On-Line Structural Breaks Estimation for Non-stationary Time Series Models

Non-stationary time series could be divided into piecewise stationary stochastic signal. However, the number and locations of breakpoints, as well as the approximation function of the respective segment signal are unknown. To solve this problem, a novel on-line structural breaks estimation algorithm based on piecewise autoregressive processes is proposed. In order to find the "best" combination of the number, lengths, and orders of the piecewise autoregressive (AR) processes, the Akaikes Information Criterion (AIC) and Yule-Walker equations are applied to estimate an AR model fit to the data. Numerical results demonstrate that the proposed estimation algorithm is suitable for different data series. Furthermore, the algorithm is used in a clinical study of electroencephalogram (EEG) with satisfactory results, and the ability to deal with real-time data is the most outstanding characteristic of on-line structural breaks estimation algorithm proposed.

Fault Line Selection Method Considering Grounding Fault Angle for Distribution Network

In the distribution network system with its neutral point grounding via arc suppression coil, when single-phase grounding fault occurred near zero-crossing point of the phase voltage, the inaccuracy of the line selection always existed in existing methods. According to the characteristics that transient current was different between the fault feeder and other faultless feeders, wavelet transformation was performed on data of the transient current within a power frequency cycle after the fault occurred. Based on different fault angles, wavelet energy in corresponding frequency band was chosen to compare. The result was that wavelet energy in fault feeder was the largest of all, and it was larger than sum of those in other faultless feeders, when the bus broke down, the disparity between each wavelet energy was not significant. Fault line could be selected out by the criterion above. The results of MATLAB/simulink simulation experiment indicated that this method had anti-interference capacity and was feasible.

Design of High Power DC Break For ICRH Of EAST

1.5MW Ion Cyclotron Wave Heating system was developed, the transmitter and the antenna both have their ground loops, which will severely perturb the system’s normal operation. To avoid perturbation, a DC break was designed. The S parameter and the VSWR (voltage standing wave ratio) of incident port were calculated; the thermal effect caused by conductor loss and dielectric loss was analyzed.

Protection of Zero-Sequence Power Variation in Mountain Wind Farm Collector Lines Based on Multi-Mode Grounding

The arc-suppression coil(ASC)in parallel low resistance(LR)multi-mode grounding is adopted in the mountain wind farm to cope with the phenomenon that is misoperation or refusal of zero-sequence protection in LR grounding wind farm.If the fault disappears before LR is put into the system,it is judged as an instantaneous fault;while the fault does not disappear after LR is put into the system,it is judged as a permanent fault;the single-phase grounding fault(SLG)protection criterion based on zerosequence power variation is proposed to identify the instantaneous-permanent fault.Firstly,the distribution characteristic of zero-sequence voltage(ZSV)and zero-sequence current(ZSC)are analyzed after SLGfault occurs in multi-mode grounding.Then,according to the characteristics that zero-sequence power variation of non-fault collector line is small,while the zero-sequence power variation of fault collector line can reflect the active power component of fault resistance,the protection criterion based on zero-sequence power variation is constructed.The theoretical analysis and simulation results show that the protection criterion can distinguish the property of fault only by using the single terminal information,which has high reliability.

Roughness evaluation in shotcrete-lined water tunnels with invert concrete based on cases from Nepal

Most of the existing roughness estimation methods for water tunnels are related to either unlined or concrete/steel-lined tunnels. With the improvement in shotcrete technology, advancement in tunneling equipment and cost and time effectiveness, future water tunnels built for hydropower projects will consist of rock support with the extensive use of shotcrete lining in combination with systematic bolting and concrete lining in the tunnel invert. However, very little research has been performed to find out tunnel surface roughness for shotcrete-lined tunnels with invert concrete, which is important in calculating overall head loss along the waterway system to achieve an optimum and economic hydropower plant design. Hence, the main aim of this article is to review prevailing methods available to calculate tunnel wall roughness, and to use existing methods of head loss calculation to back-calculate roughness of the shotcrete-lined tunnels with invert concrete by exploiting measured head loss and actual cross-sectional profiles of two headrace tunnels from Nepal. Furthermore, the article aims to establish a link between the Manning coefficient and the physical roughness of the shotcrete-lined tunnel with invert concrete and to establish a link between over-break thickness and physical roughness. Attempts are also made to find a correlation between over-break thickness and rock mass quality described by Q-system and discussions are conducted on the potential cost savings that can be made if concrete lining is replaced by shotcrete lining with invert concrete.

基于绝对节点坐标法的架空线断线工况动力学计算

为了计算架空线断线工况下的动力学变化特性,考虑架空线的绞制几何结构及其初始构型的布置特点,以绝对节点坐标法为基础,建立了架空线单元,推导了架空线单元的质量矩阵和弹性力矩阵,给出了架空线的系统动力学方程。针对钢芯铝绞线的绞制几何结构,给出了其对应的轴向、弯曲刚度计算公式。通过仿真计算得到线缆的运动图像,设计试验验证了算法模型的可靠性。结合实际架空线初始位形和初始应力特点,对不同初始应力下的架空线断线工况动力学问题进行仿真分析,绘制了悬挂点处的受力时程曲线并对曲线进行了频谱分析,研究了初始应力对断裂架空线运动过程以及悬挂点受力的影响规律。

Fault protection method of single-phase break for distribution network considering the influence of neutral grounding modes

With the rapid development of modern distribution network and the access of distributed generation,the network structure is becoming increasingly complex.Frequent single-phase break faults have seriously affected equipment and personal safety and stable operation of the power system.However,with the development and application of the composite neutral grounding modes,the protection of single-phase break fault is facing new challenges.This paper proposes a protection method of single-phase break fault for distribution network considering the influence of neutral grounding modes.The characteristics of neutral voltage and sequence current are analyzed under normal operation and single-phase break fault with different grounding modes.Following this,the protection criterion based on neutral voltage and sequence current variation is constructed.The protection method of singlephase break fault for distribution network is proposed,which is applicable for various neutral grounding modes.Theoretical analysis and simulation results show that the protection method is less affected by system asymmetry,fault location and load distribution.The method has higher sensitivity,reliability and adaptability.

110 kV复合绝缘横担结构设计及工程应用研究

为在输电线路中推广复合绝缘横担,以110 kV输电线路改造工程为背景,提出了一种线路用复合绝缘横担设计方法。从复合绝缘横担的大风、覆冰、安装及断线四种工况荷载计算着手,对复合绝缘横担开展结构设计。采用有限元软件建立两拉-两压结构形式的力学分析模型,在四种工况下对横担进行力学计算,通过力学真型实验验证了复合绝缘横担结构的稳定性和安全性。该方法设计的复合绝缘横担满足该线路安全运行要求,并成功挂网多条110 kV输电线路;针对不同线路塔型设计工作量大、生产周期长的问题,开展典型化设计工作是未来发展的趋势。

Multiple Random Forests Based Intelligent Location of Single-phase Grounding Fault in Power Lines of DFIG-based Wind Farm

To address the problems of wind power abandonment and the stoppage of electricity transmission caused by a short circuit in a power line of a doubly-fed induction generator(DFIG) based wind farm, this paper proposes an intelligent location method for a single-phase grounding fault based on a multiple random forests(multi-RF) algorithm. First, the simulation model is built, and the fundamental amplitudes of the zerosequence currents are extracted by a fast Fourier transform(FFT) to construct the feature set. Then, the random forest classification algorithm is applied to establish the fault section locator. The model is resampled on the basis of the bootstrap method to generate multiple sample subsets, which are used to establish multiple classification and regression tree(CART) classifiers. The CART classifiers use the mean decrease in the node impurity as the feature importance,which is used to mine the relationship between features and fault sections. Subsequently, a fault section is identified by voting on the test results for each classifier. Finally, a multi-RF regression fault locator is built to output the predicted fault distance. Experimental results with PSCAD/EMTDC software show that the proposed method can overcome the shortcomings of a single RF and has the advantage of locating a short hybrid overhead/cable line with multiple branches. Compared with support vector machines(SVMs)and previously reported methods, the proposed method can meet the location accuracy and efficiency requirements of a DFIG-based wind farm better.

基于配电自动化的断线及接地故障处理方法

针对断线故障检测处理方法滞后的问题,提出主干线、支线及配电变压器断线的通用快速检测处理方法。针对小电流接地系统故障接地选线及区段定位困难的问题,提出以接地参数处理接地故障的新方法。经现场试验分析,所提方法简单易行,处理故障成功率达100%,具有极大的应用前景和推广价值。

基于人工智能的钢丝绳芯输送带断丝检测技术研究

针对钢丝绳芯输送带传统断丝断丝监测方法效率较低、工人劳动强度大、检测准确度较低等问题,通过分析钢丝绳芯输送带内的钢丝绳结构,提出了一种基于人工智能的钢丝绳芯输送带断丝检测方法,利用神经网络算法提取胶带内钢丝绳断丝特征,实现了定量准确识别。以含有不同类型断丝缺陷的619钢丝绳的胶带为试验对象,利用断丝检测技术进行断丝检测,结果表明,完成长度为2 m的胶带检测仅需3.8 s,对于表面断丝较多的钢丝绳,反馈得到的信号变化率强度较大,最大值为0.498。本次研究取得了满意的实验结果,验证了方案设计的合理性。

基于密度栅格与等高面的LiDAR-DEM水面处理研究

机载LiDAR构建DEM数据处理静止水面时需要满足高程固定和边缘过渡自然的生产要求和质检要求。传统的作业方法通常需要大量的人工编辑,效率相对较低。为了解决这一问题,本文提出了一种结合点云密度栅格和DEM等值面的方法,实现了对静止水面边界和水面高程的自动提取,从而解决了DEM在静止水面中的自动平整问题,并利用ArcGIS Pro开发了相应的自动处理工具。将该方法在福建省2 m格网DEM数据制作项目中进行测试,结果表明该方法不仅满足了质检要求,而且相较于传统人工编辑方式,具有更高的效率。

小角度下穿铁路地道桥线路架空方案设计

在下穿铁路地道桥建设中,为保证既有铁路的通行不受影响,在施工时需要先对既有铁路线进行加固和架空,确保在不影响铁路行车条件下完成地道桥的施工。架空方式合理与否将对整个工程项目的安全、经济、工期产生重大影响。以下穿德天铁路地道桥为例,分别采用D便梁架空线路、门式墩架空线路和铁路线开断后大开挖三种架空方案进行对比设计,分别从设计和施工的角度对三种工法的优缺点进行比较分析,最终得出了对于技术标准低、行车对数少的支线铁路,铁路线开断后大开挖施工是一种相对投入较小,对铁路影响相对较小的工法。

输电线路防外破杆塔状态监测系统设计

以杆塔使用状况监测为例,开展输电线路防外破监测系统设计。针对现阶段杆塔状态开展监测,深入探讨处理器与传感器的选型及注意事项,提出合理的系统设计。选择ARM处理器作为杆塔前端监测系统的核心组件,前端操作系统核心部分为STM32F4处理器,以MDK-ARM构建集成开发环境(IDE)实现系统建设。设计包含系统构建、倾斜测试、无线传输等。选择具备多频段GSM/GPRS的G510模组进行测试。测试结果表明,当杆塔倾斜角增大达至阈值时会触发报警,数据会被传输到云服务器与手机,有效提高了杆塔状态监测效率,具有很好的实际应用价值。

输电线路复合绝缘子断裂原因分析及处置

文章通过分析一起输电线路复合绝缘子断裂案例,研究架空输电线路复合绝缘子断裂的机理,总结原因,结合输电线路复合绝缘子运行经验,提出目前工作的不足,总结防止输电线路复合绝缘子断裂的有效措施,希望能够对以后输电线路安全运行提供经验和参考。

基于相量测量的配电网单相断线接地识别方法

在配电网中,带有断线的单相接地故障发生得越来越频繁,经常造成重大安全事故。由于谐振接地系统和非接地系统的电源侧电气特性相同,很难区分谐振接地系统和非接地系统中的单相断线接地故障和单相接地故障。本文提出了一种区分单相断线接地故障和单相接地故障的方法,首先分析两种故障的电源侧和负荷侧电压特性,利用相位测量单元作为测量设备,选择负荷侧故障相电压和非故障相电压之间的相位差作为识别标准,然后分析了配电网中的运行条件和外部设备对识别方法的影响,计算了由其引起的相位误差,并修正识别方法,最后通过仿真验证了所提方法的有效性和鲁棒性。

LCC-HVDC输电系统的仿真分析与稳定性研究

在电力系统中,高压直流输电(HVDC)系统具有造价低、损耗小、潮流控制灵活等优势。文章详细介绍了HVDC系统的构成、工作原理以及具体的应用问题,建立了仿真模型并分析了接地短路和断线故障对系统的影响。仿真结果显示,系统在瞬时性故障结束后能够通过定电压和定电流控制实现自恢复,但在毫秒级故障中的稳定性较弱,可能导致失稳现象。文章的研究为HVDC系统在实际应用中的可靠性提供了一定的参考。

大型矿砂船停泊巴西主要港口的系泊要求

阐述大型矿砂船停泊巴西几个主要港口矿石码头的系泊要求和靠泊码头的限制条件,其中马德里亚角(PDM)港口的系泊要求远远高于国际海事组织(IMO)海上安全委员会(MSC)船舶拖带和系泊设备导则和OCIMF(石油公司国际海事论坛)系泊设备指南要求。以32.5万吨级矿砂船系泊设计为例,通过计算分析系泊缆绳最小破断负荷值,验证PDM港口系泊要求的合理性。

可见光图像中的高压线缺陷自动诊断方法

研究直升机巡检系统中,基于可见光图像的电力线缺陷诊断方法。对直升机机载系统采集到的可见光图像进行实时分析,自动诊断电力线上可能存在的断股、异物附着缺陷。研究了缺陷在可见光图像中的特征,并提出了一种基于亮度和空间信息的线对象检测方法,自动识别电力线。对线对象进行分析,获取其位置、方向、宽度信息,并进行对象分类。结合缺陷特征和对象与分类信息,设计缺陷诊断流程,诊断断股及异物缺陷。实验证明,该方法对电力线检测准确,能够发现电力线存在的可疑异物和断股缺陷,成功应用于直升机巡检系统中。

线路保护中PT断线判据的分析和改进

PT断线作为电力系统中一种常见的故障,能否及时有效地进行判别,是继电保护装置正确动作的前提条件。针对PT断线的特点,在对不同厂家的判据进行了分析后,结合一次现场实例,指出了目前判据中存在的不足之处,给出了一种PT断线的实用判据。根据该判据开发的线路保护装置已经在现场投入使用,证明了该判据的工程实用价值。