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.     

An overview of the application of installation diagnostic technology in China''''s electric power industry

Installation diagnostic technology is a synthetic applied technol-ogy emerging recently,which is a methodology for evaluatingthe stress,worsening,fault,strength,function etc.,without disassem-bling the installation.The position,degree as well as cause of abnor-mality can be detected during operation using an installation diagno-sis system,thereby predicting and evaluating its reliability and deter-mining the repairing method.     

The present situation and prospect of Shandong provincial electric power industry

Shandong province is situated on the eastern coast ofChina,the lower reaches of Yellow River.Shandong pe-ninsula is extended from the continent between the Bohai Sea andthe Yellow Sea.The longest stretch from north to south over theprovince is more than 400 km,and the longest stretch from east towest is more than 700 kin.The total area is 153,300 squarekilometers with a population about 81.597 million.Shandong province is rich in natural resources,particularly in     

Impacts of COVID-19 on Kuwait’s electric power grid

In response to a request from Kuwait’s Ministry of Electricity and Water, a resource adequacy model was developed to assess Kuwait’s ability to supply sufficient energy to meet the load demand during the COVID-19 pandemic. Power system operators and utilities use this type of model to ascertain their ability to meet demand, most notably peak demand. The model includes active power loss as well as the loss of resource capacity under medium and large contingencies. As resource adequacy models do not take into account security constraints such as transmission limits and voltage, they cannot be used for operations. However, due to their simplicity, they are appropriate for studying a wide range of scenarios for formulating policy decisions. Resource adequacy analysis can provide valuable insights into the performance of a system under urgent conditions such as the one posed by COVID-19 and similar unforeseen disruptions. This model utilizes an analysis of historical load data to forecast the 2020 peak load and develop a number of scenarios to test the capacity margin of Kuwait’s power system. The scenarios vary based upon load growth (2–25 %) and whether there is an outage or unavailable generation (no outage, 720 MW outage, 1440 MW, and 2400 MW outage).     

Effects of electrified railways on quality of electric energy supply in urban power systems

IntroductionBeing of great value to railway transport and hence to nationaleconomy,electrification of railways has been carried out very rapidlyin China in the past 30 years.By the end of 1990,some 6941 km ofelectrified railways have been opened to traffic and about 16,000 kmor one fourth of the total railway length are expected to be electrified,accounting for 45% of the total railway freight volume.At present,Shaanxi Province ranks first with respect to total     

On the synthesis of passive–adaptive systems for electric drive control

A new approach to synthesis of passive–adaptive electromechanical control systems is proposed. Decomposition of a control system structure into two subsystems, which solve a uniform problem of finite control, but have various functions, is a feature of the presented approach. The first subsystem is a control system of an electric drive, and it carries out the task of finite control that is invariant to the reference signals in the traditional statement of linear discrete–continuous systems. The second subsystem is an adaptive reference model that forms a criterion that is optimal in terms of performance and accuracy of the phase coordinate vector of an electric drive with restriction of them to acceptable levels. A discrete–continuous system of electric drive control and a functional structure of a passive–adaptive electromechanical system are set up in the MexBIOS Development Studio simulating the modeling environment. The results of simulation showed that there is an acceptable quality of system operation in both linear and nonlinear areas of operation when working out additive increments of setting the position of the drive shaft changing at random points of time. The synthesized system has low sensitivity to changes in the parameters of the object of electromechanical control.     

Maintenance oriented algorithm for economic operation of an autonomous diesel–electric station

Modern operation of power systems is based with priority and on economical aspects. The most efficient operation of a power system is based on the unit commitment and economic dispatch concepts, which are governed by well established economical criteria. This seemingly simple approach is not always possible for various reasons, e.g. in the case of autonomous diesel–electric stations (ADES) usually located in small-medium size islands. In reality, the aim of an ADES is to cover the hourly electrical demand, while is taking into account the maintenance of the involved generating units, so they are available in appropriate time periods. Usually, a specific operating policy is followed, which determines the way the generating units should be loaded, depending on the structure of the network involved. For the proper operation of an ADES a method is developed, in this work, which generally is based on such a policy of ADES operation and in addition attempts to make a compromise between economic and maintenance constraints. The proposed method is applied successfully to an ADES of a medium size Greek island.     

Curve-fitting-based method for modeling voltage–current characteristic of an ac electric arc furnace

Field measurements of voltage and current are the most effective way for characterizing the electric response of an ac electric arc furnace that describes its nonlinear behavior. Sufficient measured information can be adopted to determine the background harmonic level in a power system, to characterize specific sources of harmonics, and to develop an appropriate nonlinear voltage–current characteristic. In this paper, a curve-fitting-based method called cubic spline interpolation is proposed to model the voltage–current characteristic of an ac electric arc furnace in the steady state. Meanwhile, the actual measured data are collected for modeling use. Two classic methods, harmonic current injections and equivalent harmonic voltage sources, for modeling the electric arc furnace load are reviewed and used to evaluate the performance of proposed model. Results obtained from the measured data and computer simulations of the three electric arc furnace models are then compared according to the voltage and current waveforms, as well as the voltage–current characteristic. It is shown that the proposed model is more accurate than the two classic approaches for harmonic assessment of electric arc furnaces and can be used for modeling similar types of nonlinear loads in the harmonic penetration study.     

Effect of the variation of the charge distribution along multi-overhead transmission lines’ conductors on the calculation method of ground surface electric field

This paper presents a new methodology to calculate the ground surface electric field, produced by overhead transmission lines (OHTLs), taking into account the effect of the variation of the charge distributions along the conductors of multi-overhead transmission lines. In this paper, the effects of the conductors sag, the presence of the tower, replacing the sub-conductors of each phase with an equivalent conductor, the presence of the ground wires, and the presence of another overhead transmission line (OHTL) circuit on the electric charge distribution along the OHTL conductors and hence on the calculation of the ground surface electric fields are extensively studied. The suggested technique is verified by comparing its results with a measurement by the other. The suggested technique is based on both the Charge Simulation Method (CSM) and the Image Method (IM).     

Develop electric vehicles to alleviate city pollution

As main transportation and communication facilities,automo-biles contribute much convenience for people all over the world.However,they also bring about serious problem of pollution,espe-cially in urban areas where people are jeopardized in health by theheavy noise and the toxic substances in the exhaust gas from them.Early in 1966,air pollution investigation made by USA pointed outthat 61% of total air pollution originated from automobiles.In 1981,West Germany studied and analysed the detrimental substancesexhausted from sedans,trucks and buses per kilometer travel dis-tance,as shown in the following table:     

Suzhou and Changzhou implement uniform rural electric tariff

SinceAugust1st,twocitiesinJiangsuProvince--SuzhouandChangzhouwouldfirstcomplementuniformruralelectricitysalestariffamongothersintheprovince.Inthesruraltariffreform,allsurcharges,suchasover-quotasurchargeforresidentiallightingconsumption,wereeliminated.Thistime,theruralresidentiallightingconsumptiontariffinSuzhouapprovedbytheProvincialPricesManagementBureauis0.57yuan/kWh,whilethatinChangzhouis0.59yvan/kWh.Otherlighting,non-andordinaryindustryandagricultureproductionelectricityconsumptionta…     

A new variae-speed constant-frequency wind electric conversion system

The variable-speed constant-frequency wind electric conver-sion system can allow the rotational speed of wind turbine to varywith wind speed and operate at a constant and optimal tip speedratio. Therefore, the wind turbine can maintain high power coeffi-cient over wide range of wind speed and the speed regulatingmechanism of wind trubine can be simplified.     

Introduction to Puerto Rico’s energy transformation: An analysis of key documents and plans towards the reconstruction of the electric system

Puerto Rico’s electric system transformation depends on the execution of the current energy policy. However, key documents, such as the PREPA Fiscal Plan, do not detail how these transformations are going to be financed, and no analysis is provided for expected economic impacts that should arise from increasing electricity tariff rates to electricity consumers. This paper analyzes the three main documents developed as part of the planning for the Puerto Rico electric system transformation and reconstruction, including potential flaws and its effect on the electric utility. It also links to further studies and analyses developed toward the effect of such plans on Puerto Rico’s economy and on the electric utility.     

The legal sustainability of energy substitution in Nigeria’s electric power sector: renewable energy as alternative

Non-renewable fuel sources have been the predominant energy sources and a significant source of foreign exchange income for Nigeria, while at the same time there is a severe problem of electricity inconsistency and persistent power blackouts in Nigeria. The research aims to end the concern for deficient energy use, and to encourage energy efficiency and sustainability. Nigeria has not maximized the advantages of renewable energy after the denationalisation of its electricity industry despite the current transformation in the power industry and the rising demand for renewable energy supply. The research adopts a doctrinal legal approach with a library-based legal research technique with a comparative legal method. It reveals that the absence of a comprehensible legal regime with encouragement for the use of renewable energy is the fundamental element causing the slow utilization of renewable energy as a substitute source of energy in Nigeria. It is suggested that, among other reforms, there is a need for a comprehensible legal regime on renewable energy and the encouragement of strict implementation of energy regulatory strategies and policies with incentives for the application of renewable energy sources in Nigeria.     

The welding techniques for electric power construction in China

Soon after the founding of the Electric Power Construc-tion Research Institute (EPCRI),the Welding Engineer-ing Division (WED) was established in 1958,in order to undertakethe task of solving the electrical and mechanical problems concern-ing the welding techniques during electric power construction.After building up for thirl.y odd years,WED has expanded anddeveloped to have a staff of 33 persons,including 5 senior engineersand 21 engineers and assistant engineers,6 of them have obtainedthe M.S.degree.WED,as the research and training centre of     

Application of a system with distributed architecture for information acquisition and processing in tasks of active–adaptive voltage control in distribution electric grids

An active–adaptive control system for power grids with distributed architecture of data acquisition and processing is considered. The advantages of the proposed control principle are compared with commonly used methods. A domestic apparatus—a programmable recording bay controller (PRBC)—is described. This hardware was designed to measure the basic electrical parameters and create distributed systems for data acquisition and processing. The procedure is considered of supervisory control and data acquisition (SCADA) by the SONATA system based on a multicore distributed architecture having high reliability and supporting a rigid real-time mode. A full-function full-scale model of active–adaptive voltage control system (AAVC) was set up using proposed software and hardware. The AAVC makes it possible to use the results of calculating–measuring procedures to select a corresponding on-load tap-changer (OLTC) on the actual voltage levels in the nodes of distribution grid. This approach to centralized voltage control in distribution grids makes it possible to ensure the required level of voltage in the greatest possible number of power consumers owing to prediction of voltage change. The effect of emergencies (random failure of control equipment) during the operation of an active–adaptive voltage control system is analyzed. A qualitative evaluation of the effect of faults on regulation quality and choice of OLTC connection is carried out. It is shown that, for undisturbed operation of an active–adaptive voltage control system, additional diagnostic tools, backup, and data loss compensation are needed.     

Some facts and figures about the electric power industry in 1991

1. Power generation The national total electricity genera-tion in 1991 amounted to 670 TWh, 25TWh over the planned value and 48.7 TWhover the previous year, the annual growthrate reached 7.83%. Among the electricitygeneration, 123 TWh were hydropower,which was 1.2% less than previous year,and 547 TWh thermal power, 10.4% morethan previous year. The electricity gener-ated by power enterprises under the aus-pices of the Ministry of Energy was 410.8     

Are US electric utilities improving their sustainability disclosures and performance?

This paper examines whether voluntary sustainability disclosures are associated with sustainability performance for a sample of 47 investor-owned electric utilities that disclosed SASB-consistent sustainability information in their SEC (U.S. Securities and Exchange Commission) filings in the period 2014–2018. We collect sustainability performance indicators from company sustainability reports to determine whether companies with a good disclosure policy on a topic also have good sustainability performance on the given topic. Our findings suggest that the most frequent disclosures are grid resiliency, greenhouse gas emissions, and end-use efficiency while the least disclosed topics are energy affordability and nuclear safety. The data shows that companies that perform among the best on one sustainability performance measure may not be the best on other measures. Correlation analysis and mean difference tests indicate that there is no strong connection between sustainability performance and disclosure quality. Thus, the present strategy of voluntary sustainability disclosure may not be a direct indicator of actual sustainability performance.     

On the storage batteries used in solar electric power systems and development of an algorithm for determining their ampere–hour capacity

Storage batteries are indispensable in all stand alone solar electric systems (PV power systems). Their efficiencies and life times affect significantly the overall PV system performance and economics. Batteries specified especially for use in PV systems have to be distinguished with standing of very deep discharge rate and high cycling stability.Ordinary batteries being marketed world wide for use in automobile, are mostly not appropriate for PV power systems. The most important characteristics of lead–acid batteries are presented and discussed in this paper. Moreover, the paper illustrates an experimental procedure for developing an algorithm for determining the ampere–hour capacity of batteries operating in PV systems. This algorithm enables determining the state-of-charge of a battery by measuring voltage and electrolyte-specific gravity at definite temperature and is applicable also for large battery storage systems.