11.
PI Standard
PI value
2~4 (typically3)
1~1.5
1
1.0 or
less
Tested
material
status
Considered as
good insulation
(older types)
Not acceptable
(older types)
(very high
insulation
resistance)
Modern type of
(good) insulation
systems
Fail
Example: If the reading of B-class insulation material is 100MὨ in 1 minute, 110MὨ in
10 minutes, polarization index is 1.1 (110MὨ/100MὨ=1.1). as the insulating material
contains too much water or seriously polluted, the polarization index is below the
minimum acceptable value, you need to repair or replace parts.
12.
DAR Standard
DAR value
1.6 or more
1.25 ~ 1.6
<1.25 or less
Tested material status Excellent
PASS
Fail
13.
Use of Guard Terminal
When measuring a cable, leakage current flowing on the surface of cable jacket and
the current flowing inside the insulator are mixed and may cause error in value. In
order to prevent such error, wind a conductive wire around the point where leakage
current flows, then connect it to the Guard terminal as shown in below figure. It is to
move out the surface leakage resistance of the cable insulation measure only the
volume resistance of insulator. Make sure to use the Guard cord supplied with this
instrument to connect the instrument to Guard terminal.
