一种特高压直流输电线路神经网络双端故障测距新方法

提出一种基于高频量衰减特性的特高压直流输电线路神经网络双端故障测距方法。传统基于高频量衰减特性的特高压直流输电线路双端测距方法的测距精度依赖于线路衰减常数的准确求取,但准确计算线路衰减常数是一个难题。人工神经网络具有很强的非线性逼近拟合能力,利用人工神经网络方法,将不必准确计算线路衰减常数也能准确实现故障定位。选取不同频带内整流侧和逆变侧测距装置处检测到的故障电压行波线模分量高频部分首波头幅值比作为BP神经网络的输入样本集,故障距离作为输出样本集,对神经网络进行训练、测试,形成直流输电线路故障测距神经网络模型,将反映故障位置的特征数据输入训练后的网络模型即可实现故障测距。大量仿真结果表明:该基于高频量衰减特性的特高压直流输电线路神经网络双端故障测距方法精度较高,而且耐受过渡电阻能力强。     

关于老旧输电电缆运行状况分析及运维工作的建议

本文对广州地区运行时间超过20年的110kV及以上交联聚乙烯输电电缆线路的运行状况进行统计分析,经分析认为该部分电缆线路故障率和缺陷率均较低,且未发现有增加趋势,整体运行状况较好,同时根据实际情况在运行、规划、技术研究方面提出了相关运维建议。     

宫腔镜系统常见故障及排查探析

在宫腔镜微创手术中,宫腔镜系统是比较重要的一个组成部分,由于手术操作在密闭的环境中进行,可以减少脏器在空气中的暴露,具有术后恢复快、操作简单、出血少、安全性高、创伤小以及并发症少等诸多优点,被广泛运用在临床上.所以,熟悉宫腔镜系统中各项设备的运行原理,了解并及时维护常见故障,对确保宫腔镜手术的顺利进行有着极其重要的意义...     

佛山地区110kV电缆故障分析及预防措施

近年来随着电力电缆在城市电网的建设中广泛应用,电力电缆在运行中发生的故障也越来越多。本文对近年佛山地区110kV电缆的几起故障及其成因进行了分析,并给出了相应的预防措施。     

美国纽邦150型呼吸机的原理与故障分析

在阐述了美国纽邦150型呼吸机内部的空氧混合器、电磁线圈、气动控制阀门等关键部件和工作原理的基础上．对故障高发部位进行了深入分析，并介绍了维修保养的要点。     

Nonfragile H∞ fault detection for fuzzy discrete systems under stochastic communication protocol

In this article, considering one type of fuzzy discrete‐time networked control systems (NCSs) under stochastic communication protocol (SCP), a fuzzy‐based nonfragile H_∞ filter is developed to detect the subsistent fault signal. The Takagi‐Sugeno (T‐S) mathematical model is employed to approximate the nonlinearities in the concerned fuzzy NCSs. The SCP is adopted to decide which sensor gets the access to the communication network at certain time instant, and the scheduling model of which is constructed as a Markov chain. Taking into account that the filter gain parameters in real practice may suffer fluctuations during the implementation, a modified nonfragile fuzzy filter is designed to detect the fault occurred in the signal transmission. By using the strong centralized stochastic analysis technique and the matrix calculation method, a Lyapunov function is adopted to derive sufficient conditions under which the filtering error dynamics is stochastically stable and the H_∞ performance is satisfied. Then, the desired nonfragile fuzzy fault detection filter is realized by solving a certain linear matrix inequality. Finally, the effectiveness of the develop fault detection scheme is verified in the simulation example.     

Fault Tolerant Strategies for Automated Insulin Delivery Considering the Human Component: Current and Future Perspectives

Automated Insulin Delivery (AID) are systems developed for daily use by people with type 1 diabetes (T1D). To ensure the safety of users, it is essential to consider how the human factor affects the performance and safety of these devices. While there are numerous publications on hardware-related failures of AID systems, there are few studies on the human component of the system. From a control point of view, people with T1D using AID systems are at the same time the plant to be controlled and the plant operator. Therefore, users may induce faults in the controller, sensors, actuators, and the plant itself. Strategies to cope with the human interaction in AID systems are needed for further development of the technology. In this paper, we present an analysis of potential faults introduced by AID users when the system is under normal operation. This is followed by a review of current fault tolerant control (FTC) approaches to identify missing areas of research. The paper concludes with a discussion on future directions for the new generation of FTC AID systems.     

Fault Critical Point Prediction Method of Nuclear Gate Valve with Small Samples Based on Characteristic Analysis of Operation

The number of fault samples for the new nuclear valve is commonly rare; thus, the machine learning algorithm is not suitable for the fault prediction of this kind of equipment. In order to overcome this difficulty, this paper proposes a novel method for the fault critical point prediction of the gate valve based on the characteristic analysis of the operation process variables. The operation process of gate valve switch often contains various fault characteristics and information, and this method first adopts the Shannon entropy to describe the power spectrum of vibration signal relevant to the operation process of gate valve switch, and then employs the mean value of the power spectrum entropy as an indirect process variable and further investigates the differences between the indirect process variable under the healthy state and the fault state with a different fault degree. In addition, the power signal of the gate valve is also employed as the direct process variable and the features of the direct process variable under the healthy state and the fault state with different fault degrees are also investigated. Based on the previous indirect process variable and direct process variable, the prediction approach for the critical point of the gate valve fault is established by analyzing the change in the indirect process variable and direct process variable before and after faults. Finally, the data of a nuclear gate valve experiment are employed to demonstrate the feasibility of the proposed method and the results show that the proposed method can effectively predict the fault critical point of the mentioned nuclear gate valve. If the diagnostic threshold is set properly, the critical point prediction of a nuclear gate valve fault can be realized as 100% or close to 100%. Furthermore, the proposed method can be directly applied to the nuclear gate valve in a nuclear power plant to improve the operation reliability of the valve. At the same time, the method can be applied to the fault diagnosis and prediction of valves in other fields, such as the chemical industry.     

飞利浦大孔径CT六年运行故障统计分析及预测

目的 分析飞利浦大孔径CT六年运行故障原因,找出共性问题,制定相应保养方案并对未来几年故障发生率进行模拟预测。方法 收集2012-2018年间大孔径CT故障数据,使用SPASS 19.0软件中曲线估计功能分析故障发生次数与时间的关系,并做出预测;使用帕累托图分析功能分析故障类型。结果 6年共发生故障28次,其中刚使用半年内,故障发生率最高(5次),随后趋于平稳。经曲线估计得到线性函数模型为y=-0.033x+2.099(R²=0.003),未来3年内每半年发生故障次数约2次。帕累托图显示发生数据采集故障16次,其中治疗床和供电电源系统故障分别为3次,占比达71%,是主要故障来源。结论 大孔径CT故障统计分析有助于科室维修人员更好了解CT,制定有效保养方案,减少故障发生,并对未来故障发生率有个预判。     

A continuous available (CA) server for medical imaging applications

RATIONALE AND OBJECTIVES: The trend of medical imaging research and application is toward large database management and manipulation, which requires a robust image server to receive image data from sources and to deliver them to users reliably and in a timely fashion. This article describes the design, implementation, and clinical applications of a continuous available (CA) image server for these purposes. MATERIALS AND METHODS: The design of the CA image server is based on the concept of a triple modular redundancy server with three redundant server modules. Coupled with a majority voting mechanism in the three modules and failover software, the triple modular redundancy server takes care of all single points of failure hardware components in the CA image server automatically to achieve fault tolerance. Methods and procedures of evaluating the fault tolerance system reliability caused by network connectivity, motherboard, and disk storage failures are described. RESULTS: Thorough experimental results in laboratory and clinical environments verify that the image server achieves 99.999% hardware up time (or 5 minutes/year down time), satisfying the industrial terminology of hardware continuous availability. Performance of failover of the CA image server is automatically tabulated during these procedures. CONCLUSION: Applications of CA image server are extensive. Two examples are given including Picture Archiving and Communication System, and off-site back-up archive using the Application Service Provider model. As designed, the CA image server is portable, scalable, affordable, easy to install, and requires no human intervention during failover and system recovery.