Polarisation Index (Pi); Timed Insulation Resistance; Preventative Maintenance; Battery Replacement - Megger BM5200 User Manual

Polarisation index (PI)

Polarisation Index (PI) test performs a ratio metric test that
calculates the ratio of insulation resistance at ten minutes, IR
to insulation resistance at one minute, IR
provides a simple indication of insulation polarisation when
subjected to high voltage DC. A high PI value indicates a high
degree of insulation polarisation and therefore good insulation
condition. Generally the PI value should be two or above.
Polarisation occurs at different rates ranging from minutes to sev-
eral hours which led the IEEE to create a ratiometric PI test. The
IEEE standard 43-2000, "Recommended Practice for Testing Insula-
tion Resistance of Rotating Machinery," limits the use of PI test on
winding systems to those with IR

Timed insulation resistance

The timed IR test is a test that automatically terminates after a user
adjustable time (t). Users can select SETUP on the range switch
and adjust timer (t) using up and down arrow buttons to set the
desired time followed by a single press of the PI-t (left arrow)
button. Default time (t) is set at one minute because IR1min is
frequently referred to in international standards.
9
. This test
1min
being less than 5000 MΩ.
1min

Preventative maintenance

No user serviceable parts
There are no user serviceable parts in the BM5200 except for the
10 min
batteries.
If an instrument's protection has been impaired it should not be
used, but sent for repair by suitably trained and qualified personnel.
The protection is likely to be impaired if for example, it shows
visible damage, fails to perform the intended measurements,
has been subjected to prolonged storage under unfavourable
conditions, or has been subjected to severe transport stresses.

Battery replacement

The battery contacts are not isolated from the test leads.
Remove the test leads from the instrument before opening
the battery compartment.
The cells are housed in a battery compartment in the base of the
instrument. To change the cells, use a PZ2 pozidrive screwdriver
to remove the battery cover securing screws and lift off the battery
compartment cover. Observing the correct polarity as marked on
the battery housing, install 8 replacement IEC LR6 (AA) cells.
Replace and secure the battery compartment cover on completion.
G
WARNING