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.     

Spatially resolved evaluation of power losses in industrial solar cells by illuminated lock‐in thermography

The principles of a recently introduced measurement technique for power losses in solar cells, illuminated lock‐in thermography (ILT), are reviewed. The main advantage of ILT over dark lock‐in Thermography (DLT) is measurement under realistic operational conditions of solar cells. The main focus of this paper is to demonstrate the wide range of applications of ILT in identifying the causes of power losses in solar cells. For this purpose different evaluation methods are presented. A method for the evaluation of improvement potentials within a given cell technology is demonstrated. It is shown that different types of series resistance may be localized. Small areas of recombination losses (e.g., grain boundaries) can routinely be detected, which is not possible in dark lock‐in thermography. Good correspondence with light‐beam‐induced current images is found. A realistic evaluation of the impact of recombination losses on solar cell performance is demonstrated on two examples. Finally, process‐ or treatment‐induced recombination losses are investigated. In summary ILT is shown to be an extremely powerful tool in localizing, identifying and quantifying power losses of solar cells under realistic illumination conditions. Copyright © 2004 John Wiley & Sons, Ltd.     

无保温层屋面渗漏的红外热像检测方法

模拟了无保温层的单层屋面渗漏情况,探索了其红外热像检测方法.结果表明能准确测定渗漏的位置,同时对影响屋面温差变化的材料热容、导热系数和屋面太阳照射吸收率进行了分析,并通过对实际工程的检测,进一步证明了红外热像技术在建筑物屋面渗漏中应用的可行性.     

Electrical defibrillation optimization: an automated, iterativeparallel finite-element approach

To date, optimization of electrode systems for electrical defibrillation has been limited to hand-selected electrode configurations. Here, the authors present an automated approach which combines detailed, three-dimensional (3-D) finite-element torso models with optimization techniques to provide a flexible analysis and design tool for electrical defibrillation optimization. Specifically, a parallel direct search (PDS) optimization technique is used with a representative objective function to find an electrode configuration which corresponds to the satisfaction of a postulated defibrillation criterion with a minimum amount of power and a low possibility of myocardium damage. For adequate representation of the thoracic inhomogeneities, 3-D finite-element torso models are used in the objective function computations. The CPU-intensive finite-element calculations required for the objective function evaluation have been implemented on a message-passing parallel computer in order to complete the optimization calculations in a timely manner. To illustrate the optimization procedure, it has been applied to a representative electrode configuration for transmyocardial defibrillation, namely the subcutaneous patch-right ventricular catheter (SP-RVC) system. Sensitivity of the optimal solutions to various tissue conductivities has been studied. Results for the optimization of defibrillation systems are presented which demonstrate the feasibility of the approach     

Genetic framework for the high level optimisation of low power VLSIDSP systems

The authors present a technique for optimising CMOS based DSP systems for power. A genetic algorithm is used to reduce power, while tracking area and speed specifications, through the application of high level transformations. The algorithm searches for systems with the lowest power consumption within a large solution space. Results are presented which demonstrate the efficiency of the genetic algorithm as a power optimisation tool for complex VLSI systems     

Experiences with the Weather Parameter Method for the use in overhead line monitoring systems

Summary  Overhead lines are essential components of high voltage power systems worldwide. The performance of this network element is important for a save and reliable transmission of electrical energy. The load capability of a line is related basically to the line design itself and takes centre stage of the economic operation whereas the sag behaviour and the technical condition of the conductor and their components are more related to the line and network safety. Based on this situation overhead line monitoring systems are actually under discussion in many committees worldwide. This auxiliary equipment for overhead power lines helps to evaluate the actual transfer capability and/or to increase the system reliability. Therefore, a number of systems using different measuring methods and monitoring techniques are available on the market. More or less all methods are based on physical data and process information to achieve a suitable output to control the line stress. One of these methods is called the Weather Parameter Method, which uses local metrological weather data and system load information to estimate the conductor temperature. In a research project running over years an overhead line monitoring system was set up in cooperation with the Austrian transmission utility APG. After these years of experience a number of information and data based on the principle of the Weather Parameter Method is available and gives the scientific basement for this contribution. Three observation stations are collecting data all over the year; two stations are at a 220 kV overhead line and one station at the open air test field of the IHS in Graz in use. This contribution focuses on the coherences of the different parameters collected for the evaluation of the conductor temperature and it is not the main goal to discuss the improved performance by using a thermal management system, as mentioned in many other papers. By the knowledge of the punch-through of significant parameters in combination with the appearance probability a more accurate scheduling of the utilisation of the line under observation will be possible. A well prepared processing of many significant parameters for an overhead line monitoring system and a scientific approach based on some years of practical experience is presented in this contribution.     

Non-linear thermal simulation at system level: Compact modelling and experimental validation

In this work, a general methodology to extract compact, non-linear transient thermal models of complex thermal systems is presented and validated. The focus of the work is to show a robust method to develop compact and accurate non-linear thermal models in the general case of systems with multiple heat sources. A real example of such a system is manufactured and its thermal behaviour is analyzed by means of Infra-Red thermography measurements. A transient, non-linear Finite-Element-Method based model is therefore built and tuned on the measured thermal responses. From this model, the transient thermal responses of the system are calculated in the locations of interest. From these transient responses, non-linear compact transient thermal models are derived. These models are based on Foster network topology and they can capture the effect of thermal non-linearities present in any real thermal system, accounting for mutual interaction between different power sources. The followed methodology is described, verification of the model against measurements is performed and limitations of the approach are therefore discussed. The developed methodology shows that it is possible to capture strongly non-linear effects in multiple-heat source systems with very good accuracy, enabling fast and accurate thermal simulations in electrical solvers.     

Reliability Analysis of Industrial Electrical Systems Using Bayesian Networks Considering Power Quality and Security Characteristics Applied to the IEEE 493 Standard Network

The application of power electronics in industrial systems has increased the use of a wide variety of reliability analysis software for commercial and industrial electrical systems. However, there are power quality and security events that are not considered by these tools. This paper describes a methodology for the reliability evaluation of industrial electrical systems using Bayesian networks which incorporates the power quality and security characteristics under events such us short-circuits, random outages and electrical transients. This methodology is applied to the standard network proposed by the IEEE 493 Gold Book to compare the system reliability indices with the ones obtained by others methodologies. This work offers a solid and practical tool for the design of industrial electrical systems     

强激光设施能源系统电路的容差设计与分析

系统可靠性设计使用电路容差分析技术来保证电路特性获得稳定而可靠的输出，对于稳定性和可靠性要求高的系统进行容差分析尤其必要。能源系统作为惯性约束聚变(ICF)激光装置的重要组成部分，其可靠性直接关系到激光装置的稳定运行。能源系统电路的容差设计与分析，是激光装置可靠性设计分析必不可少的工作项目之一，对提高能源系统的可靠性进而保证整个激光装置的稳定运行具有重要意义。给出了能源系统电路设计图及其规定功能，然后在对容差设计模型进行一般性描述的基础上，利用随机优化设计方法，建立了能源系统电路容差设计随机优化模型，并对模型的设计变量、随机参数、设计准则、约束条件等进行了详细说明，最后给出了计算机仿真方法求解模型的流程及模型的可行解集。     

The volumetric erosion of electrical contacts

In this paper a method for measuring the volume of eroded electrical contacts is presented. The main emphasis is on the measurement of volume relative to a contact support surface, allowing severely eroded contacts to be measured. A noncontact system is described, which allows contacts to be evaluated for volume change without the contact being removed from contact supports. The accuracy of the measurement method is discussed and results show how the volume measurement can be used to evaluate contact performance. Results are presented on the erosion characteristics of Ag/SnO₂ contacts used in automotive relays. A new measurement methodology is presented which will allow for the evaluation of the performance of relay contacts in devices     

An analysis of reliability in the early stages of photovoltaic systems in Japan

In order to disseminate Photovoltaic (PV) technologies into the energy network, the cost down is not only important, but also improving the performance of the PV system is significant issues. Long‐term reliability is one of the most important issues in terms of PV system performance. Previous researches were mainly focused on the reliability of PV modules, but the PV system is composed of a power conditioner, wiring, junction box, and so on. To improve the reliability of PV systems, it is important to accumulate trouble cases focused on all components of PV system. In this paper, we aim at evaluation of the reliability for the PV system on the early stages of PV system's lifetime by using large number of Japanese PV systems' data from the field Test in Japan. New Energy and Industrial Technology Development Organization has been running the “Field test project in Japan” from 1992. In this project, PV system users have cooperated with the collection of monitoring data and reported on the information of maintenance and certain failures of PV systems for 4 years after installation of PV system. Using those reports each year of installation, we evaluated reliability of PV systems by means of parameters such as Mean Time Between Failure, Mean Time To Repair, and the suspension time of PV system. As a result, the main trouble of PV systems was related power conditioner, and a few trouble of PV module was caused by typhoon. Moreover, the trend of the failure rate before FY 2000 of installation was demonstrated as the trend of initial failure in “bathtub curve;” however, the trend of its after FY 2001 of installation was indicated as the accidental failure in “bathtub curve.” Further, the operator simply forgot to restart the power conditioner after maintenance or suspensions of PV system in many trouble cases, and the user did not notice that it had been suspended for a while. These trouble cases can be avoidable easily through the effective alarm such as error message of power conditioner systems with monitoring systems. Thereby, monitoring with the evaluation method of PV systems is one of the important technologies due to the long‐term reliability and stable operation. Copyright © 2010 John Wiley & Sons, Ltd.     

基于层次分析法的营销全业务量化积分评价体系构建研究

紧紧围绕现代服务体系建设要求,以评价因子为基础,以量化积分为路径,以权重配比为条件,构建了营销全业务量化积分评价体系。以层次分析法为基础进行建模仿真,探索形成适合营销专业特点的评价模型,保证结果客观公正,全程化覆盖,实现总体评价精准。该评价体系首次实现了对营销全业务总体评价的打分,同时总体评价又可细分为过程评价和专业评价,可以更加精准地实现对营销的全业务管控,保障业务规范运作。实践表明,项目实施有力推动了营销工作的自我修复和自我提升,助力电力营商环境优化。     

PSIM-based modeling of automotive power systems: conventional, electric, and hybrid electric vehicles

Automotive manufacturers have been taking advantage of simulation tools for modeling and analyzing various types of vehicles, such as conventional, electric, and hybrid electric vehicles. These simulation tools are of great assistance to engineers and researchers to reduce product-development cycle time, improve the quality of the design, and simplify the analysis without costly and time-consuming experiments. In this paper, a modeling tool that has been developed to study automotive systems using the power electronics simulator (PSIM) software is presented. PSIM was originally made for simulating power electronic converters and motor drives. This user-friendly simulation package is able to simulate electric/electronic circuits; however, it has no capability for simulating the entire system of an automobile. This paper discusses the PSIM validity as an automotive simulation tool by creating module boxes for not only the electrical systems, but also the mechanical, energy-storage, and thermal systems of the vehicles. These modules include internal combustion engines, fuel converters, transmissions, torque couplers, and batteries. Once these modules are made and stored in the library, the user can make the car model either a conventional, an electric, or a hybrid vehicle at will, just by dragging and dropping onto a schematic blank page.     

Modeling and simulation of an electronic component manufacturingsystem using hybrid Petri nets

Modelling and analysis for the design and operation of manufacturing systems is a vital need. For semiconductor manufacturing systems, which are large scale systems, discrete Petri nets do not constitute an adequate tool for modeling and analysis. In fact, use of discrete Petri nets is confronted with tile state explosion and the high cost of simulation. In this paper, hybrid Petri nets are presented as powerful tools for modeling and simulation of semiconductor manufacturing systems. This model has been used for modeling and simulation of a real life electronic components manufacturing system. It provides an accurate and first simulation of this system     

Direct stability analysis of electric power systems using energyfunctions: theory, applications, and perspective

Stability analysis programs are a primary tool used by power system planning and operating engineers to predict the response of the system to various disturbances. Important conclusions and decisions are made based on the results of stability studies. This paper presents a theoretical foundation of direct methods for both network-reduction and network-preserving power system models. In addition to an overview, new results are offered. A systematic procedure of constructing energy functions for both network-reduction and network-preserving power system models is proposed. An advanced method, called the BCU method, of computing the controlling unstable equilibrium point is presented along with its theoretical foundation. Numerical solution algorithms capable of supporting online applications of direct methods are provided. Practical demonstrations of using direct methods and the BCU method for online transient stability assessments on two power systems are described. Further possible improvements, enhancements and other applications of direct methods are outlined     

Reliability assessment platform for the power semiconductor devices – Study case on 3-phase grid-connected inverter application

Because of the high cost of failure, the reliability performance of power semiconductor devices is becoming a more and more important and stringent factor in many energy conversion applications. Thus, the need for appropriate reliability analysis of the power electronics emerges. Due to its conventional approach, mainly based on failure statistics from the field, the reliability evaluation of the power devices is still a challenging task. In order to address the given problem, a reliability assessment platform is proposed in this paper. An advanced reliability design tool software, which can provide valuable reliability information based on given mission profiles and system specification is first developed and its main concept is presented. In order to facilitate the test and access to the loading and lifetime information of the power devices, a novel mission profile based stress emulator experimental setup is proposed and designed. The link between the stress emulator setup and the reliability tool software is highlighted. Finally, the reliability assessment platform is demonstrated on a 3-phase grid-connected inverter application study case.     

Autonomous power system: Intelligent diagnosis and control

The Autonomous Power System (APS) project at NASA Lewis Research Center is designed to demonstrate the abilities of integrated intelligent diagnosis, control, and scheduling techniques to space power distribution hardware. Knowledge-based software provides a robust method of control for highly complex space-based power systems that conventional methods do not allow. The project consists of three elements: the Autonomous Power Expert System (APEX) for fault diagnosis and control, the Autonomous Intelligent Power Scheduler (AIPS) to determine system configuration, and power hardware (Brassboard) to simulate a space based power system. APEX is a software system that emulates human expert reasoning processes to detect, isolate, and reconfigure in the case of a power system distribution fault. The APEX system continuously monitors the operating status of the Brassboard and reports any anomaly (either static or incipient) as a fault condition. APEX functions as a diagnostic advisor aiding the user in isolating the probable cause of the fault. Upon isolating the probable cause, APEX automatically reconfigures the Brassboard based upon internal knowledge as well as information from the scheduler. APEX provides a natural language justification of its reasoning processes and a multilevel graphical display to depict the status of the Brassboard. AIPS is an intelligent scheduler used to control the efficient operation of the Brassboard. A database is kept of the power demand of each load on the Brassboard and its specified duration and priority. AIPS uses a set of heuristic rules to assign start and end times to each load based on priorities, as well as temporal and resource constraints. When a fault condition occurs, AIPS assists APEX in reconfiguring the system. The APS Brassboard is a prototype of a space-based power distribution system and includes a set of smart switchgear, power supplies, and loads. Faults can be introduced into the Brassboard and, in turn, be diagnosed and corrected by APEX and AIPS. The Brassboard also serves as a learning tool for continuously adding knowledge to the APEX knowledge base. This paper describes the operation of the APS as a whole and characterizes the responsibilities of the three elements: APEX, AIPS, and Brassboard. A discussion of the methodologies used in each element is provided. Future plans are discussed for the growth of the APS.     

Laser cuts increase the reliability of heavy-wire bonds and enable on-line process control using thermography

The active thermal cycling lifetime of heavy wire bonds decreases significantly with increasing wire diameter. This paper presents an innovative method for shaping the wire bond in the bonding region such that the thermo-mechanical load on the interface region between wire bond and semiconductor metallization is significantly reduced. The efficiency of the approach has been validated using finite element simulations and power cycling experiments. Moreover, the method can be used as a ‘non-destructive’ in-situ measurement technique, in which crack growth can be determined based on thermography measurements of the trenches, which act as magnifiers for the thermography camera and eliminate preconditioning such as using black colouring.     

高速公路机电系统设计与施工的质量控制

高速公路机电工程是一个系统性工程,是高速公路中一个重要的组成部分。机电工程包括＂三大系统＂、隧道机电工程以及供配电系统等。其中三大系统包括＂监控系统＂、＂收费系统＂、＂通信系统＂的建设。机电系统设计和施工质量直接关系到高速公路的运营和安全。本文根据忻保高速公路工程实践,对机电系统设计与施工的质量控制进行了简要介绍。     

Evaluating the Relative Performance of Engineering Design Projects: A Case Study Using Data Envelopment Analysis

This paper presents a case study of how Data Envelopment Analysis (DEA) was applied to generate objective cross-project comparisons of project duration within an engineering department of the Belgian Armed Forces. To date, DEA has been applied to study projects within certain domains (e.g., software and R&D); however, DEA has not been proposed as a general project evaluation tool within the project management literature. In this case study, we demonstrate how DEA fills a gap not addressed by commonly applied project evaluation methods (such as earned value management) by allowing the objective comparison of projects on actual measures, such as duration and cost, by explicitly considering differences in key input characteristics across these projects. Thus, DEA can overcome the paradigm of project uniqueness and facilitate cross-project learning. We describe how DEA allowed the department to gain new insight about the impact of changes to its engineering design process (redesigned based on ISO 15288), creating a performance index that simultaneously considers project duration and key input variables that determine project duration. We conclude with directions for future research on the application of DEA as a project evaluation tool for project managers, program office managers, and other decision-makers in project-based organizations.