The DC de-icing device based on a three-phase rectifier circuit generates a significant amount of harmonics during operation, affecting the safety of other electrical equipment in the power system. The harmonic suppression measures must be taken with the application of DC de-icing devices. In this paper, the ice-melting current parameters of the overhead ground wire in ±800 kV UHVDC transmission line are calculated. The harmonic and the reactive power characteristics of the mobile DC de-icing device using a 6-pulse three-phase fully controlled rectifier are theoretically calculated and simulated. The influences of the rectifier transformer and the rectifier triggering angle on the harmonic and the reactive power are studied, and the single tuned filters of the DC de-icing device are designed in this paper. The simulation results show that installing the Y/Δ-connected rectifier transformer and reducing the triggering angle during the DC de-icing operation can reduce the harmonic content and reactive power of the DC de-icing device. Based on the reactive power demand of the DC de-icing device, the parameters of fifth, seventh and 11th single tuned filters can be designed according to the proportion of each harmonic current, and Δ-connected the filters can be installed on the secondary side of the rectifier transformer. This filter design scheme can simultaneously meet the requirements of the harmonic suppression and the reactive power compensation of the DC de-icing device under different ice-melting currents.

When conducting the DC ice melting operation of ground wires in live transmission lines, induced voltages on insulated ground wires may damage the ice melting equipment, and it is necessary to analyze the induced voltage and take corresponding protection measures to ensure the equipment safety. In this paper, the simulation model of a ± 800 kV UHVDC transmission system is established with the application of the PSCAD/EMTDC software. The induced voltages on the insulated ground wires with various operation modes are simulated, the influence factors and the protection measures are also analyzed. The simulation results show that the induced voltage can be significantly reduced by the single-point grounding of ground wires during the steady-state operation of UHVDC transmission lines. The grounding faults transient can induce high amplitude voltages on ground wires, and parallel gaps of ground wire insulators can limit the voltage amplitude. For the ice melting equipment protection, the insulation level of the equipment should be coordinated with that of the parallel gaps.

During the de-icing operation of high voltage overhead transmission lines using a mobile DC de-icing device, the energization of the rectifier transformer will produce inrush current, which causes the relay protection to operate and makes the DC de-icing device unable to work. This paper conducts simulations on the inrush current of the rectifier transformer in a mobile DC de-icing device using a 10kV emergency generation vehicle as the AC power source. The influence of the winding connection type of the rectifier transformer on the inrush current is analyzed. This paper proposes an operation method of stepping up from zero voltage for the unloaded rectifier transformer by using the generator excitation control system of the generator in the emergency generation vehicle. The simulation results show that when the Δ/Y connected rectifier transformer is energized, the inrush current amplitude can reach 516.5A. With the application of the stepping up from zero voltage operation of the rectifier transformer, the inrush current can be limited to less than 1.0A. This ensures the mobile DC de-icing operation of transmission lines can be carried out safely and smoothly.

The mobile DC de-icing device powered by the emergency generation vehicle can be used for DC de-icing operations on the conductors and ground wires of transmission lines. The harmonics generated by the DC de-icing device may affect the safety of the generator in the emergency generation vehicle and other equipment. Based on the ice-melting current requirements and the capacity of the emergency generation vehicle, this paper designs the mobile DC de-icing device for ground wires in ±800 kV UHVDC transmission lines. With the application of the ATP-EMTP software, the models of the generator and the de-icing rectifier circuit are established, the harmonic characteristics and the reactive power characteristics of various rectifier circuits are simulated. The calculation results show that using a single 1 MW/10 kV emergency generation vehicle, when the ice-melting current is 500 A, the transmission line length for ground wire de-icing operations is 3.15 km. When the ice-melting current ranges from 280 A to 450 A, the power filter is required. For the mobile DC de-icing device of the 12-pulse rectifier, installing a 300 kvar, 11th and 13th passive power filters on the 10 kV bus can meet the harmonic limits and the safety requirements of the generator and the DC de-icing device.

In order to solve the problem of no mature and convenient voltage detector and method for UHV DC transmission line, this paper developed a kind of non-contact voltage detector for UHV DC transmission line with metal cover based on MEMS electric field sensor. This paper determined the voltage detection area of climbing the tower for UHV DC transmission line and the alarm threshold of voltage detector by means of simulation calculation and field tests, so as to realize the convenient and reliable voltage detection for UHV DC transmission line. Results show that the non-contact voltage detector developed in this paper adopts a rotating mechanism to control the opening and closing of metal cover to eliminate the influence of space charge on voltage detection. The alarm threshold of the voltage detector should be 15kV/m. Keep the metal cover closed before and after the voltage detection. During the voltage detection, the voltage detection personnel should be located at the tower body as the same height as the wire or the cross arm directly above the wire, and the insulation rod with the voltage detector installed at the end should be extended horizontally or vertically to aim at the wire, so that the distance between the voltage detector and the wire is 5~8m. Control the rotating mechanism to make the metal cover open can realize the accurate voltage detection.

为了有效检测交流输电线路复合绝缘子的导通性缺陷情况,提出了一种基于电场检测原理的复合绝缘子导通性缺陷状态检测方法,为输电线路复合绝缘子的状态评估及安全检修提供支撑.首先采用有限元仿真计算正常和含有导通性缺陷情况下的绝缘子空间电场分布并归纳其特征,分析导通性缺陷长度及位置对绝缘子电场分布和强度的影响;然后采用电场传感器进行导通性缺陷绝缘子的电场测量,获取不同缺陷条件下复合绝缘子电场分布曲线,实现了复合绝缘子导通性缺陷的检测.仿真分析及试验结果表明,该方法可有效检测出存在导通性缺陷的复合绝缘子.

A new criterion was proposed to divide the frequency range of cabin noise prediction within full frequency. The vibro-acoustic models of oil tanker for cabin noise prediction in low frequency, middle frequency and high frequency were established. The full frequency cabin noise prediction was achieved by using the Finite Element Method (FEM), the Finite Element and Statistical Energy Analysis hybrid method (FE-SEA) and the statistical energy analysis (SEA) respectively. The results were compared with the measured values, which shows that the error between the simulation value and the measured value is within 4 dB(A). The prediction results of cabin noise are accurate and reliable. The acoustical optimization design of sound absorbing material was realized by using different optimization algorithms. The optimization results show that the combination of genetic algorithm (GA) and sequential quadratic programming (SQP) can be used to get better sound package and also to reduce the optimization time. (c) 2022 Elsevier Ltd. All rights reserved.

The structures of the composite insulators are different from those of the ceramic insulators and the glass insulators, and the safety parameters of the live working on the composite insulator transmission lines are also different. In this paper, the length parameters of the conductive defects for the live working safety on the 500kV V-type composite insulator transmission line were given through the insulator tests. Compared with the ceramic insulators and the glass insulators, the defective composite insulators are difficult to find out, since the defects usually exist in the interior of the insulators. The electric field distribution characteristics of the insulator strings can be directly applied to the field test of the defective composite insulators. The electromagnetic models 500kV AC transmission line V-type composite insulator strings with the internal conductive defects were established based on the finite element method in this paper. The influences of the length and position of the defects on the electric field distribution of the insulators were analyzed. The calculation results of the electric field distribution can be used as the reference for the accurate measurement of the composite insulators with the conductive defects, and this can ensure the safety of the live working.

The accurate detection of the defective composite insulators is vital to the safety of the transmission line in the power system. The defects distribution in the V-type insulator strings is more complex than that in the I-type insulator strings, which brings many difficulties to the accurate on-site detection of the defective insulators. In this paper, the three-dimensional models 500kV AC transmission line V-type composite insulator strings with the internal conductive defects were established with the application of the finite element method. The electric field distribution of the normal insulators and the insulators with conductive defects were calculated. The influences of the defects length and position parameters on the electric field distribution of the insulators were also analyzed. The calculation results show the electric field distribution will appear distortion apparently when the conductive defects exist in the insulators. The electric field distribution characteristics of the V-type insulator srtings with the different defect lengths and position parameters can be directly applied to the accurate field detection of the defective composite insulator.

本文从电磁场理论的坡印廷矢量出发,分析了交流稳态电路中电能传输的途经及传输方向,直观清晰地解释了电源与负载间的能量交换是通过导体周围的介质实现的,导线自身不仅不传输电能而且还消耗电能;通过电能传输过程的分析,对电路的无功功率的物理意义进行了探讨,指出了部分教材对无功功率解释的不妥之处,得到了二端网络的无功功率等于其戴维南等效电路的等效电感(或等效电容)的瞬时功率的幅值的结论.

The Tengchong volcanic area is located in the southeastern margin of the collision zone between the Indian and Eurasian Plates. It is one of the youngest intraplate volcano groups in mainland China. Imaging the S-wave velocity structure of the crustal and uppermost mantle beneath the Tengchong volcanic area is an important means of improving our understanding of its volcanic activity and seismicity. In this study, we analyze teleseismic data from nine broadband seismic stations in the Tengchong Earthquake Monitoring Network. We then image the crustal and uppermost mantle S-wave velocity structure by joint analysis of receiver functions and surface-wave dispersion. The results reveal widely distributed low-velocity zones. We find four possible magma chambers in the upper-to-middle crust and one in the uppermost mantle. The chamber in the uppermost mantle locates in the depth range from ~ 55 to ~ 70 km. The four magma chambers in the crust occur at different depths, ranging from the depth of ~ 7 to ~ 25 km in general. They may be the heat sources for the high geothermal activity at the surface. Based on the fine crustal and uppermost mantle S-wave velocity structure, we propose a model for the distribution of the magma chambers.

The upper crustal anisotropy of Yunnan area, SE margin of Tibetan Plateau, is investigated by measuring the shear wave splitting of local earthquakes. The mean value of the measured delay times is 0.054 s and far less than that from Pms splitting analysis, indicating that the crustal anisotropy is contributed mostly from mid-lower crust. The fast polarization directions are mostly sub-parallel to the maximum horizontal compression directions while the stations near fault zones show fault-parallel fast polarization directions, suggesting both stress and geological structure contribute to the upper crust anisotropy. Comparing fast polarization directions from shear wave splitting of local earthquakes and Pms, large angle differences are shown at most stations, implying different anisotropy properties between upper and mid-lower crust. However, in southwestern Yunnan, the fast polarization directions of Pms and S-wave splitting are nearly parallel, and the stress and surface strain rate directions show strong correlation, which may indicate that the surface and deep crust deformations can be explained by the same mechanism and the surface deformation can represent the deformation of the whole crust. Therefore, the high correlation between surface strain and mantle deformation in this area suggests the mechanical coupling between crust and mantle in southwestern Yunnan. In the rest region of Yunnan, the crust-mantle coupling mechanisms are supported by the lack of significant crustal anisotropy with N-S fast polarization directions from Pms splitting. Therefore, we conclude that the crust and upper mantle are coupled in Yunnan, SE margin of Tibetan Plateau. (C) 2018 Institute of Seismology, China Earthquake Administration, etc. Production and hosting by Elsevier B.V. on behalf of KeAi Communications Co., Ltd.

The southeastern margin of the Tibetan Plateau (SETP) presents the highest level of seismicity in mainland China. To understand the seismicity in this region, a new seismic experiment is carried out based on the tomographic inversion of P- and S-wave arrival times from the regional earthquakes recorded by 49 seismic stations in Yunnan Province of Southwest China. In this study, we reduce the extreme disproportionality of the data distribution using an events combination method, and we use arrival times to construct the reference velocity model. Checkerboard tests and odd/even data tests are carried out to assess the reliability of the inversion results. The reliable P-wave velocity model reveals two low-velocity anomaly zones (LVAZs) bounded by major strike-slip faults. Almost all the large earthquakes in this region occurred in the two LVAZs and the trend of the two LVAZs is consistent with a global positioning system velocity field based on the Eurasia-fixed reference frame. We propose that the two LVAZs are material migration passageways in the SETP. In the vertical direction, the mechanically weak crustal materials are sliding southward with the rigid block, while the underlying mantle materials continue to be compressed by the collision. This vertical model is broadly consistent with the seismic anisotropy in the crust and lithospheric mantle from shear-wave splitting. The new regional geodynamic model gives a reasonable interpretation of the seismicity of the SETP, and we suggest that the material migration in the passageway zones plays an important role in the tectonic evolution of the SETP.

The induced electricity of 110 kV transmission lines which cross the UHV AC transmission lines may threaten personal safety of the maintenance staff.In this paper, field measurement of the induced voltage and induced current on a 110 kV crossing line inside Jinhua in Zhejiang province is performed.The electrostatic induced voltage on the measured line is 12.34 kV.We put forward the method of induction line segments, using MATLAB program to calculate each section of induction voltage and finally the overlay get line induced voltage.The calculation results show that the calculated results and the measured results are very close, which indicate that this method can meet the requirements of precision, when the cross distance or cross angle increases, the induction voltage and current will decrease gradually, and we should try to increase the distance or angle in the practical engineering, to weaken the inductive effect between lines.In order to ensure the safety of the people, grounding knife switches in both sides of the substation should be grounded during line maintenance, and temporary ground wire should be connected to both sides of the working points.

为了降低电网暂态冲击引起紧凑型变压器本体重瓦斯误动作概率,通过变电站实际参数建立ATP/EMTP仿真模型,计算不同杆塔绝缘子串闪络形成稳定电弧时的短路电流,精确预测雷击输电线路引起重瓦斯误动作的范围和概率。在此基础上提出加强线路绝缘、在变压器入口前串联小电感和变压器中性点接小电抗等3种限制短路电流的措施,以降低变压器重瓦斯误动。分析所提措施对实际电网的影响,得出可行性方案。分析结果表明,综合运用3种措施对限制短路电流具有显著效果,能有效降低变压器重瓦斯误动概率。

The induced electricity of 110 kV transmission lines which cross the UHV AC transmission lines may threaten personal safety of the maintenance staff.In this paper, field measurement of the induced voltage and induced current on a 110 kV crossing line inside Jinhua in Zhejiang province is performed.The electrostatic induced voltage on the measured line is 12.24 kV.The power frequency electromagnetic field simulation model is established, and the calculation results are consistent with the measured.Influence factors analysis shows that the electrostatic induced voltage on the 110 kV line is 12.78 kV, the electromagnetic induced voltage is 12.3 V, the induced current through ground wire is less than 1A when the UHV lines operate at full load.The induced voltage and current decrease while the crossing distance increases.Parallel lines induction is much higher than crossing lines.The electromagnetic induced voltage after ground knife-switch shut down would exceed the human safety voltage 36 V while the crossing angle is less than 30˚, so the temporary ground wire must be hanged to ensure safety of the maintenance staff.

介绍了故障的情况,在事故分析的基础上,利用ATP/EMTP软件建立仿真模型,计算了箱变低压侧雷电过电压并进行了影响因素分析,提出了相关防护措施.

Aimed at damage accidents of box-type transformer outside wind turbine when the top of wind tower being struck by lightning,an ATP / EM TP simulation model is established according to wind turbine-box type transformer system lightning protection,which is based on the mechanism analysis of the lightning overvoltage of box-type transformer at low-voltage side. We use this model to calculate the lightning overvoltage of box-type transformer at low-voltage side when surge protective device( SPD) is connected and disconnected,and analyze the influences of the waveform and peak of lightning current,impulse grounding resistance on the voltage on the lowvoltage side of box-type transformer. M eanwhile,we calculate the power frequency current after the low-voltage side short circuit of transformer. The calculation result shows that the potential differences of low-voltage side of transformer when SPD is disconnected exceed the impulse withstand voltage12 k V,and the power frequency current at low-voltage side is 4. 50-8. 75 k A. Because switch-type SPD cannot cut off power frequency current,it is suggested that switch-type SPD should be replaced by zinc oxide arrester( YH10W-0. 8 /3. 0) without followcurrent,whose lightning protection effect is verified by simulating calculation.

In order to study the effect on Induced voltage initiate by ground wire transposition in the same tower double circuit transmission line, we attempted to analyze the formation mechanism of ground wire induction voltage. Simulation models of typical 500kV double-circuit transmission line are established by ATP-EMTP software and calculations of induce voltage on ground wires are performed with different phase sequence array. The results show that, the restriction by ground wire transposition is mainly caused by the phase difference of inductive electromotive forces in the two ground wires. The restriction effect is better when phase difference is greater, and the best effect to reduce inductive voltage is adopting reverse phase sequence which the inductive electromotive forces in two sides of ground wire are almost inverse. Due to the inductive electromotive forces in ground wire transposition points are not totally inverse, the effect is not multiple while continuous and multiple transposition were made.

搭建了局放信号在电力电缆中传播的MATLAB/Simulink模型,应用振荡波局放检测法对预置故障电缆进行了局放测量试验和相应的仿真计算,同时使用不同的电缆参数进行了局放信号在电缆中传播过程的仿真.结果表明,局放脉冲信号幅值的衰减和波形的畸变程度受电缆长度和电缆一次分布参数的显著影响.局放传播特性的仿真研究,对振荡波局放检测系统局放检测程序的优化有一定参考价值,同时给振荡波局放检测法应用过程中局放反射波的确定提供了一个辅助鉴定的方法.