局部放电测量中单端信号的极性鉴别方法

局部放电选频平衡法中以现场存在的一个高压绝缘产品作为一个试样组成桥式平衡电路，干扰信号和局部放电信号在高频变压器的初级线圈中分别相减和相加，在次级线圈中以单端信号输出。本文介绍一种对衰减振荡的单端信号进行极性鉴别的方法，使选频平衡法具有区分放电试样的能力。     

局部放电选频平衡法的干扰抑制原理

全面分析了选频平衡法局部放电测试和干扰抑制的原理，采用局部放电选频平衡测试电路在模拟和实际高压电路中进行了测量，理论分析与实验结果相吻合。     

局部放电选频平衡法中选频放大器的性能研究

选频平衡法测量局部放电具有超过1000倍的干扰抑制能力。而选频平衡法的核心是选频放大器。本文对选频放大器的性能与干扰抑制比的关系进行研究,主要研究了选频放大器的通频带宽度对测量灵敏度和干扰抑制比的影响,以及试样和参考电容器的电容量之比对干扰抑制性能的影响。最后给出了在实际电路上的测量结果。     

基于空间电容耦合原理的局部放电检测方法及其传感器研究

针对局部放电在线监测中存在的问题,文中基于空间电容耦合原理研制了一种新型局部放电传感器.其分为工频电压波形传感器和局部放电传感器两部分.两者集成在同一块印刷电路板上,使用时无需接地或与被测物体接触,只需将传感器对准被测物体的高压引出线,即可同时对工频电压和局部放电信号进行检测.基于针—板电极模型搭建了局部试验平台,试验...     

基于Marx电路的纳秒级高压脉冲电源设计

为满足等离子体污水处理对高压脉冲电源的要求,设计了一种基于Marx发生器的紧凑型、高重复频率纳秒级高压直流脉冲电源,该脉冲电源以绝缘栅双极晶体管(IGBT)作为放电主开关,并使用多输出磁环变压器为IGBT提供驱动信号。Marx发生器由25级电路组成,每级电路由IGBT开关、快恢复二极管以及电容器组成。充电时,通过电感和二极管对电容充电,减小电路功率损耗;放电时,电感对输出脉冲高电压与输入电源之间进行隔离。为了保护IGBT开关在短路等情况不被过电流损坏,使用了过电流保护电路。实验结果表明,输入电压为500 V低压时,串联25级电路即可获得最大幅值为10 k V、最小脉宽为400 ns且脉冲前沿为50 ns的高压脉冲,可实现反应器中气体的电晕放电,达到污水快速净化的目的。     

高压电抗器局部放电试验电路设计

设计了一种基于串联谐振原理的高压电抗器局部放电测量基本试验电路.首先用有限元分析软件计算出给定频率段(30～300 Hz)的高压电抗器阻抗的特性,通过工频条件下的试验值与计算值做比较,证明该计算方法的正确性,其结果为谐振电容和补偿电容参数值的选择提供依据;然后,建立了试验电路的灵敏度分析模型,利用伴随网络法进行了灵敏度的计算,以灵敏度为依据对高压滤波器的参数进行了设计;最后,运用给定的方法给出了实例验证,它为高压电抗器做局部放电试验的电路设计以及参数确定提供了重要依据.     

介质阻挡放电电路参数测量的改进型Lissajous图形法

为了减少在介质阻挡放电电路参数测量中广泛使用的电压-电荷Lissajous图形法的测量误差,从介质阻挡放电电路的原始等效模型出发,对电压-电荷Lissajous测量法在未放电和放电两个阶段的约束关系进行了推导,得出了如忽略测量电容对测量过程的影响将使介质阻挡电容测量结果偏大和放电维持电压数值存在误差的结论。为解决这一问题,提出了一种改进型Lissajous图形法,该测量方法能使测量电容独立于主回路,减少了常规的李莎茹图形存在的固有误差并实现测量回路与主回路隔离。该方法具有参数测量准确、接线简单及测量工作量小等优点。实验结果表明,所提出的改进型测量方法是有效的。     

自动稳定分压系数的高压分压器

对于交流高压,使用附有输入电容分压器的静电电压表测量比较方便。在高压技术中由于特殊的不稳定因素的影响(如泄漏电流,电晕放电微击穿和其它现象),使用高压电容分压器会增加测量误差。因此,如何稳定高压电容分压器的分压系数是一个特殊的现实性问题。下面研究一下能自动稳定分压系数的高压测量仪的工作原理(见图)。     

计算局部放电电容增量和损耗因数增量的方法(摘要)

对于高压旋转电机,局部放电是引起线棒绝缘老化的重要因素之一。T.W.Dakin等人提出用平行四边形法研究绝缘系统约局部放电特性。用Dakin方法得到的局部放电电容增量△C′=dQ/dV大于用西林电桥法测量得到的结果△C″。本文提出了一个新的方法,借助于平行四边形的测量参     

基于Marx电路的固态高压脉冲电源设计

针对高压脉冲放电和低温等离子体应用的要求,设计了一种基于Marx电路的高重复频率的固态高压脉冲发生装置。该脉冲电源利用Marx电路电容并联充电、串联放电的原理,选取绝缘栅双极型晶体管(IGBT)作为放电开关,控制电路的模态切换。Marx主电路由84级单元组成,每级单元包含IGBT开关管、快恢复二极管和储能电容。实验结果表明,在输入电压为480 V直流电压,并且在300 Hz的频率下,该电源可以产生幅值为20 kV、脉宽为500 ns的高压脉冲,满足设计要求。     

局部放电选频平衡法中选频放大器性能对测量的影响

讨论了选频放大器的通频带宽度对测量灵敏度和干扰抑制比的影响,以及试样与参考电容器的电容量之比对干扰抑制性能的影响。最后给出了在实际电路上的测量结果。     

高压电缆终端在线局部放电测试分析

介绍了综合运用高频(high frequency,HF)与超高频(ultrahigh frequency,UHF)2种测试技术成功实现对运行中高压电缆终端局部放电进行测试的实例.方法是首先利用UHF检测系统初步巡检,然后根据现场情况分别采用多种信号检取方式从被试电缆终端取样测量信号,进行HF深入测量.测试的结果:获得了...     

Novel characterization of PD signals by real-time measurement ofpulse parameters

Measurements of partial discharge (PD) are used to examine the insulation characteristics of HV equipment. This test method is also suitable for low-cost components in mass production. To monitor the quality of prefabricated parts, products and production processes, short test cycles and automatic classification are indispensable. In addition, it is desirable to acquire more information about the PD signals for classification. This can be achieved with an ultra wide band (UWB) measurement system. In this paper a new test method, based on analog capture of PD parameters which describe the PD waveform, in addition to the usual parameters, is proposed. The analog values are further processed employing a digital signal processing hardware and a PC. Measurements of frequently encountered PD pulse shapes and their frequency spectra are used to discuss problems which arise from the integration in the frequency domain. These problems are avoided using integration in the time domain, which is employed to determine the apparent charge with the described measurement system. Using the PD pulse duration as an example, measurements on artificially created test samples are presented, which show the influence of the defect dimensions on the PD pulse parameters. This is feasible for test circuit dimensions not extending to a certain value, which depends on the used frequency range of the measurement system     

Effect of temperature on the partial discharge initiation voltageof capacitors

The paper describes a novel test arrangement to characterize the temperature dependence of partial discharge (PD) inception voltage in capacitors. The test arrangement consist of a temperature chamber, HV supply and PD detection circuit. The corona free operation voltage is 0 to 3.8 kV, temperature range is -50 to 200°C. Different type of capacitor PD inception voltage were measured at different temperatures. It was found that most commercial capacitor PD was lower than the rated voltage and increased with the temperature. In contrast, the higher quality chip type ceramic capacitor PD was above the rated voltage and decreased with the temperature. The paper concludes that the prediction of capacitor performance requires the measurement of PD at different temperatures     

500 kV增城变电站变压器局部放电的声发射检测

介绍了运用声发射(AE)检测技术进行变压器局部放电(PD)检测的工作原理和基本方法,以及美国物理声学公司(PAC)声发射检测系统的特点。以增城变电站2台大型变压器的局部放电声发射检测试验为实例,介绍了变压器局部放电声发射检测的试验步骤和试验方法,并分析了试验数据,检测结果表明,AE检测结果与油色谱分析及常规高压PD试验的结果基本吻合,且能够对PD源进行区域定位和三维定位,声发射检测系统可有效应用于大型变压器PD的实时在线带电检测。     

On-line partial discharge calibration and monitoring for power transformers

Partial discharge (PD) is one of the major factors causing insulation damage of power transformers. This paper describes the development of on-line partial discharge monitoring system for transformers. The developed set can monitor up to four power transformers continuously. It uses various methods to reject interference and enhances monitoring sensitivity of PD effectively. The optical cable is applied to communicate between measurement system near transformers and the upper computer in the main control building. On-line calibration of partial discharge quantity is requisite for on-line detection or monitoring. This paper describes an on-line calibration method using pulse injection through tap of high voltage transformer bushings. It also discusses the influence of limit inductance and bushing capacitance, from tap of bushing to ground, in on-line calibration circuits. Influences of multi-grounding of the transformer tank for monitoring and calibration are also discussed. Simulation in laboratory and site test shows that the method is practically valid for on-line PD calibration of power transformers within permissible engineering error range under certain defined conditions. This system has been in operation steadily in 500 kV substations for more than 2 years.     

Partial discharge detection in cables using VHF capacitive couplers

In order to detect and locate partial discharge (PD) activity within HV cables and in particular cable joints, the feasibility of using a very high frequency WHO capacitive coupler technique has been investigated. In addition, an alternative PD offline test method for cable joints or cable sections within long cable systems has been developed. By energising the joint or a short section of the cable screen only this method has the advantage of reducing the power supply requirement of the test source. The application of capacitive couplers for this PD offline test method has been investigated. In order to use this approach there must be an insulation gap between the coupler and the outer sheath of the test cable. The effect of this gap on measured sensitivity has been investigated experimentally and through the use of a simulation model. Obtained results are in good agreement. Cross-correlation techniques have been implemented to automatically estimate the signal time of flight from different-coupler outputs. Methods of calibrating the coupler applied to the alternative PD offline test method have also been investigated.     

Fundamentals in computer aided PD processing, PD patternrecognition and automated diagnosis in GIS

The partial discharge (PD) measurement is a sensitive method for testing and monitoring the insulation condition of HV apparatus. Digital PD measurements have become state of the art. Computer-based PD diagnostic systems nowadays can be used to increase the reliability of modern gas-insulated system (GIS). Also on-line monitoring of HV equipment is becoming increasingly important to enable prevention of a sudden breakdown of PD affected components. On-line monitoring must be done on-site, but an important problem of on-site PD measurement is the superposition of PD data and interference. Furthermore, reliable recognition of the type or nature of the insulation defect is necessary for any risk assessment. Traditionally, this is achieved with reference to expert knowledge. An alternative approach is presented in this paper, which treats the fundamentals of automated computer-based PD diagnosis, taking into account that successful noise suppression is essential for a successful on-site diagnosis     

开关柜局部放电暂态对地电压的分布特性研究

暂态对地电压技术在高压开关柜局部放电带电检测中越来越重要,因此需要对如何更好应用TEV技术展开研究。在分析TEV技术原理的基础上,运用时域有限差分法对金属柜体的暂态对地电压进行了仿真分析,并通过开关柜局部放电TEV信号实测对仿真结果验证,两者具有较好的一致性,说明该方法仿真分析开关柜TEV幅值分布特性的可行性。基于上述方法,对典型高压开关柜外表面上布置的42个测试点的TEV信号进行仿真分析,结果表明:TEV幅值随着传感器与放电源之间距离的增大而减小;传感器靠近柜体表面电磁波的不连续处,可获取较大的TEV幅值;独立开关柜之间的相互电磁干扰小。为TEV法在开关柜局部放电带电检测中的更好运用提供了理论依据。