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| 1 | Characteristics of Long Air Gap Discharge Current Subjected to Switching Impulse显示文摘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. | Yishi Yue Hengxin He Weijiang Chen Junjia He Chuanqi Wu Xiangen Zhao Feng Huo | 2015 | CSEE Journal of Power and Energy Systems2015，1，3： | 13 |
| 2 | Computing payment for ecosystem services in watersheds: An analysis of the Middle Route Project of South-to-North Water Diversion in China显示文摘Payment for ecosystem services (PES) has attracted considerable attention as an economic incentive for promoting natural resource management recently. As emphasis has been placed on using the incentive-based mechanism by the central government, rapid progress on PES research and practice has been achieved. However PES still faces many difficulties. A key issue is the lack of a fully-fledged theory and method to clearly define the design scope, accounting and feasibility of PES criteria. An improved watershed criteria model was developed in light of research on PES practices in China, investigations on the water source area for the Middle Route Project of South-to-North Water Diversion and ecosystem services outflows theory. The basic principle of assessment is the direct and opportunity cost for ecological conservation and environmental protection in the water source area deduct nationally-financed PES and internal effect. Then the scope and the criteria methods were determined, and internal effect was put forward to define benefits brought from water source area. Finally, Shiyan City, which is the main water source area for the Project of Water Diversion, was analyzed by this model and its payment was calculated. The results showed that: (1) during 2003-2050, the total direct cost and opportunity cost would reach up to 262.70 billion and 256.33 billion Chinese Yuan (CNY, 2000 constant prices), i.e., 50.61% and 49.38% of total cost, respectively; (2) Shiyan City would gain 0.23, 0.06 and 0.03 CNY/m3 in 2014-2020, 2021-2030, and 2031-2050, respectively. | Zhengju Dong Yan Yan Jing Duan Xiao Fu Qingrong Zhou Xiang Huang Xiangen Zhu Jingzhu Zhao | 2011 | Journal of Environmental Sciences2011，23，12： | 12 |
| 3 | Protection of ±500 kV HVDC Double-circuit Converter Station from Lightning Induced Overvoltage显示文摘In order to obtain reasonable schemes of arrester in converter stations, the arrester scheme of 'Xiluodu-Guangdong HVDC ± 500 kV double circuit transmission' project against lighting induced overvoltage, which was designed according to the main principle of lightning protection in converter station, is discussed. A calculation of the lighting induced overvoltage in Zhaotong converter station un- der various operation modes is performed with ATP-EMTP software, then the surge arrester configuration of the converter station is decided, and the arrester protection schemes of smoothing reactor and neutral line are studied. It is concluded that additional protection is necessary because of the relatively large gap between protected disconnecting switch and arrester of metallic return transfer bus. Plus, the smoothing reactor (SR) arrester near the valve hall could be removed to improve the scheme’s economic performance. | DONG Manling YUAN Zhiyong LI Tianwei ZHAO Xiangen ZHANG Jiaxin HE Junjia | 2013 | 高电压技术2013，39，8： | 1 |
| 4 | The application of fuzzy control in hydraulic excavator energy-saving control显示文摘 | GUO Xiangen ZHAO Dingxuan SHANG Tao | 2004 | Journal of Jilin University2004，34，2： | 1 |
| 5 | Schlieren techniques for observations of long positive sparks:Review and application显示文摘Understanding the mechanism of positive leader discharge is important in lightning protection engineering and the external insulation design in high voltage power transmission systems.During the propagation of a positive leader,some processes without light-emitting,for example,the insulation recovery process after the breakdown,cannot be observed by optical photography techniques.With the combination of the digital high-speed imaging system,the conventional Schlieren techniques offer new vistas in the long air gap discharge observation.The important features of high spatial resolution,high sensitivity,and easy arrangement make Schlieren techniques powerful and effective tools for characterising the discharge processes without light-emitting.This work presents a brief review of current Schlieren techniques and discusses the design of the Schlieren optics system for long spark observations.Several interesting phenomena discovered at different phases of long sparks with high-speed Schlieren techniques are also presented. | Junjia He Xiankang Wang Xiangen Zhao Juhyeong Lee Yaping Du Xiaopeng Liu Quan Gan Yang Liu Yuqin Liao | 2022 | High Voltage2022，7，5： | 0 |
| 6 | Multiple discharges before leader inception in long air gaps under positive switching impulses显示文摘There are multiple corona bursts before leader inception when the rising rate of the applied voltage or electric field is not sufficiently high enough in long positive sparks.In existing studies,no attention has been paid to whether these corona bursts occur in the same location,and they are mostly considered directly as belonging to the same discharge.However,this paper presents that in a typical rod-plate long air gap,the multiple corona bursts before leader inception are distributed in at least two different locations,and the highest probability of three discharges occurs.Also,the discharge occurs with the highest probability in the time sequence‘tip-tip-side-tip-other side’of the electrode in the first five corona bursts.For each discharge,the first corona current is a single,double exponential pulse,while the following corona currents are mostly a superposition of multiple pulses.The above findings are mainly based on experiments in a 1.4 m air gap under positive switching impulses,in which the voltage,current,and high-speed images were recorded simultaneously.Finally,based on the experimental results,this paper discusses the effects brought by ignoring the multiple discharges on key parameters of leader inception and makes some suggestions to optimise long spark experiments. | Xiangen Zhao Juhyeong Lee Gang Liu Lei Jia Yang Liu Junjia He Yaping Du | 2023 | High Voltage2023，8，1： | 0 |
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