Dielectric Strength
The maximum electric field an insulating material can withstand before breakdown, measured in kV/mm.
Dielectric strength is the maximum electric field before breakdown. For transformer oil, tested per ASTM D877/IEC 60156 (2.5mm gap). New oil: 30-40 kV/2.5mm. Decreases with moisture, particles, gases.
Solid insulation: pressboard 10-20 kV/mm, epoxy 15-25 kV/mm. System must coordinate oil, paper, pressboard for normal voltage and transients (BIL).
QDTB ensures all materials meet requirements with rigorous QC and factory testing per IEC 60076.
Related Products
Related Terms
BIL (Basic Impulse Level)
The ability of transformer insulation to withstand high-voltage surges from lightning or switching, measured in kV peak.
Insulation Class (A/E/B/F/H)
Standardized temperature ratings for transformer insulation materials defining maximum operating temperatures.
Moisture Content
The amount of water in transformer oil and solid insulation, critical for dielectric strength and insulation life.
Partial Discharge (PD)
Localized electrical discharges in small insulation regions not bridging electrodes, indicating defects or aging.
More Terms Starting with “D”
Distribution Transformer
A transformer stepping down voltage from the distribution network (11-33 kV) to utilization voltage (400/230V) for end consumers.
Dry-Type Transformer
A transformer using air or solid insulation instead of liquid, ideal for indoor applications with fire safety priority.
Dissolved Gas Analysis (DGA)
A diagnostic technique analyzing gases dissolved in transformer oil to detect internal faults before they become critical.
More in “Insulation & Testing”
BIL (Basic Impulse Level)
The ability of transformer insulation to withstand high-voltage surges from lightning or switching, measured in kV peak.
Insulation Class (A/E/B/F/H)
Standardized temperature ratings for transformer insulation materials defining maximum operating temperatures.
Lightning Impulse Test
A high-voltage test simulating lightning surges to verify transformer insulation withstands transient overvoltages.
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