0 引言 智能站二次系统改扩建需在运行系统上开展设备配置修改和试验工作,需要修改和验证智能变电站系统配置文件SCD,工作过程中稍有不慎,可能导致运行设备误停电,甚至演变成电网级事故. 500 kV智能变电站改扩建由于缺乏相关经验,安全隔离方式和范围、模型和参数的校核、停电传动调试范围、与运行装置间的二次回路验证、关联运行间隔是否需要停电传动等问题凸显,极易引发安全隔离或试验不到位引起的电网事故.改扩建设备和运行设备间二次回路验证为改扩建核心环节,该环节需要根据停电方式考虑回路试验验证二次安措和验证方式.针对以上问题,本文以某500 kV 3/2接线方式下线路保护及开关保护改造为例,提出一种500 kV智能变电站改扩建设备和运行设备间二次回路试验安全隔离方案和验证方案.

在变电站内二次检修工作中会涉及到大量的二次回路电缆识别的工作.由于现场设备接线情况复杂,图实不一致情况严重,为了最大程度降低现场作业的劳动强度,并保证作业流程的安全性,文章提出一种"基于窄带载波通信确认二次回路正确性的装置".该装置运用了窄带载波通信、LoRa无线通信等技术,使得在电路检修中能确认二次回路电缆的同一性.包括前端信号发射系统、前端窄带载波通讯载入模块、末端信号接收系统、后端窄带载波通讯载入模块、前端显示系统和数据处理系统等.

针对北京大兴国际机场进度动态管控面临的难题,结合系统论、控制论、组织论、信息论,采用四元耦合技术即目标耦合、任务耦合、组织耦合、信息耦合来解决这些问题,并结合大兴机场工程实践展示了四元耦合技术的应用.

光纤电流差动保护在电力系统中应用广泛,它利用光纤通道传输线路两端的数据,在两侧数据同步的基础上,能够简单可靠地判断出区内、区外故障.本文对某智能变电站中由于合并单元实际延时与设定的额定延时不一致造成两侧线路保护差流异常的情况进行分析,并给出现场测试建议.

Finding the characteristics of construction accidents will be beneficial to make appropriate safety strategies and policies. However, due to the socioeconomic backgrounds, the characteristics of construction accidents vary from different countries or districts. The purpose of this study is to identify the spatiotemporal characteristics of fatal construction accidents in China and to explore the causes related with behavioral factors. With the data of 4,061 fatal construction accidents in China, the spatial and temporal features were examined. The behavioral factors were also analyzed applying the technique of human factor analysis and classification system (HFACS). The results show that the numbers of accidents and fatalities differ greatly by months, weeks, hours, provinces, and regions. These differences may be affected by various organizational, managerial, and individual factors. Behavioral factors are critical for 4 main types of accidents: fall, object striking, collapse, and hoisting injury. 23 common unsafe behaviors such as failure to detect warning signs of accidents in time are explored related with these accidents. The results indicate that safety practitioners should pay attention to the spatiotemporal variances of construction accidents and focus on the behavioral factors. The flexible safety plans involving more human factors may be necessary in order to reduce construction accidents and to keep the sites safer.

This paper presents the results of experimental and analytical studies on the stress relaxation behavior of steel strand under combined prestressing forces and low temperatures. An 18-specimen test program was conducted to investigate the stress relaxation behavior of steel strand under prestressing forces of 0.5 to 0.75 times the ultimate tension capacity and at temperatures ranging from 20 degrees C (68 degrees F) to -165 degrees C (-265 degrees F). The test results show the relaxation behavior of the steel strands as the time increased from 0 to 100 hours after prestressing and the effects of low temperatures and prestressing levels on the relaxation behavior. Based on the test results and using the best subset regression method, a mathematical model was developed to predict the relationship between the relaxation rate and different influencing parameters, including time, prestressing levels, and low temperature. The accuracy of the regression model was checked through validation against 134 test data points. Finally, a design equation is proposed based on these extensive validations.

基于北京大兴国际机场项目成功的总进度综合管控实践,从管控思想、方法论和路径三方面构建大型项目总进度综合管控模型.管控思想包括项目集成、工作集成和组织集成;方法论为动态进度总控环;路径是多层级计划体系和周期性信息收集、信息处理和信息反馈.

从信息视角出发,以北京大兴国际机场项目为例,分析大型民用机场工程进度控制的信息流程.阐述进度控制信息流程的基本要素、信息流程所涉及的进度信息和主客体,并将信息流程按照控制主体的不同,分为实施层级、管理层级、治理层级及第三方进度管理咨询机构的信息流程,从而帮助清晰化和规范化大型民用机场工程进度控制信息流程,实现良好的进度管控.

To promote the safe application of prestressed concrete structures under cryogenic temperatures,experiments were carried out on 12 bonded prestressed concrete beams by cryogenic cold storage and homemade insulation-loading equipments,in which flexural properties with different tension control stresses (0fptk and 0.75fptk) at 20℃,-40℃,-70℃ and-100℃ were analyzed respectively.The results indicate that the plane-section assumption of bonded prestressed concrete beams can still be obeyed under cryogenic temperatures.Temperature and prestress have little effect on the stiffness of specimens before cracking,however the stiffness of the specimens increases as temperature drops after carcking.Prestressing can effectively delay the appearance of cracks,limit the crack width and decrease the deformation of specimens under cryogenic temperatures.When the temperature decreases,both the ultimate load and the cracking load increase,but the cracking load has a faster rate.The ratio of the cracking load to the ultimate load increases,which means that the deformation performance of specimens decrease.Considering the temperature effect of the materials,the theoretical value of ultimate bearing capacity calculated by Chinese code formula is reliable,whereas the theoretical value of cracking load is larger than the measured one,so further research should be conducted.

In China,the study of reuse waste building materials starts 1ate and there is no existing system for that.The hierarchical use of waste building materials was comprehensively summarized as well as the recycling methods of reusing waste building materials based on reference from lots of literature.Several methods of building dismantling and the ideal of design for disassembly were also introduced.Finally,some advices for the study of recycling waste materials in China were given,and the development direction of structural engineering in this field was prospected.