Electrical and chemical diagnostics of transformers insulation. B.Accelerated aged insulation samples

This paper describes the analysis of accelerated aged insulation samples to investigate the degradation processes observed in the insulation from aged power transformers. Short-term accelerated ageing experiments were performed on paper-wrapped insulated conductors and on pressboard samples. The condition of aged insulation samples was investigated by two relatively new diagnostic techniques: (a) measurements of interfacial polarization spectra by a DC method; and (b) measurements of molecular weight and its distribution by gel permeation chromatography (GPC). Several other electrical properties of the paper/pressboard samples were also studied. Possible correlations have been investigated among the different measured properties. The GPC results have been used to predict how power transformer insulation molecular weights change with temperature and time     

浅议变压器固体绝缘的化学监督

常规化学绝缘监督方法是通过气相色谱法等手段来预测变压器内的潜伏性故障，但该方法判断变压器固体绝缘老化不准确，为此，介绍了监测固体绝缘老化的重要化学监测手段-糠醛测试，阐明测试的重要意义和方法，并结合日常工作实际提出了如何把糠醛测量有机地利用到化学预试中来。     

浸漆绝缘工艺对电子变压器质量的影响

介绍了电子变压器用绝缘浸渍漆的性能要求，介绍了一些进口绝缘浸渍漆的性能指标，分析讨论了漆的烘烤温度、时间、干燥性、浸渍工艺对电子变压器的噪声、生锈、外壳爆裂、绝缘胶带脱开的影响，讨论了绝缘漆在应用中的环保问题。     

500kV电力变压器匝间绝缘模型线圈的电老化特性

针对变压器匝间绝缘是电力变压器损坏事故中的主要损坏部位的问题,设计并制作了500 k V电力变压器匝间绝缘的线圈模型,研究匝间绝缘的电老化特性。根据模型线圈预试验的结果,确定了实验方案,并基于极大似然法思想确定求取反幂模型中的参数方法;最后求取不同数据量下的参数值。分析结果表明:不同数据量下所求得的参数值不同,若使电压寿命指数N不出现异常值,至少需要在4种电压持续时间下进行实验;在10种电压持续时间下可得到可靠的电压寿命指数N,其值为13.38。最终通过简单计算及仿真分析求得了老化寿命与电场强度间的反幂模型,用于指导实际变压器的生产设计。     

Investigating the effects of oxidation and thermal degradation onelectrical and chemical properties of power transformers insulation

This paper describes the analysis of thermally accelerated aged insulation samples to investigate the degradation processes observed in the insulation of aged transformers. Accelerated ageing experiments were performed on paper wrapped insulated conductors in the presence of air and nitrogen environments over a temperature range of 115 to 145°C. Effects of oxidation on the ageing of oil-paper insulation were investigated and results are presented in this paper. The condition of aged insulation samples was investigated by a number of diagnostic techniques: (a) measurements of interfacial polarization spectra by the return voltage method, (b) measurements of molecular weight and its distribution by gel permeation chromatography, (c) surface analysis by X-ray photo-electron spectroscopy, and (d) a study of the oxidation of the oil by UV-visible spectroscopy. Results from these measurements are presented in this paper and are used to analyse the degradation process with special emphasis on oxidation     

A recent development in the electrical insulation systems ofgenerators and transformers

Mica/epoxy and oil/cellulose have dominated insulation systems of rotating machines and power transformers for over 100 years. In recent years, however, XLPE cables have been introduced to generators and transformers as HV windings. This has resulted in a new type of generator (Powerformer^TM), a new type of wind-power system (Windformer^TM) and a new type of transformer (Dryformer^TM). The new types of HV generator and transformer offer high efficiency, long life and low environmental impact and give new possibilities for the design of HV apparatus. The products developed represent new demonstrated possibilities in HV electromagnetism utilizing the potential in Maxwell's equations     

Dielectric response methods for diagnostics of power transformers

The dryness and aging state of oil-paper insulation is a key factor in both the short- and long-term reliability of a power transformer, since moisture has deleterious effects on dielectric integrity and insulation aging rates. Today, the water content of the cellulose in an in-service transformer is determined indirectly via moisture measured from oil samples, according to IEC 60422. This report summarizes the work performed by Cigre Task Force 15.01.09, and presents conclusions regarding the state of the knowledge on the applicability of the current diagnostic techniques.     

Drying of transformer insulation using zeolite

Power and distribution transformers are some of the most important components in the power network. The presence of moisture in a transformer deteriorates the transformer insulation by decreasing both the electrical and mechanical strength of the solid insulation. It is of great importance to pay attention to the moisture content of composite insulation systems in order to maintain low dielectric loss, high dielectric breakdown strength and low rates of degradation of the insulating system in HV equipment. In this paper, an approach to the said problem is presented. With the application of a synthetic hygroscopic mineral (molecular sieve zeolites) - a revolutionary, environment friendly, multipurpose mineral - a continuous drying process of the transformer oil during operation without the need for service interruption is achieved. A study of the effects of zeolite on the electrical and dielectric behaviour of the insulating liquid of the transformer is included in this paper.     

电力变压器纵绝缘

分析了电力变压器在雷电作用下的梯度电压，指出理论分析只能得到其规律性，实际线圈纵绝缘结构数据还应以实验校核。     

变压器油纸绝缘极化谱的仿真研究

回复电压测量方法能有效检测变压器固体绝缘的含水量,然而对于含有局部峰值点的回复电压极化谱,难以给出明确的诊断结论.在引入扩展德拜模型基础上,建立了绝缘极化、老化过程和等值电路参数三者之间的关系,并仿真分析了电路参数的改变引起特征量和极化谱的变化规律.仿真分析结果表明,回复电压特征量的主时间常数能诊断不同几何电容的变压器...     

Cellulose insulation in oil-filled power transformers: part II maintaining insulation integrity and life

This paper examines the practical aspects of the usage of cellulose insulation in transformers with regard to maintaining the integrity over long periods of time and preserving and extending insulation life. The factors that relate to loss of life are examined and life plots are discussed in more detail.     

油纸绝缘变压器非标准极化谱的仿真研究

针对含有局部峰值的非标准回复电压极化谱的还未能明确的诊断变压器绝缘状态,依据时域介质响应理论,结合现场回复电压测量数据,将扩展德拜模型引入介质响应等值电路,建立变压器油纸绝缘系统等值电路模型.对非标准极化谱进行仿真分析,建立非标准极化谱与等值模型参数之间的关系.仿真结果表明,各时间常数支路的变化可使极化谱产生局部峰值,而且极化谱前端的局部峰值能反映变压器绝缘油的状态情况,同时试验研究结果证明仿真结论是有效的,弥补依据非标准极化谱进行绝缘诊断的空缺.     

变压器绝缘在线监测技术简介

论述了油浸式电力变压器绝缘在线监测技术的现状及发展趋势,并分析了各种在线监测方法的原理。     

油纸绝缘变压器介质响应极化谱的探索与研究

基于扩展德拜模型,建立油纸绝缘变压器绝缘状态与介质响应等值电路之间的关系,并仿真分析模型(时间常数、支路数)改变引起回复电压特征参数和极化谱的变化规律。仿真分析结果表明,极化谱回复电压峰值与主时间常数可作为变压器绝缘诊断的判据,且时间常数不同的RC支路在回复电压极化谱的对应区段才有所影响。通过研究多台不同绝缘状态的变压器,总结出绝缘老化程度与支路数取值的内在联系,由此获取的等值参数最优,所建立模型与变压器实际状况相吻合,可作为油纸绝缘系统状态准确诊断和研究的基础。     

Suspended particles in the liquid insulation of aging power transformers

This paper examines some theoretical aspects of the relationship between the aging of oil and the deterioration of the internal insulation of the windings, and looks at some new findings that might provoke fresh consideration of the relationship between the analytical properties of liquid insulation and the dielectric properties of windings.     

Identification of the main insulation residual resource for distribution transformers

A modern method for testing control of the transformer main insulation condition on the basis of self-discharge voltage and the return voltage is described. The patented scheme of a device for measurement of these voltages is shown. Formulas for the transformers’ main insulation residual resource are listed.     

变压器中性点过电压分析与绝缘配合

电力系统发生不对称短路、非全相运行和雷击等故障时,变电站变压器中性点会出现较高的过电压,严重影响中性点绝缘的可靠性,因此需要对变压器中性点过电压和绝缘配合开展研究。文章在PSCAD/EMTDC中搭建110 kV输电系统仿真模型,计算分析线路发生各种故障时的中性点过电压,依据仿真所得过电压值,确定放电间隙距离以实现更加优化的绝缘配合。结果表明,线路发生单相接地故障时中性点最高过电压为117.73 kV;发生单相断线时中性点最高过电压为52 kV;发生雷击时中性点最高过电压为118 kV;采用放电间隙并联避雷器的中性点保护方式时,选取放电间隙距离为13 mm～14 mm时能达到最优的绝缘配合效果。该研究结果可以为110 kV变压器中性点的绝缘配合优化提供重要的理论和实验参考依据。     

一种新型油浸式变压器绝缘纸板含水量检测方法

变压器绝缘纸板绝缘材料中含有过高的水分,会加速变压器的老化,还会带来绝缘性能下降等危害,因此测试变压器绝缘纸的水含量十分必要.本文主要介绍一种综合采用极化—去极化电流和频域(变频)分析对变压器进行含量水量测试的方法,并列举现场应用实例,应用结果证明该方法的实用性.     

Partial discharge diagnostics and electrical equipment insulation condition assessment

Partial discharge (PD) measurement has long been used as a test to evaluate different insulation system designs, and as a quality control test for new equipment. However, in the past 20 years, PD measurement has been widely applied to diagnose the condition of the electrical insulation in operating apparatus such as switchgear, transformers, cables, as well as motor and generator stator windings. Improvements in the capabilities as well the lower cost of sensors, electronics and memory is partly the reason for the increased popularity of PD diagnostics. Another reason has been the development of methods-including the use of ultrawide band detection-to improve the reliability of the PD measurement in the presence of noise. In addition, rapid progress is being made in automated pattern recognition techniques that also helps to suppress noise. This paper reviews the various PD measurement technologies that have been specifically developed to improve PD diagnostic methods, and outlines how they have been implemented for stators, cables, transformers and switchgear. Areas for further research are also presented.     

大型变压器绝缘件监造典型案例分析

对变压器雷电冲击试验时所发生的放电现象进行了分析,得出故障原因是变压器绝缘层压板在生产制造过程中出现裂纹、气隙导致层压板击穿放电.