微机自动化系统在铁路变配电所的应用

铁路供电系统具有负荷沿铁路分布、点多、容量小、故障频繁等特点,原有的故障查找方式已不能适应新形式的要求。因此建立一套先进、可靠、具有发展前途的微机自动化系统具有非常重要的意义。本文主要阐述变配电所微机保护改造设计理念,具体的论述了铁路供电段实现微机自动化时,系统的设计原则,结构,功能要求。     

变配电微机型综合保护测控装置调试工法

以DPX-200型系列微机综合保护测控装置为对象介绍了用P30调试此类装置的具体步骤及工艺原理,并对该工法进行了效益分析。调试的方法具有较强的先进性和通用性。     

微机核子秤的测试

本文重点讨论微机核子秤计量系数的设置和实物标定的方法,这种标定方法具有准确,可靠的特点。     

浅析主变差动保护及带负荷测试

介绍了变电站主变压器差动保护及带负荷实验的重要性,并结合变电站实际差动保护及带负荷试验就差动保护在设计、安装、调试中所遇到的问题,提出了分析和判断方法。     

微机核子秤的测试

本文重点讨论微机核子秤计量系数的设置和实物标定的方法,这种标定方法具有准确,可靠的特点。     

基于智能建模的微机保护整定计算管理信息系统

目前国内整计算软件主要是”手工建模”及”平面建模”计算系统,本文提出并实现”基于智能建模的微机保护整定计算管理信息系统,提高工作效率的同时能够有效避免误整定等电网安全事故的发生。     

微机数字式线路保护的设计

主要论述适用于66kV及以下电压等级的配电线路的保护原理和设计思路,并简单阐述当前国内生产的电力系统二次保护设备的主要特征。     

试述微机型变压器综合自动保护整定计算

依据继电保护调试经验,结合厂家的有关资料以及保护整定计算的有关规定,对常用的变压器的整定作一些简要的阐述。     

谈变电所微机保护技术分析

从目前变电所保护情况来看,都是使用计算机进行全面的管理,采用计算机进行管理需要依照一定的标准进行,所带来的管理效果却是得到了普遍的认可,不仅操作简单方便,还能够提高工作的效率,加大变电所管理的精度。本文将着重对于变电所微机保护的技术进行分析,努力寻求一种能够帮助变电所进行集中微机保护的方案,并且根据变电所微机保护目前普遍存在的问题,提出一些有效的管理方法。     

面向过电流保护元件系列产品研发的试验数据管理系统的应用

以过电流保护元件系列产品研发的试验数据管理的需求为出发点,针对试验数据易变性和专业性的特点,通过详细的系统需求分析和系统功能模块设计,建立了面向过电流保护元件系列产品研发的试验数据管理系统。该系统在企业的有效应用不但提高了试验效率,还使技术资源得到沉淀、积累和重复利用,提高了企业的核心竞争力。     

基于阶跃温度响应的热电偶时间常数测试系统

为了更方便地测试热电偶时间常数,设计了一套热电偶时间常数测试系统,包括工控机、信号调理电路、A/D采集、数据采集处理软件和打印机等。根据热电偶对阶跃温度的响应,提出了一种全新的热电偶时间常数测试方法,设计功能完善的信号调理电路,通过PCL818L数据采集卡将采集的数据送交上位机应用软件进行分析处理,得到所需要的热电偶参数,应用软件提供各类报表输出及数据打印功能。     

An analysis of maintenance failures at a nuclear power plant

In this paper, a study of faults caused by maintenance activities is presented. The objective of the study was to draw conclusions on the unplanned effects of maintenance on nuclear power plant (NPP) safety and system availability. More than 4400 maintenance history reports from the years 1992–1994 of Olkiluoto BWR NPP were analysed together with the maintenance personnel. The human action induced faults were classified, e.g. according to their multiplicity and effects. This paper presents and discusses the results of a statistical analysis of the data. Instrumentation and electrical components appeared to be especially prone to human failures. Many human failures were found in safety related systems. Several failures also remained latent from outages to power operation. However, the safety significance of failures was generally small. Modifications were an important source of multiple human failures. Plant maintenance data is a good source of human reliability data and it should be used more in the future.     

Predictive analytics for truck arrival time estimation: a field study at a European distribution centre

Distribution centres (DCs) are the hubs connecting transport streams in the supply chain. The synchronisation of coming and going cargo at a DC requires reliable arrival times. To achieve this, a reliable method to predict arrival times is needed. A literature review was performed to find the factors that are reported to predict arrival time: congestion, weather, time of day and incidents. While travel time receives considerable attention, there is a gap in literature concerning arrival vs. travel/journey time prediction. None of the reviewed papers investigate arrival time: all the papers found investigate travel time. Arrival time is the consequence of travel time in combination with departure time, so though the travel time literature is applicable, the human factor involved in planning the time of departure can affect the arrival time (especially for truck drivers who have travelled the same route before). To validate the factors that influence arrival time, the authors conducted a detailed case study that includes a survey of 230 truckers, a data analysis and a data mining experiment, using real traffic and weather data. These show that although a ‘big data’ approach delivers valuable insights, the predictive power is not as high as expected; other factors, such as human or organisational factors, could influence arrival time, and it is concluded that such organisational factors should be considered in future predictive models.     

The modal distribution method for statistical analysis of measured structural response

The newly proposed modal distribution method statistically quantifies overall differences between measured time-histories. In this method, power spectra of measured structural response are interpreted as collections of independent modal responses. Each modal response is isolated, re-scaled, and interpreted as a statistical distribution. Data-sets (windows in a measured time-history) are then compared using standard statistical methods, resulting in a quantitative significance level of the differences between power spectra. An example is presented to validate the new method and to quantify how long a time-history is required for the new method to meet confidence level requirements. The modal distribution method is found to be very effective at detecting subtle changes of mean modal frequencies, which may be used to infer changes in structural condition. The method is general and may find a broad variety of applications, but seems particularly well suited for structural health monitoring because it can be used to infer changes in structural condition from measured response data with only limited knowledge of the excitation.     

Time-variant power spectral analysis of heart-rate time series by autoregressive moving average (ARMA) method

Frequency domain representation of a short-term heart-rate time series (HRTS) signal is a popular method for evaluating the cardiovascular control system. The spectral parameters, viz. percentage power in low frequency band (%PLF), percentage power in high frequency band (%PHF), power ratio of low frequency to high frequency (PRLH), peak power ratio of low frequency to high frequency (PPRLH) and total power (TP) are extrapolated from the averaged power spectrum of twenty-five healthy subjects, and 16 acute anterior-wall and nine acute inferior-wall myocardial infarction (MI) patients. It is observed that parasympathetic activity predominates in healthy subjects. From this observation we conclude that during acute myocardial infarction, the anterior wall MI has stimulated sympathetic activity, while the acute inferior wall MI has stimulated parasympathetic activity. Results obtained from ARMA-based analysis of heart-rate time series signals are capable of complementing the clinical examination results.     

制冷机组配电系统的保护及电器选择

低压电器是制冷机组的重要组成部分之一。本文详细描述压缩机电机的特性和保护设置、制冷机组常用低压电器的选择原则以及级间选择性,通过实例阐述电器的选择及校验过程。     

面向数控加工工时估算的模型特征识别

利用数控加工结构件的特征具有层次分布式特点,提出了基于面邻接关系的特征识别方法,将零件的面先分成基础面和约束面,再根据凹凸邻接关系组合为相应的层集合,以层作为特征识别的基础,通过层的识别和组合获得数控加工结构件的特征,并提取相关特征参数信息,结合机床的加工参数,对零件加工工时进行了估算,并进行了实例验证。     

Use of OPC to improve setting and early strength properties of low calcium fly ash geopolymer concrete cured at room temperature

Most previous works on fly ash based geopolymer concrete focused on concretes subjected to heat curing. Development of geopolymer concrete that can set and harden at normal temperature will widen its application beyond precast concrete. This paper has focused on a study of fly ash based geopolymer concrete suitable for ambient curing condition. A small proportion of ordinary Portland cement (OPC) was added with low calcium fly ash to accelerate the curing of geopolymer concrete instead of using elevated heat. Samples were cured in room environment (about 23 °C and RH 65 ± 10%) until tested. Inclusion of OPC as little as 5% of total binder reduced the setting time to acceptable ranges and caused slight decrease of workability. The early-age compressive strength improved significantly with higher strength at the age of 28 days. Geopolymer microstructure showed considerable portion of calcium-rich aluminosilicate gel resulting from the addition of OPC.     

通风机空气动力性能通用测试软件的设计与实现

设计了通风机空气动力性能通用测试软件,详细叙述了测试软件的设计方案;利用C#.NET开发了实时测试软件,可对实验室传感器状态进行实时监控,并通过串行口来实现计算机与中央控制系统的实时通信。在不同的设定下,可实现不同的试验装置类型和流量测量方式的测试目的。实际应用表明,该测试软件实用性强,运行稳定可靠。