774 / 2022-03-31 22:00:01

Electromagnetic wave propagation characteristics of valve side bushing of converter transformer

value sidebushing,electromagnetic wave,propagation

The valve side bushing of converter transformer is the most complex part of the electric field of converter transformer, usually using dry SF6 capacitor bushing. Its insulation structure is complex, with both internal and external insulation. Due to the particularity of its insulation structure, the propagation law of electromagnetic wave generated by partial discharge in its interior can be studied, so as to realize the detection of partial discharge to find its insulation defects. According to the research results, the sensors can be arranged in the engineering site, and the measured UHF electromagnetic wave signal is used to invert its internal state. According to electromagnetic theory and particularity of bushing coaxial structure, the electromagnetic wave radiated by partial discharge in the bushing is equivalent to propagating in multiple coaxial waveguides. There are transverse electromagnetic wave(TEM), transverse magnetic wave(TM) and transverse wave(TE) when propagating. All wave types in the waveguide meet Maxwell equation and Helmholtz equation. In order to solve the problem in time domain, the finite difference time domain method is used to solve the Maxwell's curl equation. The time domain characteristics of electromagnetic waves are directly reflected, and the frequency domain characteristics of electromagnetic waves are solved by Fourier transform. The leakage path of electromagnetic wave propagating in the bushing to the external space is the junction of silicone rubber insulation and metal flange. Electromagnetic wave propagation in coaxial bushing structure is affected by excitation source and distance. According to the leakage path of electromagnetic wave propagating in the bushing to the external space, it can be considered to place the PD monitoring sensor in the external insulation of silicone rubber in engineering practice. By summarizing the propagation law of electromagnetic wave in the coaxial structure of valve side bushing, it can provide reference for the inversion of internal state using the measured UHF signal in engineering practice.