An On-line Monitoring System for Partial Dischargefrom High Voltage Transformer

An on-line monitoring system for partial discharge from high voltage transformer is presented with structure of hardware and principle of software discussed and a new effective method combining DFT with DWT is proposed to get rid of both sinusoidal continuous noise and other external discharges.

Partial Discharge Simulations Used for the Design of a Non-Intrusive Cable Condition Monitoring Technique

The purpose of this paper is to investigate the effect of PD （partial discharge） activity within medium voltage XLPE （cross-linked polyethylene） cables. The effect of partial discharge was studied by means of a number of simulations. The simulations were based on the well-known three capacitor model for partial discharge. An equivalent circuit was derived for partial discharge due to a single void in the insulation material of a power cable. The results obtained from the simulations will form the basis of the design proses of a non-intrusive condition monitoring technique. The technique is based on the classification of discharge activity according to five levels of PD. Future work will include the improvement of the simulation model by investigating the high frequency model of a power cable as well as the statistical nature of PD activity. This will improve the accuracy of the simulation results when compared to actual measurements. The work discussed in this paper will be used to construct and calibrate a practical model which will make use of PD measurements for non-intrusive condition monitoring of medium voltage electrical cables.

Insulation State On-line Monitoring and Running Management of Large Generator

This study presented an insulation state monitoring method for large generator based on radio frequency (RF) technique. As an on-line condition monitor and the precondition of condition-based maintenance (CBM), the RF monitor used the high frequency current mutual inductor to detect the partial discharge signal from neutral wire of stator windings. According to the magnitude of indicative value of RF monitor, a five phase model was also proposed to manage the generator’s running better. The practices show that the proposed method is effective.

Design, Implementation and Simulation of Non-Intrusive Sensor for On-Line Condition Monitoring of MV Electrical Components

Non-intrusive measurement technology is of great interest for the electrical utilities in order to avoid an interruption in the normal operation of the supply network during diagnostics measurements and inspections. Inductively coupled electromagnetic sensing provides a possibility of non-intrusive measurements for online condition monitoring of the electrical components in a Medium Voltage (MV) distribution network. This is accomplished by employing Partial Discharge (PD) activity monitoring, one of the successful methods to assess the working condition of MV components but often requires specialized equipment for carrying out the measurements. In this paper, Rogowski coil sensor is presented as a robust solution for non-intrusive measurements of PD signals. A high frequency prototype of Rogowski coil is designed in the laboratory. Step-by-step approach of constructing the sensor system is presented and performance of its components (coil head, damping component, integrator and data acquisition system) is evaluated using practical and simulated environments. Alternative Transient Program-Electromagnetic Transient Program (ATP-EMTP) is used to analyze the designed model of the Rogowski coil. Real and simulated models of the coil are used to investigate the behavior of Rogowski coil sensor at its different stages of development from a transducer coil to a complete measuring device. Both models are compared to evaluate their accuracy for PD applications. Due to simple design, flexible hardware, and low cost of Rogowski coil, it can be considered as an efficient current measuring device for integrated monitoring applications where a large number of sensors are required to develop an automated online condition monitoring system for a distribution network.

Two Types of Compact UHF Antennas for Partial Discharge Measurement

To investigate the partial discharge (PD) online monitoring of transformers by ultra-high-frequency (UHF) approaches,high-qualified UHF antennas are focused on as one key technique. The size of UHF sensor used for PD UHF online monitoring in transformer is excessively large,therefore,it is not convenient for internal installation of transformer. Two types of compact UHF antennas with small sizes,a Hilbert fractal antenna and a small loop antenna are presented. PD experiments of three typically artificial insulation defects are executed and both antennas are used for PD measurement. The spectra of power via frequency of detected PD signals are analyzed and compared. The experimental results show that the Hilbert fractal antenna and small loop antenna are qualified for PD online UHF monitoring.

On-Line Partial Discharge Monitoring and Diagnostic System for Power Transformer

This paper introduces a computerized on-line partial discharge （PD） monitoring and diagnostic system for transformers. The system, which is already in use in a power station, uses wide-band active transducers and a data acquisition unit with modularized and exchangeable components. The system software is a power equipment monitoring and diagnostic system, which is based on the component object model, and was developed for monitoring multiple parameters in multiple power supply systems. The statistical characteristics of PDs in power transformers were studied using 7 experimental models for simulating PDs in transformers and 3 models for simulating interfering discharges in air. The discharge features were analyzed using a 3-D pattern chart with a three-layer back-propagation artificial neural network used to recognize the patterns. The results show that PDs in air and oil can be distinguished. The model can be used for interference rejection on-line monitoring of partial discharge in transformers.

基于随机森林的发电机定子线棒局部放电图谱特征识别方法

发电机定子线棒局部放电的在线监测和故障诊断对于电机故障预警、故障定位和指导机组检修有重要意义。目前存在部分不同类型局部放电相似度高,模式识别方法计算时间过长的问题,需要高精度和高效的识别方法,为此提出一种基于随机森林的定子线棒局部放电识别方法。制备了6种类型定子线棒,用特高频天线检测局部放电信号,基于相位分布局部放电(PRPD)图谱比对,提出参数幅值不对称度。基于随机森林方法识别缺陷类型,计算特征重要性,选择有效特征。最后,可视化特征相似度,与传统反向传播(BP)神经网络方法对比,验证有效性。结果表明:随机森林算法可以有效识别人工缺陷定子线棒局部放电,总体识别正确率达到93.33%。筛选半数特征后,随机森林比BP神经网络的准确率提高了10.83%,特征选择对随机森林的准确率影响很小,但识别效率大幅提高。随机森林在少量特征时识别准确率、计算时间都明显优于神经网络。幅值不对称度参数的重要性排在全部特征前1/3,具有推广价值。

电力电缆局放在线监测神经网络自动识别精度的提升方法

为了尽可能降低电缆线路局放在线监测系统装置运行中对局放信号识别的误判误报的可能性,对局放的判读机理和识别精度进行了改进和提升。基于现场运行系统回收的数万个疑似电缆内部局放的告警记录数据进行了分析分类,对判别程序中沿用的局放自动逻辑判别程序追加了相间信号相关性过滤程序,对既有的神经网络在构造上作了优选优化,对神经网络学习数据的前置处理进行了改进。对改进提升后的局放判别程序采用了包括现场记录,模拟信号发生器和人工局放模型加电压实验的3种局放数据进行检验。结果表明,改进提升后的局放判别程序不但能够使现场的非局放告警数据的告警率降低到5%的期待水平,同时也提高了识别人工模拟产生的各种类型局放信号的准确性,大大降低了局放在线监测系统误判误报的可能性。

局放在线监测系统在化工企业变电所的应用

国民经济的快速发展,使得电缆的需求量愈加增大,然而电缆存在的制造、安装缺陷等客观原因,导致电缆绝缘击穿短路等问题时有发生。电缆绝缘劣化的重要表现形式即是局放现象,通过捕捉局放高频信号,可提前掌握电缆绝缘劣化程度。阐述电缆存在的缺陷类别、局放监测的原理,通过应用实例描述局放在线监测系统架构、重要部件组成、通信组网方式、现场硬件配置、施工要求、软件界面、功能特点,并给出了实际应用效果,对相关化工企业变电所的电缆绝缘监测技术管理具有很强的指导和借鉴意义。

电力电缆状态感知与检测技术研究综述

电力电缆是电力系统中的重要设备,电缆的运行状态关系到输配电系统的安全可靠运行。电缆状态检测技术指根据电缆运行状态的历史数据,综合运用停电试验、带电检测、在线监测等技术对电缆状态量进行智能感知,为电缆运行性能综合评估提供关键参考信息。文中综述了近年关于电缆状态感知及检测技术的国内外研究现状,分别从温度、载流量、局部放电、受潮、应变/振动和接地电流等状态量进行评述,阐明了不同状态量的检测原理,介绍了目前电缆状态检测技术研究及实践中的应用情况和发展水平,并探讨电缆状态检测技术的主要发展趋势。

特高压直流GIL运行可靠性设计与研究

特高压直流GIL运行可靠性取决于内绝缘设计的可靠性。此外,导电元件直流电流密度的取值、弹簧触头的定位设计、GIL各元件中的绝缘件与金具连接处的楔形气隙的处理以及母线中支撑件的结构设计细节,都会对产品运行可靠性产生重大影响,不能忽视。对于运行环境十分严酷的UHV DC GIL为保证内绝缘工作可靠性和减少气体维护工作量,文中还提出了高气密性结构设计。为适应-50℃低温运行要求,产品选用了液化温度很低的N_(2)/SF_(6)混合气体,对两种气体的配比,压力特性和绝缘特性进行了讨论与计算。还有产品的局放、气体密度及微水含量的监视系统的可靠性设计,都会对产品运行可靠性产生直接影响。文中对上述问题的研究成果作了介绍,可供高压直流产品设计使用。对其中未解的新技术如基于冷镜露点测试原理、微机电技术制作的智能气体湿度和密度监测装置、高压直流复合绝缘套管伞面局放起始场强提出了研究方案。文中提出的诸多GIL运行可靠性设计要点,对于其他超/特高压直流气体绝缘电器可参考选用。

局放检测技术在电力电缆故障在线监测中研究及应用

局部放电检测是评估交联聚乙烯电力电缆(Cross Linked Polyethylene Cable, XLPE)绝缘状况的重要手段。文中研制了一套应用于中压XLPE电缆的局部放电在线监测系统,详细阐述了其工作原理、硬件组成、软件设计及实现方案。该系统通过监测XLPE电缆接地线中的局部放电信号,来综合评估XLPE电缆的绝缘状况。现场运行结果表明,该系统稳定、可靠。

变电设备健康状态监测系统设计

在电力系统中,某一环节的变电设备一旦出现故障且未及时检修,就会对整个电力系统运行造成严重影响。由于人工巡检难以做到实时监测,设备状态频发事件时有发生,亟须一种手段能够对这类变电设备的运行进行实时监测,同时根据变电设备的实时状态变化对变电设备可能出现的故障进行分类预警。通过实验证明了可听声局部放电模型的可行性。以该模型为基础,设计和开发了软硬一体的变电设备健康状态监测系统。该系统能够实时监测变电设备的运行状态,并通过设备的状态变化及时作出相应的故障判断与预警。该系统的成功研制对提升电力系统的设备监测效率、降低人力成本与运维成本、提高经济效益具有一定的参考价值。

ICMmonitor型局部放电在线监测系统在大型发电机组上的应用

通过在离线的情况下模拟电机发生各种局部放电的状态 ,并利用ICMmonitor型局部放电在线监测系统得到了放电量峰值、平均放电电流的棒图以及局部放电的特征图等。在已运行近 10年的机组上安装了ICMmonitor型局部放电在线监测系统 ,通过多次试验所测得的数据对发电机的绝缘状态进行了评定。

基于电容耦合法的环网柜局部放电在线监测技术研究

环网柜绝缘放电击穿故障占比较高,供电公司每年须定期巡检检测环网柜局部放电情况,但仍然存在漏检和误判现象,为了实时了解环网柜局部放电情况,提出借助环网柜带电显示器配置的电容传感器直接从环网柜内部获取放电信息,无需安装昂贵的超高频和超声波探头;提出利用无源型网络变压器滤除幅值较高的低频信号,采用50 MHz采样频率的高速A/D和FPGA快速采集局部放电信号,基于STM32嵌入式技术开发了局部放电在线监测装置,编制了相应软件对局部放电波形和频谱进行绘制。搭建局部放电实验平台对局部放电进行了对比测试,结果表明,研制的在线监测装置对局部放电监测满足设计要求,该监测装置可替代传统带电显示器,具有安装简便的优势,对保障供电安全具有重要的意义。

水轮发电机局部放电监测系统的应用研究

该文主要探究局部放电监测系统的软硬件组成及其在某水轮发电机运行监测中的应用。该系统利用前端的耦合传感器采集局部放电信号,经过信号调理单元的降噪、滤波等处理后发送到下位机进行分析,分析结果在上位机上直观呈现,让管理人员远程监控水轮发电机的运行。从应用效果来看,该系统监测到发电机的最大放电幅值和标称放电量存在异常,初步判断存在局部放电。停机拆检后发现250槽和251槽下层线棒的连接软管存在绝缘磨损情况,更换后监测数据显示最大放电幅值和标称放电量回归正常,问题得到解决。

电力设备局部放电因素分析与实时监测系统优化设计

针对电力设备依靠人工定期巡检完成运维,存在人工劳动强度大、故障处理不及时、容易发生电网供电事故等问题,根据电力设备局部放电的原理,设计了电力设备局部放电在线监测系统。该系统结构简单,成本低、操作简单、需求数据量少,实时传输局部放电数据,对设备进行实时在线监测。通过逐次比较获取放电幅值数据,转换后得到放电相位,完成图谱绘制,分析电力设备绝缘材料损坏程度。通过测试,该监测系统运行稳定可靠,降低运维人员工作量,提升效率,有利于保障电力设备的正常安全运行,避免停电事故带来的损失,具有较好的实用价值。

应用于局放检测的无线组网监测系统研究

电力设备的运行状况对电力系统有着重大意义,耦合电流脉冲信号是表示电力设备运行状况的一个重要参考量,通过实时监测耦合电流脉冲信号可有效防止事故的发生。针对不同设备的定期检修周期不同,从而造成设备欠检修和过检修的情况,开展了合电流脉冲信号无线通信组网监测系统的研究。利用罗氏线圈实时检测到耦合电流脉冲信号,再通过无线传输方式传输至局部放电监测设备,实时反映设备状态。完成了对耦合电流脉冲信号的采集方法,可在不停电的情况下采集相关数据;以无线传输的数据输送方式,将所检测到的数据及时发送至监测仪器中,做到实时监测设备状态;通过将RESTful API寄宿在系统展示层UI界面的后台代码隐藏类文件中,阻止未经授权的访问和数据泄露,保障传输数据安全。满足对电力设备的在线监测要求,在不停电状态下对设备进行健康度辨识与判断,提高了电力设备和电网运行安全性以及供电可靠性。

特高压GIS开关设备电磁波衰减特性及在线监测传感器布点方案研究

特高压气体绝缘金属封闭开关设备(gas insulated switchgear,GIS)在壳体内部布置在线监测传感器,用于实时监测局部放电产生的特高频电磁波信号,然而特高频电磁波信号在GIS内部传播时会产生不同程度的衰减,若在线监测传感器布置不合理,则可能无法发现衰减后的特高频电磁波信号,尤其是如断路器与隔离开关气室等内部组部件繁多的开关设备,特高频电磁波的衰减过程更为复杂,无法通过简单的经验公式进行计算。因此有必要对特高压开关设备内部电磁波的衰减特性及在线监测传感器布点方案开展研究。根据国内主流型号的特高压开关设备的实际结构尺寸,建立三维等比例的电磁场仿真模型,对300~1500 MHz频率范围内的特高频电磁波信号在其内部的衰减特性进行分析,结果显示,由于众多组部件对电磁波信号的衰减作用,特高压断路器气室的平均传输系数比隔离开关气室低10 dB左右。之后在满足相邻两个传感器之间平均正向传输系数不小于-70 dB的基础上,进一步研究特高压开关间隔在线监测传感器的布点方案,结果显示,一个开关间隔内需要在两个电流互感器(current transformer,CT)气室及靠近出线分支的过渡气室共布置3处传感器。研究结果可为特高压GIS在线监测传感器的布点选择提供借鉴。

基于PSO-SVM的高温炉变频电机局部放电预警监测方法

在高温炉加热过程中,非均匀的暂态随机状态会影响高温炉变频电机局部放电信号时间特性,导致时间一幅值关系的离散变量不能确定而影响监测效率,为此提出基于PSO-SVM的高温炉变频电机局部放电预警监测方法。首先,采用奇异值分解(SVD)抑制高温炉变频电机局部放电信号中的窄带干扰,获取有用信号;其次,利用局部线性嵌入(LLE)算法提取降维信号中的局部放电特征参数;最后,将其作为输入特征向量构建基于粒子群优化的支持向量机分类函数(PSO-SVM),完成对高温炉变频电机局部放电类型的识别和监测,并以此为依据求出局部放电阈值预警参数和趋势预警缺陷水平,实现对高温炉变频电机局部放电的预警监测。实验结果表明,所提方法能够有效抑制局部放电窄带干扰,并在一定程度上提高了高温炉电机局部放电信号的识别精度和预警监测效率。