Graded Diagnosis of 110 kV Porcelain Insulator Degradation based on Spatial Electric Field Distribution

A graded diagnosis method for 110 kV porcelain insulator degradation is proposed based on spatial electric-field distribution. The study is limited to a seven-disc 110 kV porcelain suspension insulator string so that modeling, feature extraction, and validation remain focused on one practical operating scenario. First, a finite-element baseline model is built for the healthy 110 kV porcelain insulator string to obtain the axial electric-field distribution pattern. Second, continuous RMS samples acquired by an unmanned-aerial-vehicle-mounted all-fiber electric-field sensor are converted into electric-field intensity, interpolated, divided into seven adaptive segments, and represented by trimmed-mean disc-level features. Finally, a dual-index decision rule combining a dynamic-rate ratio and a standard-deviation ratio is developed, followed by a four-level disc degradation grading model. Laboratory experiments on 110 kV seven-disc strings show that the method can locate degraded discs and provide severity grades. In the tested cases, the recall is higher than 94.5%, the false alarm rate is below 5.5%, and a single analysis takes less than 15 s.