Study Of The Selection Method Of Line Insulators Type And Optimizationa Of External Insulation For Hunan Power Grid

As the upgrading of voltage of power transmission lines,the requirement of insulation performance for insulators becomes stricter. Insulators not only need to continuously run in operating-voltage for a long time but also need to bear the switching overvoltage and the lighting overvoltage under transient state. And most importantly they must avoid any kind of insulation breakdown and surface flashover. How to improve the insulation performance becomes the main purpose in the research of external insulation of power transmission and transformation equipment.The essay based on the research of weather condition and pollution situation in Hunan province analyzes the operation status of power transmission lines,compares the advantages and disadvantages of various types of insulators and put forward four typical methods to choose insulators. This essay focuses on some critical problems about choosing insulators and insulator string pieces on a basis of pollution flashover tolerance. Actually we can choose the insulator,its length and pieces based on the pollution tolerance and then apply the method of specific creep age distance,the selection of switching over-voltage of insulators’characteristics and the line lighting withstand level to check the reasonableness and reliability of the results.As the pollution becoming worse in Hunan,the external insulation equipment cannot satisfy the need of pollution level nowadays. The operating department has no way but to cut off the power to clean the insulators on lines or to tolerate the lighting outrage to be exceed. The optimization of insulators becomes an urgent demand when ice storms occur. The paper analyze the causes of insulators’pollution flashover o icing flashover,recommend some measures to prevent pollution flashover and icing flashover,compare the advantages and disadvantages between V-insulator strings and Insulator strings. The research result shows that V-insulator strings can improve icing flashover voltage more effectively.Although reinforcing the insulation’s performance of transmission lines can decrease the accidents caused by pollution flashover and the risks of flashback of transmission lines , it may threaten the insulation coordination of substation. Therefore,a stimulating calculation model of ATP has been established to solve this problem. This model calculates the over-voltage or the over-current produced by the lighting traveling waves on the equipment of substation and analyzes the impact on strengthening the insulation of transmission lines.