Research on Transmission Line Tower Tilting and Foundation State Monitoring Technology Based onMulti-Sensor Cooperative Detection and Correction

The transmission line tower will be affected by bad weather and artificial subsidence caused by the foundation and other factors in the power transmission.The tower’s tilt and severe deformation will cause the building to collapse.Many small changes caused the tower’s collapse,but the early staff often could not intuitively notice the changes in the tower’s state.In the current tower online monitoring system,terminal equipment often needs to replace batteries frequently due to premature exhaustion of power.According to the need for real-time measurement of power line tower,this research designed a real-time monitoring device monitoring the transmission tower attitude tilting and foundation state based on the inertial sensor,the acceleration of 3 axis inertial sensor and angular velocity raw data to pole average filtering pre-processing,and then through the complementary filtering algorithm for comprehensive calculation of tilt angle,the system meets the demand for inclined online monitoring of power line poles and towers regarding measurement accuracy,with low cost and power consumption.The optimization multi-sensor cooperative detection and correction measured tilt angle result relative accuracy can reach 1.03%,which has specific promotion and application value since the system has the advantages of unattended and efficient calculation.

Process Analysis of Double Circuit Transmission Line Trip-out on the Same Tower Due to Lightning

In recent years,several failures of double circuit transmission line on the same tower due to lightning were happened in Beijing power grid.Although it can be reclosed successful,the lightning strike caused a grave threat to the power grid security.The cause of the accident and the accident process were studied for the sake of further understanding of the impact of lightning on power grid.As an example,110 kV double circuit transmission line(Xilong-line) was analyzed.At first,the system topology was given.Through the analysis on relay protection actions and the fault recorder data,over voltage on the insulator strings was calculated.Based on the analysis and the calculation,accident cause and the process were presented respectively.Secondly,it comes to the conclusion that the lightning failure was caused by counterattack.The wave of the lightning over voltage would spread to the not grounded neutral point of the transformers,and make the neutral protective gap breakdown,then cause freewheeling with the frequency of 50 Hz.As results of the relay protection,the double circuit transmission line all tripped out.Finally,the causes of the accident were proposed that included terrain features,large corner towers,strong thunderstorm weather and poor grounded contact of the tower.

The Integrated System of Aerial Photogrammetry and Tower Locations Optimization for Transmission Lines

This paper describes the functions and the features of the integrated system of aerial survey and tower locations optimization for transmission lines, which includes all stages from data acquisition, data transmission and data processing to automatic optimization of the tower locations and drawing. The paper also briefly describes the economic benefit gained from this system, and finally proposes the directions of the future development for this system.

The changing process and trend of ground temperature around tower foundations of Qinghai-Tibet Power Transmission line

After the construction of Qinghai-Tibet Highway and Railway, the Qinghai-Tibet Power Transmission(QTPT) line is another major permafrost engineering project with new types of engineering structures. The changing process and trend of ground temperature around tower foundations are crucial for the stability of QTPT. We analyzed the change characteristics and tendencies of the ground temperature based on field monitoring data from 2010 to 2014. The results reveal that soil around the tower foundations froze and connected with the artificial permafrost induced during the construction of footings after the first freezing period, and the soil below the original permafrost table kept freezing in subsequent thawing periods. The ground temperature lowered to that of natural fields, fast or slowly for tower foundations with thermosyphons,while for tower foundations without thermosyphons, the increase in ground temperature resulted in higher temperature than that of natural fields. Also, the permafrost temperature and ice content are significant factors that influence the ground temperature around tower foundations. Specifically, the ground temperature around tower foundations in warm and ice-rich permafrost regions decreased slowly, while that in cold and ice poor permafrost regions cooled faster. Moreover, foundations types impacted the ground temperature, which consisted of different technical processes during construction and variant of tower footing structures. The revealed changing process and trend of the ground temperature is beneficial for evaluating the thermal regime evolution around tower foundations in the context of climate change.

OPTIMIZATION OF TRANSIENT FEEDING TO PARALLEL-PLATE TRANSMISSION LINES FROM COAXIAL LINE

The transient feeding to parallel-plate transmission lines from coaxial line is optimized by using the Finite-Difference Time-Domain (FDTD) method and a simple FDTD feed model. Observing the reflected voltages, this letter presents the optimal feeding position and ratio of width to height for a given input impedance of the coaxial line.

Coupling analysis of transmission lines excited by space electromagnetic fields based on time domain hybrid method using parallel technique

We present a time domain hybrid method to realize the fast coupling analysis of transmission lines excited by space electromagnetic fields, in which parallel finite-difference time-domain (FDTD) method, interpolation scheme, and Agrawal model-based transmission line (TL) equations are organically integrated together. Specifically, the Agrawal model is employed to establish the TL equations to describe the coupling effects of space electromagnetic fields on transmission lines. Then, the excitation fields functioning as distribution sources in TL equations are calculated by the parallel FDTD method through using the message passing interface (MPI) library scheme and interpolation scheme. Finally, the TL equations are discretized by the central difference scheme of FDTD and assigned to multiple processors to obtain the transient responses on the terminal loads of these lines. The significant feature of the presented method is embodied in its parallel and synchronous calculations of the space electromagnetic fields and transient responses on the lines. Numerical simulations of ambient wave acting on multi-conductor transmission lines (MTLs), which are located on the PEC ground and in the shielded cavity respectively, are implemented to verify the accuracy and efficiency of the presented method.

Accurate Fault Location Modeling for Parallel Transmission Lines Considering Mutual Effect

:A new accurate algorithms based on mathematical modeling of two parallel transmissions lines system(TPTLS)as influenced by the mutual effect to determine the fault location is discussed in this work.The distance relay measures the impedance to the fault location which is the positive-sequence.The principle of summation the positive-,negative-,and zero-sequence voltages which equal zero is used to determine the fault location on the TPTLS.Also,the impedance of the transmission line to the fault location is determined.These algorithms are applied to single-line-to-ground(SLG)and double-line-to-ground(DLG)faults.To detect the fault location along the transmission line,its impedance as seen by the distance relay is determined to indicate if the fault is within the relay’s reach area.TPTLS under study are fed from one-and both-ends.A schematic diagrams are obtained for the impedance relays to determine the fault location with high accuracy.

Fault location for parallel transmission lines using one-terminal current traveling waves

With proper phase module transformation,parallel lines can be decomposed to the same directional net and the reverse directional net. The propagation characteristics of traveling waves in the reverse directional net were analyzed,and the refraction coefficient at the fault point for a single phase fault was derived. In addition,the module selection was discussed. Simulation results show that satisfying accuracy can be achieved with the proposed method. Moreover,it is immune to fault types,fault resistances,and outside system parameters.

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.

Online One-End Fault Location Algorithm for Parallel Transmission Lines

Fault location and distance protection are essential smart grid technologies ensuring reliability of the power system. This paper describes an accurate algorithm for locating faults on double-circuit transmission lines. The proposed approach is capable of identifying the faulted circuit of a parallel transmission line by checking the estimated fault location and fault resistance. Voltage and current measurements from only one of the terminals of the faulty line are used. No pre-fault data are required for the estimation. The lumped parameter line model considering shunt capacitance is utilized for the derivation of the algorithm. It’s assumed that line parameters are known and transmission lines are fully transposed. The method is applicable to all types of faults. It’s evinced by evaluation studies that the proposed algorithm can correctly determine the faulted circuit in most cases. For exceptional cases, the current waveforms during the fault can be used to help identify the faulted circuit. The proposed algorithm generates quite accurate fault location estimates, and may be suitable for distance relaying.

Dynamic Analysis of Overhead Transmission Lines under Turbulent Wind Loading

Transmission tower-line systems are designed using static loads specified in various codes. This paper compares the dynamic response of a test transmission line with the response due to static loads given by Eurocode. Finite element design software SAP2000 was used to model the towers and lines. Non-linear dynamic analysis including the large displacement effects was carried out. Macroscopic aspects of wind coherence along element length and integration time step were investigated. An approach is presented to compare the probabilistic dynamic response due to 7 different stochastically simulated wind fields with the response according to EN-50341. The developed model will be used to study the response recorded on a test line due to the actual wind speed time history recorded. It was found that static load from EN overestimated the strength of conductor cables. The response of coupled system considering towers and cables was found to be different from response of only cables with fixed supports.

Evaluating transmission towers potentials during ground faults

During ground faults on transmission lines,a number of towers near the fault are likely to acquire high potentials to ground.These tower voltages,if excessive,may present a hazard to humans and animals.This paper presents analytical methods in order to determine the transmission towers potentials during ground faults,for long and short lines.The author developed a global systematic approach to calculate these voltages,which are dependent of a number of factors.Some of the most important factors are:magnitudes of fault currents,fault location with respect to the line terminals,conductor arrangement on the tower and the location of the faulted phase,the ground resistance of the faulted tower,soil resistivity,number,material and size of ground wires.The effects of these factors on the faulted tower voltages have been also examined for different types of power lines.

Dynamic Responses of Long-Span Transmission Tower-Line System Subjected to Broken Wires

A macroscopic finite element modeling approach was proposed to calculate the vibration of a tower-line system subjected to broken wires with software ANSYS/LS-DYNA. In the finite element model, not only the nonlinearity of wires and suspension insulators are considered, but also the support towers are included. The incremental and iterative approaches are combined by applying the unbalanced loads incrementally during each iteration cycle. The approach was illustrated with an example of a Hanjiang- River long-span transmission line system subjected to a shield wire and a conductor failure, respectively. The analysis results showed that the proposed dynamic simulation approach can demonstrate the kinetic process of the tower-line system subjected to wire ruptures： The frequencies of line components were lower and densely distributed, but the frequencies of tower components were higher and sparsely distributed. Anyhow, the dynamic effects of wire ruptures on tower-line system could not be ignored in analysis of tower-line system subjected wire failures.

颗粒阻尼器对输电塔线系统减震性能研究

对输电塔线系统进行缩尺模型振动台实验,从时域和频域的角度,对比了调谐质量阻尼器和颗粒阻尼器对输电塔的减震效果。利用ABAQUS建立了颗粒阻尼器控制输电塔线系统的离散元-有限元高精度耦合数值模型,对比了实验和模拟结果,并对塔线系统的耗能情况及颗粒阻尼器内部颗粒运动碰撞情况进行分析。研究结果表明:在地震激励下,颗粒阻尼器的减震效果较调谐质量阻尼器有更好的鲁棒性;该文所建立的颗粒阻尼器控制输电塔线系统模型能够良好地反映试件的动力特性和地震响应;在颗粒阻尼器的控制下,塔线系统总能量降低24.12%。当颗粒之间的碰撞次数和颗粒与容器的碰撞次数满足一定比例关系时,颗粒阻尼器能实现更优的控制效果。

端接复杂电路传输线网络的电磁耦合时域并行计算方法

针对端接复杂电路传输线(TL)网络的电磁耦合问题,仍缺乏高效的场路协同仿真技术。该文将传输线方程与时域有限差分(FDTD)方法、诺顿定理和置换定理以及NGSPICE软件相结合,并引入消息传递接口(MPI)并行技术,提出一种高效的时域混合并行算法(FDTDTL-NGSPICE)。首先,根据诺顿定理和置换定理,将传输线网络分解为传输线子系统和复杂电路子系统,并构建对应的等效电路模型。然后,使用FDTDTL并行算法计算传输线子系统沿线各点的电压和电流,并获取对应诺顿等效电路的电流源和等效导纳大小。最后,使用NGSPICE对复杂电路子系统进行传导干扰分析,获得复杂电路各元件上的瞬态响应,并将端口电压反馈给传输线子系统作为边界,实现传输线网络电磁耦合的场线路联合协同仿真。通过对3类典型场景的计算实例,分别使用时域混合并行算法和电磁仿真软件CST电缆工作室(CS)进行数值模拟并对比,验证所提算法的置信度。

750kV单回并行输电线路电磁辐射环境研究

采用《环境影响评价技术导则输变电》(HJ 24—2020)附录C、D推荐的计算模式对750 kV单回并行输电线路电磁辐射环境进行计算与预测。结果表明,经过耕地、园地、牧草地、畜禽饲养地、道路等场所,当导线对地最小高度为15.5 m时,单回并行线路下的工频电场强度最大值超过10 kV/m;需将导线对地最小高度提至16.5 m,才能满足4 kV/m控制限值要求。750 kV单回并行输电线路产生的工频磁场强度小于公众曝露控制限值(100μT),一般情况下不会成为线路建设的环境制约因素;但其产生的工频电场是电磁环境影响的主要因素,电场强度控制限值(4 kV/m)是线路建设的环境制约因素,同时也是输变电电磁环境重点控制因素。现场实测结果与理论预测结果符合性较好,表明采用的预测模式具有较好的应用性,研究结果可为750 kV单回并行输电线路的建设和环境监管提供支持。

台风灾害输电线路杆塔脆弱性与风险评估:以浙江省为例

台风大风可导致输电线路杆塔断裂倒塌等事故,影响电力系统运行安全,因而台风灾害输电线路杆塔风险评估具有重要意义。以浙江省全域杆塔为例,基于杆塔属性、地理信息及台风灾情资料,提出了一种基于“超额损失”的针对连续型和离散型变量的输电线路台风灾害杆塔脆弱性评估模型;利用68 a台风参数风场再分析数据,基于极值理论,建立了台风大风危险性评估模型;基于区域灾害系统理论,通过台风大风、杆塔脆弱性之间耦合分析,建立了台风输电线路杆塔风险评估模型。结果显示:台风大风危险性呈从东南向西北递减态势,随重现期增大呈非线性增大趋势,以20和100 a一遇极大风速为例,浙江省全域风速强度分别为23.5~50.9和32.6~68.9 m/s;台风影响下的杆塔综合脆弱性总体呈南高北低且与地形联系紧密的分布态势,脆弱性高值(>1)区域主要在浙中南和沿海地区;输电线路杆塔风险总体呈南高北低、沿海高内陆低的特点,局部差异性较大。应根据具体线路特点采取差异性较大的抗风策略。

服役输电线路风致响应及寿命预测分析

庞大的输电系统是国家最重要的基础设施之一,确保其在长期风荷载作用下的安全性和可靠性,是应该重视的关键问题。采用Abaqus建立了输电塔线体系的精细化有限元模型,对风荷载进行了模拟,考虑受压杆件失稳,通过动力计算方法分析了塔线体系响应并据此确定了其薄弱位置。进一步地,以薄弱杆件的应力时程为指标,基于Miner线性准则描述的损伤规律,采用雨流法预测了不同风速下塔线体系的寿命;随后研究了风荷载模拟关键参数对结构预测寿命的影响,对线路进行整体上的评估。结果表明:以构件失效作为塔线体系结构整体破坏的准则,可为塔线体系的寿命预测提供一定的参考;结构的预测寿命主要由薄弱构件(变坡处主材)控制;此外,风荷载模拟参数对预测寿命有较大影响,持时不同预测寿命差距较大,Kaimal谱模型预测寿命比随机Fourier谱更偏于保守;粗糙长度与预测寿命负相关。

随机脉动风场作用下输电塔线体系的动力响应分析

输电杆塔及塔线体系(简称塔线体系)是整个电力系统中输电环节的核心部分,沿海地区的强风对塔线体系有着重要影响。为研究在随机脉动风场作用下塔线体系的动力响应特性,文中以广东某地区的1W2C9型鼓型自立式输电杆塔为研究对象,建立输电杆塔的单塔及一塔两线的塔线耦联有限元模型,结合Davenport风速谱与四阶自回归法模拟具有空间相关性的单塔9节点及塔线体系49节点的脉动风场,研究在此脉动风场下的单塔及塔线体系的动力响应,并探究不同风向角对其动力响应的影响。研究结果表明:单塔及塔线体系的动力响应最大值大于其拟静力响应;由于塔线耦联效应的存在,输电线会增加塔线体系的稳定性,降低其动力响应;90°是输电杆塔单塔及塔线体系动力响应的最不利风向角。

土-岩组合地基变截面锚杆承载性能与机制研究

以山区输电线路工程为背景,针对实践中广泛遇到的上土下岩二元层状地基,提出了一种变截面锚杆技术,其原理为通过增大上覆土层中锚杆的截面积,达到充分利用上覆土层和下部岩层承载力的目的。为检验变截面锚杆的性能,采用现场真型试验和数值模拟相结合的手段,探讨了其承载力提升机制,分析了不同因素对承载特性的影响规律。研究表明,较等截面锚杆,变截面锚杆的上拔、下压以及水平承载力均有所提升。其中,水平承载性能提升效果最显著。场地覆土层厚度对锚杆上拔承载力影响较大,对下压和水平承载性能影响较小。场地地形坡度对锚杆水平承载性能有较大影响,二者呈负相关。此外,“上拔荷载+水平荷载”模式下,变截面群锚基础的承载性能优于等截面群锚基础和传统复合基础,且具有土方开挖量小以及更适用于斜坡地形的优点。研究成果可为该新型基础的推广应用提供技术支撑。