Judging the quality of transformer porcelain bushings requires a systematic evaluation from four dimensions: visual inspection, electrical performance testing, sealing verification, and adaptability to the operating environment. Visual inspection is fundamental, while electrical testing is the core. The following are the specific judgment standards and operational points:
Visual Inspection: Ensure No Physical Defects or Contamination
The appearance is the first hurdle in determining the usability of a porcelain bushing. The following items should be checked:
Surface Condition of the Bushing: It should be smooth and intact, without cracks, damage, discharge burns, or enamel peeling. If the enamel peeling area exceeds 300mm², the bushing must be replaced.
Cleanliness and Contamination: The surface should be free of oil, dust, or conductive deposits to prevent flashover under high voltage.
Integrity of the Sheath Structure: The sheaths of the composite insulation bushing should not have cracks, aging, or deformation to prevent flashover in humid or foggy environments.
Flange and Sealing Area: The joint between the porcelain sleeve and the metal flange should be firm and tight, coated with waterproof sealant, and show no signs of loosening or oil leakage.
Oil Level Indicator (Applicable to Oil-Filled Sleeves): The oil level should be within the specified range, not lower than 1/3 of the lower limit mark and not exceeding 1/2 of the upper limit mark, with no oil leakage.
