Rish Insu 5Dx
32
11
THEORETICAL APPENDIX
11.1
POLARIZATION INDEX (PI)
PI is the ratio of Insulation Resistance values measured after 1 minute and after 10 minutes. The
DC test voltage is present during the whole period of the measurement (an Insulation Resistance
measurement is also running). On completion of the test the PI ratio is displayed
min)
1
(
min)
10
(
Rins
Rins
PI
General applicable values:
PI value
Insulation conditions
< 1.0
Dangerous
from 1.0 to 2.0
Not acceptable
from 2.0 to 4.0
Good
> 4.0
Excellent
11.2
DIELECTRIC ABSORBTION RATIO (DAR)
DAR is ratio of insulation resistance values measured after 30s and after 1 minute. The DC test
voltage is present during the whole period of the test (also an Insulation Resistance measurement
is continually running). At the end, the DAR ratio is displayed:
)
30
(
min)
1
(
s
Rins
Rins
DAR
General applicable values:
DAR value
Insulation conditions
from 1.0 to 1.25
Not acceptable
from 1.4 to 1.6
Good
>1.6
Excellent
