1、 TECHNICAL REPORT IECCEIRAPPORT TECHNIQUE TR 62036First editionPremire dition2007-04Mineral insulating oils Oxidation stability test method based on differential scanning calorimetry (DSC) Huiles minrales isolantes Mthode dessai pour valuer la stabilit doxydation fonde sur lanalyse calorimtrique dif
2、frentielle par balayage Reference number Numro de rfrence IEC/CEI/TR 62036:2007 THIS PUBLICATION IS COPYRIGHT PROTECTED Copyright 2007 IEC, Geneva, Switzerland All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, elec
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14、 ou si vous avez des questions, visitez le FAQ du Service clients ou contactez-nous: Email: csciec.ch Tl.: +41 22 919 02 11 Fax: +41 22 919 03 00 TECHNICAL REPORT IECCEIRAPPORT TECHNIQUE TR 62036First editionPremire dition2007-04Mineral insulating oils Oxidation stability test method based on differ
15、ential scanning calorimetry (DSC) Huiles minrales isolantes Mthode dessai pour valuer la stabilit doxydation fonde sur lanalyse calorimtrique diffrentielle par balayage PRICE CODE CODE PRIX M For price, see current cataloguePour prix, voir catalogue en vigueur Commission Electrotechnique Internation
16、aleInternational Electrotechnical Commission 2 TR 62036 IEC:2007 CONTENTS FOREWORD.3 INTRODUCTION.5 1 Scope.6 2 General remarks.6 3 Effect of temperature on oxidation induction time .6 3.1 Isothermal .6 3.2 Temperature-programmed runs .7 4 Effect of sample size on oxidation induction time7 4.1 Inhib
17、ited oil .7 4.2 Uninhibited oil .7 5 Other factors effecting oxidation induction time 8 6 Reliability of method.8 7 Different instruments 8 8 Interpretation of curves.9 9 Conclusion .9 Bibliography13 Table 1 Oxidation induction time of oil samples at different temperature programmes10 Table 2 Oxidat
18、ion induction time of oil samples at different sample weight.10 Table 3 Repeatability of oxidation induction time by PDSC 10 Table 4 Reproducibility of oxidation induction time by PDSC11 Table 5a DSC Results analyzed at different laboratories Uninhibited oil12 Table 5b DSC Results analyzed at differ
19、ent laboratories Inhibited oil12 TR 62036 IEC:2007 3 INTERNATIONAL ELECTROTECHNICAL COMMISSION _ MINERAL INSULATING OILS OXIDATION STABILITY TEST METHOD BASED ON DIFFERENTIAL SCANNING CALORIMETRY (DSC) FOREWORD 1) The International Electrotechnical Commission (IEC) is a worldwide organization for st
20、andardization comprising all national electrotechnical committees (IEC National Committees). The object of IEC is to promote international co-operation on all questions concerning standardization in the electrical and electronic fields. To this end and in addition to other activities, IEC publishes
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30、ittees is to prepare International Standards. However, a technical committee may propose the publication of a technical report when it has collected data of a different kind from that which is normally published as an International Standard, for example “state of the art“. IEC 62036, which is a tech
31、nical report, has been prepared by IEC technical committee 10: Fluids for electrotechnical applications. 4 TR 62036 IEC:2007 The text of this technical report is based on the following documents: Enquiry draft Report on voting 10/676/DTR 10/690/RVC Full information on the voting for the approval of
32、this technical report can be found in the report on voting indicated in the above table. This publication has been drafted in accordance with the ISO/IEC Directives, Part 2. The committee has decided that the contents of this publication will remain unchanged until the maintenance result date indica
33、ted on the IEC web site under “http:/webstore.iec.ch“ in the data related to the specific publication. At this date, the publication will be reconfirmed, withdrawn, replaced by a revised edition, or amended. TR 62036 IEC:2007 5 INTRODUCTION The existing methods to assess oxidation stability of miner
34、al insulating oil are very time consuming. A faster method is necessary for effective quality control and status monitoring. Differential scanning calorimetry (DSC) as a technique has been used for monitoring grease and lubricants oxidation stability. The use of DSC for evaluation of oil oxidation s
35、tability was originally suggested to IEC, TC 10 following publication of a literature review of DSC oxidation tests performed on petroleum products (10/367/INF April 1996). During IECs TC 10 meeting in Geneva, 1998, it was decided to set up a working group for development of a standard based on DSC
36、for rapid evaluation of mineral insulating oil oxidation stability. 6 TR 62036 IEC:2007 MINERAL INSULATING OILS OXIDATION STABILITY TEST METHOD BASED ON DIFFERENTIAL SCANNING CALORIMETRY (DSC) 1 Scope The purpose of IEC 62036, which is a technical report, is to develop a rapid oxidation stability te
37、st method based on differential scanning calorimetry (DSC) to assess the oxidation stability of mineral insulating oils. 2 General remarks The main function of insulating oil is insulation and cooling. The expected life span of transformer oil is 25 to 40 years, largely depending on operating temper
38、ature and electrical load. Specifications are prepared and used to fulfil all criteria required for proper functioning of the oil in service. Life expectancy from insulating oil has a large economic impact on the cost of operation of a unit. The oxidation stability test is an important test as this
39、will evaluate, to some extent, the life of the oil in service. Resistance of an oil oxidation is very much dependant on the refining process and type of crude oil. Both under-refined and over-refined oils may exhibit poor oxidation stability. The complex process of oxidation of in-service oils occur
40、s slowly at the normal operating temperature of the transformer and is dependant on temperature, oxygen and catalyst. In the first stage of oil oxidation, radicals and peroxides are produced. These compounds are unstable and rapidly convert to volatile and soluble acids and finally producing insolub
41、le material or sludge. All of these products have an adverse effect on electrical and physical properties of oil. The oil may reach a stage where it is not fit for its intended purpose. To establish a long service life for the oil, an oxidation stability test is performed on the unused oil. There ar
42、e several standard test methods for evaluation of the oxidation stability of transformer oil. The recommended international test method is IEC 61125. This test involves oxidizing the oil at 120 C for 164 h and then measuring the acidity, sludge and dielectric dissipation factor (DDF). Other national
43、 test methods are based on the same principal and are time consuming. On delivery, it is required to test the oil for compliance with the specification. As this test is very time consuming, results are usually retrospective. Clearly, existing methods are time consuming and not very sensitive. Althou
44、gh there is no direct relation between the oil oxidation stability test and service life of the oil, oils that are very stable and resist oxidation are clearly preferred. Therefore, a fast method of determining the oxidation stability is needed for rapid evaluation of the oil and compliance to the s
45、pecification. In order to evaluate high pressure differential scanning calorimetry (PDSC) as a technique for testing oxidation stability of transformer oil and to establish a suitable method, transformer oil samples were analysed under varying conditions. 3 Effect of temperature on oxidation inducti
46、on time 3.1 Isothermal Six samples of transformer oil (A-F) were analysed using PDSC at different temperature programmes. Samples B and D were inhibited transformer oil, the remainder were uninhibited and sample F was a used oil. Oxygen at 300 psi was applied in each case and the sample weight was k
47、ept constant at 4 mg. The results are shown in Table 1. It was found that below 165 C, no phase transition occurred in any of the six samples. Temperatures higher than expected, of up to 260 C were required to give peaks in a reasonable time. At the lower TR 62036 IEC:2007 7 temperature, only sample
48、 D gave a peak at around 45 min. When this sample was run at 170 C, the peak become sharper and clear and occurred at an onset of around 40 min. At 175 C, the peak occurred at around 30 min and was sharper still. The same trend was observed in sample B, showing decreasing induction time with increas
49、ing temperature, but oxidation occurred after a slightly longer time. Sample B and D were inhibited oils, which showed a clear and sharp peak following the rapid oxidation and depletion of the inhibitor. 3.2 Temperature-programmed runs The uninhibited oils, A, C, E and F showed no clearly defined peak in the thermograms of isothermal runs. Oxidation did not occur
