Identification of parameters of models of electric network elements on the basis of Tellegen’s theorem

An evaluation criterion of the permissibility of using the parameters of a model to identify modes of electric network elements with consideration for the constancy of parameters being identified and the error of results based on Tellegen’s theorem is presented. Calculating formulas of proposed criterion for various elements of an electric power system are developed. The proposed criterion makes it possible to detect the presence of distorted information and evaluate the identification error.     

Features of Charging–Discharging of Supercapacitors

We present the results of experimental investigations of supercapacitors produced by Panasonic using several methods, namely, measurements of temporal dependences of charging–discharging currents, cyclic dc charging, and cyclic voltammetry. The values of the internal resistance, static and dynamic capacitance, as well as their dependences on the bias voltage of the capacitors, have been determined. Measurements have shown that the initial stage of relaxation of current is well approximated by the exponential time dependence, and then transition to a powerlike dependence occurs. This well-known effect is explained on the basis of the allowance for specific transport properties of a porous fractal-type medium. These processes are adequately described by the fractional-differential model of anomalous diffusion. A weak dependence of relaxation curves on the voltage at low values of the latter (<3 V) and the change in the power-law exponent at elevated voltages (>3 V) is explained by the appearance of new percolation paths blocked at low charging voltages due to the presence of high-potential barriers. The internal resistance and the static capacitance have been determined by measuring the voltage across the supercapacitor in the mode of dc charging. These parameters have been shown to depend on the voltage applied to the capacitor. The dependence of the dynamic capacitance on the voltage has been determined using cyclic voltammetry. It has been shown that the capacitance depends not only on the voltage, but also on the prehistory of charging and discharging of the capacitor. Comparison of the experimental results and the published data on the models and equivalent circuits with passive R, L, and C elements allows one to conclude that such models and equivalent circuits can be applied only when explaining a limited number of phenomena, in particular, behavior at small relaxation times.     

科杂志Chinese Journal of Surgery of Integ

外科 北京100700 ,北京100700基因芯片;;中医外科;;疮疡;;肿瘤;;泌尿外科0中国中西医结合外科杂志Chinese Journal of Surgery of Integrated Traditional and Western Medicine62-64R269E056;5;EE056_5;裴晓华0009000300020010生活质量与癌症疼痛研究进展万冬桂北京中日友好医院肿瘤科 北京100029生活质量;;恶性肿瘤;;疼痛;;综述0中国中西医结合外科杂志Chinese Journal of Surgery of Integra     

The evaluation of the safety of shaft system of large turbine generator set

1.IntroductionWith the increase of the capacity of the turbine generator set,the safety of the shaft system of the set(including the exciter)isthreatened for the following three reasons:1.The length of the shaft system increases.The length of theshaft system is 15 m for a 50 MW set,32-40 m for a 300 MW set and90 m for a 900 MW nuclear power set.The increased number of theconcentrated masses leads to the increase of both the number of the     

Peculiarities of modernization of hydrogenerators of Chirkeisk HPP (4 × 250 MW)

The principal design peculiarities of a new stator for the Chirkeisk HPP, as well as the method of its assembly at the HPP and installation on site, are described.     

Calendar of major academic activities of CSEE, 1992

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Development of the geoinformation system “Renewable sources of Russia”: Statement of the problem and choice of solution methods

Approaches to the development of the geoinformation system (GIS) “Renewable energy sources of Russia” are considered. To develop such a system it is planned to create a geographically oriented database on renewable energy sources (RES) at different Russian territories, local climatic characteristics, necessary for simulating power systems operating using RES, the objects of renewable power engineering in operation, etc.     

Highlights of Fifty Years Development of China''''s Power Industry

Attheturnofthecentury,thePeople'sRepublicofChinagreetstheyearof50thNationalAnniversary.Inthecourseoftheseextraordinary50years,powerindustryamongotherindustriesofChinahasattainedoutstandingachievements,andcontributedgreatlytothenationaleconomyandsocialdevelopment.1.InstalledCapacityandElectricityGenerationIncreasedTremendouslyFacingtheveryweakandbackwardpowerindustryleftoverbyoldChinaafterfoundingofmewChina,Chinalaidmuchstressonpowerindustry,implementingthepolicyofpowerdevelopmentaheadofo…     

History of LXI

In 1972H ewlett-Packard engineers invented the H ewlett-Packard Interface B us H P-IB as an open ( ) 3 (standard com m unications bus IEE E-488 from instrum ents to the com puter.It later becam e as G PIB gen鄄 ) (eral-purpose interface bus and was found on nearly every instrum ent.For 30years G PIB instrum ents also 4 ) 5known as rack-and-stack instrum ents were…     

Combustion Engineering Technology Research Center of Power Plant of China

l.Intr0ducti0nNPCCisahigh-techenterprisewhichdealswith"science,industry.trade,education"together.Inl993.CombustionEngineeringTechnologyCenterofLiaoningProvincewassetupafterauthorizationbyLia0ningprovincialgovernment.Inl996,Combus[ionEngineeringTechnologyResearchCenter0fPowerPIantofChinawasapprovedbytheStateScienceandTechn0logyCommissi0ntobesetup.NPCC,whichisalsocalledCombusti0nEngineeringTechnologyCenterofLia0ningProvinceandC0mbustionEngineeringTechnologyResearchCenterofPowerPl…     

Application of time-domain synthesis in constitution of breaking-capacity testing circuits

IntroductionThis paper presents a time-domain synthesis method for determiningthe topological structure and components parameters of breaking-capacity testing circuits according to transient recovery voltage (TRV) re-quirements specified by IEC standards.Composition of testing circuits,therefore,could rely on theoretical analysis,not mainly on physicalconcept and experience as before.Breaking-capaciiy testing is a dynami-cal process which should supply suitable breaking current related to ratedbreaking current and TRV complying with standard requirements,It hasgreat influence on synthesis of testing circuits,because the structure andcomponent parameters of circuits are determined not only by TRV     

A Brief Introduction to the Key National Disciplines of College of Electrical and Electronic Engineering of Huazhong University of Science and Technology

The electrical engineering discipline of HUST is amongthe first batch of disciplines approved by the Academic DegreeEvaluating Committee of the State Council of China as entitledto confer the mastership and the doctorate (1981), the firstbatch of postdoctoral programs (1985), and the first batch ofdisciplines entitled to award the doctorate in top level discipline(1996). The electrical machinery and electrical apparatus discipline,and the power system and its automation discipline were elected asthe key national disciplines January 2002. Also, the electrical amchinery discipline is one of the original two key nationaldisciplines, and its Electrical Machinery State SpecializedLaboratory is the only state key laboratory in this field.     

Development of Key Technologies of Large Hydro Unit in HEC

<正>Introduction to HEC Harbin Electric Machinery Company Limited (HEC) is a pivotal company that produces large electric machinery and accessorial control equipment in China. The hydro units made by HEC have accounted     

Suggestions on Promotion of FGD Industrialization of Thermal Power Plants

Introduction SO2 emission is the main cause of atmospheric pollution and acid rain growing in China. In recent years the state issued a series of laws, rules and policies concerning the promotion of SO2control in thermal power plants and speeded up constr…     

Suggestions on Promotion of FGD Industrialixation of Thermal Power Plants

In order in thoroughly solve the problem of , SO2 pollution and promote the sound development of the Thermal power FGD, this article proposes the technical principles of FGD process selection to standardize the supplying market and the post-assessment of FGD facilities.The selection principles can be detailed as：1）the limestone-gypsum proccss is preferred in the case that the mass fraction of sulphur content in power coal is more than 1% and the capacity of a unit is no less than 200MW.2）the matured low-cost technologies such as dry or semi-dry processes are applicable in the case that the mass fraction of sulphui coment in power coal is less than 1% and the capacity of a unit is less than 200MW.3） the seashore power plants with less than 1% mass fraction of sulphur content in power coal can take the seawater process into consideration.     

Determination of the density of zinc powders for alkaline battery

On May 4th,2006,the international publication of a patentapplicationtitled“alloyed zinc powders for alkaline batteries withhigh Pyknometer density”WO2006/045470 A1[1],appeared·Theintention of this investigation was to see whether it is possible torepro…     

Study of cooling wat er circulation A glimpse of thermo-hydraulic i nvestigation of cooling water problems in China

1.GeneralNotwithstanding that China possesses huge hydropower po-tential,thermal power has been playing a major role in China's elec-tric power industry due to the fact that China is very rich in coalresources and that coal-fired power generation is significantlybenefitted by its lower capital cost,shorter construction period andquicker return.The share of thermal power generation in the pastdecade is about 3/4 in installed capacity (Fig.1) and nearly 80% ingeneration capacity.This trend is expected to be continued in thecoming decade.