Measuring the pre-breakdown current of long sparks in air is important for investigating the discharge mechanism.Since the breakdown of long air gaps is conducted by a series of streamer-leader processes,the correspon...Measuring the pre-breakdown current of long sparks in air is important for investigating the discharge mechanism.Since the breakdown of long air gaps is conducted by a series of streamer-leader processes,the corresponding current signals cover a bandwidth of 0 to more than 20 MHz.Measurement accuracy of the current from the high voltage side is affected by the displacement current and impulse electromagnetic interference.In this paper,a coaxial current sensor with a DC bandwidth of 74.45 MHz is developed.A displacement current-restrained electrode structure is proposed to reduce the equivalent capacitance between the current sensor and the ground over 30 times.Combined with the digital optical fiber synchronous acquisition unit,a current measurement system for long air gap discharge is established.For the purpose of the UHV system’s external insulation optimization design,the discharge current waveform of a 6 m rod-plane air gap under positive switching impulse voltage with 250µs and 1000µs time to crest is obtained.Discharge images and stressed voltage are combined to analyze the continuous feature of a current waveform under critical time to crest impulse and discontinuous feature under long front duration impulse.For the purposes of a lightning protection study,the current waveform of a 10 m rod-plane air gap is subjected to negative switching impulse.Finally,the pulse characteristics of the current corresponding to the single channel and branching stepped negative leader are discussed.展开更多
为满足更长间隙距离、更高电压等级气体开关在较低工作系数下的可靠触发,设计了一种基于毛细管放电的大气压等离子体射流喷射装置,即两间隙毛细管等离子体喷射装置(two gap capillary,TGC)。通过引入中间电极将毛细管通道分为触发通道...为满足更长间隙距离、更高电压等级气体开关在较低工作系数下的可靠触发,设计了一种基于毛细管放电的大气压等离子体射流喷射装置,即两间隙毛细管等离子体喷射装置(two gap capillary,TGC)。通过引入中间电极将毛细管通道分为触发通道和主通道,借助触发通道在放电初始时的弱毛细管放电引燃主通道的放电,实现了重复放电。等离子体射流在触发后的169μs时达到了11 cm左右。主通道电弧电阻呈现"U型"分布,电阻值开始时随主通道电弧电流的增长快速减小,最低时不到200 m?,而后随着电流的跌落快速增加。同时,主通道电弧电阻值在电流增长时要高于电流跌落时,这一差异在流过主通道电弧电流较小时十分明显,而后随着电流幅值的增加逐渐减小。由于没有传统放电结构金属丝电爆的过程,电容器所储能量主要释放于喷射装置主通道,主通道电弧能量沉积效率几乎是传统放电结构的2倍,达到了62.7%。喷射装置寿命大概在300次左右,使用扫描电子显微镜(SEM)拍摄触发通道表面,发现喷射装置TGC中间电极的烧蚀和触发通道的碳化是影响TGC寿命的关键因素,对TGC的寿命优化设计还需做进一步的努力。展开更多
为进一步提高介质阻挡放电(DBD)降解甲醛的效率,并控制副产物的生成量,采用正负双极性高压脉冲电源对同轴式介质阻挡反应器供电,系统地研究了脉冲电压、脉冲重复频率、放电间隙、气体体积流量及甲醛初始质量浓度等影响因素对甲醛降解率...为进一步提高介质阻挡放电(DBD)降解甲醛的效率,并控制副产物的生成量,采用正负双极性高压脉冲电源对同轴式介质阻挡反应器供电,系统地研究了脉冲电压、脉冲重复频率、放电间隙、气体体积流量及甲醛初始质量浓度等影响因素对甲醛降解率及臭氧生成质量浓度的影响。实验结果表明:升高脉冲电压有利于甲醛的降解,当脉冲电压达到19 k V时,脉冲电压继续升高对甲醛降解率的影响不大,而臭氧生成质量浓度随着脉冲电压的增加而不断增大;放电间隙对甲醛降解率有很大的影响,随着放电间隙的减小,甲醛降解率增大,但放电间隙过小时,臭氧生成质量浓度较大;随着气体体积流量的增大,甲醛降解率降低;随着脉冲重复频率的增大,甲醛降解率增大,当脉冲重复频率达到60 Hz时,继续增加脉冲重复频率,甲醛降解率增大不明显;在一定实验条件下,甲醛初始质量浓度越大,甲醛降解率降低,而甲醛去除质量浓度增大并趋近于反应器的最大处理量。展开更多
基金supported by the Fund of the National Basic Research of China(2011CB 209403).
文摘Measuring the pre-breakdown current of long sparks in air is important for investigating the discharge mechanism.Since the breakdown of long air gaps is conducted by a series of streamer-leader processes,the corresponding current signals cover a bandwidth of 0 to more than 20 MHz.Measurement accuracy of the current from the high voltage side is affected by the displacement current and impulse electromagnetic interference.In this paper,a coaxial current sensor with a DC bandwidth of 74.45 MHz is developed.A displacement current-restrained electrode structure is proposed to reduce the equivalent capacitance between the current sensor and the ground over 30 times.Combined with the digital optical fiber synchronous acquisition unit,a current measurement system for long air gap discharge is established.For the purpose of the UHV system’s external insulation optimization design,the discharge current waveform of a 6 m rod-plane air gap under positive switching impulse voltage with 250µs and 1000µs time to crest is obtained.Discharge images and stressed voltage are combined to analyze the continuous feature of a current waveform under critical time to crest impulse and discontinuous feature under long front duration impulse.For the purposes of a lightning protection study,the current waveform of a 10 m rod-plane air gap is subjected to negative switching impulse.Finally,the pulse characteristics of the current corresponding to the single channel and branching stepped negative leader are discussed.
文摘为满足更长间隙距离、更高电压等级气体开关在较低工作系数下的可靠触发,设计了一种基于毛细管放电的大气压等离子体射流喷射装置,即两间隙毛细管等离子体喷射装置(two gap capillary,TGC)。通过引入中间电极将毛细管通道分为触发通道和主通道,借助触发通道在放电初始时的弱毛细管放电引燃主通道的放电,实现了重复放电。等离子体射流在触发后的169μs时达到了11 cm左右。主通道电弧电阻呈现"U型"分布,电阻值开始时随主通道电弧电流的增长快速减小,最低时不到200 m?,而后随着电流的跌落快速增加。同时,主通道电弧电阻值在电流增长时要高于电流跌落时,这一差异在流过主通道电弧电流较小时十分明显,而后随着电流幅值的增加逐渐减小。由于没有传统放电结构金属丝电爆的过程,电容器所储能量主要释放于喷射装置主通道,主通道电弧能量沉积效率几乎是传统放电结构的2倍,达到了62.7%。喷射装置寿命大概在300次左右,使用扫描电子显微镜(SEM)拍摄触发通道表面,发现喷射装置TGC中间电极的烧蚀和触发通道的碳化是影响TGC寿命的关键因素,对TGC的寿命优化设计还需做进一步的努力。
文摘为进一步提高介质阻挡放电(DBD)降解甲醛的效率,并控制副产物的生成量,采用正负双极性高压脉冲电源对同轴式介质阻挡反应器供电,系统地研究了脉冲电压、脉冲重复频率、放电间隙、气体体积流量及甲醛初始质量浓度等影响因素对甲醛降解率及臭氧生成质量浓度的影响。实验结果表明:升高脉冲电压有利于甲醛的降解,当脉冲电压达到19 k V时,脉冲电压继续升高对甲醛降解率的影响不大,而臭氧生成质量浓度随着脉冲电压的增加而不断增大;放电间隙对甲醛降解率有很大的影响,随着放电间隙的减小,甲醛降解率增大,但放电间隙过小时,臭氧生成质量浓度较大;随着气体体积流量的增大,甲醛降解率降低;随着脉冲重复频率的增大,甲醛降解率增大,当脉冲重复频率达到60 Hz时,继续增加脉冲重复频率,甲醛降解率增大不明显;在一定实验条件下,甲醛初始质量浓度越大,甲醛降解率降低,而甲醛去除质量浓度增大并趋近于反应器的最大处理量。
