Dielectric Absorption Index (Dai); Polarization Index (Pi) - MEGABRAS MD-5060x Guia Del Usuario

Dielectric Absorption Index (DAI)

This key makes it possible to visualize the Dielectric Absorption Index value on
the display. For this kind of tests, the megohmmeter should be connected,
applying voltage to the sample for 1 minute (60 seconds). After this period, the
operator must press the DAI key to read the absorption index value on the
display. If this key is pressed before the 1-minute period has elapsed, the dis-
play will show DAI = - - -.
The Dielectric Absorption Index is the ratio between the insulation resistance
value measured after 60 seconds and the value measured after 30 seconds.
This value is useful to determine whether it is necessary to perform preventive
and predictive maintenance on the coils (transformers, engines and motors,
generators, etc.).

Polarization index (PI)

This key makes it possible to visualize the Polarization Index value on the dis-
play. For this type of tests, the megohmmeter must be connected and apply
voltage to the sample for 10 minutes. After this period, the operator must press
the PI key to display the PI value on the megohmmeter display. If the key is
pressed before the 10-minute period has elapsed, the display will show PI= - - -.
If it is pressed after the 10-minute period, it will indicate the PI value. The po-
larization index is the ratio between the insulation resistance value measured
after 10 minutes and the value measured after 1 minute.
This index is useful to determine whether it is necessary to perform preventive
and predictive Maintenance in order to detect any insulation resistance wear
and tear due to the excess of dust, dirt, grease, or else the action of chemical or
physical agents, etc.
R
DAI =
60 seconds
R
30 seconds
R
PI =
10 minutes
R
1 minute
15