Electric Field Relaxation of HVDC GIL Spacer With Surface Conductivity Gradient Material (σ-SFGM) Using Electrospinning Technology
Hang Yao, Boxue Du, Hucheng Liang, Xiaoxiao Kong, Jianan Dong
Abstract
This study discusses the application of the surface conductivity gradient materials ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sigma $ </tex-math></inline-formula> -SFGMs) for relaxing the electric field concentration around the epoxy-based spacer in high-voltage direct current gas-insulated transmission lines (HVDC GIL). Based on the ±500-kV HVDC GIL model, the iterative method is applied to optimize the thickness gradients of the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sigma $ </tex-math></inline-formula> -SFGM layers on convex and concave surfaces of the basin-type spacer. It is proven that the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sigma $ </tex-math></inline-formula> -SFGM layers can significantly suppress the electric field distortion around the high voltage electrode by increasing the homopolar charges and reducing the heteropolar charges on both spacer surfaces. To fabricate the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sigma $ </tex-math></inline-formula> -SFGM spacer, a thickness-graded layer of high conductivity is formed on a truncated cone-type spacer by electrospinning. Experimental test results show that the application of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sigma $ </tex-math></inline-formula> -SFGM exhibits a promoting effect of about 11.5% on the dc flashover voltage of the cone-type spacer. The <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sigma $ </tex-math></inline-formula> -SFGM spacer can withstand over ten thermal-shock cycles, indicating that the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sigma $ </tex-math></inline-formula> -SFGM layer fabricated by electrospinning is more reliable than that fabricated by dip coating.