Step Voltage Test; Interpreting The Results - AEMC 1000N User Manual

Megohmmeter Model 1000N/1100N

STEP VOLTAGE TEST

Method
In this test, the operator applies two or more test voltages in steps. The
recommended ratio for the test voltage steps is 1 to 5. At each step, test
voltage should be applied for the same length of time, usually 60
seconds. The application of increased voltage creates electrical stresses
on internal insulation cracks. This can reveal aging and physical damage
even in relatively dry and clean insulation which would not have been
apparent at lower voltages.
Test Duration
A series of "steps," each step lasting 60 seconds.

Interpreting the Results

Compare the readings taken at different voltage levels, looking for any
excessive reduction in insulation resistance values at the higher voltage
levels. Insulation that is thoroughly dry, clean, and without physical
damage should provide roughly the same resistance values despite
changes in test voltage levels. If resistance values decrease substantially
when tested at higher voltage levels, this should serve as a warning that
insulation quality may be deteriorating due to dirt, moisture, cracking,
aging, etc.
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