Wanxing Feng

Lightning warning method of transmission lines based on multi-information fusion: Analysis of summer thunderstorms in Jiangsu

At present, multi-threshold method is commonly applied in thunderstorm warning of transmission line with atmospheric electric field mill, the problem of false alarm is easily happened in application. Therefore, a multi-information fusion lightning warning method based on atmospheric electric field mill, lightning location information and lightning disaster risk assessment technology is proposed. The implementation procedure of the method is as follows: electric field intensity and the distance between the lightning and transmission line as warning factors are chose to get preliminary lightning warning level, the final lightning flashover probability is achieved by combining with lightning disaster risk assessment technology. An example of some 220 kV line is presented to describe the warning method in detail. The proposed method considers a variety of factors, can improve warning accuracy and lay the foundation for the application to the actual project in the future.

On the relationship between the cloud-to-ground lightning characteristics and th air quality over Guangzhou megacity, South China

The relationship between the cloud-to-ground lightning characteristics and the air quality data over Guangzhou megacity, South China was investigated in this report. A simple method was proposed to cluster lightning location data into two types of thunderstorms: the traverse thunderstorms and the local ones. It was found that the AQI (air quality index), PM10 concentration, PM2.5 concentration, NO2 concentration and O3 concentration were positively correlated to the number of cloud-to-ground lightning flashes for the local thunderstorms. It was also found that the ratio of the positive cloud-to-ground flashes showed decreasing trend and the duration of the local thunderstorm showed increasing trend as the PM10 concentration increased. No obvious correlation was observed for the cloud-to-ground lightning count and the SO2 concentration.

Method of lightning warning based on atmospheric electric field and lightning location data

In view of the shortcomings of traditional lightning protection measures in the initiative defense, it is necessary to research lightning warning technology, which can provide decision support for avoiding the lightning strike risks of infrastructures. This paper adopted atmospheric electric field and time-differencial calculation, combined with prediction of lightning moving trend based on Lightning Location System, achieved the technology of small-scale and short-time lightning warning for targeted areas. Finally, its effectiveness and practicality are verified by applying this method to transmission line in power grid.

A movement prediction method of CG flashes based on lightning and convective clouds clustering and tracking technology

Movement prediction of CG flashes is one of the most important lightning prediction techniques in severe weather. Since the randomness and instability of lightning occurrence, very limited approaches have been proposed for this objective. In this paper, a movement prediction method of CG flashes was presented, based on both CG flashes in the past and the clouds in satellite nephogram(cloud image). An improved lightning spatial clustering method was developed and introduced on time-series flashes over a certain period of time, and thus independent, random-happen flashes are aggregated and classified into different thunderstorm groups similar to thunderclouds, meanwhile based on fuzzy C-means algorithm convective clouds were identified and segmented from the cloud images, and then with comparison between the thunderstorm groups and convective clouds in different time sections, the track of CG flashes were extracted. Therefore, on the set of extracted track point, the movement prediction can be calculated by any regression functions. Experiments were made and the result shows that the probability of detection (POD) is around 75%, and false alarm rate (FAR) is around 30%.

Three direction finding methods of thunder source using microphone array

In this paper, we have investigated three methods, namely Generalized Cross-Correlation (GCC), Frequency Domain Beam-forming and Approximated Maximum Likelihood (AML), for estimating the direction of thunders measured with a microphone array. The performances of these methods are compared by simulations in terms of the error of angle estimation and also by signal experiments in terms of bi-dimensional representation, coherence measure and error point number for lightning channels measured simultaneously by a high-speed video camera. Comparison results show that both Beam-forming and AML obtain more accurate and complete direction finding than GCC, which is extremely consistent with the reconstructed lightning channel from the camera data. Moreover, Beam-forming and AML obtain additional information regarding thunder sources on top of the lightning channel, which cannot be observed in the camera data due to obstruction. However, the computation of AML is in general much more complicated than the other two methods. Therefore, we conclude that the Frequency Domain Beam-forming based technique suits future practical applications.