1、BRITISH STANDARD BS 5797:1986 IEC 628:1985 Incorporating Amendment No. 1 Methods for Measurement of gassing of insulating liquids under electrical stress and ionization UDC 621.315.615:665.767.035.8:620.1BS5797:1986 This British Standard, having been prepared under the directionof the General Electr
2、otechnical Engineering Standards Committee, was published under the authority ofthe Board of BSI and comes intoeffect on 29August1986 BSI 11-1999 First published October 1979 First revision August 1986 The following BSI references relate to the work on this standard: Committee reference GEL/115 Draf
3、t for comment 83/28430 DC ISBN 0 580 15257 X Committees responsible for this British Standard The preparation of this British Standard was entrusted by the General Electrotechnical Engineering Standards Committee (GEL/-) to Technical Committee GEL/115, upon which the following bodies were represente
4、d: Association of Consulting Engineers ERA Technology Ltd. Electricity Supply Industry in England and Wales Institute of Petroleum Institution of Electrical Engineers London Regional Transport Transmission and Distribution Association (BEAMA Ltd.) The following bodies were also represented in the dr
5、afting of the standard, through subcommittees and panels: British Lubricants Federation Limited Electric Cable Makers Confederation Electric Cable Makers Confederation (Supertension Cables Group) Amendments issued since publication Amd. No. Date of issue Comments 5617 August 1987 Indicated by a side
6、line in the marginBS5797:1986 BSI 11-1999 i Contents Page Committees responsible Inside front cover National foreword ii Section 1. General 1 Scope 1 2 General notes on the methods 1 Section 2. Method A 3 Outline of method 2 4 Apparatus 2 5 Reagents 3 6 Preparation of the apparatus 3 7 Procedure 3 8
7、 Calculation of the results 4 9 Number of tests 4 10 Report 4 11 Precision 4 Section 3. Method B 12 Outline of method 5 13 Apparatus 5 14 Reagents 6 15 Preparation of apparatus 6 16 Procedure 7 17 Calculation of the results 8 18 Number of tests 8 19 Report 8 20 Precision 8 Figure 1 Schematic diagram
8、 of gassing-cell and gas-burette assembly 9 Figure 2 Detailed dimensions of the glass cell and the inner (high-voltage) electrode 10 Figure 3 Gassing-cell and burette assembly 11 Figure 4 Gassing-cell 12 Figure 5 Inner electrode 13 Figure 6 Holding device, preferably made of resin-bonded laminated p
9、aper connected by means of countersunk polyamide screws 14 Figure 7 Schematic representation of the test preparations 15 Publications referred to Inside back coverBS5797:1986 ii BSI 11-1999 National foreword This British Standard has been prepared under the direction of the General Electrotechnical
10、Engineering Standards Committee and supersedes BS5797:1979 which is withdrawn. It is identical with IEC Publication628:1985 “Gassing of insulating liquids under electrical stress and ionization” published by the International Electrotechnical Commission (IEC) as amended by the corrigendum dated Octo
11、ber1986. Terminology and conventions. The text of the International Standard has been approved as suitable for publication as a British Standard without deviation. Some terminology and certain conventions are not identical with those used in British Standards. The comma has been used in the figures
12、as a decimal marker. In British Standards it is current practice to use a full point on the baseline as the decimal marker. The Technical Committee has reviewed the provisions of ISO683/XIII, to which reference is made in the text, and has decided that they are acceptable for use in conjunction with
13、 this standard. A related British Standard to ISO683/XIII is BS1449-2:1983 “Specification for stainless and heat resisting steel plate, sheet and strip” in which grade304S31 is equivalent to No.11 tubing mentioned in the text. WARNING. This British Standard calls for the use of substances that may b
14、e injurious to health if adequate precautions are not taken. It refers only to the technical suitability and does not absolve the user from legal obligations relating to health and safety at any state. Attention is especially drawn to the warning note in clause1 of the standard. A British Standard d
15、oes 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 obligations. Cross-references International Standards Corresponding Britis
16、h Standards ISO 383:1976 BS 572:1985 Specification for interchangeable conical ground glass joints (Technically equivalent) ISO 653:1980 BS 5074:1974 Short and long solid-stem thermometers for precision use (Technically equivalent) ISO 4803:1978 BS 5895:1980 Specification for borosilicate glass tubi
17、ng for laboratory apparatus (Identical) Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages1 to 16, 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 indic
18、ated in the amendment table on the inside front cover.BS5797:1986 BSI 11-1999 1 Section 1. General 1 Scope This standard describes two procedures each using different apparatus to measure the tendency of insulating liquids to evolve or absorb gas when subjected, in cells having specific geometries,
19、to electrical stress of sufficient intensity to cause an electric discharge through a gas phase in which a gas-oil interface is located. The methods described in this standard are suitable for purchase specifications, general selection of insulating liquids, product development and quality assurance
20、. WARNING! Attention is called to national regulations associated with the use of high voltage, hydrogen and solvents. 2 General notes on the methods 2.1 These methods indicate whether insulating liquids are gas absorbing or gas evolving under the test conditions. The gassing behaviour of any one in
21、sulating liquid is primarily a function of its chemistry but changes in certain test parameters can modify the results significantly. 2.2 These methods can operate under a variety of gas phase, temperature and voltage stress conditions. In order to establish uniform criteria of measurement, specific
22、 test conditions are specified which experience has shown to be most informative of the general performance expected from the liquid dielectric in electrical equipment should ionization occur. At present, however, though it is generally agreed that gas absorbency of the impregnant has a positive eff
23、ect in minimizing ionization problems in impregnated insulation systems used at high electrical stress, correlation of gassing-cell test results with equipment performance is limited. Engineering judgement is necessary in interpreting the test results in relation to any intended application. 2.3 Bot
24、h methods, have been originally designed for the range of gassing rates characteristic of mineral insulating liquids. The use of these methods with other liquids may require some adaptations in the dimensions of the test cell.BS5797:1986 2 BSI 11-1999 Section 2. Method A 3 Outline of method This met
25、hod determines the gassing tendency of an insulating liquid under a hydrogen atmosphere and expresses the results in terms of gassing rate over a relatively short test period. After being dried and saturated with hydrogen gas, the insulating liquid and the hydrogen pocket above the liquid are subjec
26、ted in the specified cell to a radial electrical stress under the following experimental conditions: The rate of evolution or absorption of gas resulting from reactions at the gas-oil interface, is calculated as volume per unit of time from changes in pressure with time. 4 Apparatus 4.1 Gassing-cell
27、 and gas-burette assembly The gassing-cell illustrated in Figure 1, page9, with dimensions given inFigure 2, page10, consists of the following components: Cell made of borosilicate glass with a relative permittivity of5 0.2 at80 C measured at a stated frequency (50Hz or60Hz). The part under stress i
28、s constructed of16 0.2mm inside diameter and18 0.2mm outside diameter precision selected lightwall tubing according to ISO Standard4803. This cell has an outer electrode (earth)60mm high made of solvent-resistant silver paint with a vertical slit for observing the oil level and a copper band for ear
29、th connection. Hollow high-voltage electrode made of10 0.1mm outside diameter centreless-ground and polished stainless steel seamless tubing No.11 according to ISO Standard683/XIII and containing a1.0mm stainless steel capillary tubing as a gas passage. The electrode shall be supported and centred b
30、y a precision machined24/29 recessed polytetrafluoroethylene plug. A 3.0 mm needle valve (E) with gas inlet is on top of the electrode. NOTEAfter repeated tests at 80 C, the shape of the polytetrafluoroethylene plug should be checked because it may deform and no longer be leak-tight. Gas burette (Fi
31、gure 1) made of7mm outside diameter borosilicate glass tubing with an etched scale(mm), tapered glass joint10/19 (G) for connecting to the gassing-cell, a by-pass stopcock (D) and three glass bulbs (A, B and C). The correlation between the reading (mm) and the volume (mm 3 ) must be known. NOTEIncre
32、ased capacity of gas-burette is required for highly gas absorbing liquids. 4.2 Heating device A transparent oil bath, preferably filled with silicone liquid, with thermostatic control and liquid circulating system to maintain the bath medium at80 0.5 C. The bath may be equipped with suitable support
33、s for holding the gassing-cell and gas burette. NOTEIf the level of the oil filling drops below a defined minimum, the high voltage should be disconnected automatically by safety switches. The bath may be provided with an effective circulating cooling system to allow rapid cooling after the test. 4.
34、3 Transparent safety shield Fitted with safety electrical interlock switches to protect the operator from parts under high voltage. 4.4 High-voltage transformer The transformer and its controlling equipment shall be of such size and design that, with a filled gassing-cell in the circuit, the peak fa
35、ctor (ratio of peak value to r.m.s. value) of the test voltage shall not differ by more than 5% from that of a sinusoidal wave while maintaining10kV2%. 4.5 Thermometer Any convenient thermometer for measuring a temperature of80 0.1 C (e.g.ISO Standard653 STL/0.1/60/85). voltage: 10 kV; frequency: 50
36、 Hz or 60 Hz; temperature: 80 C; test duration: 120 min at 50 Hz or 100 min at 60 Hz.BS5797:1986 BSI 11-1999 3 4.6 Syringe A convenient glass syringe, volume 10 cm 3 . 5 Reagents 5.1 Hydrogen with oxygen content less than 10 mm 3 /dm 3and water content less than2mm 3 /dm 3from a cylinder with two-st
37、age pressure reducer and a fine flow regulator. 5.2 Dibutyl phthalate, technical grade. 5.3 1,1,1-trichloroethane, technical grade. 5.4 n-heptane, analytical grade. 5.5 Silicone vacuum grease 6 Preparation of the apparatus General remark: As the gassing tendency of liquids may be strongly influenced
38、 by solvents, it is important that no traces of solvent remain after the cleaning procedure. 6.1 Clean the glass cell by first rinsing it inside and outside with1,1,1-trichloroethane then with n-heptane. Then, refill the cell with n-heptane and scrub with a stiff brush of polyamide fibres to remove
39、deposits from previous test. Insert a smaller brush into the tapered joint (G) and scrub out silicone grease, taking care that none of the grease enters the cell. Again rinse with n-heptane and blow dry with clean compressed air. Check the painted-on silver electrode, and touch up if necessary. 6.2
40、Clean the hollow electrode by blowing out the capillary tube with clean compressed air, rinsing the oil off the entire electrode with1,1,1-trichloroethane and wiping off any deposit with tissue paper. Polish the surface of the stainless steel shaft of the electrode with a suitable device, such as a
41、buffing wheel; wipe off the buffing compound carefully with tissue paper moistened with1,1,1-trichloroethane. Rinse again first with1,1,1-trichloroethane, then with n-heptane. Blow dry with clean compressed air and complete drying in an oven at80 C. 6.3 Apply a light coat of silicone vacuum grease t
42、o the stopcock (D) and the standard tapered joint (G) and assemble the glass cell and burette, but do not insert the electrode into the glass cell. 6.4 Fill the burette to the half-full mark with dibutyl phthalate. 6.5 Clean the syringe with n-heptane then blow dry with compressed air. 7 Procedure 7
43、.1 Filter about 10 cm 3of the oil sample through a previously dried filter paper and rapidly introduce5 0.1cm 3of the filtered oil into the glass cell by means of the hypodermic syringe. 7.2 Lightly coat the polytetrafluoroethylene plug of the electrode with the test liquid (to act as a gas-seal) an
44、d insert the electrode into the glass cell. 7.3 Check the bath temperature, which shall be maintained at80 0.5 C during the test. 7.4 Suspend the gassing-cell and gas burette assembly in the oil bath at the level indicated inFigure 1, page9, and connect the lead from the outside electrode to earth.
45、7.5 Attach the gas inlet and outlet connections. The gas outlet should lead outside the building, either directly or through a fume hood. 7.6 Close the stopcock (D) and open the valve (E) to allow the saturating gas to bubble through the test oil and the burette liquid at a steady rate of3dm 3 /h fo
46、r60min. 7.7 Open the stopcock (D) and continue bubbling the saturating gas through the test oil for an additional5min. 7.8 After a total of 65 min of gas bubbling, first close the valve (E) and then the stopcock (D), making certain the liquid levels in the two legs of the burette are equal. 7.9 Conn
47、ect the high-voltage lead to the centre electrode.BS5797:1986 4 BSI 11-1999 7.10 Place the transparent safety shield in position and take the burette reading after checking the bath temperature. 7.11 Turn on the high-voltage and adjust to 10 kV. 7.12 Record the time and the burette level and check t
48、he observation slit on the outer electrode for onset of the gassing reaction. 7.13 After 10 min, record the burette level. 7.14 After an additional 120 min (if50Hz) or100min (if60Hz) again record the burette level and then turn off the high-voltage. 8 Calculation of the results Calculate the gassing
49、 tendency in the presence of hydrogen as follows: G = (B 130 (or 110) B 10 ) K/t where: Value of G will be positive if gas is evolved and negative if gas is absorbed. 9 Number of tests Tests should be run in duplicate. 10 Report The report shall include the following: IEC Publication 628 Method A; gassing tendency (mm 3 /min), mean value of duplicate tests; test voltage; test voltage frequency (50 Hz or 60 Hz); test temperature; test duration; gas phase. 11 Precision Repeatability: The results should be considere
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