Studies on the motion and radiation of interior plasmas in gas-filled hohlraums with different laser entrance hole sizes

An experiment on 100 k J laser facility is performed to study the motive features and radiation properties of plasmas from different areas inside gas-filled cylindrical hohlraums.These hohlraums are designed to possess one open end and one laser entrance hole(LEH)with different diameters,which would or not result in the blocking of the LEH.An x-ray streak camera that is set at 16 degrees with respect to the hohlraum axis is applied to acquire the timeresolved x-ray images from the open end.Based on the images,we can study the evolutions of the wall plasma,corona bubble plasma and LEH plasma simultaneously through an equivalent view field of hohlraum interior.Multi-group flat response x-ray detectors are applied to measure the x-ray fluxes.In order to understand these characteristics,our two-dimensional radiation hydrodynamic code is used to simulate the experimental results.For the accuracy of reproduction,dielectronic recombination and two parameter corrections are applied in our code.Based on the comparison between experiments and simulations,we quantitatively understand the blocking process of LEH and the motion effects of other plasmas.The calibrated code is beneficial to design the gas-filled hohlraum in a nearby parameter space,especially the limit size of LEH.

Third-Harmonic Generated in EH32 Mode of a Gas-Filled WavegUide by fs Laser Pulses

In this paper it is reported for the first time that the third harmonic generated in EH32 mode of a gas-filled waveguide by fs pulses has higher generation efficiency. The new finding contrasts with the experiment in It. G. Durfee Ⅲ, S. Backus, M.M. Murnane, and H.C. Kapteyn, Opt. Left. 22 （1997） 1565]. Some possible factors, which produce the contradiction, are discussed briefly.

Signal-Pressure Curves of Cascaded Four-Wave Mixing in Gas-Filled Capillary by fs Pulses

The theoretical framework for the cascaded four waves mixing (CFWM) in gas-filled capillary by fs pulses is constructed. Based on the theoretical framework, the signal-pressure curves (SPC) of the CFWM in gas-filled capillary by fs pulses are calculated. With a comparison between the theoretical and experimental SPC we have discussed the influence of the walk-off and Phase modulation on the SPC. At the same time, we have discussed the possible origin of the first three peaks of the SPC.

基于深度学习的配电网开关柜电晕放电检测设计

在配电网运行过程中,电晕放电量过大导致间隙击穿,开关柜输出电量信号出现过度电离,降低了运行稳定性。为此,提出基于深度学习的配电网开关柜电晕放电检测方法。利用与电晕信号相关的深度学习识别模型,定义单调非递增函数,并以此为基础,计算信号取样值,实现深度学习下的配电网开关柜电晕信号取样。确定电晕信号串表达式,根据开关柜脉冲求解结果,完成实时放电检测。实验结果表明,所提方法可将电晕放电量最大值控制在100 pC以下,能够避免开关柜输出电量信号出现过度电离的情况。

Statistical characteristics of transient enclosure voltage in ultra-high-voltage gas-insulated switchgear

Transient enclosure voltage（TEV）,which is a phenomenon induced by the inner dielectric breakdown of SF_6 during disconnector operations in a gas-insulated switchgear（GIS）,may cause issues relating to shock hazard and electromagnetic interference to secondary equipment.This is a critical factor regarding the electromagnetic compatibility of ultra-high-voltage（UHV）substations.In this paper,the statistical characteristics of TEV at UHV level are collected from field experiments,and are analyzed and compared to those from a repeated strike process.The TEV waveforms during disconnector operations are recorded by a self-developed measurement system first.Then,statistical characteristics,such as the pulse number,duration of pulses,frequency components,magnitude and single pulse duration,are extracted.The transmission line theory is introduced to analyze the TEV and is validated by the experimental results.Finally,the relationship between the TEV and the repeated strike process is analyzed.This proves that the pulse voltage of the TEV is proportional to the corresponding breakdown voltage.The results contribute to the definition of the standard testing waveform of the TEV,and can aid the protection of electronic devices in substations by minimizing the threat of this phenomenon.

A Novel Modularizing Design Method of 10 kV High Voltage Switchgear for Live Maintenance

Due to imperfect manufacturing technology, design defects and environmental impact, the failure rate of 10 kV switchgear is very high. For this reason, based on taken present situation of traditional switchgear and the current technical requirements for switchgear into account, a new reliable and safe modular high voltage switchgear design method is presented in this paper, which can reduce the failure rate of switchgear and improve the reliability of power supply. The electric field and temperature rise simulation model are established to check the reasonability and validity. By using the finite element software, the simulation results show that the design in this paper has a maximum temperature rise of 55 K for the main cabinet and a maximum temperature rise of 45 K for the deputy cabinet, which is far below the international standard of 70 K. The areas where the partial discharge is likely to occur within the switchgear are places such as the connection between bus-bar and cabinet, bus-bar joint and bus-bar corner. In order to avoid potential dangers, the discharge point must be located in time to prevent insulation fault of electrical equipment of the high voltage switchgear. The simulation results demonstrate that the design method in this paper greatly improve the reliability of switchgear and meets the demands of power system.

THE STUDY ON MEASURING TECHNIQUE OF PARTIAL DISCHARGE IN GAS INSULATED SWITCHGEAR USING ULTRA HIGH FREQUENCY METHOD WITH EXTERNAL SENSORS

Objective In order to find early latent faults and prevent catastrophic failures, diagnosis of insulation condition by measuring technique of partial discharge(PD) in gas insulated switchgear (GIS) is applied in this paper, which is one of the most basic ways for diagnosis of insulation condition. Methods Ultra high frequency(UHF) PD detection method by using internal sensors has been proved efficient, because it may avoid the disturbance of corona, but the sensor installation of this method will be limited by the structure and operation condition of GIS. There are some of electromagnetic (E-M) waves leak from the place of insulation spacer, therefore, the external sensors UHF measuring PD technique is applied, which isn't limited by the operation condition of GIS. Results This paper analyzes propagated electromagnetic (E-M) waves of partial discharge pulse excited by using the finite-difference time-domain (FDTD) method. The signal collected at the outer point is more complex than that of the inner point, and the signals' amplitude of outer is about half of the inner, because it propagates through spacer and insulation slot. Set up UHF PD measuring system. The typical PD in 252kV GIS bus bar was measured using PD detection UHF technique with external sensors. Finally, compare the results of UHF measuring technique using external sensors with the results of FDTD method simulation and the traditional IEC60270 method detection. Conclusion The results of experiment shows that the UHF technique can realize the diagnosis of insulation condition, the results of FDTD method simulation and the result UHF method detection can demonstrate each other, which gives references to further researches and application for UHF PD measuring technique.

Denoising Method for Partial Discharge Signal of Switchgear Based on Continuous Adaptive Wavelet Threshold

Partial discharge(PD)is an important reason for the insulation failure of the switchgear.In the process of PD detection,PD signal is often annihilated in strong noise.In order to improve the accuracy of PD detection in power plant switchgear,a method based on continuous adaptive wavelet threshold switchgear PD signals denoising is proposed in this paper.By constructing a continuous adaptive threshold function and introducing adjustment parameters,the problems of over⁃processing of traditional hard threshold functions and incomplete denoising of soft threshold functions can be improved.The analysis results of simulated signals and measured signals show that the continuous adaptive wavelet threshold denoising method is significantly better than the traditional denoising method for the PD signal.The proposed method in this paper retains the characteristics of the original signal.Compared with the traditional denoising methods,after denoising the simulated signals,the signal⁃to⁃noise ratio(SNR)is increased by more than 30%,and the root⁃mean⁃square error(RMSE)is reduced by more than 30%.After denoising the real signal,the noise suppression ratio(NRR)is increased by more than 40%.The recognition accuracy rate of PD signal has also been improved to a certain extent,which proves that the method has a certain practicability.

Automatic wiring method for switchgear design

An automatic 3D wiring method for switchgear design is proposed in this paper. First, wiring constraints are created, and a corresponding evaluation model is proposed. Then, based on the structure of the cabinet, we propose a contour expansion scheme to construct rough paths. Different wiring features of the switchgear are used to connect rough local paths. All the paths are represented in a uniform data structure and forma path network. Finally, an improved A* algorithm is used to search the wiring path between the components in the routing network; the evaluation model is considered as heuristic rules for path searching. The result can satisfy the practical requirements of switchgear design. Experimental results are also provided.

A Wireless Solution for Train Switchgear Contact Temperature Monitoring and Alarming System Based on Wireless Communication Technology

We present a temperature monitoring and warning system, which is based on wireless communi- cation technology and applied in train switchgear in this paper. The system is consists of three parts, including wireless temperature detection module, inter-vehicle transmission networks module and?remote monitoring server. The switchgear contact temperature data are collected via the wireless temperature detection module and exchanged in inter-vehicle wireless networking by Zigbee modules. Then the temperature of train switchgear cabinets can be monitored remotely through the GPRS wireless communication.

Design of Distributed Temperature Measurement System for Switchgear

This paper develops a novel distributed temperature measurement system based on DSP and DS18B20 digital thermometer. The real-time temperature of each node in the switchgear is obtained by several DS18B20s which are connected on the 1-wire bus together. RS-485 master-slave communication protocol is used to centralize monitoring temperatures of several switchgear cabinets. The system also has the function of temperature alarm. The operation of simulation experiment has showed that the system is able to complete monitoring real-time temperatures in high voltage switchgear.

Shanghai Hua Tong Switchgear Works -A Major Switchgear Manufacturer for Power Transmission, Substation and Distribution in China

Founded in 1919, Shanghai Hua Tong Switchgear Works ("HTSW" in short for below) is one of large enterprises on state level. With high and new technology, it is designed as an export base for mechanical and electrical product of the Ministry of Machinery Industry as well. It has been awarded the honor of first grade factory in the competition for key and major project construction in Shanghai year by year,

Solutions to Consider in Current Transformer Selection for APR1400 Nuclear Power Plant Medium Voltage Switchgears

This paper discusses a preferable solution to mitigate the CT （current transformer） saturation problem, and at same time, reduce the accuracy errors when considering the selection of CTs for installation on the medium voltage switchgear of a nuclear power plant. This consideration is important for both measurement and protection functions of the digital protective relays. This is a study to ascertain the best options for a suitable solution to prevent CT saturation in relations to its protective capabilities during short circuit fault without compromising the CT accuracy class during normal operation of the system, while ensuring its conformity to the design requirement is within limit. The advantages of current transformers have proven not only to be reliable and safe, but also are of easy handling, reduction of the cost and components on the MV （medium voltage） switchgear. The purpose of this research is to identify best approach to resolve the existing problems in the current protection system. With the view of LPCT （low power current transformer） which has been newly constructed by few manufacturers to provide good protection and a wide range of measuring function without errors, some other solutions will be considered in this research.

Mayr电弧模型下GIS中快速暂态过电压的仿真分析

SF6气体绝缘封闭组合开关(GIS)中隔离开关进行分合母线时,产生快速暂态过电压(VFTO),幅值高且上升速率极快,威胁GIS及相邻设备的绝缘。选取某800 kV GIS隔离开关分合母线的试验电路为研究对象,采用电磁暂态程序(EMTP/ATP)进行建模仿真,隔离开关燃弧时采用Mayr电弧模型,分析其对VFTO的影响,得出考虑Mayr电弧模型时操作隔离开关、断路器侧隔离开关及变压器侧隔离开关的电压波形,并与考虑时变电阻模型的VFTO进行对比。对VFTO波形进行离散傅里叶分析,得到过电压频率、幅值的变化特征,研究结果为GIS绝缘设计提供参考。

基于多层融合振动数据分析的GIS设备机械缺陷诊断方法研究

气体绝缘金属封闭开关设备(gas insulated metal enclosed switchgear,GIS)机械缺陷是导致设备故障的重要因素,针对单测点、单证据机械缺陷诊断模型信息缺失和精度不足问题,该文提出一种多层融合振动数据分析的GIS设备机械缺陷诊断方法。首先,基于真型GIS设备振动模拟平台试验研究测点位置与缺陷类型对振动行为的影响特性;然后,联合统计分析、模态分解、尺度变换方法提出机械振动信号整体与局部信息关注的复合参数分析方法,引入主成分分析开展多测点振动信息的特征层融合降维;最后,提出改进放缩权重的Dempster-Shafer(DS)证据理论和Bagging投票机制的强/弱基学习器决策层融合机制,联合构建多层融合振动数据分析的GIS设备机械缺陷诊断模型。结果表明:不同类型机械缺陷信号的响应幅值、特征频点和畸变程度存在显著差异,复合特征参量大小及分散程度各不相同;同时,测点位置对缺陷信号的复合振动特征参量的表现形式及分布区间也具有一定影响;基于多层融合数据分析的诊断模型实现缺陷有效识别,辨识准确率为98.66%,相比单一分类器诊断效果提升5.83%。该文可为GIS设备机械缺陷诊断方法提供有价值的参考。

GIS多频振动信号产生机理及实验研究

当前国内外对气体绝缘金属封闭开关设备(gas insulated metal enclosed switchgear,GIS)的异常振动,尤其是引发振动的激励源、多频振动产生机理等问题缺少实质性研究进展。首先,建立受力模型,研究引发GIS振动的激励源,得到引发分箱型GIS振动的力源值,并指出正常运行状态,三相母线间电动力是主频振动的主要激励源。触头接触不良将导致触头斥力合力增大,地脚螺栓松动将导致系统固有频率的变化,影响非线性振动响应频谱特征;然后,将GIS按照薄壁圆柱壳进行研究,计算GIS壳体多阶固有频率,建立有效的非线性振动方程,首次利用解析方法揭示非线性GIS系统多频振动信号的产生机理;最后,研制成功振动信号采集系统,在550 k VGIS产品上设置典型机械缺陷,经实验验证,系统激发出的振动响应幅值极值点及频率与理论分析结果一致。论文的研究成果可为GIS机械缺陷的检测及诊断提供一定的支持和参考。

大电流KYN28型高压开关柜改善温升解决方法

为解决大电流KYN28型高压开关柜温升发热问题,分析了该开关柜的温升发热机理,确定了主回路内阻、接触电阻、感应电阻3个发热源,并计算了发热的总功率。采用增大配电柜两侧散热面积、增大配电柜通风口面积、强制对流风冷、柜体内风道设计改进等措施,平衡发热功率,使散热功率大于发热的总功率。在实验室使用HZDL-WS-6300/12全自动温升试验系统进行测量,在符合标准规定的环境下,测得温升下降约10%,得到明显改善,总体结果基本符合预期。证明所提措施可以解决温升问题,并认为解决温升问题时需要结合设备运行,实时监视温升情况,以确保设备运行安全。

基于专家知识与监测数据联合驱动的高压开关柜状态评估

高压开关柜(HVS)作为电力系统的关键设备,对其工作状况进行有效评估可以保障电力系统的安全稳定运行。在工程实践中,由于高压开关柜长期服役于潮湿、高温等恶劣环境下,不可避免的传感器失效或人为因素会导致其设备状态数据存在随机缺失的现象,从而破坏了数据的完整性和可用性,使得对数据质量要求较高的数据驱动方法难以直接用于解决高压开关柜状态评估的问题。为了解决上述问题,研究了一种基于专家知识和监测数据联合驱动的高压开关柜状态评估方法。首先,对高压开关柜系统的内部构成进行了深入分析,并根据区域中设备的功能不同将其分为电缆室、母线室和断路器室三大区域。其次,进一步分析了系统状态、各区域状态及其关键部件状态两两之间的因果关系,从而建立了适用于高压开关柜状态评估的三层贝叶斯网络(BN)拓扑结构。然后,引入专家领域知识设计了适用于高压开关柜系统的3种约束罚函数,并通过求解带有约束的优化问题,改善了不完整数据集下的贝叶斯网络参数估计性能,进而实现了对高压开关柜系统状态的精确评估。最后,在自主设计的10 kV高压开关柜样机上开展了对比验证实验,结果表明,相比于支持向量机(SVM)方法和反向传播(BP)神经网络方法,本文所提方法在状态评估精度上更具优势。

Ag表面对SF_(6)初级分解产物氧化反应的影响作用研究

运行经验显示SF_(6)在气体绝缘开关设备(GIS)中的热稳定性低于预期,GIS内部的金属表面可能对SF_(6)初级分解与次级反应具有显著的影响作用,但作用机理尚不明晰。该文基于密度泛函理论获得了O_(2)在Ag表面的解离-吸附构型,并建立了低氟硫化物与Ag表面O原子的反应模型,初步揭示了GIS过热故障状态下SF_(6)初级分解产物在Ag表面的氧化反应机理;基于过渡态理论和反应动力学理论,计算获取了界面反应的能垒和反应速率常数,并与气相反应对比,分别确定了三种低氟硫化物的氧化反应路径及其主要场所,并分析了Ag表面对反应的促进/抑制作用机制。结果显示,Ag表面可显著促进SOF_(4)与SOF_(3)的产生,但不利于SF2的表面氧化反应。