Timely extinction of dc fault arc is very important for the stable operation of dc transmission system. However, there are no exact arc extinguishing parameters for reference to design arcing horn. Here, a double-supply experimental platform was built, in which a pair of Yacob ladder electrodes was used to achieve the whole arc evolution process from generation, then development until self-extinction finally. Arc performance was captured by a high-speed camera, and four parameters of arc self-extinguishing conditions were recorded. Furthermore, a dynamic arc model was established to interpret the characteristics of arc behavior and self-extinction. The research results show that dc arc self-extinguishing lengths are 24, 20, 17, and 11 cm when the initial current is 200, 150, 100, and 50 A, respectively. Arc length is mainly dependent on initial current, and a smaller electrode angle is helpful for arc climbing higher and farther. The waveforms of voltage and current of arc evolution are both piecewise functions separated by obvious turning points. Self-extinguishing voltage, current, and length are all linear functions of initial current while the duration of arc climbing process is a power function. Arc model shows the arc evolution process is actually a variable acceleration process in the early period and a uniform motion process later. This article is a preliminary study that can provide some references for the design of arcing horn used in dc transmission grounding lines.

In this article, an air discharge experimental platform is built and an air streamer discharge simulation model is constructed. The uniform electric field air streamer discharge at low temperature and subatmospheric pressure is studied. The result shows that the distributions of electron density, positive ion density, electric field, space charge density, and photoionization rate are basically consistent with those under standard conditions. The captured discharge shape is basically consistent with the simulation results, but the simulated propagation velocity is slightly higher than the actual propagation velocity. The streamer radius is positively correlated with the streamer propagation velocity and negatively correlated with the space charge density. The trend of the actual current waveform is basically consistent with the simulation current waveform, but the actual current peak is slightly smaller than the simulation current peak.

Based on the plasma-modified model and photoionization optimization model, this article constructs a low temperature and subatmospheric pressure air surface dielectric barrier discharge (SDBD) model with 37 plasma chemical reactions composed of 18 particles. Through the model, the characteristics of air SDBD at low temperature and subatmospheric pressure are studied. Under a dc voltage of 12 kV, with the propagation of the streamer, the parameters, such as electron density, N₂⁺ density, N₂(C) density, O₂⁻ density, electron temperature, space charge density, electric field, and photoionization rate, show a downward trend at an altitude of 11,000 m but always maintain N₂(C) density > electron density > N₂⁺ density > O₂⁻ density. In addition, the propagation velocity of streamer along the surface is positively correlated with altitude. Electron, N₂⁺, N₂(C), and O₂⁻ density are negatively correlated with altitude. Photoionization rate is positively correlated with the altitude in the streamer development stage. In the streamer propagation stage, except for the sudden drop at the altitude of 11,000 m, it is basically consistent at other altitudes.

Typhoons are a serious threat to transmission towers and lines in coastal areas. The anti-wind performance of a transmission tower needs to be reinforced and optimized to avoid tower collapse. Here, an improved real-time wind-field mathematical model and a tower-line coupled simulation model were established to reproduce the wind field distribution, mechanical vibration, and interaction between the wind field and tower. The damage prediction of the transmission tower was analyzed. Furthermore, an actual scaled tower-line model was built, which was used to measure the acceleration and displacement responses in the anti-wind experiments. The research results show that the improved model is feasible and correct based on the verification of Typhoon Mujigae. The tower’s vibration response is mainly characterized by low frequencies, whereas the lines indicate a high frequency response. The transmission line has a remarkable impact on tower vibrations in high turbulence. A flow direction angle of 50° and a long span are dangerous conditions for transmission systems in coastal regions. The acceleration and displacement responses of the main bars show opposite trends to that of the auxiliary cross-bars. The contribution of this article is the possibility of tower collapse prediction and prevention.

Using the simulation system, this article builds a low-temperature and subatmospheric air streamer discharge model. The research focuses on the discharge characteristics under square wave voltage. Streamer discharge shows different discharge patterns and discharge modes in the falling phase of voltage. In addition, electron and positive ion densities are positively correlated with frequency and duty cycle, and negatively correlated with rise (fall) time. The electric field and streamer propagation velocity keep the same change trend, but the response time of streamer propagation velocity lags behind the electric field. Frequency, duty cycle, and rise (fall) time have little effect on both. The relationships between space charge density, the photoionization rate, frequency, duty cycle, and rise (fall) time are consistent with electron density and positive ion density.