
R , R , R , ... R are simplified to R
1 2 3 n
constant voltage is applied to the circuit, the following equation is true.
V = R
Where
Req=
If R and R , R , ... R
g 1 2 n
than R and approaches zero.
g
R
Example:
If R and R , R , ... R
g 1 2 n
R
V = R
In this example, we can see that as long as the number of multiple electrodes is large enough, the
equivalent resistance is negligible with respect to the ground resistance to be measured.
, then only R
eq
+ R
g eq
1
( Σ
)
1
Ri i = 1, 2, ......, n
are similar values, and n is a large number (such as 200), then R
>> R (Req
g eq
are all 10 Ω, respectively and n = 200. Then R
= 1
eq
1 + 1 + ... + 1
10 10
=10 + 0.05 =10.05 Ω
+ R
g eq
and R are left in the circuit (refer to Figure B). If a
g eq
0)
eq
= 0.05Ω
10
will be much less
eq
by calculation equals
a R
a
12