Research Progress of On-line Monitoring Technology for Electromagnetic Environment of Power Transmission and Transformation Projects

Based on the collection of relevant literature and cases,the research and application status of on-line monitoring technology for electromagnetic environment of power transmission and transformation projects at home and abroad were introduced.Moreover,the problems existing in the on-line monitoring of electromagnetic environment were expounded,and the development prospect was forecasted.

High Precision Ultrasonic Guided Wave Technique for Inspection of Power Transmission Line

Due to the merits of high inspection speed and long detecting distance, Ultrasonic Guided Wave(UGW) method has been commonly applied to the on-line maintenance of power transmission line. However, the guided wave propagation in this structure is very complicated, leading to the unfavorable defect localization accuracy. Aiming at this situation, a high precision UGW technique for inspection of local surface defect in power transmission line is proposed. The technique is realized by adopting a novel segmental piezoelectric ring transducer and transducer mounting scheme, combining with the comprehensive characterization of wave propagation and circumferential defect positioning with multiple piezoelectric elements. Firstly, the propagation path of guided waves in the multi-wires of transmission line under the proposed technique condition is investigated experimentally. Next, the wave velocities are calculated by dispersion curves and experiment test respectively, and from comparing of the two results, the guided wave mode propagated in transmission line is confirmed to be F(1,1) mode. Finally, the axial and circumferential positioning of local defective wires in transmission line are both achieved, by using multiple piezoelectric elements to surround the stands and send elastic waves into every single wire. The proposed research can play a role of guiding the development of highly effective UGW method and detecting system for multi-wire transmission line.

Towards a (More) Electronic Transmission and Distribution (eT&D)

The challenges and the path towards a(more)electronic transmission and distribution(eT&D)is presented in this paper.The challenges are first identified together with key stakeholders in the drive for grid modernization.A fundamental question is then asked about the investment priority.Six basic characteristics are reviewed,leading to the composition of structured microgrids as the basic functional cell of a modern grid.One example of fractal radial structure and one fractal meshed structure are presented.The likely evolution path is then proposed together with basic technology sets.Specific foundation technologies are discussed in detail,including adiabatic power conversion,3MC technology,medium voltage conversion,distribution-level electronic power transformer and FACTs hardware integration,and back-to-back converters as a universal interconnect element.The rapidly emerging on-wire sensing technology is also discussed.It is pointed out that the distribution-level large electronic power transformer will provide a key component to enable hybrid ac/dc grid flow control and ancillary support for a flexible electronic transmission and distribution(eT&D)systems.

柔性低频输电系统的主变稳态负序差动保护

为了解决常规纵差保护难以适用于低频系统的问题,通过分析低频系统的序分量抑制策略,并根据低频系统故障进入稳态后单侧有负序注入的特征,提出一种基于稳态负序分量的主变差动保护方法。为防止该差动保护在区外故障时因电流互感器饱和出现误动,通过对比分析三类制动电流计算方式的制动性能,得到了差动保护的制动方程和制动系数。为解决励磁涌流、电流互感器断线可能导致误动的问题,提出了相电压突变量的差动保护开放条件。仿真分析表明,该方法能够灵敏反映区内金属性故障及轻微故障,在区外故障伴随电流互感器饱和时有可靠的制动裕度。

Research on the risk-evaluation model of power transmission and transformation projects based on multilevel fuzzy-thought weighting for cloud-model improvement

The risk evaluation of power transmission and transformation projects is a complex and comprehensive evaluation process influenced by many factors and involves many indicators.In order to solve the uncertainty and fuzziness problems in the process of the multilevel fuzzy risk evaluation of power transmission and transformation projects,this paper introduces the cloud theory,which is specialized in the study of uncertainty problems and constructs the multilevel fuzzy comprehensive risk-evaluation model of power transmission and transformation projects based on the improved multilevel fuzzy-thought weighting based on the cloud model.Finally,the risk of the Beijing 220-kV Tangyu power transmission and transformation project is evaluated and the feasibility of the evaluation model is verified.The results of the evaluation and the evaluation layer cloud model are combined with MATLAB simulation to show that the risk level of the project is between large risk and general risk.

Prediction model for cost data of a power transmission and transformation project based on Pearson correlation coefficient-IPSO-ELM

In view of the difficulty in predicting the cost data of power transmission and transformation projects at present,a method based on Pearson correlation coefficient-improved particle swarm optimization(IPSO)-extreme learning machine(ELM)is proposed.In this paper,the Pearson correlation coefficient is used to screen out the main influencing factors as the input-independent variables of the ELM algorithm and IPSO based on a ladder-structure coding method is used to optimize the number of hidden-layer nodes,input weights and bias values of the ELM.Therefore,the prediction model for the cost data of power transmission and transformation projects based on the Pearson correlation coefficient-IPSO-ELM algorithm is constructed.Through the analysis of calculation examples,it is proved that the prediction accuracy of the proposed method is higher than that of other algorithms,which verifies the effectiveness of the model.

基于暂态特征参数的数字式非接触负载测量研究

无线能量传输系统暂态过程中的高阶非线性问题是负载测量和辨识的一个难点,在处理由于高阶非线性出现的拍频信号时,现有模拟包络检波方法存在信号易失真、电路灵活性差以及测量范围有限等问题。针对此,提出基于希尔伯特变换的数字包络检波方法。在希尔伯特变换的基础上,设计数字包络检波器,提取电压拍频信号的包络线,并通过仿真和实验对所提方法进行验证,结果表明:对于不同待测负载,该方法均能够准确提取电压拍频包络线,实现负载阻值1~2000Ω范围内误差小于5%的测量。该方法拓宽了基于暂态特征参数的非接触负载测量的范围,为无人机等飞行器电池内阻的测量提供了新思路。

0.2~2.0GHz100W超宽带GaN功率放大器

设计并实现了一款基于0.25μm GaN高电子迁移率晶体管(HEMT)工艺的100 W超宽带功率放大器。基于SiC无源工艺设计了集成无源器件(IPD)输入预匹配电路芯片;设计了基于陶瓷基片的T型集成输出预匹配电路;基于建立的传输线变压器(TLT)的精确模型,设计了宽带阻抗变换器,在超宽频带内将50Ω的端口阻抗变换至约12.5Ω,再通过多节微带电路与预匹配后的GaN HEMT芯片实现阻抗匹配。最终,以较小的电路尺寸实现了功率放大器的超宽带性能指标。测试结果表明,功率放大器在0.2~2.0 GHz频带内,在漏极电压36 V、输入功率9 W、连续波的工作条件下,输出功率大于103 W,漏极效率大于50%,输入电压驻波比(VSWR)≤2.5。

直流偏磁对500 kV变压器振动特性的影响分析

特高压直流工程单极-大地回路运行时,直流电流侵入大型变压器绕组,致使变压器振动加剧。为了深入了解直流偏磁对大型变压器振动特性的影响,分析了变压器的振动机理及直流偏磁的影响机制。在白鹤滩—江苏±800 kV特高压直流输电工程调试期间,对500 kV三相变压器的中性点电流、振动信号进行了实测,量化了直流偏磁程度,分析了不同直流偏磁程度下变压器振动信号时域及频谱特征。提取了波形畸变比、奇偶次谐波能量比、累计能量占比、功率谱熵等特征量来分析直流偏磁对大型变压器振动特性的影响。结果表明:直流偏磁导致波形畸变,1个工频周期内2个半周期对应的振动波形不再对称分布;随着直流偏磁程度增加,振动信号主频分量改变,50 Hz倍频谐波分量增多,其中50 Hz奇次谐波增幅要大于偶次谐波,且影响主要集中在600 Hz以内;由于铁心饱和作用,直流偏磁增大到一定程度时,磁不平衡性降低,振动信号复杂度不再增加。

基于博弈论组合赋权和改进优劣解距离法的输变电工程建设时序规划

针对输变电工程建设时序有待优化的问题,对输变电工程建设优先级评价方法进行了研究。首先,从必要性、经济性、效率性、环保性4个维度出发,构建输变电工程建设优先级评价指标体系;然后,基于博弈论的思想将分别通过序关系分析法和指标相关性权重确定法求得的主客观权重进行结合,引入灰色关联分析法对基于组合赋权的优劣解距离法进行改进,构建输变电工程建设优先级评价模型;最后,对某省电网规划项目库中4个拟建220 kV输变电工程进行建设优先级评价并展开建设时序规划。结果表明:所提出的评价方法适用性较强,能够有效辅助电网基建规划。

基于三维模型的输变电运维业务应用开发及实践

三维模型可拓展信息记录与展示的维度,极具应用潜力,已在电力规划、建设、运维等多个环节初步发挥作用。如何更好地应用三维模型,成为行业关注的热点和难点。该文首先梳理总结三维模型在输变电运维场景的传统典型应用,然后从时、空2个维度剖析当下三维模型应用开发不足及与数字孪生技术融合的价值潜力,提出数字孪生三维模型应用路径,最后结合场景给出若干新应用开发建议。研究成果可为明晰三维模型的应用开发提供参考。

具有可变增益恒压特性的双线圈无线电能传输系统补偿网络设计与分析

为了实现具有恒压特性的双线圈无线电能传输(WPT)系统中补偿网络的优化设计,该文在变压器T网络模型基础上定义等效耦合系数kr与等效变比n1,为双线圈WPT系统的高阶补偿网络设计与分析提供一种新方法。首先建立变压器T网络等效模型,给出具有恒压特性的串联-串联(S-S)型双线圈WPT系统元件参数表达式。其次结合等效耦合系数与等效变比,提出具有可变增益恒压特性的串联/并联-串联(SP-S)型与串联/并联-串联/并联(SP-PS)型双线圈WPT系统的补偿网络参数确定的新方法。在此基础上,考虑寄生电阻对系统传输特性的直接影响,以WPT系统的电压增益稳定性与传输效率为指标,得出不同等效参数下传输特性表达式,推导出在线圈偏移情况下最佳等效参数kr与n1的表达式,为WPT系统的补偿网络的优化设计提供理论依据。最终通过实物实验验证所提系统的恒压输出特性及其参数设计方法的正确性和有效性。

基于平行双线结构的低频场发生器设计

针对电磁辐射抗扰度测试天线在低频时辐射效率低、体积大、难以生成高电场强度的问题,设计了一款平行双线传输线电场发生器。该场发生器输入端使用阻抗比为1∶4的传输线变压器巴伦,实现了输入端与负载的阻抗匹配,以及非平衡端转化为平衡端;为保证场发生器电气性能的稳定性和可靠性,平行双线传输线采用直径为100 mm的铜管,负载采用耐大功率的无感陶磁电阻,能够承受2 500 W的连续波输入功率。实验结果显示该场发生器在10 kHz~100 MHz的频率范围内电压驻波比均小于1.9,在距场发生器中心0.5 m远处可产生高达200 V/m的电场强度,在1 m远处可产生50~100 V/m的场强。该电场发生器可旋转改变电极化方向,具有覆盖范围广、场强分布均匀、场强幅度高的特点,广泛应用于低频辐射抗扰度测试。

极端气象条件下基于深度学习网络特征的变压器故障预测

根据极端气象条件下变压器产生故障时的环境参数,结合变压器故障预测中常用的油中溶解气体的含量,提出一种基于深度学习网络的故障预测方法。针对已有的变压器故障诊断方法泛化能力弱、时效性低、精度低等缺点,引入极端气象参数,并通过对多组数据序列进行时因分析,提取数据随着时间的变化关系;其次,设计一种新型的神经网络,将油气参数与极端气象参数的时间特征融合,并通过深度学习网络进行故障分类与预测。仿真实验结果表明,相比于其他传统故障预测方法,所提出的极端气象条件下基于深度学习网络的变压器故障预测方法准确率有显著提高。

输变电工程表土剥离技术指标研究

表土是植物赖以生存的表层土壤,表土剥离和保护是水土保持的重要任务,研究输变电工程表土剥离厚度指标对指导绿色电网建设具有重要意义。将白鹤滩—江苏±800 kV特高压直流输变电工程沿线不同区域土壤有机质含量实测值与根据90 m分辨率全国土壤有机碳分布数据集得到的有机质含量预测值进行对比分析,发现预测值具有良好的可靠性,可以作为表土剥离等级划分的依据。将90 m分辨率全国土壤有机碳分布数据集参照全国第二次土壤普查中土壤有机质分级标准划分出土壤养分等级,利用ArcGIS软件绘制出全国范围的土壤养分分级图及表土剥离分级图,并参照表土利用方式确定出表土剥离厚度,即:有机质含量<10 g/kg的地区,土壤养分等级为5~6级,表土的剥离等级为2级,对应的剥离厚度为20~30 cm;而有机质含量≥10 g/kg的地区,土壤养分等级为1~4级,表土的剥离等级为1级,对应的剥离厚度根据需要加深10~20 cm。同时,针对水土保持区划一级区的表土剥离分级和水土保持功能,提出了适宜的表土剥离建议。

基于AHP-熵权法的输变电工程低碳评价体系及方案优选

“双碳”目标要求下,输变电工程项目向节能减碳方向发展势在必行。为掌握输变电工程减碳与成本及效益之间的本征关系,建立输变电工程成本效益评价指标体系。运用层次分析法(analytic hierarchy process,AHP)确定各项指标对成本及效益的影响权重,再采用熵权法对指标权重进行标准化及客观化修正,之后对每种技术方案选取1000个采样点进行敏感性分析,从而建立起较为完善的输变电工程综合评价体系。基于所建立的指标体系与数学模型对110 kV和220 kV案例进行分析,所得准则层与指标层误差均不足10%。随后提出8种备选减碳方案,逐一计算该8种方案全生命周期净现值与现金流,并对方案综合评分。最终得出结论:准则层中权重占比最高的为“新型变压器”技术,指标层中权重占比最高的为“变压器负载损耗”,且依据方案7改造有望以较低成本实现较高效益。

基于AI技术的输变电脆弱线路自动识别与控制应用

输变电系统是电力输送的重要纽带,为了降低运维成本和提高识别效果,提出一种基于AI技术的输变电脆弱线路自动识别与控制应用方法。利用人工智能技术(AI)的决策树贪心算法(ID3)度量线路不同运行特征之间的信息量,得到线路特征,引入互信息特征选取(MIFS)优化决策树,利用调节系数和惩罚项平衡线路运行特征间的冗余度,并且引入加权度数,衡量节点权重并重点考虑所有连接线路的有功总量。在综合分析电纳介数和加权度数等指数前提下得到综合的脆弱线路自动识别指标,建立识别模型,最后改变输变电线路的潮流传输及负载变化实现控制。实验证明所提方法能够准确识别出脆弱线路位置,方法有效可行,其控制应用也有效降低了运维成本。

220 kV输变电工程线路施工技术分析

电力工程和建设项目有着很大的区别,为了保证输电线路的正常运转,必须对输变电工程线路施工技术进行讨论和研究,并对技术的保障措施进行归纳,保证建设的高效进行。与此同时,在企业的经营方式上,建立健全管理机制、检查制度,加大技术研发的投入,以此来提高企业的日常运营和维修工作的效率和技术水平。因此,该文着重对220 kV输电线路的建设中应注意的问题进行探讨。

面向输变电场景的无线传感网通信性能测试研究

无线传感网在输变电设备状态监测领域的应用,能够有效提升电网运行效率,实现更高的经济价值和社会效益。通过分析无线传感网在输变电场景下的通信特征,提出通信性能测试方法,构建闭环测试平台,对无线传感网的接入容量、组网性能等关键指标开展测试验证。结果表明,所提测试方法能有效评估无线传感网的终端接入、数据传输能力,可为无线传感网在电力系统的推广提供技术支撑。