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.

Combined approach for analysing evolutionary power spectra of a track-soil system under moving random loads

The pseudo-excitation method combined with the integral transform method (PEM-ITM) is presented to investigate the ground vibration of a coupled track-soil system induced by moving random loads. Commonly in the track model, the rail, sleepers, rail pads, and ballast are modelled as an infinite Euler beam, discretely distributed masses, discretely distributed vertical springs, and a viscoelastic layer, respectively. The soil is regarded as a homogenous isotropic half-space coupled with the track using the boundary condition at the surface of the ground. By introducing a pseudo-excitation, the random vibration analysis of the coupled system is converted into a harmonic analysis. The analytical form of evolutionary power spectral density responses of the simplified coupled track-soil system under a random moving load is derived in the frequency/wavenumber domain by PEM-ITM. In the numerical examples, the effects of different parameters, such as the moving speed, the soil properties, and the coherence of moving loads, on the ground response are investigated.

Mitigation of Transients in Capacitor Coupled Substations Using Traditional RLC Filter Techniques

This article presents an extensive examination and modeling of Capacitor Coupled Substations (CCS), noting some of their inherent constraints. The underlying implementation of a CCS is to supply electricity directly from high-voltage (HV) transmission lines to low-voltage (LV) consumers through coupling capacitors and is said to be cost-effective as compared to conventional distribution networks. However, the functionality of such substations is susceptible to various transient phenomena, including ferroresonance and overvoltage occurrences. To address these challenges, the study uses simulations to evaluate the effectiveness of conventional resistor-inductor-capacitor (RLC) filter in mitigating hazardous overvoltage resulting from transients. The proposed methodology entails using standard RLC filter to suppress transients and its associated overvoltage risks. Through a series of MATLAB/Simulink simulations, the research emphasizes the practical effectiveness of this technique. The study examines the impact of transients under varied operational scenarios, including no-load switching conditions, temporary short-circuits, and load on/off events. The primary aim of the article is to assess the viability of using an established technology to manage system instabilities upon the energization of a CCS under no-load circumstances or in case of a short-circuit fault occurring on the primary side of the CCS distribution transformer. The findings underscore the effectiveness of conventional RLC filters in suppressing transients induced by the CCS no-load switching.

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.

A New Principle of Fault Identification of on the Same Tower Based on Traveling Wave Reactive Powers

In order to improve the reliability of fault identification of the double-circuit transmission lines on the same tower, a new algorithm for fast protection of double-circuit transmission lines on the same tower based on the reactive powers of traveling wave is proposed. With the implementation of S-transform, the initial traveling wave reactive powers are calculated and the change characteristics of reactive power under different fault conditions are studied. The protection criterion is constructed by analyzing the ratio of the reactive powers of the same end on double-circuit transmission lines and the ratio of the reactive powers at both ends on the same line. According to the ratio of reactive power on the same side of the line and both ends of the same line, it is possible to identify whether the faults of the double-circuit line of the same tower occurred in or out of the protection zone. A large number of simulation results show that the protection performance is sensitive and reliable, and quick to respond. The criterion is simple and is basically not affected by fault initial angles, fault types, and transitional resistances.

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。

数字化背景下的中国电力企业项目绩效评价与优化

随着物联网、大数据、云计算、人工智能等不断发展,电力行业的数字化转型已经发展到了一个新的阶段。电力企业在新一轮国家电改的形势下,也将面临着日益严峻的数字化市场竞争和组织内部降本增效的压力。研究以国家电网Y电力企业为例,从PMO组织级项目管理视角,建立一套整合项目管理和组织驱动相结合的战略框架体系,通过摘权法TOPSIS分析,结合DEA-Malmquist模型对该企业1149个数字信息化项目的绩效管理进行效率和效果综合评价。借鉴平衡计分卡思路,引人非财务性等组织激励性指标,运用项目绩效管理方法促进组织管理流程和业务流程优化。

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。

基于区块链数据安全机制的输变电工程建设动态计算技术研究

针对现今输变电工程施工过程中不确定性因素较多、造价计算偏向静态等问题,文章建立了基于区块链数据安全机制的输变电工程造价实时动态计算模型,实现了造价实时动态计算技术与计算结果的精准高效。文章以区块链可信数据交换技术为底层模型,利用区块链去中心化信任体系、链上数据不可篡改等特性,构建输变电工程的数据上传、交互、储存与计算的架构体系;使用粒子群算法优化径向基神经网络参数,构造输变电工程造价数据预测计算模型;采用杰卡德距离对计算结果进行校正,且在反馈误差的同时进一步优化计算模型。利用仿真算例验证了模型的先进性与可行性。

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。

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。

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。

基于三端轴式松耦合变压器的无线电能传输系统

松耦合变压器是电磁感应耦合式无线电能传输(inductively coupled power transfer,ICPT)系统中实现电能传输的重要设备。然而,松耦合变压器输出功率小、传输效率低的问题极大限制了其推广应用。提出了一种三端轴式松耦合变压器结构,分别针对该新型变压器相邻线圈对同名端同向和反向两种情况建立数学模型;然后对LCC-S补偿方式下基于三端轴式松耦合变压器的ICPT系统存在的频率分裂现象进行分析,通过仿真验证了三端轴式松耦合变压器可通过不同线圈对间的互感来提升系统的传输特性,并对同名端同向和同名端反向两种情况的输出功率和传输效率进行对比;最后通过实物实验证实了基于三端轴式松耦合变压器的ICPT系统能够提高输出功率和传输效率,同名端同向时传输效率较高,提高了16.4%;同名端反向时输出功率较高,提高了33.2%。

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。

佛山市某污水厂技改工程实例

介绍了佛山某污水处理厂技改工程的工艺流程和设计参数。在用地紧张的条件下,改造原有构筑物,新建“深度处理+超滤反渗透+浓水处理”为主体工艺的中水回用系统。实际运行结果表明,技改后满足扩容减排的政策要求,出水水质稳定达标排放,为类似污水处理厂的技改提供了相关设计经验。