110kV变压器常存在的问题分析与处理

针对110 kV变压器试验中常存在的问题,结合实例,通过套管的介损和电容量的现场测试及变压器套管结构的分析,发现套管顶端部件接触不良是引起介损严重超标的主要原因,以及有载调压开关接触点氧化造成直流电阻不合试验规程要求,针对性地提出了主变压器套管介损和绕组直流电阻现场测试和处理方法。     

TEMP-500IU型CVT现场预试方法

对于电容单元C11、C12采用常规正反接线法进行电容、介损值测量;对于电容单元C13、C2通过操作中间变压器高压端外部的操作把手合上中间变压器一次绕组首端接地刀闸,实现采用反接法测试它们的电容及介损值．克服了采用自激法测试存在的弊端,同时阐述了该型CVT特殊接线方式的中间变压器一次绕组对二次绕组及地的电容、介损值的测量接线方法及注意事项。     

110kV同塔三回输电线路异常雷击同跳故障机理分析及防护

为分析同塔非对称排列三回输电线路异常雷击同跳故障机理,以华东电网一条110kV非对称排列三回输电线路异常雷击同跳故障为例,分析了故障产生原因为雷电反击;再分析了雷击时刻各相绝缘子电压分布,研究了不同雷电流下闪络情况,找到了造成异常三回同跳的原因,并提出防止多回同跳的措施。结果表明,由于工频电压叠加作用,使得各相绝缘子电压分布不一致,B相电压较低无法闪络,#1回A相因工频电压较低难以建弧,#2、#3回A、C相耐受电压在临界击穿电压附近,造成部分相击穿并闪络,部分相未击穿或无法成功建弧;降低接地电阻、架设耦合地线、改变相序排列及布设避雷器等措施可有效降低故障发生概率。研究结果为110kV非对称同塔三回线路防雷改造提供指导。     

XLPE表面缺陷对电场及击穿电压的影响

电缆中间接头施工过程中易造成XLPE表面划伤、附着污染颗粒和表面受潮三种缺陷,为评估缺陷对接头运行性能的影响,建立了电缆中间接头XLPE绝缘片状模型,分析了不同缺陷下电场的变化,探究了不同缺陷对电场及击穿电压的影响程度。结果表明,XLPE在划伤时划痕处的电场产生严重畸变,为非划痕处的1.6倍;受潮时XLPE表面附着污染水中导电杂质越多,污染水的电导率越高,从而使其导电性能增强,电场强度变大,是同界面处非受潮部分的1.22~1.40倍;XLPE表面附着污染颗粒时,颗粒与其交界面处电场发生较严重畸变,是同界面无缺陷时的1.50倍左右,划痕对XLPE绝缘的电场影响最严重。通过试验结果显示正常无缺陷时的击穿电压为129.6kV,划伤缺陷的击穿电压为59.1kV,受潮缺陷的击穿电压为69.7kV,杂质缺陷的击穿电压为59.2kV,划痕对XLPE绝缘的击穿电压影响最严重。研究成果为探究不同缺陷对电缆中间接头XLPE绝缘性能的影响提供了重要依据。     

特高压试验研究再创两项世界纪录

2007年9月12日上午,国家电网公司特高压直流试验基地。随着特高压交直流户外试验场一道亮光闪过,2400kV操作冲击电压击穿了±1000kV等级直流输电线路模拟杆塔塔头的空气间隙,该试验属世界首创,试验取得圆满成功。随后,已经带电±800kV运行的特高压双回直流试验线段成功升压至±1200kV,设备和线段一切正常,开始稳定运行。两项试验的成功,标志着国家电网公司特高压直流试验基地冲击试验和升压试验再创两项世界纪录。     

微间距气压对场致发射影响的分析与计算

为研究微米间隙中气体的击穿特性,在3～100μm间隙距离中进行1～100 kPa可变气压的放电试验。试验发现10μm以下间距击穿电压曲线偏离巴申曲线,固定间距只改变压强时,击穿电压随气压的变化与较长间隙不同,3～5μm间距的击穿电压会随气压升高而降低。通过求解阴极附近离子数密度公式,发现微间距条件下阴极附近有较高的离子数密度,离子数密度会随气压的升高而增加,随间距增大而减小。离子数密度越高,在阴极表面附近形成离子附加电场就越强,与外电场耦合后促进场致发射,击穿会更易发生。计算了离子增强场效应系数γ’,并将其与Townsend二次发射系数γ对比,发现离子增强场效应对5μm以下的间隙放电影响最强烈,随间距的增加其影响逐渐减弱,10μm后击穿过程可用Townsend理论来解释。     

基于综合分析法的110kV变压器故障判断

通过一例110kV变压器状态检修后发现的电容量异常,对变压器停运后进行绕组变形测量、电容量测量、局放、绝缘油色谱等诊断性试验项目的综合分析、并与历年例行试验数据对比,准确判断了故障原因,通过变压器吊罩准确地印证了分析结果,为变压器故障原因查找提供了典型案例。     

35kV干式空心并联电抗器切断过电压抑制装置设计及仿真研究

断路器分闸产生的过电压是引起干式空心并联电抗器匝间绝缘老化、击穿的重要因素之一。为抑制过电压对35 kV并联电抗器造成的损害,设计了一种阻容式过电压抑制装置,通过理论计算选择出抑制装置的电容和电阻值。采用MATLAB软件对不同截流电流值下过电压抑制装置的保护效果进行了仿真验证,仿真结果表明可有效抑制过电压;通过可靠性试验验证了装置样机运行的安全稳定性。     

振荡水柱驱动介电弹性体采集能量多种循环分析

介电弹性体是一种超弹性绝缘材料,薄膜上下表面敷上电极,其发电过程相当于可变电容。将振荡水柱波浪能转换装置与介电弹性体相结合,利用介电弹性体的电容行为将机械应变能转换为电能,所产生的电能主要取决于系统结构和介电弹性体材料参数以及所使用的能量收集循环模式。基于线性波和势流理论、流体动力学理论建立波浪驱动介电弹性体电弹性形变发电模型,分析振荡水柱式波浪能转换装置气室内空气压强驱动介电弹性体形变和由此引起电容变化情况。应用介电弹性体发电理论分析恒电荷、恒电压、恒电场3种能量收集循环模式对振荡水柱波浪能采集发电特性的影响,结果表明：介电弹性体材料的输出能量随着波浪周期、振幅的增大而增大,随着振荡水柱气室放置处水深和前墙开口的增大而增大,随着介电弹性体薄膜的半径增大而增大,随着薄膜厚度的增大而减小;在恒电场发电方式下,介电弹性体能够产生最大能量。     

特高压试验研究再创两项世界纪录

2007年9月12日上午，国家电网公司特高压直流试验基地。随着特高压交直流户外试验场一道亮光闪过，2400kV操作冲击电压击穿了±1000kV等级直流输电线路模拟杆塔塔头的空气间隙。该试验属世界首创，试验取得圆满成功。随后，已经带电±800kV运行的特高压双回直流试验线段成功升压至±1200kV，设备和线段一切正常，开始稳定运行。两项试验的成功，标志着国家电网公司特高压直流试验基地冲击试验和升压试验再创两项世界纪录。     

Aging and failure mode of electrochemical double layer capacitors during accelerated constant load tests

Electrochemical double layer capacitors of the BCAP0350 type (Maxwell Technologies) were tested under constant load conditions at different voltages and temperatures. The aging of the capacitors was monitored during the test in terms of capacitance, internal resistance and leakage current. Aging was significantly accelerated by elevated temperature or increased voltage. Only for extreme conditions at voltages of 3.5 V or temperatures above 70 °C the capacitors failed due to internal pressure build-up. No other failure events such as open circuit or short circuit were detected. Impedance measurements after the tests showed increased high frequency resistance, an increased distributed resistance and most likely an increase in contact resistance between electrode and current collector together with a loss of capacitance. Capacitors aged at elevated voltages (3.3 V) exhibited a tilting of the low frequency component, which implies an increase in the heterogeneity of the electrode surface. This feature was not observed upon aging at elevated temperatures (70 °C).     

Dielectric properties of Australia lignite at radio frequency

Dielectric properties (dielectric constant and loss factor) of Australia lignite were determined using an impedance analyzer and other instruments over the moisture contents of 8–48%, temperature of 25–100°C, and frequency of 1–50 MHz. Both dielectric constant and loss factor of lignite samples increased monotonically with the increase of moisture content at all temperatures and frequencies. Dielectric constant increased with the increase of frequency, and loss factor changed quadratically: first decreased and then increased. Dielectric constant increased with the increase of temperature at low moisture contents (8–28%), but it decreased at high moisture contents (38–48%), and loss factor increased with the increase of temperature at all moisture contents. The penetration depth of radio frequency energy of Australia lignite was obtained through the equation. It decreased with the increase of moisture content, temperature, and frequency.     

Temperature and dynamics problems of ultracapacitors in stationary and mobile applications

Ultracapacitors as a powerful energy storage systems are used in various areas of power electronics. Depending on the application, temperature and dynamics properties of these components have to be considered. These properties strongly depend on the characteristics of basic materials of the capacitors.The frequency and temperature dependence of the capacitance as well as of the internal resistance, ESR, is manly affected by the electrodes of activated carbon and the electrolyte. Under operating conditions differences of 15% and more of the capacitance due to a different structure of the electrodes are observed. Due to the reduced solubility of the conducting salt and the increased viscosity of the solvents for temperatures below freezing point the conductivity of the electrolyte drops drastically with decreasing temperatures. Thus, increases of the ESR between 200 and 700% between room temperature and −30 °C depending on the electrolyte are registered. Due to the slightly different selfdischarge of the single capacitors equivalent to a voltage drop of 4–12% within 3 days, the individual cell inside a module has to be protected by a cell voltage balancing unit. By an active cell voltage balancing unit connected in parallel to the capacitors a voltage drop will be leveled out after 1 h.In addition to the electrical characteristics of the ultracaps also the thermal properties of the single cell as well as of the modules have to be considered for the design in of these storage devices. By cooling elements integrated in the surface of the module casing and forced cooling the effective current load can be nearly doubled. Based on this know how ultracap modules were designed, which fulfill all the requirements of the applications in automotive and industrial electronics.     

基于差动电压的并联电容器在线监测系统设计

针对近期宁波500 kV变电站内电容器组故障率偏高的情况,发现利用传统的运行维护措施已经无法满足电网对无功补偿电容器稳定运行的要求。充分利用在线监测原理,在不需要增加或改动一次设备的情况下,针对电容器差动电压变化值,通过后台软件的功能扩展和高级应用,设计了一套并联电容器在线监测系统。该系统可实现对无功补偿电容器组的故障预警和差动电压数据查询,为设备的状态检修提供数据支持。     

Analysis of grid connected induction generators driven byhydro/wind turbines under realistic system constraints

Results of an investigation dealing with the behaviour of grid-connected induction generators (GCIGs) driven by typical prime movers such as mini-hydro/wind turbines are presented. Certain practical operational problems of such systems are identified. Analytical techniques are developed to study the behavior of such systems. The system consists of the induction generator (IG) feeding a 11 kV grid through a step-up transformer and a transmission line. Terminal capacitors to compensate for the lagging VAr are included in the study. Computer simulation was carried out to predict the system performance at the given input power from the turbine. Effects of variations in grid voltage, frequency, input power, and terminal capacitance on the machine and system performance are studied. An analysis of self-excitation conditions on disconnection of supply was carried out. The behavior of a 220 kW hydel system and 55/11 kW and 22 kW wind driven system corresponding to actual field conditions is discussed     

谐波影响下电力电容器的协调无功降损方法

传统采用退火—逐步优化算法对电力系统中的电容器,进行多形态高载荷负荷协调时,未综合考虑谐波影响下电容器的负荷状态,无法对总谐波畸变进行有效控制,降损效果差;因此提出新的谐波影响下电力电容器的协调无功降损方法,通过谐振影响下的电力电容器优化配置数学模型,综合考虑谐波影响下电力电容器电能消耗总金额和配置电容器所需的费用,获取谐波影响下电容器的电压总谐波畸变率;通过微粒群优化算法,确保各节点电压总谐波畸变率控制在规定限值以内,对电容器进行优化配置,实现电容器的无功降损控制。实验结果说明,采用所提方法优化配置后的电容器可有效抑制谐振发生,可降低约37%的电网损耗,具有节能高的优势。     

Multi-objective energy management approach in distribution grid integrated with energy storage units considering the demand response program

The penetration of renewable energy sources and energy storage (ES) units into the distribution system has increased, and it is important to examine their effect on the systems' operation scheme and security. Voltage stability index is defined as a security objective function, and its improvement by energy management in the distribution network is a major challenge in this study. The dynamic distribution feeder reconfiguration (DDFR) is introduced as an efficient approach for energy management in the distribution network, considering energy loss, voltage stability index, and operational cost as objective functions in the presence of distributed generators, solar PV panels, ES units, and capacitors. The demand response program, including interruptible/curtailable service, is proposed to enable energy consumers to rethink their energy consumption patterns based on incentive and punitive policies. A modified particle swarm optimization algorithm is presented to solve the considered optimization problem. The suggested approach is tested on the 95-node test system and its superiorities are shown through comparison with other evolutionary algorithms. Based on the obtained results, after presenting a new model based on DDFR for energy management in the distribution system, energy loss and voltage stability are reduced by 25% and 2.8%, respectively. After applying the demand response program in the proposed model, energy loss and operational cost are reduced by 26% and 5.9%, respectively.     

南宁变电站电容器组跳闸及其处理

500 kV南宁变电站在启动过程中,手动投入3号变低压侧两台电容器组后,电容器组端电压越限跳闸。文章通过对本站500 kV电压控制曲线、主变绕组额定电压、电容器投入后容升效应及电压整定值等因素的分析,说明了在正常运行方式下,3号变低压侧仅可投入一组电容器。结合运行单位的需求,分析了减少单组电容器组容量的改造方案,及改造后电容器投入条件,并校验了改造后谐振和谐波情况。最后就以上问题对具体技术和设计管理提出了建议。     

800 kV气体绝缘金属封闭开关设备的研制

分析了国内外800 kV气体绝缘金属封闭开关设备(GIS)的制造水平,详细介绍了西安西开高压电气股份有限公司800 kV GIS的结构特点及型式试验情况:800 kV GIS除断路器外其余部分均按照1 100 kV电压等级设计,有较大的设计裕度;该产品进行了整套型式试验,绝缘试验分别按800 kV和1 100 kV电压等级进行了绝缘验证,对充气套管外绝缘进行了海拔3 000m的修正试验验证;断路器具有很强的短路开断能力,可满足时间常数120 ms条件下的短路开断要求,直流分量达81%。型式试验表明,该产品完全满足我国750 kV电网对800 kV GIS设备的需要。