Analytic analysis of the full voltage and current conditions of typical electric equipment in UHV converter valve

Abstract

There are many typical electrical equipment in UHV converter valve hall, especially the UHV converter transformer bushing. Infrared thermal imager shows that the temperature gradient distribution is significant, mainly because of the combined effect of voltage and current with rich frequency. This paper attempts to deeply analyze the voltage and current waveform at each key node of the UHV converter valve hall from the theoretical level, and deduces the analytical formula with a 12 pulse rectifier (double bridge rectifier), obtaining the Fourier decomposition results of the actual voltage waveform of the converter bushing: the DC component is 697.6kV, fundamental frequency is 50Hz, the peak value of the 1-27th harmonic component, THD=46.79%. Furthermore, the nonlinear relationship between the dielectric heating enhancement coefficient and the temperature is obtained by coupling the voltage and current waveform with the converter transformer bushing structure through the theoretical formula. At the same time, the Fourier decomposition component of the voltage at the first 2500Hz of the waveform is intercepted in the calculation of the dielectric joule heating, and the voltage waveform at the first 2500Hz is reconstructed, with good reconstruction results. The research results of this paper can provide a good theoretical guidance and technical support for the operation and maintenance of typical power equipment in UHV converter valve hall.