TDLAS Fiber Optic Sensing Technology for SF6 Gas Insulated Large Cavity Distribution of DC and Polarity Reversal Electric Field in Ultra-high Voltage Gas Circuit Breaker

This article studies the distribution of DC electric field and polarity reversal electric field in gas circuit breaker. When analyzing DC electric field, the valve side outlet device of the converter gas circuit breaker is used as a model to calculate its nonlinear and anisotropic DC electric field, and calculation results are compared with those without considering nonlinearity and anisotropy. When analyzing the polarity reversal electric field, the insulation structure of the valve side winding end of the converter gas circuit breaker was used as a model to focus on the effect of different polarity reversal durations on internal insulation assessment of the converter gas circuit breaker. Concept80 broadband dielectric spectrometer tests the impedance of the sample and uses its built-in calculation software to obtain capacitance of sample, further calculating the complex capacitance and loss tangent of the sample. The maximum testing voltage of the Concept80 testing system is 1V, with testing frequency range of 1µHz~3GHz and temperature range of - 150°C~+500°C. The center wavelength of filter corresponding to the measurement channel is 7.75 µm, and the bandwidth of the filter is 180nm. The center wavelength of the filter corresponding to the reference channel is 3.95 µm, and the bandwidth is 90nm. It does not absorb other decomposition products of CF4 and SF6 gas. It can eliminate measurement errors caused by environmental factors and zero drift caused by the system itself, and improve measurement accuracy. The assessment standard for the DC polarity reversal test is that there should be no more than 10 partial discharge pulses greater than 2000 pC within any 10 minute time period. During the experiment, it is also necessary to record the number of pulses greater than 500pC during the reversal process, but this is only for information and not used as an analytical standard.