1、BRITISH STANDARD BS EN 60156:1996 IEC156:1995 Insulating liquids Determination of the breakdown voltage at power frequency Test method The European Standard EN60156:1995 has the status of a British Standard ICS29.040.20BSEN60156:1996 This British Standard, having been prepared under the directionof
2、the Electrotechnical Sector Board, was published underthe authority of the Standards Board and comes into effect on 15 April 1996 BSI06-1999 The following BSI references relate to the work on this standard: Committee referenceGEL/10 Draft for comment 93/215954 DC ISBN 0 580 25270 1 Committees respon
3、sible for this British Standard The preparation of this British Standard was entrusted to Technical CommitteeGEL/10, Fluids for electrotechnical applications, upon which the following bodies were represented: British Cable Makers Confederation British Lubricants Federation Limited Chemical Industrie
4、s Association Electricity Association Health and Safety Executive Institute of Petroleum Institution of Electrical Engineers London Regional Transport National Association of Waste Disposal Contractors Transmission and Distribution Association (BEAMA Limited) Amendments issued since publication Amd.
5、 No. Date CommentsBSEN60156:1996 BSI 06-1999 i Contents Page Committees responsible Inside front cover National foreword ii Foreword 2 Text of EN 60156 3 List of references Inside back coverBSEN60156:1996 ii BSI 06-1999 National foreword This British Standard has been prepared under the direction of
6、 the Electrotechnical Sector Board and is the English language version of EN60156:1995 Insulating liquids Determination of the breakdown voltage at power frequency Test method, published by the European Committee for Electrotechnical Standardization (CENELEC). It is identical with IEC156:1995 publis
7、hed by the International Electrotechnical Commission (IEC). This standard supersedes BS5874:1980 which is withdrawn. 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
8、British Standard does not of itself confer immunity from legal obligations. Cross-reference Publication referred to Corresponding British Standard EN60060-2:1994 BS EN60060 High voltage test techniques (IEC60-2:1994) BS EN60060-2:1995 Measuring systems Summary of pages This document comprises a fron
9、t cover, an inside front cover, pagesi andii, the EN title page, pages2 to10, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.EUROPEAN STANDARD
10、 NORME EUROPENNE EUROPISCHE NORM EN60156 August 1995 ICS29.040.20 Descriptors: Electrical insulating materials, liquid electrical insulating materials, tests, determination, breakdown voltage English version Insulating liquids Determination of the breakdown voltage at power frequency Test method (IE
11、C156:1995) Isolants liquides Dtermination de la tension de claquage frquence industrielle Mthode dessai (CEI156:1995) Isolierflssigkeiten Bestimmung der Durchschlagspannung bei Netzfrequenz Prfverfahren (IEC156:1995) This European Standard was approved by CENELEC on1995-07-04. CENELEC members are bo
12、und to comply with the CEN/CENELEC Internal Regulations which stipulate 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
13、Central Secretariat or to any CENELEC member. This European Standard 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 sam
14、e status as the official versions. CENELEC members are the national electrotechnical committees of Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom. CENELEC European Committe
15、e for Electrotechnical Standardization Comit Europen de Normalisation Electrotechnique Europisches Komitee fr Elektrotechnische Normung Central Secretariat: rue de Stassart 35, B-1050 Brussels 1995 Copyright reserved to CENELEC members Ref. No. EN60156:1995 EEN60156:1995 BSI 06-1999 2 Foreword The t
16、ext of document10/338/DIS, future edition2 of IEC156, prepared by IEC TC10, Fluids for electrotechnical applications, was submitted to the IEC-CENELEC parallel vote and was approved by CENELEC as EN60156 on1995-07-04. The following dates were fixed: Annexes designated “normative” are part of the bod
17、y of the standard. In this standard, Annex ZA is normative. Annex ZA has been added by CENELEC. Contents Page Foreword 2 Introduction 3 1 Scope 3 2 Normative references 3 3 Electrical apparatus 3 3.1 Voltage regulator 3 3.2 Step-up transformer 3 3.3 Current-limiting resistors 3 3.4 Switching system
18、4 3.5 Measuring device 4 4 Test assembly 4 4.1 Test cell 4 4.2 Electrodes 4 4.3 Stirring (optional) 4 5 Preparation of electrodes 5 6 Test assembly preparation 5 7 Sampling 5 7.1 Sample containers 5 7.2 Sampling technique 5 8 Condition of the sample 5 9 Test procedure 5 9.1 Sample preparation 5 9.2
19、Filling of the cell 5 9.3 Application of voltage 6 10 Report 6 11 Test data dispersion 6 Annex ZA (normative) Normative references to international publications with their corresponding European publications 9 Figure 1 Example of suitable cell and spherical electrodes 6 Figure 2 Example of suitable
20、cell and partially spherical electrodes 7 Figure 3 Graphical representation of coefficient of variation (standard deviation/mean ratio) versus mean breakdown voltage 8 latest date by which the ENhas to be implemented at national level by publication of an identical national standard or by endorsemen
21、t (dop)1996-07-01 latest date by which the national standards conflicting with the EN have to be withdrawn (dow)1996-07-01EN60156:1995 BSI 06-1999 3 Introduction As normally applied, breakdown voltage of insulating liquids is not a basic material property but an empirical test procedure intended to
22、indicate the presence of contaminants such as water and solid suspended matter, and the advisability of carrying out drying and filtration treatment. The breakdown voltage value of insulating liquids strongly depends on the particular set of conditions used in its measurement. Therefore, standardize
23、d testing procedures and equipment are essential for the unambiguous interpretation of test results. The method described in this International Standard applies to either acceptance tests on new deliveries of insulating liquids, or testing of treated liquids prior to or during filling into electrica
24、l equipment, or to the monitoring and maintenance of oil-filled apparatus in service. It specifies rigorous sample-handling procedures and temperature control that should be adhered to when certified results are required. For routine tests, especially in the field, less stringent procedures may be p
25、racticable and it is the responsibility of the user to determine their effect on the results. 1 Scope This International Standard specifies the method for determining the dielectric breakdown voltage of insulating liquids at power frequency. The test portion, contained in a specified apparatus, is s
26、ubjected to an increasing a.c. electrical field by means of a constant rate of voltage rise until breakdown occurs. The method applies to all types of insulating liquids of nominal viscosity up to350mm 2 s 1at40C. It is appropriate both for acceptance testing on unused liquids at the time of their d
27、elivery and for establishing the condition of samples taken in monitoring and maintenance of equipment. 2 Normative references The following normative documents contain provisions which, through reference in this text, constitute provisions of this International Standard. At the time of publication,
28、 the editions indicated were valid. All normative documents are subject to revision, and parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below. Members of IEC and ISO ma
29、intain registers of currently valid International Standards. IEC52:1960, Recommendations for voltage measurement by means of sphere-gaps (one sphere earthed). IEC60, High-voltage test techniques. IEC475:1974, Method of sampling liquid dielectrics. 3 Electrical apparatus The electrical apparatus cons
30、ists of the following units: a) Voltage regulator b) Step-up transformer c) Switching system d) Energy limiting devices Two or more of these units may be integrated in any equipment system. 3.1 Voltage regulator Uniform increase of voltage with time by manual means is difficult and, for this reason,
31、 automatic control is essential. Voltage control may be achieved by one of the following methods: a) Variable ratio auto-transformer b) Electronic regulator c) Generator-field regulation d) Induction regulator e) Resistive type voltage divider 3.2 Step-up transformer The test voltage is obtained by
32、using a step-up transformer supplied from an a.c.(48Hz to62Hz) voltage source whose value is gradually increased. The controls of the variable low-voltage source shall be capable of varying the test voltage smoothly, uniformly and without overshoots or transients. Incremental increases (produced, fo
33、r example, by a variable auto-transformer) shall not exceed2% of the expected breakdown voltage. The voltage applied to the electrodes of the liquid-filled cell shall have an approximately sinusoidal waveform, such that the peak factor is within the following limits:1,41 0,07. The centre-point of th
34、e secondary winding of the transformer should be connected to earth. 3.3 Current-limiting resistors To protect the equipment and to avoid excessive decomposition of the liquid at the instant of breakdown, a resistance limiting the breakdown current may be inserted in series with the test cell. The s
35、hort-circuit current of the transformer and associated circuits shall be within the range of10mA to25mA for all voltages higher than15kV. This may be achieved by a combination of resistors in either or both the primary and secondary circuits of the high-voltage transformer.EN60156:1995 4 BSI 06-1999
36、 3.4 Switching system 3.4.1 Basic requirements The circuit shall be opened automatically if an established arc occurs. The primary circuit of the step-up transformer shall be fitted with a circuit-breaker operated by the current resulting from the breakdown of the sample, and shall break the voltage
37、 within10ms. The circuit may be opened manually if a transient spark (audible or visible) occurs between the electrodes. NOTEThe sensitivity of the current-sensing element depends on the energy-limiting device employed and only approximate guidance can be given. Normally, triggering of cut-off by a
38、current of4mA maintained for5ms is acceptable, while fast energy-limiting (see3.4.2) triggering by a transient current of1A maintained for14s has been found satisfactory. 3.4.2 Special requirements for silicone liquids Silicone liquids can give rise to solid decomposition products through the action
39、 of electric discharges, which may cause gross errors in the observed results. In such cases, all feasible steps shall be taken to minimize the energy available for dissipation in the breakdown discharge. Whilst current limiting as above, combined with isolation of the step-up transformer primary wi
40、thin10ms, is adequate for hydrocarbons. More satisfactory performance for silicone liquids is obtained by short circuiting of the primary circuit of the transformer by a low-impedance or by use of a low-voltage device for detection of breakdown acting within a few microseconds. This device may be of
41、 either analogue (for example, modulating amplifier) or switching (for example, thyristor) type. By the use of this device, the output voltage of the step-up transformer shall be reduced to zero within1ms of detection of breakdown, and shall not thereafter increase again until the next step of the t
42、est sequence is commenced. 3.5 Measuring device For the purpose of this standard, the magnitude of the test voltage is defined as its peak value divided by. This voltage may be measured by means of a peak-voltmeter or by means of another type of voltmeter connected to the input or output side of the
43、 testing transformer, or to a special winding provided thereon; the instrument then used shall be calibrated against a standard up to the full voltage which it is desired to measure. A method of calibration which has been found satisfactory is the use of a transfer standard. This is an auxiliary mea
44、suring device which is connected in place of the test cell between the high-voltage terminals to which it presents the same impedance as the filled test cell. The auxiliary device is separately calibrated against a primary standard, for example, a sphere gap in accordance with IEC52 (see also IEC60)
45、. 4 Test assembly 4.1 Test cell The volume of the cell shall be between350ml and600ml. The cell shall be made of material that is electrically insulating, transparent and chemically inert, resistant to the insulating liquid and the cleaning agents which may be used. The cell shall be provided with a
46、 cover and shall be designed to permit easy removal of the electrodes for cleaning and maintenance. Examples of suitable cell designs are given in Figure 1 and Figure 2. 4.2 Electrodes The electrodes shall be made either of brass, bronze or austenitic stainless steel. They shall be polished and, in
47、shape, either spherical(12,5mm to13,0mm diameter) as shown in Figure 1 or partially spherical of the shape and dimensions given in Figure 2. The axis of the electrode system shall be horizontal, and at least40mm below the surface of the test liquid in the cell. No part of the electrode shall be clos
48、er than12mm to the cell wall or stirrer. The gap between the electrodes shall be2,50mm 0,05mm. The electrodes shall be examined frequently for pitting or other damage, and shall be maintained or replaced as soon as such damage is observed. 4.3 Stirring (optional) The test may be conducted with or wi
49、thout stirring. Differences between tests with or without stirring have not been found statistically significant. Astirrer, however, may be convenient especially with apparatus capable of automatic operation. Stirring may be achieved by means of a two-bladed impeller of effective diameter20mm to25mm, axial depth5mm to10mm, rotating at a speed of250r.p.m to300r.p.m. The impeller shall not entrain air bubbles and preferably rotate in such a direction that the resulting liquid flow is directed downward. It shall be constructed so that it is easily
