Relationships between observed and perceived deviations from normative work procedures

Deviations from anticipated courses of events are often associated with accidents, while the effects of deviations that decrease productivity but do not obviously lead to human injury are less clear. A systemic approach to production and safety is introduced, and it is proposed that production deviations have effects that may lead to safety violations and personal injury. In addition, the relationship between observed and perceived production deviations from 12 senior (60–79 years old) males' routine work using three firewood processing machines is analysed. For simple machine work, perceived deviations were positively related to observed deviations per work cycle and inversely correlated to the perception of work efficiency. For more complex machine work it was more difficult to match observers' and operators' perceptions of deviations. Despite challenges in the production deviation concept, this approach offers a holistic understanding of the performance of human–machine-environment systems and complements assessments of deviations from safe working practice.     

Equation error versus output error methods

Abstract

For the identification of linear processes on the basis of ARX-models, equation error least squares (EELS) (often indicated as the one step ahead prediction error method) is frequently used rather than output error least squares (OELS). This is mainly because the minimum of the convex EE-criterion can easily be found, in contrast to the OE-criterion, which often displays multiple local minima. Both methods lead to the correct parameter values when the system is in the model set chosen. But in many practical situations, such as human behaviour, the real process under study will be of infinite order causing essentially different models to be found from either EE or OE criteria. Various aspects of these differences are analysed in this study. Much attention has been paid to the performance of a simulation based on a model estimated with an EELS. This simulation performance can be predicted and bounds can be given without executing the simulation itself. Furthermore the simulation performance is very poor for systems where the energy in the initial impulse response samples is very small compared with the energy in the remainder of the response. For these systems an equation error estimate cannot even provide a proper initial guess for an OELS minimization algorithm. Examples are presented that illustrate this effect.     

窃电与反窃电技术分析

分析失压和欠压窃电、TA短接分流、电压相序颠倒等错误接线和强磁干扰的窃电方式,介绍窃电情况的检查判断与电量的追补计算方法,提出使用新一代多功能电能表、推广反窃电监测报警系统等防范窃电的措施.     

保护用电流互感器饱和特性及其误差曲线研究

当电力系统发生故障时,一次电流比正常运行时的电流大几倍甚至几十倍,此时,保护用电流互感器的铁芯发生饱和,引起二次电流的畸变,从而使继电保护及其二次设备误动作。笔者对保护用电流互感器的误差与饱和特性进行了分析,介绍了实际工作中电流互感器误差曲线的绘制以及二次负载的校核方法,并提出了减小电流互感器误差的具体措施。     

测量误差理论与术语定义的发展与变化

阐述了测量误差理论的发展历程与发展方向,回顾了与误差理论和数据处理相关的国家计量技术规范跟随国际计量技术规范发展的过程,分析了国家计量技术规范中主要误差术语定义的变化情况和变化趋势。术语定义的变化表明：术语变化的趋势更具有严密的科学性、逻辑性和可操作性。     

高压线路参数测试仪示值误差测量结果的不确定度评定

高压线路参数测试仪在电力系统中测量各种线路工频参数值,以作为计算系统短路电流、继电保护整定、推算潮流分布和选择合理运行方式等工作的实际依据。为了保证量值的可靠传递及满足认可实验室对检测结果的要求,文章就高压线路参数测试仪示值误差测量结果的不确定度进行了评定。     

电力市场环境下中长期负荷预测的应用分析

电力市场环境下负荷预测误差风险直接影响售电公司经营效益和供电的安全性和稳定性.为提高售电公司的经济性和稳定性,从负荷预测误差与负荷类型的研究角度出发,利用灰色系统理论、最小二乘支持向量机模型对中长期负荷进行了预测,并提出了预测加权误差这一概念,重点讨论某地区主要负荷类型与其预测加权误差之间的关联关系.分析结果使得负荷预...     

华东电网CPS考核标准运行分析

介绍了华东电网目前频率质量控制的现状和考核标准,结合实际运行数据分析了现行考核标准CPS在实际运行中所表现出的约束效力和其有待改进之处,由分析结果提出了对考核标准的改进方法和今后电网的频率质量控制手段.     

电压互感器二次回路压降的自动补偿装置

为了实时动态地消除电压互感器二次回路压降带来的计量误差,对电压互感器二次回路压降的自动补偿进行了研究.在对电压互感器二次回路压降进行理论分析的基础上,提出了动态补偿原理,进行了系统硬、软件设计.通过单片机的智能控制,实时跟踪电压互感器二次压降变化,实时调整信号放大倍数,实现动态补偿和阻抗匹配.模拟补偿试验和现场测试结果均表明:在额定线电压为100 V的情况下,无论线路电阻在0.3～5ù的规定范围内如何变化,补偿后合成电压均小于144mV,即符合"不大于额定二次电压的0.25%"这一规定标准,且其角差小于1′.     

信号的取样方式对介质损耗角测量的影响

分析了非整周期采样时介质损耗角(介损角)测量容易导致较大误差的问题,指出了电压和电流信号的取样方式对介损角测量的准确性有很大影响.如果信号中仅存在基波且传感器采集所得电压和电流信号同相位时,则非整周期采样的频谱泄漏和栅栏效应给介损角计算导致的误差将完全抵消,理论上介损角测量不会因为非整周期采样导致误差.仿真表明,在实际取样时若选择合适的传感器,直接使用DFT算法,即使非整周期采样严重时误差仍然很小,误差绝对值的最大值小于4×10-5 rad(设定的介损角0.003 rad)计算误差随设备介损角的增加而增大,介损角增大到0.02 rad时,误差绝对值的最大值约为2×10-4 rad;计算误差与直流分量关系不显著,直流分量在基波分量的10%范围内变化时,误差绝对值的最大值约为4×10-5 rad;计算误差随3次谐波的增加而线性增大,3次谐波分量达到基波分量的20%时,如果使用阻容串联电路模拟电容型设备,误差绝对值的最大值约为7×10-5 rad;如果使用阻容并联等值电路则同样条件下误差约为5×10-5 rad.因此,使用电容型设备末屏串入电容的电流取样方式能有效减少非整周期采样给介损角测量带来的误差.