Temperature rise distribution characteristics of C3F7CN/CO2 gas-insulated transmission pipeline considering heat source variation

Abstract

The traditional insulating gas SF6 is listed as a greenhouse-gas in the Kyoto protocol, and regulatory measures for the use of $\mathbf{SF}_6$ have been implemented in a variety of industries. $\mathbf{SF}_{6}/\mathbf{N}_{2}$ and $\mathbf{C}_{3}\mathbf{F}_{7}\mathbf{CN}/\mathbf{CO}_{2}$ gas mixtures are environmentally friendly gas insulation partial replacement and complete replacement solutions with good application prospects, but they have higher operating temperature rise compared to GIL equipment with $\mathbf{SF}_6$ gas, which can affect the design of the equipment's current capacity and operational safety. In this paper, high current temperature rise experiments were conducted using genuine GIL to obtain the temperature rise of key locations inside the GIL under $\mathbf{SF}_6$ gas, $\mathbf{SF}_{6}/\mathbf{N}_{2}$ and $\mathbf{C}_{3}\mathbf{F}_{7}\mathbf{CN}/\mathbf{CO}_{2}$. It is found that the highest temperature rise inside the GIL is at the conductive spring, and is greatest when the gas is $\mathbf{C}_{3}\mathbf{F}_{7}\mathbf{CN}/\mathbf{CO}_{2}$, reaching 60.77°C. In addition, considering the non-uniform axial distribution of temperature rise caused by the variation of heat source due to different internal structure of GIL, the temperature distribution of high-voltage conductor and conductive spring cross-section is simulated and calculated, and the comparison with experimental results is verified. The results of this study provide a reference for the engineering application of environmentally friendly hybrid insulating gases $\mathbf{SF}_{6}/\mathbf{N}_{2}$ and $\mathbf{C}_{3}\mathbf{F}_{7}\mathbf{CN}/\mathbf{CO}_{2}$.