METREL MI 3290, Instruction Manual

Page: 87 / 162

MI 3290 Earth Analyser Tests and Measurements
87
where:
Z
tot
..................................... Total selected earth impedance
Z
sel1-4/1
................................ Selected Earth impedance
I
gw
...................................... Inductive current or grounding wire current
I
f1-4
..................................... Measured current with Flex clamp
U
S-E
.................................... Test voltage between S and E terminal
Note:

“Inductive current” -
I
gw
in the example is actually an inductive coupling current
between wires L1 ( i
1
), L2 ( i
2
), L3 ( i
3
) and overhead grounding wire loop. The current
has the same frequency as the L1, L2 and L3 current (usually power frequencies 50
Hz or 60 Hz).
Z
e1
L1
L2
L3
i1
i2
i3
overhead grounding wire
Igw
overhead grounding wire loop
R
e1
ne
x
to
w
er
Z
e2
Z
e3
Z
e3
Figure 11.37: Substitute circuit for Passive (Flex Clamps) measurement
Test can be started from the Passive (Flex Clamps) measurement window. Before carrying
out a test the following parameters (Number of turns F1 - F4, Distance and Limit (Ztot)) can
be edited.
Figure 11.38: Passive (Flex Clamps) measurement menu
Test parameters for Passive (Flex Clamps):
Number of turns F1
Set the number of turns for Flex 1 input terminal: [1, 2, 3, 4, 5, 6]
Number of turns F2 Set the number of turns for Flex 2 input terminal: [1, 2, 3, 4, 5, 6]
Number of turns F3 Set the number of turns for Flex 3 input terminal: [1, 2, 3, 4, 5, 6]
Number of turns F4 Set the number of turns for Flex 4 input terminal: [1, 2, 3, 4, 5, 6]
Distance (r) Distance between E and S probe (user defined).
Limit (Ztot) Limit value selection: [
OFF, 0.1 Ω – 5.00 kΩ]
Passive (Flex Clamps) Measurement procedure:

Select the Passive (Flex Clamps) measurement function.

Set the test parameters (number of turns, distance and limit).

Connect the test leads and flex clamps to the instrument and to the test object.

Press the Run key to start the measurement.

Wait until the test result is displayed on the screen.

Press the Run key again to stop the measurement.

Press the cursor keys to toggle between multiple result views (optional).

Save results (optional).