风机调速系统在静电除尘器中的应用

采用可编程逻辑控制器和变频器构成的风机调速系统可以使风机平稳起动,减小了起动时大电流对电网的冲击,延长了设备的使用寿命;同时能更精确地控制除尘器运行时电场内部的压力,有效避免压力波动剧烈,为除尘器的安全高效运行提供了保证。以某铝业公司沥青烟气净化静电除尘器风机调速系统为例具体介绍了系统设计、硬件选型、电路设计等,并对节能效益进行了评价。     

Numerical simulation of three-dimensional electrohydrodynamics of spiked-electrode electrostatic precipitators

The three-dimensional flow interaction between the primary flow and the secondary flow (often called an electric wind or ionic wind) for tuft/point corona in the wire-duct type electrostatic precipitators (ESPs) has been investigated in the past. This study was further extended to incorporate the alternately oriented point corona on the wire-plate type electrodes, which are commonly used for the industrial ESPs. The secondary flow distribution without gas flow consists of a pair of long-elliptic and circulatory cells between spikes points along the wire. However, the flow rotation between spiked points is the same direction, which is opposite to that of the point corona electrode. The flow interaction is described using dimension-less number, N/sub EHD/, which is the ratio of the ionic wind velocity to the primary flow velocity. When the primary flow exists, a pair of long-elliptic spiral flows is formed in the direction of the gas flow between ground plates. When the relative distance between the spike point spacing and the wire-to-plate spacing (or the ratio of S/sub z//d) is greater than 0.17, the organized long-elliptic spiral flow is formed. When S/sub z//d is less than 0.1, the organized spiral flow is diminished, resulting in turbulence.     

燃煤电厂静电除尘器改造方案

随着我国环保标准日益严格，很多燃煤电厂静电除尘器已不能满足排放标准的要求，需进行改造。该文首先分析了造成静电除尘器除尘效率低下的主要原因；提出3种改造方案：增加电场；改造为袋式除尘器；改造为静电袋式复合除尘器。并从技术性能和经济性2个方面对3种改造方案进行了比较．以郑州热电厂200MW机组静电除尘器改造为例对3种方案进行了对比分析．结果表明：改造为静电袋式复合降尘器的方案是静电除虫器改造的最佳方案，并认为静电袋式复合除尘是我国除尘技术来来的发展方向之一。     

新型高效静电除尘器在火力发电厂输煤系统中的应用

通过对火力发电厂输煤系统3种除尘方式在设备初投资、长期运行费用以及维护管理的繁简程度方面进行比较,认为在火力发电厂输煤系统中采用新型高效静电除尘器除尘不仅能大大地提高除尘效率．节省劳动力,并且设备运行的可靠性、稳定性和自动化程度也较高。     

Enhanced precipitation efficiency of electrostatic precipitators bymeans of impulse energization

To assess the benefits of impulse energization with different coals, experimental industrial research was performed at a 70 MWe thermal power plant. Two technologies for impulse power supplies were tested over 10000 h of operation. The results of the tests, performed according to ASME standards, demonstrated that impulse energization has great advantages over conventional energization and ensures a collection efficiency from 99.6 to 99.9%, corresponding to emission levels below 50 mg/Nm³, with a reduction in absorbed power from about 0.5 to about 0.1 Wh/Nm³. Tests showed that with impulse energization there was a considerable decrease both in solid particulate emissions (about 90%) and in energy consumption (about 80%), as compared with conventional (AC rectified voltage) energization. Almost the same improvement was obtained when the flow rate in the experimental channel was increased to 1.8 times the nominal value, thus indicating low sensitivity to gas velocity variations. Thus, the suitability of the technology for complying with the targets set by environmental regulations, even in the presence of difficult solid particulate, was proved     

A new approach to calculation of flue gas scrubbing efficiency in electrostatic precipitators

The majority of existing approaches to computation of electrostatic precipitator (ESP) efficiency do not take into account particle reentrainment from collecting electrodes. The first attempts to take into consideration particle reentrainment were made only recently. However, the existing reentrainment models for ESP are not sufficiently substantiated. A general model, which takes into account precipitation of particles, entering the ESP inlet (direct precipitation), as well as precipitation of reentrained particles (secondary precipitation), is presented in the paper. The model describes physical processes in an ESP using three integral parameters. These parameters are direct precipitation coefficient, secondary precipitation coefficient, and reentrainment coefficient, which is the ratio of reentrained particle flux to precipitation flux. An improved technique for computation of direct precipitation that takes into account particle charge distribution function is proposed. The influence of gas flow turbulence on charge distribution function parameters, as well as on other parameters of precipitation phenomena, is taken into account. The method has low computational costs. The secondary precipitation coefficient is also computed using this method. The most difficult task is calculation of the reentrainment coefficient. We suggest using data of periodical ESP testing to determine the reentrainment coefficient. The analysis of experimental data indicates that a fly ash layer on collecting electrodes is of paramount importance. It has been shown that the flux per unit length of particles falling into hoppers is proportional to weight (thickness) per unit length of the fly ash layer. Distributions of precipitation flux, flux into hoppers, reentrained particle flux along the ESP duct, and particle penetration through the ESP are computed using experimental data. A novel model that is based on a flux balance equation for each length element of an ESP duct is presented. The model has the form of a connection between physical phenomena that take place on two successive length elements of the collecting electrode. The model qualitatively agrees with experimental data. However, correction of the secondary precipitation coefficient and the reentrainment coefficient is required for quantitative agreement. In this regard, a model of layer growth and determination of functional relations between layer weight, hopper flux, and particle penetration play a key role.     

工业用油静电净化技术研究

油静电净化技术被认为是用于高精度净化液压油等工业用油领域最有前景的技术之一。在实际应用中,静电净油设备中发生的电泳和介电电泳（DEP）现象使得纳微米级的污染物被吸附去除。本文概述了静电净油机的类型及净油机理,包括反应器的构造电场类型的影响等,并分析了它们的优缺点,最终提出了一系列产生梯度电场的设想,包括填充高介电介质和使用非平行电极板等。此外,还分析了电泳和介电电泳现象对中性杂质分子或极性胶体污染物的加速吸附作用。     

Features of electromagnetic processes in high-voltage power supplies with a series resonant inverter

Electromagnetic processes in high-voltage power supplies (HVPSs) based on a series resonant inverter are considered. It is shown that the analysis of a switching process in these devices should take into account the magnetizing inductance of the high-voltage transformer and capacitance of its windings. In order to decrease the dynamic losses in power semiconductor devices, the operating conditions were found and quantitative dependences between parameters of the HVPS were revealed by means of the developed HVPS mathematical model. The study results have been used in development of series of HVPSs for high-power electrophysical installations.     

高压电力电容器典型缺陷的静电场仿真研究

缺陷的几何形状,材料的基本参数及空间电荷的分布,都影响着局部放电发生的机理与参量.为了研究高压储能电容器的局部放电现象,从绝缘材料的典型缺陷出发,讨论局部放电与缺陷的关系.     

发电厂不同厂用电环并操作问题

具有不同电压等级高压母线的电厂,在发生6 kV厂用电环并切换时将形成高低压环网并产生环流,其大小主要取决于环网断口两侧电压相量差,两侧电压幅值差直接影响无功环流大小,两侧电压相位差直接影响有功环流大小.以某具体电厂为例,使用BPA程序建立计算模型,分析了不同运行方式下高低压环网中环流的大小及其影响.在高低压母线间联络变压器投运下,断口两侧电压之间主要是幅值差,将产生较大的无功环流;在高低压母线间联络变压器退出运行下,断口两侧电压之间主要是相位差,产生较大的有功环流.通过调节变压器分接头可以减小引起无功环流的电压幅值差;有功环流的调整相对较困难,为了防止较大的有功环流必须避免高低压联络变压器退出运行情况下进行环并操作,也可以通过采用移相器等措施调整相位以减少有功环流.     

单片微机在高压脉冲充磁机中的应用

目前充磁机普遍采用专用可控硅模块控制或PLC设计控制电路。单片机具有体积小、功耗低、控制能力强、扩展灵活及使用方便等特点。为了使充磁设备更加数字化、智能化,方便远程操作和保存测试数据,采用单片机设计充磁机控制电路,给出了设计思路、关键要点及其程序控制的基本流程。     

考虑历史洪水的混合分布对不同尾型分布的应用对比研究

考虑历史洪水的混合分布(Historical Flood Concerned Mixed-distribution Method,HFCMM)非一致性洪水频率分析克服了样本序列长度和传统方法不考虑物理成因的不足。以武江坪石和犁市站为例,采用考虑历史洪水的L矩法估参,构建了武江非一致性年最大实测流量序列混合分布模型,并对比了厚、薄、混尾三类不同尾型分布拟合混合分布水文频率曲线的不同应用结果。结果表明:1采用不同尾型分布拟合所得水文频率曲线相对于传统结果皆存在高水尾端上翘;2厚尾分布和三参数混尾分布能在高水端提高拟合优度,而二参数混尾分布不能明显提高高水拟合效果;3采用薄尾分布拟合样本所得水文频率曲线的低水端易上翘,混合分布处理非一致性洪水序列时不宜采用薄尾分布;4HFCMM厚尾分布与三参数混尾分布相对于传统皮尔逊三型更适用于武江流域洪水频率分析。     

基于不同检测方法的高压电流互感器误差比较与分析

目前对高压电流互感器的误差检测有多种方法,但缺乏对各检测方法所得误差结果差异性和准确性的比较分析。采用单相检测法检测电流互感器误差、考虑电压对电流互感器误差的影响计算电流误差的综合绝对值、额定电压下检测电流互感器误差3种检测方法分别对高压电流互感器的误差开展检测和比较分析,并对其差异原因进行了理论分析。结果表明,电压会使电流互感器的比差和角差向负方向偏移,当电流较小(特别是20%额定电流以下)时,电压对电流误差影响较大,随着电流增大,其影响逐渐减小直至可以忽略;低压下测得的电流互感器误差在电流较小时不够准确,电流误差的综合绝对值远大于在高压下直接测得的电流误差,对高压电流互感器的误差检测宜采用在额定电压状态下直接测量的方式。     

Electrical breakdown in high-voltage winding insulations of different manufacturing qualities

Due to an increasing demand for new, or the refurbishment of power stations, high-voltage rotating machines continue to play a significant role in generating electrical energy. An important component of these machines is their electrical insulation. Although much research has been done to improve the material, about a quarter of all failures still are related to insulation problems. Research to improve winding insulation is very complex because a large number of factors influence insulation life, among them the raw materials, size of the mica tapes, geometrical characteristics of the bar and taping- or manufacturing techniques. The results show that electrical tree propagation is the main electrical degradation mechanism that leads to breakdown of the main wall insulation and that poor impregnation of the insulation and type of taping can reduce time to breakdown significantly.     

PLC在高压断路器控制中应用

针对高压断路器控制及信号回路二次接线较复杂的情况,改进控制方法,利用可编程逻辑控制器PLC(Programmable Logic Controller)实现对其控制。以单相高压真空断路器为例,改进断路器二次接线,设计了控制程序,实现断路器的分、合闸操作及正常信号的显示,以及自动跳闸后的事故信号动作显示,并实现控制电路的闭锁要求。采用PLC控制,元件数量及种类减少,简化了二次接线,故障查找及修改二次接线容易,同时提高了控制的可靠性,简化了操动机构。     

工业内窥镜应用于变压器短路故障综合诊断实例

变压器故障情况的准确诊断,对制定变压器检修方案及对策至关重要。文章介绍了一台220kV主变压器绕组变形的现场综合诊断实例,采取以工业内窥镜视频窥视为主,结合短路阻抗试验、绕组频响特性试验及绕组电容量测试结果对变压器进行综合诊断,最终确定变压器低压绕组严重变形,建议将变压器返回生产厂家修理。     

高压断路器防跳回路的应用及问题探讨

针对电力工程中保护装置、断路器及操作箱型号多样、设计不统一,导致现场调试中断路器本体机构箱的防跳回路与保护装置操作箱的防跳回路无法配合、无法重合闸的问题,一般采用解除操作箱防跳回路的方法。对常见的操作箱和断路器本体防跳回路并联防跳和串联防跳二选一的设计原则讨论后,提出在同时保留操作箱和断路器本体防跳回路的情况下,采用合闸监视回路中串入断路器的常闭辅助触点的方法,确保防跳断路器不会经过合闸监视回路自保持,不会出现无法再次合闸或跳、合闸监视灯同时亮的现象。该方法已在实际中应用并证明防跳功能是正确、可靠的。     

光纤布里渊传感系统在高压电缆检测中的应用

电力电缆线路运行温度和应变的在线监测是保障电力系统安全与稳定的必要措施。文章介绍了光纤布里渊传感器的测量原理,深入地分析比较了传统传感器与分布式传感器的性能,得出光纤布里渊传感器具有检测和定位精度高、受环境影响小、可长距离分布式测量等优点,并探讨了该技术在高压电缆检测方面的应用方法及应用前景。     

高压开关设备技术方向探讨

近几年,随着我国电网新增装机容量的快速增长,输配电设备市场快速增容。但我国电网建设一直滞后于电源建设,电网与电源投资的比例为33％／67％,而国外为60％／40％,电网建设欠帐较多。这次拉动内需,国家对电网建设加大了投资,对改善这种状况具有积极意义。随着西电东送、区域电网联网、高压进城等工程的推进,加上全球大气温室效应提升,环境污染加重,电网建设对相关产品的技术水平有了新的要求。     

高压变频调速技术在发电厂中的应用

针对电厂风机或水泵等辅机系统采用阀门、挡板调节管路流量而造成大量电能资源浪费问题,结合水泵或风机变频调速节能控制原理,提出利用变频调速方案对电机控制系统进行节能升级改造。结合电厂3#机组一次高压风机系统实际情况,探讨高效可行的电机变频调速节能升级改造方案。3#机组一次风机改造后1年运行反馈数据分析结果表明,变频调速技术通过动态调节电机转速来控制流量降低轴功率,具有非常良好的节能效果,同时改造方案降低电机起动电流和起动次数,避免频繁起动对电机和电网的冲击破坏,具有广阔的推广应用前景。