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
目前对阀控式铅酸蓄电池建模的研究很少,而且都是针对一种放电倍率,而工业上往往要求蓄电池能工作在不同放电电流下。基于红河变电站实验环境,利用变电站直流屏使用丰日2 V 200 Ah蓄电池GFM-200和新威充放电仪器,并使用Matlab仿真软件...目前对阀控式铅酸蓄电池建模的研究很少,而且都是针对一种放电倍率,而工业上往往要求蓄电池能工作在不同放电电流下。基于红河变电站实验环境,利用变电站直流屏使用丰日2 V 200 Ah蓄电池GFM-200和新威充放电仪器,并使用Matlab仿真软件对蓄电池建模,实现了一个等效电路模型,满足了不同放电电流仿真的要求。仿真数据与实验数据相比较,结果显示二者有较好的吻合度,可为蓄电池性能研究和正确使用提供参考。展开更多
通过正交对比试验和对结果数据的方差分析,考察了粘合剂组成、化成制度、化成电解液、干燥方式、平整压力、棉纸、保存方式以及激活电解液组成对干荷式锌银蓄电池涂膏锌负极大电流密度180 m A/cm2放电性能的影响。结果表明:激活电解液...通过正交对比试验和对结果数据的方差分析,考察了粘合剂组成、化成制度、化成电解液、干燥方式、平整压力、棉纸、保存方式以及激活电解液组成对干荷式锌银蓄电池涂膏锌负极大电流密度180 m A/cm2放电性能的影响。结果表明:激活电解液组成、干燥方式和粘合剂组成对放电性能有特别显著的影响;化成制度对放电性能有显著影响;而化成电解液、平整压力、棉纸和保存方式对放电性能影响不大。展开更多
One-dimensional manganese oxide nanobelt bundles with birnessite-type structure have been synthesized by a hydrothermal process in a NaOH solution employing K-type layered manganese oxide as a precursor. The obtained ...One-dimensional manganese oxide nanobelt bundles with birnessite-type structure have been synthesized by a hydrothermal process in a NaOH solution employing K-type layered manganese oxide as a precursor. The obtained manganese oxide nanobelt bundles exhibit excellent discharge properties and cycle stability. The initial capacity is 376 mAh-g-1 and the reversible capacity of 243 mAhog-1 is maintained after the 50th cycle at a current density of 20 mA·g-t. Meanwhile, the manganese oxide nanobelt bundles show an excellent cycle performance even if at relative high current density.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.
文摘目前对阀控式铅酸蓄电池建模的研究很少,而且都是针对一种放电倍率,而工业上往往要求蓄电池能工作在不同放电电流下。基于红河变电站实验环境,利用变电站直流屏使用丰日2 V 200 Ah蓄电池GFM-200和新威充放电仪器,并使用Matlab仿真软件对蓄电池建模,实现了一个等效电路模型,满足了不同放电电流仿真的要求。仿真数据与实验数据相比较,结果显示二者有较好的吻合度,可为蓄电池性能研究和正确使用提供参考。
文摘通过正交对比试验和对结果数据的方差分析,考察了粘合剂组成、化成制度、化成电解液、干燥方式、平整压力、棉纸、保存方式以及激活电解液组成对干荷式锌银蓄电池涂膏锌负极大电流密度180 m A/cm2放电性能的影响。结果表明:激活电解液组成、干燥方式和粘合剂组成对放电性能有特别显著的影响;化成制度对放电性能有显著影响;而化成电解液、平整压力、棉纸和保存方式对放电性能影响不大。
文摘One-dimensional manganese oxide nanobelt bundles with birnessite-type structure have been synthesized by a hydrothermal process in a NaOH solution employing K-type layered manganese oxide as a precursor. The obtained manganese oxide nanobelt bundles exhibit excellent discharge properties and cycle stability. The initial capacity is 376 mAh-g-1 and the reversible capacity of 243 mAhog-1 is maintained after the 50th cycle at a current density of 20 mA·g-t. Meanwhile, the manganese oxide nanobelt bundles show an excellent cycle performance even if at relative high current density.
