Effect of manufacturer, winding age and insulation type on stator winding partial discharge levels

With thousands of machines monitored for as long as 25 years with the same method, on-line partial discharge (PD) testing has become a recognized, proven tool to help maintenance engineers identify which stator windings need off-line testing, inspections and/or repairs. With over 63,000 test results acquired with the same test method, what constitutes a winding with low, moderate or high PD has been identified. This paper presents tables that enable test users to easily identify with some certainty which stators are likely to suffer from groundwall insulation deterioration, with only a single measurement on a machine. The practical importance of these tables is that if one applies PD sensors to a machine and, in the first measurement, one obtains a Qm that exceeds the 90 percentile of the relevant Qm distribution, then one should be concerned enough at the PD level to take action, such as more frequent testing and/or off-line tests and inspections at the next convenient machine shutdown. Within the statistical accuracy possible with several thousands of independent results, it seems that critical PD levels only depend on operating voltage, hydrogen pressure, manufacturer, and the specific type of PD sensor and instrumentation used.     

Evaluation of the state of the insulation system of a stator winding of high-voltage electric machines based on measurements of statistical characteristics of partial discharges

The statistical characteristics of amplitude and amplitude-phase spectra of PDs in the insulation of model specimens with artificial flaws in a semiconducting coating are investigated. The algorithm for distinguishing the flaws in the stator winding insulation of high-voltage electrical machines based on statistical parameters of the PD spectra is developed and practically implemented.     

On-line monitoring of partial discharges on stator windings oflarge rotating machines in the petrochemical environment

This paper describes a joint collaboration program between a major large electric machine manufacturer and a petrochemical manufacturer to investigate the effectiveness of time- and frequency-domain techniques for the online monitoring of the health of high-voltage machine stator insulation systems. Information is given on the factory and site testing carried out, as well as on the analysis and discussion of the results. It is concluded that both techniques can be used in the petrochemical environment for general assessments, but the time domain technique is required if identification of specific locations of discharge sites is needed     

判断电动机定子绕组首末端的方法

一般电动机定子的绕组首、末端均引到出线板上，并采用符号D1、D2、D3表示首端，D4、D5、D6表示末端。电动机定子绕组的6个线头可以按其铭牌上的规定接成“Y”形或“△”形。但实际工作中，常会遇到电动机三组定子绕组引出线的标记遗失或首、末端不明的情况，此时可采用以下几种方法予以判别。     

双馈异步发电机定子匝间短路故障诊断研究

分析双馈异步发电机定子绕组匝间短路故障负序电流的来源,提出以负序电流作为故障特征量进行故障诊断,建立双馈异步发电机仿真模型,通过改变模型中短路匝数和短路电阻的大小实现了匝间短路故障模拟.对仿真发电机在风速恒定的条件下发生定子绕组匝间短路故障进行了模拟.结果表明,定子发生匝间短路故障后,会在定子中增加负序电流分量,定子负...     

多相电机定子绕组改进绕组函数的有限元分析

提出改进绕组函数的有限元算法,解决了改进绕组函数的准确计算问题。根据有限元算法和叠加原理,分析了线圈和多相电机相绕组的改进绕组函数的基本特征,并根据该基本特征研究了多相电机气隙磁动势分布和气隙电感。结果表明,多相电机相绕组的改进绕组函数与绕组函数之间的差别为与多相电机结构有关的函数,电机正常运行时,该函数通常只含偶次谐波,并会影响电机气隙磁动势分布的计算,进而影响交、直轴电感曲线的谐波,但对交、直轴电感曲线的直流分量影响较小,基本可以忽略。     

无刷双馈电机定子绕组的设计

介绍了无刷双馈电机工作原理及其定子绕组的设计原则和方法,利用双极槽号相位图和单板槽号相位图对具体定子绕组进行了设计和分析。用本文所介绍的方法设计出的无刷双馈电机定子的单套或双套绕组方案,能保证定子绕组各支路感应电势相等以及其他电气性能要求,从而保证了无刷双馈电机的运行性能及可靠性,对无刷双馈电机设计有一定的指导意义。     

600MW汽轮发电机定子绕组水电接头泄漏分析

某电厂一台600MW机组在常规大修中，发现定子绕组多处水电接头漏水，检查发现水盒和空心导线等处泄漏，采取现场修理的办法，成功消除了漏水缺陷。本文详细介绍漏水处理的经过。     

Forces acting on induction machine stator core due to winding faults

A newly developed model for direct calculation of the Fourier components of currents is presented. Any connection of stator coils including shortings, can be analysed. A formula giving forces acting on the stator has the form of a sum of various waves. The waves causing elliptical deformations of the stator yoke have been specially investigated. The calculation and measurement results given refer to a 7.5 kW machine.Ein neu entwickeltes Modell zur direkten Berechnung der Fourierkomponenten der Ströme wird vorgestellt. Beliebige Verknüpfungen der Ständerwindungen, darunter auch Kurzschlüsse, können analysiert werden. Der Ausdruck für die Kräfte hat die Form einer Summe von verschiedenen Wellen. Eingehender wurden jene Wellen untersucht, die zu elliptischen Verformungen des Ständers führen. Die Berechnungs- und Meßergebnisse betreffen eine 7,5 kW Maschine.     

300MW发电机定子绕组高压预试及故障处理

发电机端部绝缘从制造角度来讲是1个较薄弱的部位,运行中发生故障的几率较高,而交、直流耐压试验是判断发电机定子绕组绝缘优劣最常用、有效的手段。本文分析了某公司300 MW发电机定子C相线圈和B相引线绝缘磨损故障,介绍了用高压预示查找故障点并进行定子线棒局部更换,局部修理引线绝缘的过程,总结了发电机故障诊断及其处理的经验和方法。     

溪洛渡左岸电站定子绕组安装技术

详细介绍了溪洛渡左岸首台770 MW发电机定子绕组安装工艺.在借鉴三峡水轮发电机定子绕组安装经验基础上,重点阐述了溪洛渡左岸电站哈尔滨电机厂有限责任公司生产的定子绕组的结构设计及安装特点,同时,对安装遇到的难点进行了分析并给出了解决措施.经试验表明,安装后的机组各项技术指标均符合国家标准要求.这次成功的安装为百万千瓦机组定子绕组的安装积累了可行借鉴经验.     

外高桥发电广发电机定子绕组堵塞故障的早期发现

定子绕组采用水内冷冷却方式的发电机,由各种原因引发的定子绕组热故障,不但在发电机事故中所占比例较大,而且造成的经济损失惨重.介绍2007年5月外高桥发电厂3号发电机因小混床树脂颗粒直径太小且凝集力很强,在毛口处很容易形成堆积堵塞,导致4根线棒堵塞故障情况.该机装有的发电机故障诊断专家系统中的定子绕组温度指纹计算和动态阈值判断定子绕组热故障的功能,在开机过程中、有功功率为125 MW故障线棒槽内检温计温度为55～58℃(未超过现行规程规定的报警阈值)时早期报警,避免了重大事故的发生及其所带来的巨大的经济损失.     

水轮发电机定子绕组不对称支路电磁参数计算模型

为了探讨水轮发电机定子绕组不对称支路参数的计算问题,根据交流电机多回路理论,建立了绕组不对称支路参数计算的数学模型,给出了应用有限元方法计算绕组不对称支路参数的通用方法。通过对样机计算表明,该方法可用于任意线圈组合的电磁参数计算,且计算结果准确;绕组各支路电磁参数的不一致完全体现了各支路不对称程度,不对称支路间的环流损耗随绕组不对称度的增大呈指数关系增长;采用有限元方法进行不对称绕组支路电磁参数的计算,为支路不对称绕组的设计提供了依据,同时也为发电机绕组故障分析打下了良好的理论基础     

大型发电机定子绕组端部的模态试验分析

介绍了模态分析的基本理论,以及用DI 2200实时快速傅立叶分析仪和ME'scopeVES模态分析软件对600MW发电机定子绕组端部所做的模态试验分析。     

Historical development of rotor and stator winding insulation materials and systems

This article presents an overview of some of the significant developments in rotating machine insulation systems that have occurred in the past century. This article describes the chronological development of insulation materials and systems, together with some of the key innovations in manufacturing. For the most part, it was the innovation in materials and manufacturing from wound stator groundwall insulation that paced the development of machine insulation systems.     

Implications for the application of adjustable speed driveelectronics to motor stator winding insulation

Medium voltage (2300V to 4160V) motor stator insulation has been designed to withstand voltage surges from circuit breaker operation for many decades. It is probable that the surges created by ASDs will not pose a threat to properly designed and manufactured insulation. However, as ASDs become more popular in the higher voltage ranges, we will have to watch carefully to ensure that insulation problems do not increase     

Digital analysis of partial discharges

In this paper relevant aspects of digital processing of partial discharge (PD) as measured by conventional PD detection methods are discussed. Moreover, a systematic study of PD quantities is presented and discussed within the scope of practical PD analyzers, including recognition of defects in certain HV insulation configurations     

Automated recognition of partial discharges

An overview of automated recognition of partial discharges (PD) is given. The selection of PD patterns, extraction of relevant information for PD recognition and the structure of a data base for PD recognition are discussed. Mathematical methods useful for the design of the data base are examined. Classification methods are interpreted from a geometrical point of view. Some problems encountered in the automation of PD recognition are addressed     

Assessing the condition of hydrogenerator stator winding insulationusing the ramped high direct-voltage test method

Ramped high direct-voltage tests have proven to be an effective and nondestructive means for reducing in-service stator winding failures. The measured current versus applied voltage response obtained during these off-line tests can be used to detect cracks and fissures, moisture absorption, tape separations, conductive surface contamination, lack of epoxy cure, and internal delamination. Ramped voltage test results have been used to determine when corrective actions are needed and what the appropriate actions are. When done properly, the test can identify stator windings that are approaching failure without accelerating the deterioration process