Insulation Resistance Tester (Also Called Intelligent Dual Display Insulation Resistance Tester) Has Three Types Of Tests Used To Measure Insulation Resistance. Each Test Uses Its Own Method, Focusing On The Specific Insulation Characteristics Of The Device Under Test . The User Needs To Choose The One That Best Suits The Test Requirements.
Point Test: This Test Is Suitable For Devices With Small Or Negligible Capacitance Effects, Such As Short Wiring.
The Test Voltage Is Applied Within A Short Time Distance, Until A Stable Reading Is Reached, And The Test Voltage May Be Applied Within A Fixed Time Period (Usually 60 Seconds Or Less). Collect Readings At The End Of The Test. Regarding Historical Records, Graphs Will Be Drawn Based On The Historical Records Of Readings. The Observation Of The Trend Is Carried Out Over A Period Of Time, Usually Several Years Or Months.
This Quiz Is Generally Performed For Quizzes Or Historical Records. Changes In Temperature And Humidity May Affect The Readings, And Compensation Is Necessary If Necessary.
Endurance Test: This Test Is Suitable For Guessing And Preventive Protection Of Rotating Machinery.
Take Successive Readings At A Specific Moment (Usually Every Few Minutes) And Compare The Differences In Readings. Outstanding Insulation Will Show The Continued Increase In Resistance Value. If The Readings Stagnate And The Readings Do Not Increase As Expected, The Insulation May Be Weak And May Require Attention. Wet And Contaminated Insulators May Reduce Resistance Readings Because They Add Leakage Current During The Test. As Long As There Is No Significant Temperature Change In The Device Under Test, The Influence Of Temperature On The Test Can Be Ignored.
Polarization Index (PI) And Dielectric Absorption Ratio (DAR) Are Generally Used To Quantify The Results Of Time-Resistant Tests.
Polarization Index (PI)
The Polarization Index Is Defined As The Ratio Of The Resistance Value In 10 Minutes To The Resistance Value In 1 Minute. It Is Recommended To Set The Minimum Value Of PI For AC And DC Rotating Machinery At Temperatures Of Class B, F And H To 2.0, And The Minimum Value Of PI For Class A Equipment Should Be 2.0.
Note: Some New Insulation Systems Respond Faster To Insulation Tests. They Generally Start From The Test Results In The GΩ Range, And The PI Is Between 1 And 2. In These Cases, The PI Calculation Can Be Neglected. If The Insulation Resistance Is Higher Than 5GΩ In 1 Minute, The Calculated PI May Be Meaningless.
Step Voltage Test: This Test Is Particularly Useful When The Additional Voltage Of The Device Is Higher Than The Available Test Voltage Generated By The Insulation Resistance Tester.
Gradually Apply Different Voltage Levels To The Device Under Test. The Recommended Test Voltage Ratio Is 1:5. The Test Time For Each Step Is The Same, Usually 60 Seconds, From Low To High. This Test Is Generally Used At A Test Voltage Lower Than The Additional Voltage Of The Device. The Rapid Addition Of Test Voltage Levels Can Cause Additional Stress On The Insulation And Invalidate The Shortcomings, Resulting In Lower Resistance Values.
Test Voltage Selection
Since The Insulation Resistance Test Consists Of A High DC Voltage, It Is Necessary To Select An Appropriate Test Voltage To Prevent Excessive Stress On The Insulation, Which May Cause Insulation Failures. The Test Voltage May Also Change According To International Standards.
Post time: Feb-06-2021
