The leader propagation is one of the most important stages in long air gap discharge.The mechanism behind leader re-illumination remains unclear.In high humidity conditions(20.0–30.1 g/m^(3)),we have conducted experi...The leader propagation is one of the most important stages in long air gap discharge.The mechanism behind leader re-illumination remains unclear.In high humidity conditions(20.0–30.1 g/m^(3)),we have conducted experiments of long sparks in a 10 m ultra-high voltage(UHV)transmission line gap under switching impulse voltages.The positive leaders predominantly propagate discontinuously,with almost no significantly continuous propagation occurring.The leader channels are intensely luminous and each elongation segment is straight,with streamers resembling the“branch type”which differs from the“diffuse type”streamers at the front of continuous propagation leaders.The distribution of the propagation velocities is highly random(3.7–18.4 cm/μs),and the average velocity(9.2 cm/μs)significantly exceeds that of continuous propagation(1.5–2.0 cm/μs).Analysis suggests that the current-velocity models suitable for continuous leader propagation do not align well with the experimental data in re-illumination mode.Based on the discharge current waveforms and optical images,it is speculated that the newly elongated leader in re-illumination mode does not evolve gradually from the stem(about 1 cm)but rather evolves overall from a thermal channel much longer than stem.展开更多
Electro-optic electric field sensors based on LiNbO3 are widely used for the measurement of electric fields or transient voltages.However,the working bias of the sensor is influenced by the temperature due to the ther...Electro-optic electric field sensors based on LiNbO3 are widely used for the measurement of electric fields or transient voltages.However,the working bias of the sensor is influenced by the temperature due to the thermo-optic effect of LiNbO_(3).An athermal electrooptic electric field sensor was demonstrated by coating a thin layer of TiO_(2)film which has a negative thermo-optic coefficient,on the common-path interferometer based sensor to compensate LiNbO_(3)'s positive thermo-optic coefficient.Both calculation and experimental studies were conducted.The experimental results reasonably agree well with the calculated values,and the results show the sensor coated with a 640 nm thick TiO_(2)film has a much smaller temperature dependence of 0.011°/℃compared to the initial value of 0.1°/℃.展开更多
基金supported by National Key R&D Program of China(No.2022YFB3206800)Scientific Research Fund of Hunan Provincial Education Department(No.23A0240)+1 种基金Scientific Research Fund of Hunan Provincial Education Department(No.23C0128)CSUST Training Program of Innovation and Entrepreneurship for Undergraduates(No.202410536044)。
文摘The leader propagation is one of the most important stages in long air gap discharge.The mechanism behind leader re-illumination remains unclear.In high humidity conditions(20.0–30.1 g/m^(3)),we have conducted experiments of long sparks in a 10 m ultra-high voltage(UHV)transmission line gap under switching impulse voltages.The positive leaders predominantly propagate discontinuously,with almost no significantly continuous propagation occurring.The leader channels are intensely luminous and each elongation segment is straight,with streamers resembling the“branch type”which differs from the“diffuse type”streamers at the front of continuous propagation leaders.The distribution of the propagation velocities is highly random(3.7–18.4 cm/μs),and the average velocity(9.2 cm/μs)significantly exceeds that of continuous propagation(1.5–2.0 cm/μs).Analysis suggests that the current-velocity models suitable for continuous leader propagation do not align well with the experimental data in re-illumination mode.Based on the discharge current waveforms and optical images,it is speculated that the newly elongated leader in re-illumination mode does not evolve gradually from the stem(about 1 cm)but rather evolves overall from a thermal channel much longer than stem.
基金State Grid Corporation of China,Grant/Award Number:52120519000M。
文摘Electro-optic electric field sensors based on LiNbO3 are widely used for the measurement of electric fields or transient voltages.However,the working bias of the sensor is influenced by the temperature due to the thermo-optic effect of LiNbO_(3).An athermal electrooptic electric field sensor was demonstrated by coating a thin layer of TiO_(2)film which has a negative thermo-optic coefficient,on the common-path interferometer based sensor to compensate LiNbO_(3)'s positive thermo-optic coefficient.Both calculation and experimental studies were conducted.The experimental results reasonably agree well with the calculated values,and the results show the sensor coated with a 640 nm thick TiO_(2)film has a much smaller temperature dependence of 0.011°/℃compared to the initial value of 0.1°/℃.
