This paper presents an approach to accurately forecast the yearly occurrence of flashovers caused by lightning-induced voltage in overhead power lines in the presence of layered ground.The aim is to improve the accura...This paper presents an approach to accurately forecast the yearly occurrence of flashovers caused by lightning-induced voltage in overhead power lines in the presence of layered ground.The aim is to improve the accuracy of flashover rate estimation by using the insulator volt-time model.In particular,two-layer horizontal ground structures are considered.A 3D finite element method is used to calculate induced voltages and a Monte Carlo simulation is applied to determine the annual flashover rate.Volt-time insulator characteristics are used to identify the flashover condition.The results are compared with those obtained by using the standard 1.5 times the critical flashover(CFO)threshold criterion.The results indicate that the conventional 1.5 times the CFO criterion may underestimate the rate of flashovers,particularly in regions with horizon-tally stratified soil,as the volt-time method offers a more accurate presentation of the flashover process.Furthermore,the effect of upper soil depth,upper soil conductivity,pole spacing,and different flashover distance calculation techniques on flashover rates are analysed.This paper presents a new mathematical formula for estimating yearly flash-overs based on the results obtained by the volt-time method in the presence of stratified ground.The derived analytical formula provides an insightful tool for power system engineers to evaluate the lightning performance of overhead lines and implement efficient mitigation strategies.展开更多
This paper introduces the configuration and the operation principles of a high power direct current circuit breaker （DCCB）. The commutating current principle of the breaker is described in details with its theory an...This paper introduces the configuration and the operation principles of a high power direct current circuit breaker （DCCB）. The commutating current principle of the breaker is described in details with its theory and simulation analysis. The test results presented show that the DCCB meets the requirements for quenching protection. It will be used as the main breaker for quench protection in EAST.展开更多
文摘This paper presents an approach to accurately forecast the yearly occurrence of flashovers caused by lightning-induced voltage in overhead power lines in the presence of layered ground.The aim is to improve the accuracy of flashover rate estimation by using the insulator volt-time model.In particular,two-layer horizontal ground structures are considered.A 3D finite element method is used to calculate induced voltages and a Monte Carlo simulation is applied to determine the annual flashover rate.Volt-time insulator characteristics are used to identify the flashover condition.The results are compared with those obtained by using the standard 1.5 times the critical flashover(CFO)threshold criterion.The results indicate that the conventional 1.5 times the CFO criterion may underestimate the rate of flashovers,particularly in regions with horizon-tally stratified soil,as the volt-time method offers a more accurate presentation of the flashover process.Furthermore,the effect of upper soil depth,upper soil conductivity,pole spacing,and different flashover distance calculation techniques on flashover rates are analysed.This paper presents a new mathematical formula for estimating yearly flash-overs based on the results obtained by the volt-time method in the presence of stratified ground.The derived analytical formula provides an insightful tool for power system engineers to evaluate the lightning performance of overhead lines and implement efficient mitigation strategies.
基金supported by the National Meg-Science Project of the Chinese Government
文摘This paper introduces the configuration and the operation principles of a high power direct current circuit breaker （DCCB）. The commutating current principle of the breaker is described in details with its theory and simulation analysis. The test results presented show that the DCCB meets the requirements for quenching protection. It will be used as the main breaker for quench protection in EAST.
