Sonel MIC-5010 - Dielectric Discharge Indicator - DD

MIC-5010, MIC-5005 – USER MANUAL
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3.1.4 Dielectric Discharge Indicator - DD
In the dielectric discharge test the discharge current is measured after 60 seconds from the end
of measurement (charging) of the insulation. The DD is a value characterising the insulation quality
independent from the test voltage.
The measurement operates in the following way: first the insulation is charged with a current for
a set period. If this voltage is not equal to the set voltage the object is not charged and the meter aban-
dons the measurement procedure after 20 seconds. After the charging and polarisation is complete, the
only current flowing through the insulation is the leakage current. Then the insulation is discharged and
the total dielectric discharge current starts to flow through the insulation. Initially this current is the sum
of the capacity discharge current, which fades quickly and the absorption current. The leakage current
is negligible, because there is no test voltage.
After 1 minute from closing the circuit the current is measured. The DD value is calculated
using the formula:
CU
I
DD
pr


min1
where:
I
1min
– current measured 1 minute after closing the circuit [nA],
U
pr
– test voltage [V],
C – capacitance [F].
The measurement result testifies to the insulation condition, you may compare it with the table below:
DD value
Insulation condition
>7
Bad
4-7
Poor
2-4
Not too good
<2
OK
Set the rotary switch of function se-
lection at DD. The meter is in the
voltage measurement mode.