Novel Bushing With Adaptively Field Grading Structure: Experiment and Validation

In the previous part, simulation works were conducted to analyze the field grading effect of nonlinear materials in the application of bushing, and the aim of this paper is to present the experimental investigations. The adaptive field grading (AFG) bushing samples are prepared by a novel method based on wet winding technology, and the assembly quality is verified by scanning electron microscope, thermal gravimetric analyzer, and conductivity test of slice samples with multi-layered structure. The initial partial discharge voltage and phase-resolved partial discharge pattern characteristics of the AFG bushing samples are obtained. Taking S0without a field grading layer as the control group, it exhibited noticeable internal partial discharge at 36 kV. At the same time, S2and S3samples with nonlinear materials had higher initial partial discharge voltages, which are 66.67% and 38.89% higher than those of the former samples, respectively. The insulation strengths under the lightning impulse voltage of the AFG bushing samples are also tested. The S0sample was broken down under severe high-voltage impulses, while the S2sample remained well-insulated after 15 positive and negative lightning impulses. It is hoped that this work will provide an innovative technical roadmap for bushing design and manufacturing.