1、BRITISH STANDARD BS EN 50353:2001 Insulating oil Determination of fibre contamination by the counting method using a microscope The European Standard EN 50353:2001 has the status of a British Standard ICS 29.040.10 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBS EN 50353:200
2、1 This British Standard, having been prepared under the direction of the Electrotechnical Sector Policy and Strategy Committee, was published under the authority of the Standards Policy and Strategy Committee on 07 November 2001 BSI 07 November 2001 ISBN 0 580 38664 3 National foreword This British
3、Standard is the official English language version of EN 50353:2001. The UK participation in its preparation was entrusted to Technical Committee GEL/10, Fluids for electrotechnical applications, which has the responsibility to: A list of organizations represented on this committee can be obtained on
4、 request to its secretary. Cross-references The British Standards which implement international or European publications referred to in this document may be found in the BSI Standards Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Find” facility
5、 of the BSI Standards Electronic Catalogue. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligation
6、s. aid enquirers to understand the text; present to the responsible European committee any enquiries on the interpretation, or proposals for change, and keep the UK interests informed; monitor related international and European developments and promulgate them in the UK. Summary of pages This docume
7、nt comprises a front cover, an inside front cover, the EN title page, pages 2 to 16, an inside back cover and a back cover. The BSI copyright date displayed in this document indicates when the document was last issued. Amendments issued since publication Amd. No. Date CommentsEUROPEAN STANDARD EN 50
8、353 NORME EUROPENNE EUROPISCHE NORM September 2001 CENELEC European Committee for Electrotechnical Standardization Comit Europen de Normalisation Electrotechnique Europisches Komitee fr Elektrotechnische Normung Central Secretariat: rue de Stassart 35, B - 1050 Brussels 2001 CENELEC - All rights of
9、exploitation in any form and by any means reserved worldwide for CENELEC members. Ref. No. EN 50353:2001 E ICS 29.040.20 English version Insulating oil - Determination of fibre contamination by the counting method using a microscope Huiles isolantes - Dtermination de la contamination par fibres par
10、la mthode du comptage avec utilisation dun microscope Isolierl - Bestimmung der Faserverunreinigungen mittels eines Zhlverfahrens mit einem Mikroskop This European Standard was approved by CENELEC on 2000-12-01. CENELEC members are bound to comply with the CEN/CENELEC Internal Regulations which stip
11、ulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the Central Secretariat or to any CENELEC member. This European Standa
12、rd exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CENELEC member into its own language and notified to the Central Secretariat has the same status as the official versions. CENELEC members are the nationa
13、l electrotechnical committees of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom.EN 50353:2001 - 2 - Contents Page Foreword 3 Introduction. 4 1 Scope 4 2 Nor
14、mative references. 4 3 Terms and definitions. 4 4 Principle. 5 5 Reagents. 5 6 Apparatus 5 7 Cleaning procedure. 6 8 Sampling 7 9 Filtration procedure 7 10 Microscope calibration. 8 11 Fibre counting and sizing procedure 9 12 Calculation and expression of results. 10 13 Precision 10 14 Test report.
15、10 Figure 1 - Schematic representation of a suitable filtration apparatus . 11 Annex A (normative) Method for low fibre concentrations 12 A.1 Reagents. 12 A.2 Apparatus 12 A.3 Initial set-up and cleaning 13 A.4 Sampling, and filtration of oil sample 13 A.5 Blank tests. 14 A.6 Counting method . 14 A.
16、7 Calculation and expression of results. 15 A.8 Precision 15 A.9 Test report. 15 Figure A.1 Schematic representation of a suitable filtration apparatus for low fibre concentrations 16- 3 - EN 50353:2001 Foreword This European Standard was prepared by the CENELEC BTWG 99-1, Insulating oil. The text o
17、f the draft was submitted to the Unique Acceptance Procedure and was approved by CENELEC as EN 50353 on 2000-12-01. The following dates were fixed: - latest date by which the EN has to be implemented at national level by publication of an identical national standard or by endorsement (dop) 2002-04-0
18、1 - latest date by which the national standards conflicting with the EN have to be withdrawn (dow) 2004-01-01 Annexes designated “normative“ are part of the body of the standard. In this standard, annex A is normative. Warning This European Standard calls for the use of substances and/or procedures
19、that may be injurious to health if adequate precautions are not taken. It refers only to technical suitability and does not absolve the user from legal obligations relating to health and safety at any stage. _EN 50353:2001 - 4 - Introduction It is generally recognized that fibres and other particles
20、 have a detrimental effect on the dielectric strength of insulating oil. It has long been a requirement to include in specifications for insulating liquids that the fluid be clear and free from visible particulate matter or sediment. This Standard provides the methodology for testing for contaminati
21、on by fibres and consists of filtering a known volume of the insulating liquid under vacuum assisted conditions through a membrane filter to collect contaminants on the filter surface. The membrane is then examined microscopically to count and size the fibres. 1 Scope This European Standard specifie
22、s two methods for determining the fibre contamination of mineral insulating oil used in electrotechnical equipment, based on filtering a sample of oil and examining and counting the number of fibres on the surface of the filter using an optical microscope. Fibres down to 100 m in length can be sized
23、 and counted by these methods. The methods are applicable both to unused oils and to oils in service. The method specified in the main text is applicable to oil samples taken from barrelled oil or from electrotechnical equipment in service, in which the fibre concentration is expected to be relative
24、ly high. The alternative method specified in annex A is applicable to samples taken from new oil in bulk containers, or from large transformers which have not been operated much since they were filled, in which the fibre concentration is expected to be relatively low. NOTE These methods are also sui
25、table for other insulating liquids such as silicones and synthetic esters. 2 Normative references This European Standard incorporates by dated or undated reference, provisions from other standards. These normative references are cited at the appropriate places in the text and the publications are li
26、sted hereafter. For dated references, subsequent amendments to or revisions of any of these publications apply to this European Standard only when incorporated in it by amendment or revision. For undated references the latest edition of the publication referred to applies. IEC 60475 Method of sampli
27、ng liquid dielectrics ISO 5598 Fluid power systems and components - Vocabulary 3 Terms and definitions For the purposes of this European Standard, the terms and definitions given in ISO 5598 and the following apply. 3.1 blank count count of the number of fibres introduced from other sources, such as
28、 reagents or cleaning of glassware 3.2 effective filtration area area of a membrane filter open to flow during filtration of the fluid- 5 - EN 50353:2001 NOTE For commercially obtainable gridded membrane filters of diameter 37 mm, this is generally accepted as 100 grid squares of dimension 3,1 mm, w
29、ith a nominal area of 960 mm 2 . 3.3 detectable fibre fibre longer than 100 m with a length-to-width ratio greater than or equal to 5:1 NOTE For the purposes of this standard, detectable fibres are defined as longer than 100 m because experience has shown that only these fibres cause severe degradat
30、ion of dielectric strength in practical situations. 4 Principle A known volume of insulating oil is filtered, using vacuum assistance, through a membrane filter to separate contaminants from the sample liquid and deposit them on the surface of the membrane filter. The contamination is examined micro
31、scopically to size and count any fibres present. 5 Reagents NOTE These chemicals are used for cleaning and rinsing the apparatus. 5.1 Liquid detergent, without solid residue. 5.2 Distilled or de-mineralized water. 5.3 2-propanol, acetone-free. 5.4 Solvent - petroleum ether, boiling range 100 o C to
32、120 o C preferred, but heptane, hexane and cyclohexane are suitable alternatives. WARNING - Petroleum ether and many of its alternatives are highly flammable solvents which have low flash points. It is essential that appropriate safety measures are observed during use of these solvents. Only small q
33、uantities (e.g. not greater than about 100 ml) should be used on the workbench and larger quantities should be handled in a fume cupboard to avoid the inhalation of fumes from these solvents. 6 Apparatus NOTE An example of suitable apparatus is shown in Figure 1. 6.1 Membrane filter holder, consisti
34、ng of the following components: - a glass funnel of 250 ml capacity, with a loosely fitting glass cap; a clamping device; a suitable base to support the membrane filter (e.g. a glass frit). NOTE If problems are experienced due to build-up of electrostatic charge on the filter during filtration, it m
35、ay be necessary to use an earthed metal anti-static base to support the membrane filter. 6.2 Membrane filters, with a pore diameter of 1,2 m or less. Gridded filters shall be used for manual counting and ungridded filters shall be used if an automatic counting system is to be employed (see 6.8).EN 5
36、0353:2001 - 6 - NOTE 1 It is essential that a type of filter is selected which is known to be compatible with the oil sample and with the solvents which are to be used (see clause 5). NOTE 2 Black membranes may be helpful for the purpose of counting, by improving the visibility of fibres where most
37、of them are translucent, transparent or white in colour. 6.3 Vacuum flask (for waste filtrate), glass, with side arm, of 1 l capacity and capable of accepting the membrane filter holder (6.1). 6.4 Vacuum pump, capable of establishing a vacuum to assist the flow of oil through the membrane. NOTE A co
38、ndensing trap may be used to protect the vacuum pump from vapours. 6.5 Filtered-solvent dispenser, comprising a pressure-operated system which discharges the solvent through an in-line membrane filter with a pore diameter of 1,2 m or less. NOTE The type of filter selected shall be compatible with th
39、e solvents used (see clause 5). 6.6 Tweezers, stainless steel, flat ended, un-serrated. 6.7 Petri dishes, glass, with cover. 6.8 Microscope, capable of producing magnifications of 50, equipped with fine and coarse focus controls, having an eyepiece graticule, and fitted with a mechanical stage so th
40、at the effective filtration area of the filter can be scanned. NOTE The microscope may be fitted with an image analysis system if automatic determination of fibre size distribution is required. 6.9 Stage micrometer, graduated in 0,1 mm and 0,01 mm divisions, with its calibration traceable to nationa
41、l standards. 6.10 External lamp, of variable intensity, if the microscope does not include an inbuilt light source. 6.11 Sample bottles, minimum capacity 250 ml, cylindrical, wide-mouthed, clear glass with a non-fibre-shedding, oil-tight closure. 7 Cleaning procedure Clean the filtration apparatus,
42、tweezers and petri dishes, and the sample bottles and closures as follows: a) wash the glassware, and the tweezers, in warm tap water/liquid detergent solution; b) rinse three times with distilled or de-mineralized water; c) rinse with filtered 2-propanol to remove water; d) rinse with filtered petr
43、oleum ether, using a spirally directed jet where possible; e) suspend the funnel in suitable sized beaker, wash down with petroleum ether and then cover; f) leave a little solvent in each sample bottle and cap with a pre-cleaned closure. NOTE Solvent evaporation slightly pressurises the bottle and t
44、herefore excludes contamination when the bottle is opened.- 7 - EN 50353:2001 8 Sampling Clean the sampling equipment in accordance with clause 7. Ensure that the sampling equipment is free from fibrous contamination by flushing with the oil being sampled. Extract a sample (of minimum volume 250 ml)
45、 of the insulating oil from the reservoir/ container in accordance with the method laid down in IEC 60475. NOTE The fibre count of an oil sample from any item of electrotechnical equipment can depend on the sampling point, the time elapsed since filling, the oil circulation rate and/or the time the
46、oil is left to stand. Circulation of oil in the tank of the electrical equipment before taking the samples can be expected to yield more consistent fibre count results. Storage of the samples will generally lead to sedimentation and coalescence of fibres and particles. Therefore, the analysis should
47、 be undertaken as soon as possible after sampling. It has been established that analysis of a sub-sample from a sample container may produce inaccurate results. Therefore the total contents of the sample container shall be used for the test. 9 Filtration procedure 9.1 General A blank test, to determ
48、ine the blank count, in accordance with 9.3, shall be carried out before the filtration of each batch of oil samples (see 9.2). If the batch of oil samples is so large that the analysis takes more than a week, a blank test, to determine the blank count, shall be carried out once a week. It is essent
49、ial to minimize fibre contamination during filtration and counting. Therefore, it is recommended that these procedures are carried out in either: a) a laminar flow cabinet; or b) a clean room reserved specifically for microscopy, in which no activities likely to generate fibres are carried out. Precautions should also be taken to minimize fibre shedding from the operators clothing. It is recommended that operators should wear non fibre-shedding overclothes and should cover their hair. NOTE The material of these overclothes shall not pose high r
