Power transformer is one of the most important equipment in the power system.Its operating condition affects the reliability of power supply directly.Therefore,in order to guarantee transformer operation safely and re...Power transformer is one of the most important equipment in the power system.Its operating condition affects the reliability of power supply directly.Therefore,in order to guarantee transformer operation safely and reliably,it is necessary to assess condition of power transformer accurately.Return voltage method based on voltage response measurements is still a new non-intrusive diagnosis method for internal insulation aging of transformer.In this paper the technique and application of return voltage measurement and some results of voltage response measurements of several transformers was introduced.Voltage response measurements were performed on various transformers with different voltage grades,various operating periods,different moisture contents and aging degrees on site.Derived moisture contents from return voltage measurement were compared with the corresponding moisture contents obtained from the analysis of oil samples.Based on on-site experiments and theoretical analysis,the criteria for insulation state of transformer are proposed.Moisture condition of transformer insulation can be determined by using return dominant time constant,and a good correlation between aging degree and the return voltage initial slopes of the aged transformers.Field test performed on several transformers,its interpretation of results are also presented,which proves that return voltage measurements can be used as a reliable tool for evaluating moisture content in transformer insulation.展开更多
Using solid waste as a substitute for conventional cement has become an important way to reduce carbon emissions.This paper attempted to utilize steel slag(SS)and fly ash(FA)as supplementary cementitious material by u...Using solid waste as a substitute for conventional cement has become an important way to reduce carbon emissions.This paper attempted to utilize steel slag(SS)and fly ash(FA)as supplementary cementitious material by utilizing CO_(2)mineralization curing technology.This study examined the dominant and interactive influences of the residual water/cement ratio,CO_(2)pressure,curing time,and SS content on the mechanical properties and CO_(2)uptake rate of CO_(2)mineralization curing SS-FA-Portland cement ternary paste specimens.Additionally,microstructural development was analyzed.The findings demonstrated that each factor significantly affected compressive strength and CO_(2)uptake rate,with factor interactions becoming more pronounced at higher SS dosages(>30%),lower residual water/cement ratios(0.1-0.15),and CO_(2)pressures of 0.1-0.3 MPa.Microscopic examinations revealed that mineralization primarily yielded CaCO_(3)and silica gel.The residual w/c ratio and SS content significantly influenced the CaCO_(3)content and crystallinity of the mineralization products.Post-mineralization curing,the percentage of pores larger than 50 nm significantly decreased,the proportion of harmless pores smaller than 20 nm increased,and pore structure improved.This study also found that using CO_(2)mineralization curing SS-FA-Portland cement solid waste concrete can significantly reduce the negative impact on the environment.展开更多
随着可再生能源占比的提升,气电联合配网(integrated electricity-gas distribution systems,IEGDS)发展迅速,其研究的必要性也随之凸显。为解决IEGDS考虑可再生能源接入后的多设施规划及可靠性评估问题,提出了考虑可靠性约束的IEGDS分...随着可再生能源占比的提升,气电联合配网(integrated electricity-gas distribution systems,IEGDS)发展迅速,其研究的必要性也随之凸显。为解决IEGDS考虑可再生能源接入后的多设施规划及可靠性评估问题,提出了考虑可靠性约束的IEGDS分布鲁棒优化(distributionally robust optimization,DRO)规划模型。可靠性评估通过系统平均中断频率指标(system average interruption frequency index,SAIFI)与预期能源未供应指标(expectation energy not supplied,EENS)量化,给出一种显式可靠性评估模型。利用Wasserstein距离衡量的DRO规划模型来处理可再生能源出力、电与气负荷的随机性。最后经过案例分析得出,投建设施种类的增加不仅能降低总成本,还能提高系统运行可靠性与灵活性,可再生能源出力与气电负荷的不确定性导致总成本提升60%以上。随着可靠性要求提升总成本也随之提高,但得到的方案在实际应用中更具价值与参考性。展开更多
为清晰阐明钝性弹道冲击下人体头部的受损机理,基于THUMS(Total Human Model for Safety)模型,通过材料参数优化、比例缩放及流固耦合方法,构建符合中国50百分位成年男性头部特征的有限元模型。以LS-DYNA(Livermore Software Technology...为清晰阐明钝性弹道冲击下人体头部的受损机理,基于THUMS(Total Human Model for Safety)模型,通过材料参数优化、比例缩放及流固耦合方法,构建符合中国50百分位成年男性头部特征的有限元模型。以LS-DYNA(Livermore Software Technology Corporation's Dynamic Analyzer)软件为仿真平台,采用任意拉格朗日-欧拉算法定义脑脊液流体特性,优化颅骨与脑组织的弹塑性材料参数,并通过网格变形技术实现头部尺寸与解剖结构的本土化适配。选取前额、顶壁、枕部及后窝等典型易损区,对比Nahum尸体实验及THUMS模型数据,验证模型的生物力学响应。研究结果表明:改进模型在易损区域的颅内压峰值分别为150 kPa、75 kPa、53 kPa及69 kPa,与实验数据误差为4%~10%,且动态响应曲线形态一致;脑组织最大von Mises应力(29.5 kPa)与颅骨主应力(18.7 kPa)均接近Marjoux和Yoganandan仿真实验阈值,证实模型可有效预测颅脑损伤风险。结合北约AEP-103标准评估表明,典型冲击下前额颅内压峰值达511.1 kPa,远超颅骨骨折阈值(150 kPa),凸显现有防护装备的优化需求。该模型应用性强,可为钝性弹道冲击下的头部损伤评估与安全防护提供方法参照和理论支撑。展开更多
基金Project Supported by Science and Technology Fund of Fujian E-lectric Power Limited Company(NC2006044)Scientific Research Fund of Fujian Education Depart ment(JB06045)
文摘Power transformer is one of the most important equipment in the power system.Its operating condition affects the reliability of power supply directly.Therefore,in order to guarantee transformer operation safely and reliably,it is necessary to assess condition of power transformer accurately.Return voltage method based on voltage response measurements is still a new non-intrusive diagnosis method for internal insulation aging of transformer.In this paper the technique and application of return voltage measurement and some results of voltage response measurements of several transformers was introduced.Voltage response measurements were performed on various transformers with different voltage grades,various operating periods,different moisture contents and aging degrees on site.Derived moisture contents from return voltage measurement were compared with the corresponding moisture contents obtained from the analysis of oil samples.Based on on-site experiments and theoretical analysis,the criteria for insulation state of transformer are proposed.Moisture condition of transformer insulation can be determined by using return dominant time constant,and a good correlation between aging degree and the return voltage initial slopes of the aged transformers.Field test performed on several transformers,its interpretation of results are also presented,which proves that return voltage measurements can be used as a reliable tool for evaluating moisture content in transformer insulation.
基金Project(52479115)supported by the National Natural Science Foundation of ChinaProject(2024SF-YBXM-615)supported by the Key Research and Development Program of Shaanxi Province,China+1 种基金Project(2022943)supported by the Youth Innovation Team of Shaanxi Universities,ChinaProject(300102283721)supported by the Fundamental Research Funds for the Central Universities,China。
文摘Using solid waste as a substitute for conventional cement has become an important way to reduce carbon emissions.This paper attempted to utilize steel slag(SS)and fly ash(FA)as supplementary cementitious material by utilizing CO_(2)mineralization curing technology.This study examined the dominant and interactive influences of the residual water/cement ratio,CO_(2)pressure,curing time,and SS content on the mechanical properties and CO_(2)uptake rate of CO_(2)mineralization curing SS-FA-Portland cement ternary paste specimens.Additionally,microstructural development was analyzed.The findings demonstrated that each factor significantly affected compressive strength and CO_(2)uptake rate,with factor interactions becoming more pronounced at higher SS dosages(>30%),lower residual water/cement ratios(0.1-0.15),and CO_(2)pressures of 0.1-0.3 MPa.Microscopic examinations revealed that mineralization primarily yielded CaCO_(3)and silica gel.The residual w/c ratio and SS content significantly influenced the CaCO_(3)content and crystallinity of the mineralization products.Post-mineralization curing,the percentage of pores larger than 50 nm significantly decreased,the proportion of harmless pores smaller than 20 nm increased,and pore structure improved.This study also found that using CO_(2)mineralization curing SS-FA-Portland cement solid waste concrete can significantly reduce the negative impact on the environment.
文摘随着可再生能源占比的提升,气电联合配网(integrated electricity-gas distribution systems,IEGDS)发展迅速,其研究的必要性也随之凸显。为解决IEGDS考虑可再生能源接入后的多设施规划及可靠性评估问题,提出了考虑可靠性约束的IEGDS分布鲁棒优化(distributionally robust optimization,DRO)规划模型。可靠性评估通过系统平均中断频率指标(system average interruption frequency index,SAIFI)与预期能源未供应指标(expectation energy not supplied,EENS)量化,给出一种显式可靠性评估模型。利用Wasserstein距离衡量的DRO规划模型来处理可再生能源出力、电与气负荷的随机性。最后经过案例分析得出,投建设施种类的增加不仅能降低总成本,还能提高系统运行可靠性与灵活性,可再生能源出力与气电负荷的不确定性导致总成本提升60%以上。随着可靠性要求提升总成本也随之提高,但得到的方案在实际应用中更具价值与参考性。
