R-Dar-Pi / R(T) Button - AEMC 1060 User Manual

2.5.3

R-DAR-PI / R(t) Button

First Function - R-DAR-PI
The R-DAR-PI button allows automatic measurement of:
• Polarization Index (PI)
• Dielectric Absorption Ratio (DAR)
These two parameters are useful on long cables, or when monitoring the aging of
insulation on electrical machines.
On this material, measurement is adversely affected at the beginning, due to inter-
fering currents (from capacitive charges, dielectric absorption) which eventually
cancel each other out. Therefore, in order to get an accurate measurement of the
leakage current, it is necessary to carry out the measurement over a long period
of time, to reduce the influence of any interfering currents at the beginning of the
measurement.
Next we calculate the PI or the DAR ratios:
PI = R / R
10 min
DAR = R / R
1 min
The quality of insulation depends on the results found.
DAR
< 1.25
< 1.6
> 1.6
Using the R-DAR-PI Function:
During or after measurement, the R-DAR-PI button allows you to scroll through
the following values:
• DAR (for measurements lasting > 1 min).
• PI (for measurements lasting > 10 min).
• Capacitance in μF (only after the measurement has stopped and the cir-
cuit has been discharged).
• Insulation resistance in MΩ, GΩ or TΩ.
Automatic Measurement of DAR or PI:
• If the button is pressed when in voltage measurement mode before pro-
ceeding with a measurement, the following is displayed:
M
Megohmmeter Models 1050 /1060
(2 values to record during a 10 min measurement)
1 min
(2 values to record during a 1 min measurement)
30 s
PI
< 1
< 2
> 2 to < 4
> 4
DAR
State of the insulation
Inadequate, even dangerous
Good
Excellent
PI
13