变压器局部放电超高频信号外传播特性的试验研究

介绍了目前内置超高频传感器在电力变压器局部放电监测中的应用情况,分析了利用外部传感器检测局部放电产生的超高频信号的可行性,设计了一套基于超高频法的电力变压器局放测量系统。实验结果表明,超高频电磁波可以透过变压器夹缝衍射出来,为变压器局部放电检测提供了一种新途径。     

用于变压器局部放电检测的超高频传感器的初步研究

传统的局部放电检测方法，由于测量频带窄、抗干扰能力差、信息量少，已经不能满足变压器局部放电检测（特别是在线检测）的需要，因此，近年来提出的超高频检测技术得到了较快的发展。根据GIS中超高频检测的经验，并结合变压器的结构和放电特性，该文研制了一种宽带超高频传感器，其有效带宽为500～1500MHz。用天线理论对传感器的特性加以分析并在实验室中进行了性能实测，结果表明该传感器具有良好的使用特性，该文用该传感器研究局部放电信号，在其有效频率范围内可以精确地提取放电发射的电磁信号，从而为进一步研究超高频局部放电检测技术在变压器中的应用奠定了基础。     

变压器局部放电在线监测超高频Hilbert分形天线研究

论述了Hilbert分形天线基本原理,并根据分形天线电磁场理论,提出了应用于变压器局部放电超高频在线监测的Hilbert分形天线优化设计方法。通过仿真计算,研究了几何参数对Hilbert分形天线性能的影响,设计出用于变压器局部放电监测的3阶Hilbert分形天线。通过气隙放电、沿面放电、电晕放电3种典型变压器绝缘缺陷局部放电实验,采用分形天线和脉冲电流传感器对这3种局部放电进行了测量,并分析了分形天线的局部放电测量信号功率谱。实验结果证明该天线能够有效应用于变压器局部放电超高频在线监测。     

三相共箱式GIS局部放电超高频信号特征的研究

GIS在制造和装配过程中难免会留下一些潜伏缺陷,导致在运行中引起GIS内部局部放电。研制了一种超高频宽带振子天线——套筒天线传感器,并对其性能进行了仿真计算,结果表明可以用作局部放电检测的超高频传感器。为研究三相共箱式GIS中存在缺陷引起的局部放电超高频信号的特征,建立了6种典型缺陷模型来模拟局部放电故障,采用自建的局放检测系统测量得到了各种缺陷下GIS局部放电的宽频带特征,为三相共箱式GIS局部放电缺陷的监测和诊断奠定了良好的基础。     

GIS局部放电检测用外置传感器性能仿真分析及其设计

超高频局部放电检测法是通过超高频传感器传感GIS内部局部放电所产生的0.3~3 GHz的超高频电磁波,从而实现局部放电的检测和定位,并实现抗干扰。利用高频有限元仿真软件Ansoft HFSS对用于GIS局部放电的常用外置传感器进行仿真,分析了传感器设计参数对其性能的影响,在此基础上设计出工作频带为354~443 MHz的矩形微带贴片窄带传感器和0.5~3 GHz的双臂平面等角螺旋传感器。     

超高频方法在变压器局部放电检测中的应用

为了探讨局部放电超高频检测技术的应用,将数字化测量和超高频检测技术相结合,分析了局部放电超高频检测技术的原理。在简要介绍了局部放电超高频检测系统硬件和软件的组成后,实测并分析了检测系统的抗干扰性能。通过变电站电力变压器的现场局部放电测量,及时发现了设备的局部放电水平异常,避免了事故的发生。分析和实测表明,超高频方法较其它方法相比能有效避开电晕干扰,更易于发现设备绝缘系统早期绝缘缺陷,检测结果能准确反映设备绝缘状况,适用于电力变压器局部放电在线监测。     

直流电压下油纸绝缘中局部放电的超高频特性

为研究直流电压下油纸绝缘中局部放电的超高频特性,组建了一套直流电压下局部放电试验系统以及由局放超高频检测和超宽带检测组成的测量系统,其中脉冲电流超宽带检测的作用是确保超高频检测获取的信号来自于试品自身的局部放电。试验设计了6种油纸绝缘局放模型以模拟换流变压器的典型缺陷,并引入毫瓦分贝(DBM)频谱分析对超高频信号进行了统一化处理,以比较不同缺陷模型对应的超高频信号。直流下试验结果表明:局部放电电流脉冲具有极快的上升沿,能激励起大于300MHz的超高频电磁波,它可以通过超高频传感器加以耦合接收。各种缺陷模型局部放电的DBM频谱分布各异,超高频段能量幅值最大处也不一样。因此若想以高信噪比实现直流下局部放电超高频信号的在线监测,需要使用中心频率可调的窄带滤波器。这些特性为直流输电系统中使用油纸绝缘的电工设备进行局部放电超高频信号在线监测提供了试验依据。     

用超高频局部放电测量法实现电力变压器局部放电的在线监测

高频局部放电测量法(UHF法)与传统的脉冲电流法完全不同，它采集的被测信号为局部放电过程所产生的超高频电磁波：利用UHF法可有效解决电力变压器局部放电在线监测中的抗干扰问题。文中结合变压器结构设计的放油阀式和人孔／手孔盖式超高频信号传感器安装在220kV和110kV电压等级变压器上，成功地捕捉到变压器内部局部放电产生的超高频信号。对变压器局部放电故障诊断的判据等问题进行讨论，为变压器超高频局部放电在线监测方法的应用积累了经验。     

油中局部放电检测脉冲电流法与超高频法比较

为了研究局部放电检测中超高频法参量与脉冲电流法参量之间的关系,比较分析了局部放电检测中超高频法和脉冲电流法在原理上的区别。利用脉冲电流法和超高频法对油纸绝缘的几种典型模型下的局部放电活动同时进行测量,比较分析同一模型下的局部放电中超高频法参量与脉冲电流法参量之间的关系并探讨了局部放电检测中脉冲电流法对超高频法的标定问题。研究表明,在反映放电活动强弱上,超高频法的参量和脉冲电流法的参量之间有着相同的变化趋势,但是二者之间不存在直接的线性关系。     

基于超高频的直流电场下油纸绝缘局部放电检测与特性研究

为研究直流电场下的局部放电特性,开发了直流电场下局部放电的超高频信号测量系统,设计了针板、悬浮、沿面和气隙四种放电模型,通过对不同放电模型中局部放电产生的超高频信号进行测量和特性分析,研究了不同放电模型中超高频信号的频谱特性。结果表明:直流电场下不同放电模型中的局部放电可产生几百纳秒的超高频信号,其频谱分布中幅值较高的频段并不相同;在不同极性直流电场下,针板放电模型中超高频信号都存在300~500 MHz的超高频段,且负极性时还存在600~700 MHz的超高频段,除针板放电模型外的其他模型在不同极性直流电场作用下局部放电产生的超高频信号频谱较为相似;当外施直流电场升高时,局部放电产生的局部放电超高频信号的频谱幅值明显增大,但主要峰值的频率位置和频段并未发生明显变化,该特点可作为区分放电模式的有效依据。     

Comparison of on-line partial discharge detection methods for HV cable joints

The capacitive coupler, acoustic emission (AE) sensor and radio frequency current transducer (RFCT) have been used to detect partial discharge (PD) activity within a 132 kV prefabricated cable joint containing a known defect. Although each of the three methods has been applied individually under different situations, a comprehensive investigation and comparison of these three methods has not yet been made. Results obtained were compared to measurements made using the conventional electrical detection method. The quantification of the capacitive coupler measured signal in mV with a discharge apparent quantity in pC has been investigated and an on-line quantification method proposed. The capacitive coupler has good detection sensitivity and PD location can be realised by studying the time of Right between signals from two sensors. The difference in pulse shape, spectrum and time of flight between an internal discharge and external interference has been investigated. The AE approach has the advantage of being free from electrical interference. However, investigation indicated that AE signals were significantly attenuated within the cable joint. RFCTs were used to detect the discharge current flowing through the cable sheath. Where the detection sensitivity was low, a wavelet de-noising method was applied to process the RFCT signals and proved to tie effective in increasing the measurement signal to noise ratio.     

Partial discharge on-line monitoring for HV cable systems using electro-optic modulators

A technique for the remote inspection and monitoring of partial discharge (PD) activity using an optical network is described. The network uses a LiNbO/sub 3/, modulator to modulate the intensity of the transmitted laser light approximately proportional to the voltage applied across the modulator. The laser light is transmitted along an optical fibre and measured remotely by a high-speed optical receiver. A capacitive coupler has been used to detect partial discharge activity and act as the modulator's input voltage source. The electro-optic modulator is passive and does not require a power supply at the site of the PD detection sensor. The system has the additional advantages of being immune to electromagnetic interference, having very little signal transmission attenuation, with good sensitivity, compact size, as well as being convenient to use and safe. Both simulation experiments and practical PD tests on two cable systems have indicated that the optical system provides a feasible remote PD monitoring technique for high voltage cable systems.     

Pattern analysis of partial discharges in SF6 GIS

The measurement of partial discharge(PD) of several faults in gas-insulated system (GIS) is discussed. Phase-resolved PD patterns have been measured using three different PD detection measuring systems: according to the IEC 270 recommendations, a VHF/UHF measuring system with narrow band filtering, and the UHF measuring system with wide band filtering. PD patterns are compared using computer-based discrimination tools. The influence of the selected center frequency on the PD patterns is discussed for the narrow band VHF/UHF measuring system. The influence of the number and type of GIS components between the discharging defect and the capacitive coupler on the shape of the PD patterns is analyzed. For several GIS components the signal reduction is studied. It was found that the shape of PD patterns is independent on the used PD detection circuit and the propagation path of the PD signals. As a result, discrimination and classification of PD distributions of several studied defects are possible using digital tools     

超高频技术检测高压电力电缆及接头中局部放电的研究

本文介绍了超高频技术检测高压电力电缆及接头中局部放电的特点 ,对超高频电容耦合器做了一定的研究 ,并给出了试验系统和结果 ,此外简介了国内外在这方面的发展现状     

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...     

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.     

高压电缆附件局部放电超高频检测与分析

为保障XLPE电力系统安全运行,开展高压系统附件局部放电(PD)检测研究,建立了110kV交联聚乙烯电缆接头的数学物理模型并利用时域有限差分法对其内部产生的PD超高频(UHF)电磁波的传播特性进行数值仿真。研究检测位置和金属护套以及半导电层等4种因素对UHF信号波形畸变和能量衰减的影响,并通过实验室电缆接头PD实测验证的仿真结果表明:金属护套和半导电层对UHF信号波头和频率有较大的衰减作用,在-20dB衰减条件下,UHF传感器距离接头的理论值应<3m,且上限频率≤500MHz。     

Ultra-wide-band PD diagnostics of power cable terminations in service

During the past decade the PD probing in the ultra-high frequency (UHF) range has successfully been proven for on-site PD diagnostics of GIS cable terminations in service. Therefore it was decided to apply this non-conventional method also for condition assessment of the insulation integrity of outdoor cable terminations. In order to evaluate the minimum detectable PD level the paper deals with comparative PD studies using the IEC and the UHF method. Moreover, experimental studies on the attenuation of PD pulses traveling through power cables were performed in order to assess the spatial selectivity of the UHF method applied.     

Calibrating the UHF technique of partial discharge detection usinga PD simulator

The paper describes a technique for simulating the presence of partial discharges in gas-insulated substation (GIS) equipment. The technique employs a pulse generator to inject current pulses through a suitable protrusion. The current pulses have similar temporal characteristics to those produced by an actual discharge event, with the added advantage that their magnitudes can be controlled accurately. Because the pulses are highly reproducible, they are ideally suited for investigating the UHF technique of partial discharge detection. The paper discusses the relationship between the magnitude of the UHF signal received by a coupler and the discharge magnitude. It also shows that the coupler signal is dependent on the protrusion length and on the spatial relationship between the protrusion and the coupler. The implications for practical discharge measurements in GIS also are discussed     

局部放电UHF检测量纲标准化的探讨

特高频(UHF)局部放电检测技术取得了广泛应用,但不同产品的检测结果量纲表示方法不统一,相互之间缺乏可比性,从而难以对此类检测系统性能进行统一有效的量化评价。本文重点探讨了局部放电特高频检测的量纲问题,基于局部放电特高频信号的物理本质和局部放电UHF耦合器的特性,提出了采用“局部放电辐射信号的脉冲电场强度幅值”来表征特高频局部放电信号强度的思想。通过对当前主流局部放电特高频检测产品的量纲表示进行了深入的解析,探讨了以电场强度的量纲“uV/m”来统一局部放电特高频检测结果的技术可行性。