Characterizing the Contamination Degree of Bore Insulators in Solid-Armature Launchers Using Partial Surface Conductivity

The contamination degree, which is used to evaluate the degradation of insulation performance in solid-armature rail launchers, is proposed based on the study of pollution flashover in power systems. Two methods for describing the contamination degree, namely the leakage current method and the partial surface conductivity method, are introduced based on the contamination characteristics of bore insulators. The correlation between two descriptive parameters, the leakage current <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${I} _{\text {leak}}$ </tex-math></inline-formula> and the partial surface conductivity <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sigma _{p}$ </tex-math></inline-formula>, and flashover voltage <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${U} _{f}$ </tex-math></inline-formula> was investigated under various sample sizes and experimental conditions. Results indicate that the partial surface conductivity method, in general, is more suitable for describing the contamination degree of bore insulators. In cases where faults or severe contamination occur on insulators, the flashover voltage <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${U} _{\boldsymbol {\sigma }}$ </tex-math></inline-formula> predicted by <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sigma _{\!p}$ </tex-math></inline-formula> is closer to the measured value <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${U} _{f}$ </tex-math></inline-formula> than the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${U} _{I}$ </tex-math></inline-formula> predicted by <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${I} _{\text {leak}}$ </tex-math></inline-formula>, with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${U} _{I}$ </tex-math></inline-formula> typically being higher than <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${U} _{f}$ </tex-math></inline-formula>. For a large sample size of 288 samples, the correlation coefficient between <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sigma _{p}$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${U} _{f}$ </tex-math></inline-formula> was found to be −0.89. The relationship between <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sigma _{p}$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${U} _{f}$ </tex-math></inline-formula> follows a power function, and the regression fitting yielded the equation <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${y} = 0.853~{x} ^{-0.1}$ </tex-math></inline-formula>. The establishment of the contamination degree and the application of descriptive methods provide valuable insights into the damage distribution and degradation mechanisms of bore insulators.