Corona Discharge Characteristics Of 750kV AC Power Transmission Line In High Altitude Area Under Sandy And Dusty Condition

Both the voltage level and altitude of the 750kV AC power transmission line in Northwest China are high, besides the sand and dust weather there is frequent, which will have influence on the corona discharge characteristics of the bundle conductors of the 750kV power transmission lines. Researches in the past were mainly focused on corona discharge characteristics in precipitation conditions (rain, snow and fog), corona discharge characteristics of power transmission line conductor in sandy and dusty condition are of significant theoretical and practical project meaning, which have never been systematically studied.Sponsored by the National Natural Science Foundation of China (51277073) and the scientific project from Northwest China Grid Limited (NWG-GH-KJ-(2012)78), this paper mainly studies AC corona discharge characteristics of power transmission line conductors in high altitude areas under sandy and dusty weather condition. The main contents are introduced in the following:Influence of altitude factor on corona discharge of power transmission line conductor is studied. First, a pressure adjustable corona discharge ion mobility measure platform based on drift tube method is established with using needle-ring discharge model as the ion source, using vacuum pump to control the air pressure in the drift tube, and using the open-close of the ion shutter as timing reference. Finally, positive and negative ion mobilities in different simulation altitudes are gained; then the structure of outer strand of the conductor is taken into consideration, and each strand of the conductor is replaced with a certain number of simulation charges, besides each cage wall is also replaced with simulation charges. Corona onset is judged at each position of the surface of the strand. The emerging, drift, combination and neutralization of the ions in corona discharge process are simulated. Corona discharge model of the stranded conductor in different altitudes are presented with ion mobility measure results in different simulated altitudes. The correctness and advantage are proved by comparison of the calculated results with the test results.Influence of space insulation particle on corona onset process is studied. First, UV imager is used to detect the onset and develop process of the conductor with the plastic ball simulating space particle. Influence of space insulation particle on corona discharge is studied by adjusting the size of the particle, the number of the particles and particle-conductor distance. The displaced dipole method and charge simulation method are used together to calculate the electric field strength and corona onset voltage of the conductor with the consideration of space insulating particles. Electric field distribution of conductor in sandy condition is calculated.A set of corona discharge characteristics of power transmission line conductor in high altitude simulated sandy and dusty condition is established. First, a sandy and dusty condition simulation system which can adjust the wind speed, sand concentration, and sand particle size is developed based on simulation and feasibility analysis; then some important parameters in sandy and dusty condition such as wind speed, sand concentration, sand particle size are chosen based on the characteristics of sandy and dusty weather in Northwest China and the practical difficulties; finally, a set of corona discharge characteristics of power transmission line conductor in high altitude simulated sandy and dusty condition is established together with the corona loss measurement system and corona discharge detect system.Corona onset characteristic of 750kV power transmission line conductor in high altitude sandy and dusty condition is studied. Corona resistive current in different sandy and dusty conditions at 3 test spots of different altitudes are gained. Corona onset electric field strength is gained with the tangent line method. Influence of sandy and dusty condition on corona onset characteristics of 750kV power transmission line LGJ400-50 and LGJ500-45 conductor is analyzed from wind speed, sand concentration, sand particle size and sand particle deposition on conductor.Corona loss characteristic of 750kV power transmission line conductor in sandy and dusty condition is studied. Corona loss test of power transmission line conductor in sandy and dusty condition is done at 3 test spots of different altitudes, corona loss test results of bundle conductors are gained in sandy and dusty condition. Influence of sandy and dusty condition on corona loss characteristics of 750kV power transmission line LGJ400-50 and LGJ500-45 conductor is analyzed from wind speed, sand concentration, sand particle size and sand particle deposition on conductor. Finally, corona loss of 750kV conductors is compared with that in other weather conditions to judge the influence degree of sandy and dusty condition on corona loss of 750kV power transmission line conductors.