Yinan Geng

Electric field step in air gap streamer discharges

Electric field (E-field) in air gap streamer discharges under positive lightning impulse was measured by specifically developed integrated electro-optic sensors. An E-field step phenomenon was observed. The E-field firstly agreed with the Laplace field, then suddenly increased with a rise time of μs. The occurrence probability of this phenomenon increased as the applied voltage increased. The discharge current waveforms and photos taken by a fast camera prove the E-field step was caused by the space net charge. From the E-step rise time and the corona area range, the average electron drift speed under the experiment situation was estimated about 0.2 × 106 – 0.6× 106 m/s.

An electro-optic integrated sensor for lightning impulse electric field measurements

In order to meet the demands of lightning impulse electric field measurements in power system EMC, the design of an electro-optic integrated sensor is presented in this paper. The disadvantage of the Mach-Zehnder structure of the sensor is analyzed, and a novel structure is proposed to solve the problem. The sensor system is established and the calibration of the sensor is carried out. A maximum linear measurable electric field over 1100 kV/m is reached with the novel sensor. A measurement of a nonuniform lightning impulse electric field was performed, and results of the sensor measurement are within proper relative error when compared with simulation results.

Analysing on characteristics of lightning shielding failure of UHVAC double circuit transmission line based on leader progression method

Shielding failure of lightning is the key problem for safe operation of UHV transmission lines. Taking the feature of 1000KV AC double circuit transmission lines into account, the leader progression method with proper criterion was employed. The lightning shielding failure rate of top phase, middle phase and bottom phase of two different transmission line tower types were compute, in three different geography conditions. The research work is helpful for improving the lightning performance of UHV transmission lines.

Simulation of shielding failure flash-over of transmission line based on leader progression model

Transmission line lightning failures threaten safe and reliable operation of power grid. Guangzhou is one of areas with the strongest lightning activities in China. Lightning protection in Guangzhou power grid has reference role to construction and operation of power grid in other places with frequent lighting in China. Therefore, selection of key parameters in leader progression model is studied. Distribution rule of lighting activities and line lighting trip-out in Guangzhou is analyzed; shielding failure features of typical 500kV power transmission line in Guangzhou are analyzed. The study shows that lighting trip-out frequency has certain relevance to cloud-to-ground lightning frequency. Operation data show that Guangzhou 500kV line shielding failure flash-over rate is 0.125 times / (100 km·year). Two terrains of plain and mountain are considered. The line shielding failure flash-over rate is 0.108 times / (100 km·year) according to calculation.

Analysis on shielding failure of large lightning current of transmision lines

Shielding failure of lightning is the key problem for safe operation of transmission lines. Using Electro-geometry Method to simulate the process of shielding failure, large currents hit a conducting wire hardly, however actually they did sometimes. So, Leader Progression Method is used to analyze the relationship between amplitude of lightning current and other parameters, such as wires position, ground tilt angle and so on.