Jianxun Hu

Research on Complex Gap Discharge Model of Live Working on EHV and UHV High-Voltage Transmission Lines

This paper obtained the switching impulse flashover characteristic of live working complex gap on extra high voltage (EHV) and ultra high voltage (UHV) high-voltage transmission lines by a large number of experiments. Based on the experimental data and the leader inception discharge model, the complex gap discharge development during the process of entering equipotential and its influencing factors have been analyzed with the electric filed calculation method. Moreover, considering the practical conditions in live working sites, a complex gap discharge model appropriate for side live working on EHV and UHV high-voltage transmission lines has been proposed by introducing a revision coefficient km. It has been found that km is related to the working position and the structure of high-voltage electrode. Through further research on the establishment of the functional relationship, it can provide a comparable accurate theoretical calculation method for the research on the complex gap of live working and can give a guideline for optimizing the test plans.

Experimental Investigation on Live Working Requirements for 1000kV Ultra High Voltage AC Transmission Line

To provide technical support and reference for the design and maintenance of 1,000kV AC transmission line, the experimental investigation on live working was carried out systematically. First, according to the system parameters, the over-voltage level and its statistical distribution during the process of live working were analyzed and calculated. And then, at 1:1 ratio scale simulated tower, tests were performed on different live working positions. Based on these, the minimum approach distance and complex gaps were obtained, and the minimum effective insulating length of insulating tools was found too. According to the practical conditions of the lines, suitable full-set screening clothes were developed and tested. And the electric field intensity on human-body surface inside and outside of the screening clothes at different working positions was measured. The results indicate that the climbing worker should dress screening clothes, and the equal potential worker should wear additional electric field shield mask, and use potential rod during the equal potential process.

Research of Safety Protection for Live Working on 1000kV AC Ultra High Voltage Transmission Line

Safety protection research for live working on 1000 kV AC transmission line was made. The screening clothes for live working was developed and tested. Both material of clothes and the characteristics were researched with standards. According to the actual situation of operation, the electric field intensity on different parts of body and the current passing through human were measured in equal-potential process. The research results show the clothes can meet the safety protection requirements for live work on 1000 kV transmission line. The working man should wear full set screening clothes with face screening mask and the potential rod should be used during equal-potential process.

Research on Minimum Approach Distance for Live Working on 1000kV Ultra High Voltage AC Transmission Line

The switching impulse discharge performances of live working electric structure on outer phase, middle phase and tension string in 1000kV AC transmission line were studied. And based on the results, by calculation and analysis of the risk of live working, the minimum approach distance for live working was determined.

Research of Effect of Wind-Blown Rain on Power Frequency Flashover Characteristic of Conductor-Tower Air Gap

At 1:1 ratio scale simulated tower, the effect of rainfall, wind and wind-blown rain on power frequency flashover characteristic of conductor-tower air gap was initial systematically researched at inner and outdoor. The result is that, rainfalK wind speedy wind direction^ wind-blown rain can effect the power frequency flashover characteristic of air gap. The rain reduce the flashover voltage obviously, especially the air gap is small. When the air gap is 1.2m, and the rainfall intensity is 14.4mm/min, the flashover voltage reduced 13.3%, when the air gap is 0.6m, the flashover voltage reduced 16.2% with the same rainfall intensity. The resistivity of rainwater also has influence on the power frequency flashover characteristic of air gap, but its influence is less than that of rainfall intensity. When the resistivity of rainwater is greater than 4x10 3 Omegaldrcm, as the resistivity increase further, the increasing of flashover voltage has the tendency of saturation; when the resistivity of rainwater is less than 2x10 3 Omegaldrcm, the flashover voltage decreases rapidly as the decreasing of the resistivity, and when the resistivity decreases further, the decreasing speed of flashover voltage has the tendency of increasing. The influence of rainfall path is not obviously to the flashover. The wind direction and speed also influence the flashover voltage, when the wind direction is parallel to the discharging path, the strong wind decreases the flashover voltage of conductor-tower air gap, when the wind direction is vertical to the discharging path, the strong wind increases the flashover voltage of conductor-tower air gap. When there is wind-blown rain, and the wind path is parallel to the discharging path, the flashover voltage is less than that when there is only rainfall. And in the test, the influence of wind-blown rain to the power frequency flashover of air gap is about the lineal superposition of the influence on only rainfall and only wind. - Through the test, the following result is putted forward, in the extremely atrocious weather, the air gap of which the power frequency withstand voltage is more than the maximum operating phase voltage of 500kV transmission line is 1.25m when there is no step bolt (The data is not corrected to the high altitude localities.).The research could supply technical base for the design of minimum air gap space of electric transmission line in adverse weather, reduce the windage yaw discharge fault and accident rate, and improve safety operation level and economic benefit of transmission line construction.