Bushings provide insulated passage for conductors through the grounded tank while controlling electric field stress and preventing surface tracking. In oil filled designs, oil impregnated paper or resin systems inside the bushing maintain high dielectric strength. Proper oil level, sealing, and moisture control are critical because bushing insulation is sensitive to water ingress and thermal aging. Many failures originate in bushings, so utilities use bushing power factor testing, infrared inspection, and oil sampling or online monitors to detect deterioration early and prevent catastrophic faults.
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