MI 3200 TeraOhm 10 kV
Measurements
26
min
1
min
10
R
R
iso
iso
PI
Note: When determining Riso (1min) pay close attention to the capacitance of the object
under test. It has to be charged-up in the first time section (1 min). Approximate
maximum capacitance using:
V
s
F
U
t
C
10
3
max
.
where:
t ........... period of first time unit (e.g. 1min)
U ......... test voltage.
To avoid this problem, increase the
DIAG. Starting time
parameter in
CONFIGURATION menu, because start of timer in the DIAGNOSTIC TEST functions
depends on the test
voltage. The timer begins to run when test voltage reaches the
threshold voltage, which is product of the
DIAG. Starting time
and nominal test voltage
(Unominal).
Analysing the change in the measured insulation resistance over time and calculating
the DAR and PI are very useful maintenance tests of an insulating material.
DIELECTRIC DISCHARGE TESTING (DD)
DD is the diagnostic insulation test carried out after the completion of the Insulation
Resistance measurement. Typically the insulation material is left connected to the test
voltage for 10
30 min and then discharged before the DD test is carried out. After 1
minute a discharge current is measured to detect the charge re-absorption of the
insulation material. A high re-absorption current indicates contaminated insulation
(mainly based on moisture):
F
C
V
U
mA
Idis
DD
.
min
1
,
where:
Idis 1min ...... discharging current measured 1 min after regular discharge
U ................. test voltage
C ................. capacitance of test object.
Measurement procedure:
- Select
DIAGNOSTIC TEST
function in
MAIN MENU
.
-
Connect the test leads to the instrument and to the measured object.
- Press
the
START/STOP
key to start the measurement.
-
Wait until set timer runs out, the result is displayed.
- Wait until the object under test has discharged
