检索结果-南通市图书馆

A Novel Hybrid Approach to Estimate Customer Interruption Costs for Industry Sectors

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Engineering（科研） 2013年第10期5卷 34-40页

作者： Sinan Kufeoglu matti lehtonen Aalto University Espoo Finland

The power system infrastructure, operations and market have gone through radical changes for the last couple of decades. The society has become more dependent to the continuous electric power supply and hence the concept of electric power reliability has become more significant. At this point, understanding the economic outcomes of power outages is vital and imperative for both utilities and the customers. There are certain methodologies to understand the costs of power interruptions. This paper suggests a novel hybrid method that comprises of customer surveys and direct analytical methods to reach customer specific, objective and reliable results for the industry sector customers. The paper also brings a statistical approach to censor the zero and extreme responses given via the surveys.

关键词： Customer Interruption Cost (CIC) Power Interruption Customer Survey Industry Sector

Reluctance Network Analysis for Complex Coupled Inductors

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Power and Energy Engineering 2017年第1期5卷 1-14页

作者： Jyrki Penttonen Muhammad Shafiq matti lehtonen Department of Electrical Engineering Aalto University Espoo Finland Vensum Ltd. Helsinki Finland

The use of reluctance networks has been a conventional practice to analyze transformer structures. Basic transformer structures can be well analyzed by using the magnetic-electric analogues discovered by Heaviside in the 19th century. However, as power transformer structures are getting more complex today, it has been recognized that changing transformer structures cannot be accurately analyzed using the current reluctance network methods. This paper presents a novel method in which the magnetic reluctance network or arbitrary complexity and the surrounding electrical networks can be analyzed as a single network. The method presented provides a straightforward mapping table for systematically linking the electric lumped elements to magnetic circuit elements. The methodology is validated by analyzing several practical transformer structures. The proposed method allows the analysis of coupled inductor of any complexity, linear or non-linear.

关键词： Power Transformer Coupled Inductor Reluctance Networks Electromagnetic Modeling

Effect of Climate Change on Transformers Loading Conditions in the Future Smart Grid Environment

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Open Journal of Applied Sciences 2013年第2期3卷 24-29页

作者： Murtaza Hashmi matti lehtonen Seppo Hanninen Energy Systems Knowledge Centre VTT Technical Research Centre of FinlandFinland Department of Electrical Engineering Aalto UniversityFinland

The steady-state calculations are performed using IEC guidelines to determine the hot spot temperatures of distribution and power transformers in the worst projected Finnish environment due to long summer periods. Moreover, the effect of increase in winding resistance due to increase in ambient temperatures has been taken into account. The primary objective of the research is to investigate the possible extreme circumstances due to climate change. It is concluded that the power and distribution transformers should be progressively de-rated under such circumstances for their safe operations, which will not only prove cost-effective for utilities but also improve the reliability of the power supply to their valued customers in the challenging future smart grid environment.

关键词： Distribution Transformer Power Transformer Winding Resistance Climate Change Electricity Distribution Company Reliability Smart Grid

A Novel Transient Current-Based Differential Algorithm for Earth Fault Detection in Medium Voltage Distribution Networks

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Energy and Power Engineering 2012年第1期6卷 81-88页

作者： Mohamed F. Abdel-Fatta matti lehtonen Department of Electrical Engineering Aalto University PO Box 13000 Espoo FI-OOO76 Aalto Finland Department of Electrical Power and Machines Engineering Faculty of Engineering Zagazig University Zagazig Sharqia PO Box 44519 Egypt

This paper presents a novel transient current differential algorithm for earth fault detection in unearthed （isolated） and compensated neutral medium voltage （MV） networks. The proposed algorithm uses the transient residual currents, which are very sensitive for earth faults detection. The transient values of residual currents are calculated for each feeder in the network and used as an earth fault indicator. The flow of residual currents is investigated. It is found that the residual current for the faulted feeder is equal to the summation of all residual currents for all other healthy feedersl Based on this investigation, a differential technique is proposed. A percentage restrain performance is proposed to ensure the selectivity and security of the algorithm. The transient algorithm is very sensitive for earth fault incidence. To apply the proposed algorithm, the residual currents can be measured easily by one sensor for each feeder with no need to voltage measurement. The proposed algorithm is less dependent on the fault resistance and the faulted feeder parameters. The network is simulated by ATP/EMTP program. Different fault conditions are covered in the simulation process： different fault inception angles, fault locations and fault resistances.

关键词： Earth faults earth capacitance transient impedance transient frequency unearthed and compensated MV networks.

A New Transient Impedance-Based Algorithm for Earth Fault Detection in Medium Voltage Networks

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Energy and Power Engineering 2012年第2期6卷 240-249页

作者： Mohamed F. Abdel-Fattah matti lehtonen Department of Electrical Engineering School of Electrical Engineering Aalto University Espoo 00076 Finland Department of Electrical Power and Machines Engineering Faculty of Engineering Zagazig University Zagazig Sharqia PO Box 44519 Egypt

This paper presents a new earth-fault detection algorithm for unearthed （isolated） and compensated neutral medium voltage （MV） networks. The proposed algorithm is based on capacitance calculation from transient impedance and dominant transient frequency. The Discrete Fourier Transform （DFT） method is used to determine the dominant transient frequency. The values of voltage and current earth modes are calculated in the period of the dominant transient frequency, then the transient impedance can be determined, from which we can calculate the earth capacitance. The calculated capacitance gives an indication about if the feeder is faulted or not. The algorithm is less dependent on the fault resistance and the faulted feeder parameters; it mainly depends on the background network. The network is simulated by ATP/EMTP program. Several different fault conditions are covered in the simulation process, different fault inception angles, fault locations and fault resistances.

关键词： Earth faults earth capacitance transient impedance transient frequency unearthed and compensated MV networks.

PVC nanocomposites for cable insulation with enhanced dielectric properties,partial discharge resistance and mechanical performance

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

High Voltage 2020年第4期5卷 463-471页

作者： Nagat M.K.Abdel-Gawad Adel Z.El Dein Diaa-Eldin A.Mansour Hanaa M.Ahmed Mohamed M.F.Darwish matti lehtonen Department of Electrical Power and Machines Engineering Faculty of Engineering at ShoubraBenha UniversityCairoEgypt Department of High Voltage Networks Faculty of Energy EngineeringAswan UniversityAswanEgypt High Voltage and Superconductivity Laboratory Department of Electrical Power and Machines EngineeringFaculty of EngineeringTanta UniversityTantaEgypt Department of Mathematics and Engineering Physics Faculty of Engineering at ShoubraBenha UniversityCairoEgypt Department of Electrical Engineering and Automation School of Electrical EngineeringAalto UniversityEspooFinland

The current study aims to develop polyvinyl chloride(PVC)nanocomposites with enhanced electrical and mechanical properties by incorporating titanium oxide(TiO_(2))nanoparticles within PVC *** loading of nanoparticles and different nanoparticle surface states were *** surface states are unfunctionalised,functionalised using vinyl silane and functionalised using amino *** choice of a most suitable surface state was a critical factor that guarantees a good dispersion of nanoparticles and consequently enhances the compatibility between TiO_(2)and PVC *** process followed in the PVC/TiO_(2)nanocomposites preparation,loaded with different wt.%of TiO_(2)nanoparticles,was the solvent *** dielectric properties measured here were the relative permittivity(ɛr),dielectric loss(tanδ),breakdown strength(AC and DC under uniform field)and the internal partial discharges(PDs)within insulation *** measurements have been performed under room temperature and at frequency ranged from 20 to 1.0 ***,the mechanical properties of the samples like elongation,elasticity modulus and tensile strength were also *** silane showed better improvements in both electrical and mechanical performances compared to the amino silane,especially in cases of high weight fractions of TiO_(2).This is because of the improvement in the PVC-TiO_(2)interfacial region arise from the similarity of polarity and surface tension values of vinyl silane with that of PVC matrix and TiO_(2)nanoparticles.

关键词： dielectric insulation resistance

Intelligent Agent-Based Architecture for Demand Side Management Considering Space Heating and Electric Vehicle Load

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Engineering（科研） 2014年第11期6卷 670-679页

作者： Farhan H. Malik Mubbashir Ali matti lehtonen Department of Electrical Engineering and Automation Aalto University Espoo Finland

Contraction of resilience on generation side due to the introduction of inflexible renewable energy sources is demanding more elasticity on consumption side. It requires more intelligent systems to be implemented to maintain power balance in the grid and to fulfill the consumer needs. This paper is concerned about the energy balance management of the system using intelligent agent-based architecture. The idea is to limit the peak power of each individual household for different defined time regions of the day according to power production during those time regions. Monte Carlo Simulation (MCS) has been employed to study the behavior of a particular number of households for maintaining the power balance based on proposed technique to limit the peak power for each household and even individual load level. Flexibility of two major loads i.e. heating load (heat storage tank) and electric vehicle load (battery) allows us to shift the peaks on demand side proportionally with the generation in real time. Different parameters related to heating and Electric Vehicle (EV) load e.g. State of Charge (SOC), storage capacities, charging power, daily usage, peak demand hours have been studied and a technique is proposed to mitigate the imbalance of power intelligently.

关键词： Demand Response (DR) Electric Vehicles (EVs) Heat Storage Smart Grids

Design, Implementation and Simulation of Non-Intrusive Sensor for On-Line Condition Monitoring of MV Electrical Components

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Engineering（科研） 2014年第11期6卷 680-691页

作者： Muhammad Shafiq matti lehtonen Lauri Kutt Muzamir Isa Department of Electrical Engineering School of Science and Technology Aalto University Espoo Finland School of Electrical Systems Engineering Universiti Malaysia Perlis Malaysia

Non-intrusive measurement technology is of great interest for the electrical utilities in order to avoid an interruption in the normal operation of the supply network during diagnostics measurements and inspections. Inductively coupled electromagnetic sensing provides a possibility of non-intrusive measurements for online condition monitoring of the electrical components in a Medium Voltage (MV) distribution network. This is accomplished by employing Partial Discharge (PD) activity monitoring, one of the successful methods to assess the working condition of MV components but often requires specialized equipment for carrying out the measurements. In this paper, Rogowski coil sensor is presented as a robust solution for non-intrusive measurements of PD signals. A high frequency prototype of Rogowski coil is designed in the laboratory. Step-by-step approach of constructing the sensor system is presented and performance of its components (coil head, damping component, integrator and data acquisition system) is evaluated using practical and simulated environments. Alternative Transient Program-Electromagnetic Transient Program (ATP-EMTP) is used to analyze the designed model of the Rogowski coil. Real and simulated models of the coil are used to investigate the behavior of Rogowski coil sensor at its different stages of development from a transducer coil to a complete measuring device. Both models are compared to evaluate their accuracy for PD applications. Due to simple design, flexible hardware, and low cost of Rogowski coil, it can be considered as an efficient current measuring device for integrated monitoring applications where a large number of sensors are required to develop an automated online condition monitoring system for a distribution network.

关键词： Non-Intrusive Sensors Condition Monitoring Partial Discharge Rogowski Coil ATP-EMTP

Load Flow Analysis Framework for Active Distribution Networks Based on Smart Meter Reading System

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Engineering（科研） 2013年第10期5卷 1-8页

作者： Merkebu Zenebe Degefa Robert John Millar matti Koivisto Muhammad Humayun matti lehtonen Department of Electrical Engineering Aalto University Espoo Finland

With the expansion of distributed generation systems and demand response programs, the need to fully utilize distribution system capacity has increased. In addition, the potential bidirectional flow of power on distribution networks demands voltage visibility and control at all voltage levels. Distribution system state estimations, however, have traditionally been less prioritized due to the lack of enough measurement points while being the major role player in knowing the real-time system states of active distribution networks. The advent of smart meters at LV loads, on the other hand, is giving relief to this shortcoming. This study explores the potential of bottom up load flow analysis based on customer level Automatic Meter Reading (AMRs) to compute short time forecasts of demands and distribution network system states. A state estimation frame-work, which makes use of available AMR data, is proposed and discussed.

关键词： Active Network Demand Response Dynamic Rating Load Forecast Load Modeling Smart Meter State Estimation