Electrical motors are the prime movers of any work whether in domestic, commercial or industrial applications. Even though there are various types of motors, this chapter mostly deals with squirrel cage induction motors (SCIMs), which are widely used in industries globally. When a three-phase supply is given to a stator of 120° displayed, in space, windings, they produce a resultant magnetic flux of constant magnitude, at synchronous speed. There are some abnormal conditions which induction motors are experiencing: crawling, clogging or magnetic locking or tooth locking, and single phasing. In case of slip ring induction motor, rotor rheostat control method is used for speed control of motor. The main disadvantage of normal SCIM is poor starting torque which especially makes hurdles to use SCIM in frequent starting of heavy loads like compressors.
A conductor in an electrical power network is an element which permits flow of electric current through it by offering low resistance. The most commonly used conducting material is either aluminum or copper. A cable is nothing but either a single or multi-conductor, used to transmit and distribute electrical energy, communication signals or radio TV signals. They can be used from LV to HV and can be laid overhead, underground or in water. The following are some of the materials used for insulation of electrical cables: poly vinyl chloride (PVC), paper insulated or paper insulated lead covered (PILC), cross-linked polyethylene (XLPE), poly ethylene, and rubber. PVC cables are used for LV and XLPE cables are used for HV. Based on laying method and number of cable groups, etc., the current carrying capacity of a sample power cables will be de-rated.
The purpose of an electrical protection system is to ensure the maximum rather continuous availability of power supply to the loads. Following are the important desirable qualities of any protective system: selectivity, sensitivity, stability, speed, and dependability or reliability. Current transformer is helpful in isolating the measuring and protective devices from the high-voltage systems so that the safety of these devices and human is ensured. Voltage transformer or potential transformer is a step down transformer used for step down of power systems higher voltages to an acceptable range of voltage to meters and protective relays. Absolute measuring instruments give the magnitude of quantity under measurement in terms of physical constants of the instrument, e.g., Tangent Galvanometer. These instruments do not require comparison with any other standard instrument. A multi-function meter is widely used in the industry sector. It is widely used for control panels, generator panels, power distribution panels, etc.
The ash blocking situation of air preheaters of three 600 MW boilers in Inner Mongolia Datang International Tuoketuo Power Generation Co.Ltd was briefed,the main causes of ash blocking of air preheaters(such as large departure of fuel coal characteristics of boilers from the designed value,uneasy and unsmooth ash conveying of economizer ash hopper etc.)were analyzed,and The relevant preventive measures(such as,to strengthen the comprehensive handling of air heater,to satisfy the required igniting energy amount as much as possible when the coal pulverizing system going into operation)were put forward,thus the forced outage of boiler problem due to the ash blocking of air preheaters was solved.
文章针对配电自动化通信系统对数据传输可靠性和实时性等方面的要求,提出用无线通信方式弥补传统配电网自动化系统通信方式的不足.对通用分组无线业务(GPRS)技术的发展进行了概述,阐述GPRS技术的优越性与可行性.分析我国配电网的发展及其存在的问题,提出一种基于GPRS技术的配电变压器监测系统.实践证明该系统具有实时性、传输速率快、可靠性高、费用低等特点.
介绍"国家标准GB/T 2624.2-2006<用安装在圆形截面管道中的差压装置测量满管流体流量>第2部分:孔板"中关于直管段长度规定的变化.分析和讨论了在贯彻、实施这些规定时存在的问题,并提出几点建议.
State estimation method of distribution network based on load current takes load current as state variable, the branch measurement function is represented with load current, and the state estimation value of branch current can be obtained, which reduces the solution space of state estimation problem and raises the convergence of algorithm and calculation speed. Through the comparison of this algorithm and three-phase power flow algorithm, the results show that the state estimation algorithm in the aspects of effect, speed and convergence is excellent than conventional method.
唯特利公司（Victaulic Company of America）的沟槽式连接方案全面革新了传统管道连接方式,使管道连接更加经济、安全、环保。为了探寻唯特利的沟槽式连接方案的优异特性,我们采访了唯特利亚太区副总裁兼总经理夏凯奇（David Sharkey）。
电力设备>:经历改革开放30周年,我国输变电设备制造业取得了不菲的成就.但是,改革开放前20年,也就是从1978-1998年,我国输变电设备制造业发展缓慢、滞后,那么请您谈谈其中的缘由及应该吸取的教训?
The paper discussed the relay protection of wind farm,analyzed the impact of wind farm integration on power system protection.Dynamic simulation of Matlab/Simulink was used,and the power system with single machine to infinitive bus including wind power generation was simulated.The conclusion of dynamic simulation shows that an adaptive relay protection for wind farm should be used when the short circuit fault occurred on the tie-line and through analysis of fault voltage and current curve in different type of the fault for DFIG.
In order to ensure the safe operation of desnlfnrigation facility,No.2 boiler in Luohe power plant was overall retrofitted,on the basis of reserving the original housing of electrostatic precipitator,to adopt electrostatic-baghouse integrated type precipitation,high frequency switth-power souree etc.advanced techwologies.The paper briefed the retrofitting scheme,equipment configuration and type selection etc.of electrostatic-baghouse integrated precipitation system,and separately analyzed the performances and characteristics of electrostatic zone,baghouse zone,bypass system,pre-dedust deveice and control system.Before and after retrofitting the main parameters of inlet and outflet flue gases of precipitator were measured and tested,this system had high precipitation efficiency,energy-saving,steady operation and on-line repair etc.advantages.
The process of the regenerable CaO adsorbing CO_2 during calcium-based sorbents pyrolysis/carbonation cycles is one of the efficient ways to capture CO2 from coal-fired power plants.CaO calcined from limestone exhibits a sharp decrease in carbonation conversion due to sintering as the number of carbonation/pyrolysis cycles increases.So it was proposed that calcium-based sorbents were modified with three kinds of solvents including ethanol water solution,acetic acid solution and KMnO4 water solution to improve CO_2 adsorption capacity of CaO during long-term pyrolysis/carbonation cycles.The results show that the ethanol water solution and acetic acid solution modifications obviously increase cyclic carbonation conversion of CaO,and its anti-sintering performance is also enhanced,as well as the specific surface area and pore volume of CaO are significantly increased.The cyclic conversion of sorbent modified with KMnO4 solution is also improved because the active material decomposed from KMnO4 catalyses the carbonation reaction of CaO.The experimental data show that shells are proved to be feasible as a CO_2 sorbent.The modified calcium-based sorbent and shells are new and efficient CO_2 sorbents for industrial applications.
The selection of grounded neutral system is the one of key problem in 20 kV distribution network retrofit.The paper gave the characteristics and its suitable scope of 3 kinds of grounded neutral system for distribution network such as non-grounded neutral system,neutral grounded through arc suppression coil and neutral grounded through little resistance.The statistics of outgoing line type for 10 kV and 35 kV substation were made in Jiangsu province such as overhead transmission line,cable line and hybrid line.The selective schemes of grounded neutral system were given for the different outgoing line type of 20 kV distribution network,which can be as reference for retrofit of 20 kV distribution network in Jiangsu province.
The paper introduced a kind of partial discharge (PD) measuring system for high voltage cables and its application in Beijing. The PD Check developed by TechImp Co. realized the separation and identification of discharge pulse. Whole pulses was taken in using a high-speed broad band sampling system at first, then discharge pulses were separated from noises by character which was calculated from pulses, and discharge types were ascertained at last. Tests in lab and fieldwork show that this system can effectively and accurately detect insulation flaws in the electric devices.
The paper, with the fourth phase project of Huadian International Zouxian Power Plant as example,detailed the features and control scheme of feedwater control system of ultra-supercritical pressure 1 000 MW generating units.In order to improve the reliability of control system,the following measures were adopted:to decrease the intermediate interfaces, to optimize the protection loop,and to put forward the problem of needing to further optimize the system.
The galloping of overhead transmission line is severely calamitous in China.The transmission line galloping is getting more seriously with the development of power grid construction,as well as the catastrophe meteorological condition's frequent appearance, threaten seriously to power grid operation.The characteristics of galloping in China,especially the newly ones appeared in recent years,were analyzed.Domestic electric researchers have carried out considerable and fruitful research works on transmission line anti- galloping,and the anti-galloping techniques applicable to China power grid have been established.The techniques,such as avoiding, withstanding,and preventing,are all-around and involved in the line designing,constructing,and running stages.The preventing techniques are mainly presented here on the emphases of the analysis on the anti-galloping devices suitable to different voltage and characteristics transmission lines.
Malleable cast ironware produces hysteresis and eddy current loss under alternating current in transmission!line. Non-magnetic steel material is developed by the ways of technical energy saving, half-year actual test of contrast test and operation in network for energy saving ironware detected by test research institute has been proved to be good in energy saving, in order to popularize in transmission line, partial fittings of original malleable cast ironware of operation line is obstructed by magnetic circuit, which made energy saving reconstruction in transmission line has better maneuverability
