High-Voltage Electrical Equipment Must Maintain Excellent Insulation During Operation, So A Series Of Insulation Experiments Should Be Carried Out From The Beginning Of Equipment Production. These Tests Include: Raw Material Tests In The Production Process, Intermediate Tests In The Production Process, Product Qualitative And Factory Tests, Use On-Site Installation Tests, And Insulation Preventive Tests For Protection And Operation During Use. The Testimony Of Electrical Equipment And Preventive Experiments Are The Two Most Important Experiments. The People’s Republic Of China Electric Power Industry Code And National Code: DL/T 596-1996 “Preventive Test Procedures For Power Equipment” And GB 50150-91 “Electrical Equipment Replacement Test Specifications” Specify The Contents And Specifications Of Each Experiment.
2. Insulation Preventive Experiment
Preventive Insulation Test Of Electrical Equipment Is An Important Measure To Ensure The Safe Operation Of Equipment. After The Test, The Insulation Status Of The Equipment Can Be Grasped, The Danger In The Insulation Can Be Found In Time, And The Protection Can Be Removed. If There Is A Serious Problem, It Is Necessary To Replace The Equipment To Avoid Irreparable Losses, Such As Power Outages Or Equipment Damage Caused By Insulation Failure During Operation.
Insulation Preventive Experiments Can Be Divided Into Two Categories: One Is Non-Destructive Experiment Or Insulation Characteristic Experiment, Which Refers To Various Characteristic Parameters Measured At Low Voltage Or By Other Methods That Will Not Damage The Insulation, Including Measuring Insulation Resistance, Leakage Current, Dielectric Loss Tangent, Etc. Then Determine Whether The Insulation Has Any Shortcomings. Experiments Have Shown That This Method Is Useful, But It Cannot Be Used To Reliably Determine The Electrical Strength Of The Insulation. The Other Is A Destructive Test Or A Pressure Test. The Voltage Applied In The Test Is Higher Than The Operating Voltage Of The Equipment, And The Requirements For Insulation Testing Are Very Strict. In Particular, There Is A Greater Risk Of Exposing And Gathering Shortcomings, And To Ensure That The Insulation Has A Certain Electrical Strength, Including DC Withstand Voltage, Communication Withstand Voltage, Etc. The Disadvantage Of The Withstand Voltage Test Is That It Will Cause Some Damage To The Insulation.
3. Electrical Equipment Handover Test
In Order To Meet The Needs Of Electrical Installation Engineering And Electrical Equipment Replacement Experiments, And Promote The Promotion And Application Of New Technologies For Electrical Equipment Replacement Experiments, The National Standard GB 50150-91 “Electrical Equipment Replacement Experiment Specifications” Specifically Introduces The Contents And Specifications Of Various Experiments. In Addition To Some Insulation Preventive Experiments, Electrical Equipment Replacement Experiments Also Include Other Characteristic Experiments, Such As Transformer DC Resistance And Ratio Experiments, Circuit Breaker Loop Resistance Experiments, Etc.
4. The Basic Principle Of Insulation Preventive Experiment
4.1 Insulation Resistance Test Insulation Resistance Test Is The Most Widely Used And Most Convenient Item In The Insulation Test Of Electrical Equipment. The Value Of Insulation Resistance Can Effectively Reflect The Shortcomings Of Insulation, Such As Total Humidity, Contamination, Severe Overheating And Aging. The Most Commonly Used Instrument For Testing Insulation Resistance Is An Insulation Resistance Tester (Insulation Resistance Tester).
Insulation Resistance Testers (Isolation Resistance Testers) Usually Have Types Such As 100 Volts, 250 Volts, 500 Volts, 1000 Volts, 2500 Volts, And 5000 Volts. The Insulation Resistance Tester Should Be Used In Accordance With DL/T596 “Preventive Experimental Procedures For Power Equipment”.
4.2 Leakage Current Test
The Voltage Of The General DC Insulation Resistance Tester Is Lower Than 2.5KV, Which Is Much Lower Than The Working Voltage Of Some Electrical Equipment. If You Think The Measuring Voltage Of The Insulation Resistance Tester Is Too Low, You Can Measure The Leakage Current Of Electrical Equipment By Adding DC High Voltage. Commonly Used Equipment For Measuring Leakage Current Includes High-Voltage Experimental Transformers And DC High-Voltage Generators. When The Equipment Has Shortcomings, The Leakage Current Under High Voltage Is Much Larger Than That Under Low Voltage, That Is, The Insulation Resistance Under High Voltage Is Much Smaller Than That Under Low Voltage.
There Is Not Much Difference Between The Leakage Current And Insulation Resistance Of The Medical Withstand Voltage Tester Measuring Equipment, But The Leakage Current Measurement Has The Following Characteristics:
(1) The Test Voltage Is Much Higher Than That Of The Insulation Resistance Tester. The Shortcomings Of The Insulation Itself Are Easily Exposed, And Some Convergence Shortcomings Without Penetration Can Be Found.
(2) Measuring The Connection Between The Leakage Current And The Applied Voltage Helps To Analyze The Types Of Insulation Defects.
(3) The Microampere Used For Leakage Current Measurement Is More Accurate Than The Insulation Resistance Tester.
4.3 DC Withstand Voltage Test
DC Withstand Voltage Test Has Higher
Communication Withstand Voltage Experiment Sometimes Makes Some Weaknesses In Insulation More Prominent. Therefore, It Is Necessary To Conduct Experiments On Insulation Resistance, Absorption Rate, Leakage Current And Dielectric Loss Before The Experiment. If The Test Result Is Satisfactory, The Communication Withstand Voltage Test Can Be Carried Out. Otherwise, It Should Be Dealt With In Time, And The Communication Withstand Voltage Test Should Be Carried Out After Each Target Is Qualified To Avoid Unnecessary Insulation Damage.
4.5 Test Of Dielectric Loss Factor Tgδ
The Dielectric Loss Factor Tgδ Is One Of The Fundamental Goals Reflecting The Insulation Performance. The Dielectric Loss Factor Tgδ Reflects The Characteristic Parameter Of Insulation Loss. It Can Actively Discover The Overall Insulation Of Electrical Equipment Affected By Wetting, Degeneration, And Deterioration, As Well As The Local Defects Of Small-Sized Equipment.
Comparing The Medical Withstand Voltage Tester To Insulation Resistance And Leakage Current Tests, The Dielectric Loss Factor Tgδ Has Significant Advantages. It Has Nothing To Do With The Test Voltage, Test Sample Size And Other Factors, And It Is Easier To Distinguish The Insulation Change Of Electrical Equipment. Therefore, The Dielectric Loss Factor Tgδ Is One Of The Most Fundamental Tests For The Insulation Test Of High-Voltage Electrical Equipment.
The Dielectric Loss Factor Tgδ Can Be Useful To Find The Following Insulation Shortcomings:
(1) Moisture; (2) Penetrate The Conductive Channel; (3) The Insulation Contains Free Air Bubbles, And The Insulation Delaminates And Shells; (4) The Insulation Is Dirty, Degenerated, And Aging.
Medical Withstand Voltage Tester
Post time: Feb-06-2021
