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The reference standard for step voltage testing is IEEE 95-
2002.
Ramp voltage test
The ramp voltage test is an overvoltage test similar to the SV
test but with improved control and warning of potential
insulation failure. The slow continuous voltage ramp is less
likely to result in unpredictable damage to the insulation than
the rapid step increases employed in SV test.
If a PI test was performed to verify the winding’s suitability for
over voltage testing, the winding must be completely
discharged before the over voltage test is performed.
The typical voltage ramp
(dV/dt) is 1 kV/min
which is the default for
MIT525, MIT1025 and
MIT1525. This value is
user adjustable from the
settings function with the
mode rotary switch set to ramp. Up and down buttons are
used to adjust dV/dt to the required rate and OK confirms the
setting. Press and hold TEST to start.
The test will ramp the voltage until it reaches the selected test
voltage unless a breakdown or sudden rise in current is
detected. The result displayed after the test is the final
insulation resistance, voltage and current. If the result is saved
a complete curve of current (
µ
A) and voltage (kV) is recorded
and can be read into PowerDB, PowerDB Lite or converted to
a spreadsheet so that the current vs. voltage curves can be
compared to published curves in IEEE 95-2002.
