Dielectric strength tester, commonly known as voltage endurance tester or high-voltage breakdown test instrument, is a specialized device used to measure the ability of electrical insulating materials (such as plastics, films, ceramics, insulating oil, wires and cables, etc.) to withstand high voltages.
The core purpose is to determine the highest voltage that the tested object can withstand before experiencing breakdown (failure), thereby evaluating whether the insulation performance meets safety standards and requirements.
I. Pre-operation Preparation
(1) Personnel Safety Preparation
Training requirements: Operators must undergo strict training to fully understand the instrument’s performance and the hazards of high voltage.
Personal Protection: Wear insulated shoes and stand on an insulated pad; it is recommended to use high-voltage insulated gloves, but be aware that the gloves may affect the operational flexibility.
Mental State: Do not operate if you are fatigued or have taken medication.
(2) Environment and Equipment Inspection
Environmental Inspection: Ensure the laboratory environment is dry and clean, without flammable or explosive substances.
Instrument Inspection
Check the power cord and high-voltage line of the instrument for intactness.
Confirm that the instrument and test platform are reliably grounded – this is the life-saving line!
Check the interior of the test chamber for cleanliness and dryness, and for any foreign objects such as metal debris.
Self-check of safety functions
Open the test chamber door and confirm that the instrument’s high-voltage output automatically cuts off (the door-open interlock protection function is normal).
Press the emergency stop button and confirm that the instrument cannot start.
(3) Sample Preparation
Prepare samples according to the test standards (such as ASTM D149, IEC 60243), ensuring the samples are clean and free of defects.
Measure and record the thickness of the sample (at least measure 3 points and take the average value), and the dielectric strength is usually converted into the value per unit thickness (kV/mm).
Select the appropriate electrodes and install them on the instrument.
II. Operation Steps
(1) Parameter Settings
Turn on the power supply and preheat the instrument (if required).
On the control panel, set the test parameters:
Test mode: Select “Short-time Voltage Rise”, “Dielectric Strength”, etc.
Voltage Upper Limit: Set a value slightly higher than the expected breakdown voltage to prevent excessive voltage after breakdown from damaging the instrument.
Rise Rate: Set according to standard requirements (such as 500 V/s).
Breakdown Current Criterion: Set according to standards and requirements (such as 10 mA), when the leakage current exceeds this value, the instrument determines that the sample has broken down.
Test Time (Dielectric Strength Mode): Usually set to 60 seconds.
(2) Install the Sample
Ensure the high voltage is turned off and the voltage adjustment knob is at zero.
Place the sample steadily between the lower electrodes.
Operate the handle to smoothly lower the upper electrodes and ensure good contact with the sample surface, avoiding excessive force that may damage the sample.
Close the test chamber door.
(3) Execute the Test
Reconfirm the safety of the site, ensuring no one is in the dangerous area.
Press the “Start” or “Test” button.
The instrument will automatically rise the voltage according to the set program.
Operators should closely observe the display of the voltmeter and ammeter, and pay attention to listening for any “buzzing” sound of discharge.
III. Test Completion and Judgment
(1) Test Passed (Dielectric Strength Mode)
During the specified test time, the sample does not break down, and the leakage current remains below the set value. The instrument automatically stops at the set time, displaying “PASS” or “Passed”, and the breakdown voltage value will be recorded on the display. Then, the instrument emits an alarm, and the high voltage is automatically cut off, with the voltage instantly dropping.
(2) Sample Breakdown
During the test, the sample experiences breakdown.
IV. Post-Test Processing
After the test, do not immediately open the chamber door.
First, use the instrument’s discharge device to automatically discharge the sample and the high-voltage end.
Manual Discharge: Use a discharge rod with an insulated handle to reliably contact the high-voltage electrodes and the ground wire for thorough discharge, which is a crucial step to prevent electric shock.
After discharge, open the chamber door and remove the sample.
Observe and record the morphology of the breakdown point (such as scorch marks, holes).
Clean the electrodes and prepare for the next test.
Post time: Feb-05-2026