测定油中糠醛含量判断变压器固体绝缘老化程度

通过高效液相色谱法检测变压器油中的糠醛含量,配合气相色谱分析,对变压器内部绝缘材料过热故障和设备的寿命及老化程度给出估计。本文叙述了检测方法及实测油样的情况。     

变压器油中糠醛含量与固体绝缘老化关系的研究

通常诊断油浸式变压器寿命的方法主要是利用气相色谱法测定油中的一氧化碳和二氧化碳的生成总量来判别绝缘纸老化的程度,这种方法准确性较差。糠醛含量法是一种油浸式变压器绝缘监督的新方法。为此,阐述了糠醛含量法的基本原理,介绍了油中糠醛质量浓度的测定方法,分析了油中糠醛质量浓度与一氧化碳、二氧化碳的体积分数之间的关系。根据糠醛的质量浓度值取对数后与代表绝缘纸老化程度的纤维素聚合度之间有较好的线性关系的情况,介绍了计算纤维素聚合度的经验公式,并列举了实例验证公式的准确程度。研究结果表明,糠醛含量法是一种油浸式变压器绝缘老化监督较为实用、准确、方便灵活的方法。     

检测变压器油中糠醛含量以监督其绝缘老化

检测变压器油中糠醛含量，对其纸绝缘老化情况进行判断，是近几年发展起来的一项监督新技术。本文闸述了油中糠醛含量的检测以及它与变压器纸绝缘老化程度的关系，并对省电网主变油中糠醛含量检测结果进行分析研究     

用油中糠醛含量估计变压器的绝缘老化状况

一、前言长期以来,变压器以及其他充油电气设备,依靠气相色谱测定绝缘油中的溶解气体,以此监视设备的运行状况,对设备的安全经济运行起到积极作用。但是,用气相色谱法确定变压器的固体绝缘老化程度时,常常得不到明确的结论。其主要原因是:由绝缘纸老     

变压器油中糠醛含量与绝缘纸老化关系的研究

用高效液相色谱法检测绝缘油中的糠醛含量可以判断绝缘纸老化程度。对安徽省近百台变压器的绝缘油进行了取样分析,通过图表及统计理论分析,确定了变压器油中的糠醛浓度与其运行年数成指数关系,并运用概率统计的基本原理,确定了回归直线的置信范围,将其划分为正常老化区、非正常老化区及缓和化区3个部分,并进行了分析。     

变压器油中糠醛含量分析方法研究

检测变压器油中糠醛含量是判断变压器绝缘纸老化程度的有效方法.比较了检测变压器油中糠醛含量所采用的液相色谱法和分光光度法,其中液相色谱法具有准确度高、重现性好的优点.通过试验得到液相色谱法的检测条件:检测波长265 μm或270μm;流动相为甲醇与水的混合液,二者的体积比为1:1;检测流量0.8 mL/min;萃取荆为甲醇,采用5 mL甲醇萃取5 mL试验用油;萃取时间(1～2)min.采用液相色谱法对江西省235台不同运行年限和不同电压等级的变压器油中糠醛含量进行了检测,发现变压器运行年限越长,油中糠醛含量越大,符合实际运行规律.     

基于糠醛含量分析的电力变压器绝缘老化诊断

对油中糠醛含量、溶解气体含量和绝缘纸聚合度等数据进行了分析,并提出了电力变压器绝缘老化诊断模型.     

变压器中纸绝缘热老化的试验研究

本文介绍了利用高效液相色谱法判断变压器中纸绝缘热老化的原理。用此方法对纸在试验室不同条件下进行了老化研究。通过测定纸的聚合度(DP)及用液相色谱法测定变压器油中的糠醛含量而发现:在油纸绝缘中,纸的聚合度降低与油中糠醛含量的增强为线性关系。作者还对近200台220千伏及以下的运行变压器的油中糠醛含量作了普测,取得了有实用价值的数据。     

Thermal aging characteristics of insulation paper in mineral oil in overloaded operation of transformers

A sudden capacity increase in demand during the summer peak, or in contingencies such as malfunctioning transformers, may cause an overload in normal transformers. In this paper, on the basis of overloaded transformer operation in distribution substations, thermal aging testing in oil was carried out under various overload patterns, such as short‐term overload and long‐term overload, but with the winding insulation paper's lifespan loss kept constant. From the results, various characteristics, such as the mean degree of polymerization and production of furfural and (CO₂ +CO), and their effects on the lifespan loss of the insulation paper, were obtained. © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 182(2): 1–8, 2013; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21292     

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.     

Limit values of the gas concentration in the oil of current transformers with capacitor insulation

The calculation results of the concentrations of the gases solved in the oil of the regular working condenser type instrument current transformers (U-shape dead tank 330 kV, and “bar-primary” live tank 330, 500, and 750 kV) is presented. The volume of each sample is 400 and more CT. The unified normative values of the maximum admissible concentrations of gases (on the level of the integral distribution function F = 0.95) for three groups of CTs (“Hair-pin” subtypes and two groups of the toroid type with different types of oils) are proposed.     

The transport of copper through oil-impregnated paper insulation in electrical current transformers and bushings

In an investigation of OIP (oil impregnated paper) insulation removed from current transformers and bushings that have failed or have been taken out of service, the authors observed dark stains near the paper adjacent to copper braids that is used for capacitive grading. They investigate their cause and how they might affect the performance of the insulation. Analytical tests show that the stains were copper oxides, the type of oxide depending on the availability of oxygen.     

Influence of oil aging on the space charge dynamics of oil‐immersed paper insulation under a DC electric field

The formation of space charge in oil/paper insulation system can lead to material degradation in the region of high electric field. Therefore, it is important to understand the factors that affect space charge formation in oil/paper insulation system. In this paper, the effect of oil aging on space charge dynamics in oil/paper insulation system is investigated using the pulsed electroacoustic (PEA) technique under a DC electric field at room temperature. The ultraviolet/visible (UV/vis) spectrum of the oil shifts to longer wavelengths, and the oil acidity increases as the aging time increases. It has been found that the oil property has a significant effect on the space charge distribution in the oil/paper insulation sample. The more the deterioration of the oil, the larger amount of negative and positive charges accumulated in the bulk of the oil/paper insulation sample. The total amount of slow moving charges, the surface trap energy density, and the electric field distortion of the oil/paper insulation sample increased with the degree of deterioration due to oil aging. © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

一种油浸式电力变压器纸绝缘老化评估新特征量

针对油中糠醛含量随变压器运行时间变化的分散性较大,难以准确评估油浸式变压器纸绝缘老化状态的不足,对甲醇、乙醇等低分子醇作为变压器纸绝缘老化评估新特征量进行了理论分析与实验研究。对绝缘纸的老化机理以及化学键断裂进行分析,从理论上探究甲醇、乙醇等低分子醇的产生原理及主要生成途径。采用气相色谱-质谱联用法对现场2台老旧变压器绝缘油样品中的甲醇、乙醇及糠醛含量进行了测定。实验结果表明,2组样品中均未检测到糠醛,但却检测到数量可观的乙醇。进一步地,对现场2台刚投运变压器的检测结果对比分析,分析结果揭示了乙醇可以作为一种有效表征变压器绝缘纸老化的新特征量,且比糠醛特征量相比更为有效。     

采用改进Davidson-Cole介电模型的变压器油纸绝缘状态分析

为利用频域介电谱准确分析变压器油纸绝缘状态,引入考虑直流电导率与跳跃电导率的改进DavidsonCole介电模型。运用测量的频域介电谱数据参数化改进Davidson-Cole介电模型,将其转化为非线性优化问题。选用混合蛙跳优化算法对改进Davidson-Cole介电模型参数进行辨识,得到了弛豫时间τ、圆弧不对称度β和直流电导率σ_(dc)等特征参数。研究了老化与受潮对油纸绝缘试样的改进Davidson-Cole模型参数的影响特性,结果表明β与糠醛含量、σ_(dc)与水分含量有着良好的指数关系;τ与糠醛含量、水分含量有着良好的对数关系。通过线性拟合获得了糠醛含量、水分含量与模型参数的量化关系式,其拟合优度较高,因此可利用改进Davidson-Cole模型定量评估变压器油纸绝缘状态。     

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.     

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。     

Background information on high temperature insulation forliquid-immersed power transformers

The availability of insulation materials having a higher temperature rating than cellulose has led to the design of high temperature power transformers for specialized applications where size and weight are important considerations. Such applications include traction transformers, mobile transformers, and power transformers with special loading requirements. Even though such equipment has been in use for many years, there are presently no standards which address high temperature materials in liquid-immersed transformers. Recognizing this deficiency, the IEEE Transformers Committee has established a Working Group to investigate what standards or guides could be formulated. As a first step, the Working Group has prepared this “state-of-the-art” paper to document background information on the materials and their application. It is hoped that discussion of this paper will help to establish future directions for standards