No abstract

No abstract

This study provides fundamental knowledge on the breakdown properties of N2-CO2 gas mixture with a ratio of 20:80, 50:50, and 80:20. The gas mixtures were tested under HVAC and HVDC voltages with 1 bar (abs) pressure. The plane-plane and needle-plane electrodes were used with gap lengths between 0.5 cm to 2.5 cm. It is found that the breakdown voltage of N2-CO2 mixture increased with the increased of CO2 content. The breakdown voltage is also affected by the increment of gap distance for both electrode geometrics; plane-plane to represent the uniform field and needle-plane as the non-uniform field. The gas under uniform field configuration has a higher ability to withstand higher voltage levels compared under non-uniform field configuration. However, the non-uniform field provides a very high electric field intensity, which implies very high electric field stress. By increasing the percentage CO2 in N2-CO2 mixture, the insulation strength can reach about 64% that of pure SF6 gas at the 0.1 MPa.

This paper presents the simulation results of electric field distribution within suspension insulators on different stress control techniques under dry-clean and polluted conditions. Finite element method (FEM) is adopted to estimate the electric field behaviour along the insulator profile. For this study, COMSOL Multiphysics version 5.3a is used to perform the modelling and executing the field analysis. The effectiveness of zinc-oxide (ZnO) micro-varistor and grading ring as mitigation tools for the electric field intensity enhancement was examined in this study. The reference data from the dry-clean condition was used as the benchmark to examine the effect of pollution on electric field distribution on the insulator surface. It was found that the application of the combined techniques of ZnO micro-varistor and grading ring is the best scheme for stress control as it reduced the electric field intensity up to almost 84% for both dry-clean and polluted conditions. This study also found that the positioning the grading and corona ring is crucial as it will affect the electric field intensity distribution

No abstract