Inference life-models of electrical insulating materials by using aKalman filter

A Kalman filter is applied to life tests for characterizing electrical or thermal endurance of electrical insulating materials. This recursive estimator provides updated life model parameter values after each life test. The life models are: (1) inverse power law and the exponential law, used for electrical or multi-stress ageing; and (2) Arrhenius model, used for thermal ageing. The state, prediction, and updating equations of the Kalman filter algorithm are specified for insulation endurance inference. Insight into the definition of the state variables, which are directly related to the model parameters, and determination of system and observation errors are developed. A recursive breakdown test detects important changes in the prevailing ageing process. The range of validity of the life model, as well as information on electrical and thermal threshold are considered. A flow chart of the filtering algorithm is presented. Example experimental results relevant to insulating materials and systems subjected to electrical and thermal life tests are processed according to the algorithm     

Regulatory requirements for medical equipment

Medical equipment is highly regulated and held to a higher level of safety than nearly all other types of equipment on the market. This is because patients who are not able to respond to hazardous conditions or pain, an actual electrical connection between the equipment and patient may exist, and certain types of medical equipment function as life support, the failure of which could result in the death of the patient. Understanding the certification and regulatory requirements before the design phase of the equipment will result in a cost reduction in equipment development, faster certification turnaround and increased product safety.     

Basics of condition evaluation in distribution networks

In this paper the development of a tool for a fast and simple evaluation of the technical condition of electrical networks will be presented. With this tool it is possible to compare different networks and network sections of different power suppliers as well as utilities of the same voltage level or network sections of the same utilities. Whole networks, but also individual components such as transformers and switchgears can be evaluated. An exact condition evaluation of networks represents a disproportionately large expenditure of time. To get a fast overview over the technical condition of networks and electrical components the knowledge of experts is necessary. The presented method takes into consideration both: expert knowledge as well as the consideration of age, maintenance and operating loads of networks and their components. These aspects are included in reliability computation mathematical functions which will be used in the developed technical condition evaluation tool. Beside the evaluation of the technical condition the tool is based on the maintenance expenditure and the priority of the examined networks, too.     

Estimation for a life model of transformer insulation undercombined electrical and thermal stress

A life model for power transformer insulation is proposed. It is the Arrhenius model with a weighting factor for the enhanced reaction under combined thermal/electrical stress. Laboratory tests are used to evaluate the model's parameters. The thermal and thermal/electrical stress aging data on Fish paper are presented and analyzed. The estimates from the life model are close to the experimental results. It is hoped that the life model is extendable to other engineering materials. The model's parameters can be evaluated from two laboratory tests, thermal aging and combined thermal/electrical aging. For the Fish paper, when thermal stress is increased by 30°C, the life is reduced by a factor of 2; at 70°C life was 238 hours and at 100°C life was 120 hours. The material life was further reduced by a factor of nearly 2 when subjected to thermal/electrical stress: at 80°C life was 200 hours, whereas at 80°C and 600 Vac life was 118 hours. Electrical stress is important in accelerating the material degeneration     

基于灰靶理论的变压器绝缘状态监测

变压器发生绝缘故障是电力系统事故的主要诱因,要保证变压器在电力系统中的安全运行,对其绝缘状态实施在线监测是非常必要的。变压器在线监测的关键是实现绝缘状态的评估,评估结果受多个内外因素的随机性约束,影响因子多,建模复杂。针对这一问题,本文建立了基于灰靶理论的变压器绝缘状态监测系统,通过计算各项指标对绝缘状态的影响复合权重,从而确保评估结果的合理性。经实验验证,该系统能实现对变压器设备绝缘状态的有效判断,为变压器的检修计划提供重要参考。     

数字智能化除湿烘干装置的实现原理及应用分析

随着数字化技术和智能化控制技术的发展,将数字智能化技术应用在带绝缘液电气设备除湿烘干装置中,可以提高除湿烘干装置的应用性能,实现带绝缘液电气设备的自动化除湿烘干,保证带绝缘液电气设备的安全运行.本文重点阐述了数字智能化除湿烘干装置的实现原理,以及数字智能化除湿烘干装置在实际中的相关应用.     

A Kinetics Study on Electrical Resistivity Transition of In Situ Polymer Aging Sensors Based on Carbon-Black-Filled Epoxy Conductive Polymeric Composites (CPCs)

Sensors based on carbon-black-filled bisphenol A-type epoxy conductive polymeric composites (CPCs) have been prepared and applied to monitor thermal oxidation aging of polymeric materials. Thermogravimetric analysis (TGA) is applied to characterize weight loss of epoxy resin in the aging process. By using a mathematical model based on the Boltzmann equation, a relationship between the electrical resistivity of the sensors based on epoxy/carbon black composites and aging time is established, making it possible to monitor and estimate the aging status of polymeric components in situ based on a fast and convenient electrical resistance measurement.     

基于半马尔科夫过程的变压器故障率预测及研究

设备的故障率曲线是制定维修策略的重要指标之一。为了合理估计变压器的故障率,本文提出了基于半马尔科夫过程的预测模型。模型中考虑了变压器的热老化过程和随机故障过程。热老化过程根据绝缘纸平均聚合度的取值范围划分为4个状态,状态间的转移时间假设服从威布尔分布,威布尔分布的尺度参数由经验公式获得;随机故障过程考虑了由雷击和短路冲击引起的2个随机故障状态,老化状态和随机故障状态之间的转移时间假设服从指数分布,转移率由故障统计数据获得。对模型中威布尔分布的形状参数进行适当取值后,可获得符合实际统计结果的变压器故障率曲线。     

End-to-end WAN service availability

This paper seeks to understand how network failures affect the availability of service delivery across wide-area networks (WANs) and to evaluate classes of techniques for improving end-to-end service availability. Using several large-scale connectivity traces, we develop a model of network unavailability that includes key parameters such as failure location and failure duration. We then use trace-based simulation to evaluate several classes of techniques for coping with network unavailability. We find that caching alone is seldom effective at insulating services from failures but that the combination of mobile extension code and prefetching can improve average unavailability by as much as an order of magnitude for classes of service whose semantics support disconnected operation. We find that routing-based techniques may provide significant improvements but that the improvements of many individual techniques are limited because they do not address all significant categories of network failures. By combining the techniques we examine, some systems may be able to reduce average unavailability by as much as one or two orders of magnitude.     

环境试验设备相对湿度测量不确定度评定研究

环境试验是检测试验室和开展相关项目的检测机构、公司用于检测产品模拟环境条件下的快速试验.环境试验设备营造的极限环境中,相对湿度的大小直接影响试验结果——相对湿度大将加快样品的损坏,相对湿度小则样品损坏速度减慢.良好的环境试验设备能够提供准确、稳定的环境条件.对试验设备进行准确性、重复性和稳定性进行计量是对环境试验设备进行评估的重要手段,而对计量结果的不确定度分析则能描述计量结果的准确性并有效的实现量值传递.本文主要分析计算相对湿度测量结果扩展不确定度,其评定结果将直接反映环境试验设备性能评估的精确程度,并间接反映环境试验设备性能的好坏.     

用红外热像仪与红外测温仪诊断电气设备故障的对比研究

电气设备是故障多发装置。利用红外测温仪或红外热像仪能够检测出设备发热异常部位并确定其表面温度,再结合红外诊断标准便可对异常设备的故障严重程度进行判别,从而实现对电气设备的故障诊断。针对电气设备控制箱电气元件的发热缺陷,利用ST80+红外测温仪与FLIR E320红外热像仪进行了温度监测,并通过运用表面温度法和相对温差法进行故障严重程度诊断,对两种设备监测诊断的差异进行了分析。结果表明,利用红外热像仪能较准确地监测诊断出电气元件的过热缺陷,利用红外测温仪能检测出多数控制箱电气元件过热缺陷,但对部分缺陷的严重程度等级判别低于热像仪的判别结果。     

Study on the Validity of Electronic Parts Stress Models

By using data on the failure rates of electronic components collected by a European Bank, we try to form an idea on the validity of the various models (Bazovsky model, MIL HDBK-217A standard model, exponential model, RADC TR-67 models) that represent the variations of the failure rate with respect to the thermal and electrical stresses. Two different approaches have been programmed on a computer: 1) conventional, using the linear regression analysis 2) more modern using the Fletcher-Powell method or methods derived from it (Fletcher-Reeves or Davidon). The results are given for four types of components. The models studied reflect, more or less accurately, what happens in real life. We define and give a value to a criterion, allowing the model to be chosen closest to reality. This paper, apart from its practical interest on the validity of currently accepted models and its theoretical interest on the use of methods for seeking extremes, shows how the computer can assist the reliability engineer with the filing of data, the statistical processing of these data, etc., right up to the automatic tracing of networks of curves.     

Test System for Thermoelectric Modules and Materials

We present a design for a complex measuring device that enables its user to assess the parameters of power-generating thermoelectric modules (TEMs) (or bulk thermoelectric materials) under a wide range of temperatures (T _cold = 25°C to 90°C, T _hot < 450°C) and mechanical loading (P = 0 N to 10⁴ N). The proposed instrument is able to monitor the temperature and electrical output of the TEM, the actual heat flow through the module, and its mechanical load, which can be varied during the measurement. Key components of our testing setup are (i) a measuring chamber where the TEM/material is compressed between thermally shielded heating blocks equipped with a mechanical loading system and water-cooled copper-based cooler, (ii) an electrical load system, (iii) a type K thermocouple array connected to a data acquisition computer, and (iv) a thermostatic water-based cooling system with electronically controlled flow rate and temperature of cooling water. Our testing setup represents a useful tool able to assess, e.g., the thermoelectric parameters of newly developed TEMs and materials or to evaluate the thermoelectric parameters of commercially available modules and materials for comparison with values declared by the manufacturer.     

10kV中压配电线载波信道的建模

近年来，利用中压配电网作为电力自动化的载波通信媒介日益受到人们的关注，对其传输特性的研究也成为了热点问题。论文针对中压配电网的网络结构及由此产生的阻抗不匹配和传输衰减等问题，提出了一种仿真模型。该模型对于信道中的不同噪声给出了不同的模型，特别是采用Middleton的A类噪声模型作为脉冲干扰的模型。对于信道的多径衰减给出了详尽的计算模型。在此基础上考虑了信道的时变性，提出利用信道的阻抗调制特性实现对不同信道状态的转换。相对于前人的模型，该模型更符合中压配电线信道实际特点，为研究克服电力线信道恶劣传输特性的信号处理方法提供了参考模犁，因而更具实用价值。     

Recipe for recycling

Across-the-board recyclers can keep discarded electronic products out of landfills by identifying and extracting component parts for resale and materials for reprocessing. The complete recycling of electrical and electronic equipment will in the future probably be handled by independent recyclers who become specialized in understanding the varieties of discarded equipment. They will plan the logistics of recovering any assemblies, components, and materials of value, and will develop the technologies necessary to extract them in a way that is economical and environmentally sound. The actual recycling activities will also probably take place in central locations, if for no other reason than the substantial costs of moving material and equipment. The integrated recycling approach ranks the means of disposal in order of feasibility: refurbishing; or equipment brokering, possibly to underdeveloped countries; component recovery; or full material recycling     

Thin-Wire Model Using Subcellular Extensions in the Finite-Difference Time-Domain Analysis of Thin and Lossy Insulated Cylindrical Structures in Lossy Media

Recently, a subcellular thin-wire model for the finite-difference time-domain (FDTD) simulation of resistively coated cylinders with lossless insulating and surrounding media was presented. In this paper, it is shown that this model can be extended to lossy cases. The material discontinuity between lossy insulating and surrounding media is corrected as the time-domain boundary condition. The convolution term of the boundary condition is solved by employing a recursive technique. Applying the contour-path integration to the FDTD unit cells around the wire, one may find the coarse-grid-based equation with the correction term and factors for the material discontinuity and the quasi-static field behavior around the wire. In the 2-D cylindrical coordinates with rotational symmetry, the validity of the proposed model is confirmed by an impedance analysis of insulated and resistive antennas according to the electrical properties of insulating and surrounding media, as well as the choice of cell size.      

电器附件产品中绝缘材料部件的安全性要求及检测方法

文章通过对在电器附件中使用的绝缘材料性能、要求进行分析,并以IEC 60884等标准为例介绍电器附件产品中绝缘部件的安全性要求及检测方法。     

Electrical aging behavioral modeling for reliability analyses of ionizing dose effects on an n-MOS simple current mirror

Nowadays, a deterministic approach based on physics of failure is necessary to estimate the lifetime of integrated circuits. Therefore, the reliability analyses via electrical/aging simulations are performed during the design phase. Our previous works consisted in generating an aging behavioral model of a circuit in order to assess its degradation level and to predict its lifetime according to its mission profile. This paper presents obtained experimental results using our developed methodology to evaluate the influence of total ionizing dose effects on an n-MOS simple current mirror taking into account technological dispersions.     

优化理论与最优控制在断路器操作回路中的应用

优化理论与最优控制理论是现代控制理论理论的核心,它是通过一些控制手段和约束条件,在特定条件下将控制效果达到最佳.坚强智能的电力系统的离不开继电保护,继电保护装置就是能反映电力系统中各电气设备发生故障或不正常工作状态,并作用于断路器跳闸或发出信号的一种自动装置.本文从优化理论和最优控制的角度,对继电保护作用于电路器的控制的最优化展开介绍,使得断路器安全可靠的运行,保证电力系统的稳定性.