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In breakdown voltage test of transformer oil what is standard gap length between two electrodes?
5 mm
3 mm
4 mm
5 mm
5 mm
The breakdown voltage test, also known as the dielectric strength test, is performed according to standards like IS 6792 or IEC 60156. The standard requires the testing gap between two mushroom-shaped electrodes (often 12.5mm or 13mm in diameter) to be exactly 2.5 mm for repeatable and accurate results.
The breakdown voltage test, also known as the dielectric strength test, is performed according to standards like IS 6792 or IEC 60156. The standard requires the testing gap between two mushroom-shaped electrodes (often 12.5mm or 13mm in diameter) to be exactly 2.5 mm for repeatable and accurate results.
E=dVтАЛ тАФ where E is the electric field strength, V is the breakdown voltage, and d=2.5┬аmm is the electrode separation.
VavgтАЛ=n1тАЛтИСi=1nтАЛViтАЛ тАФ representing the average breakdown voltage calculated over multiple successive test cycles.
The test measures the voltage at which the insulating oil loses its dielectric property and allows an arc to form between the electrodes. A motor-driven mechanism increases the AC voltage across the gap at a constant rate of 2 kV/s until breakdown occurs. The 2.5 mm gap is internationally standardized to ensure the dielectric stress distribution is consistent across different testing equipment.
The standard electrode gap for transformer oil testing is 2.5 mm.
The test is performed in a clean, moisture-free oil testing vessel.
The rate of voltage rise is typically maintained at 2 kV per second.
Presence of moisture or contaminants drastically reduces the breakdown voltage.
Provides a quantitative measure of oil health.
Reliable indicator of dielectric insulation capability.
Standardized methodology allows for global benchmarking.
The test does not identify the specific nature of the contaminant (e.g., moisture vs. carbon).
Requires specialized testing equipment.
Periodic maintenance testing of power transformers.
Quality control for new insulating oil batches.
Post-repair assessment of oil-filled electrical equipment.
The standard is governed by IEC 60156 and IS 6792, which dictate the specific electrode geometry and the 2.5 mm gap.
Other gap values like 1.0 mm or 4.0 mm are sometimes used in non-standard research contexts, but 2.5 mm is the industry standard for field testing.
A is correct тАФ The standard gap length between electrodes for a transformer oil breakdown voltage test is precisely 2.5 mm.
Always remember that transformer oil dielectric strength is inversely affected by moisture; a decrease in breakdown voltage usually points to high moisture content or particulate sludge in the oil.