Novel Bushing With Adaptively Field Grading Structure: Simulation and Mechanism

Bushing has become a critical component endangering the safe functioning of power transmission and limiting its development to higher voltage and power levels. The main technical bottleneck that restricts high voltage bushing is the uneven distribution of electric fields due to its “plug-in” structure. In this paper, a novel adaptive field grading (AFG) bushing with a simple multi-layered structure based on nonlinear materials is introduced. A frequency-domain steady-state simulation method considering the field-dependent dielectric and loss characteristics of nonlinear materials to design the AFG bushing is proposed. Referring to the size of the AC transformer capacitive bushing, the finite element models of the 40.5 kV AFG bushing are established, and the electric field distributions are obtained. Optical electric field sensors are used to test the surface electric field distribution of the bushing samples, validating the accuracy of the simulation method. Combining simulation and experimental test results, the influence of doping concentrations and lengths of the field grading layer on the electric field distribution is studied, and the grading mechanism of nonlinear material is summarized. The results demonstrate the potential of nonlinear materials to relieve electric field concentration in bushings and provide a solid basis for its design and application.