1、Designation: D 5288 97 (Reapproved 2004)An American National StandardStandard Test Method forDetermining the Tracking Index of Electrical InsulatingMaterials Using Various Electrode Materials (ExcludingPlatinum)1This standard is issued under the fixed designation D 5288; the number immediately follo
2、wing the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method
3、 was developed using copper electrodesto evaluate the low-voltage (up to 600 V) tracking resistance ofmaterials in the presence of aqueous contaminants.2NOTE 1At this time, only industrial laminates have been examinedusing this method which was developed at the National ManufacturersElectrical Assoc
4、iation (NEMA) laboratory located at the University ofCincinnati. It was found that a closer end point (less scatter) was obtainedthan with platinum electrodes, and materials tested tended to be ranked byresin system.1.1.1 Other electrode materials may be considered for usewith this test method depen
5、ding upon the application of theinsulating material.1.2 This test method is similar to Test Method D 3638,which determines the comparative tracking index of materialsusing platinum electrodes to produce the tracking on thespecimen surface.1.3 The values stated in metric (SI) units are the standard.T
6、he inch-pound equivalents of the metric units are approxi-mate.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applic
7、a-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:3D 618 Practice for Conditioning Plastics and ElectricalInsulating Materials for TestingD 1711 Terminology Relating to Electrical InsulationD 1898 Practice for Sampling of Plastics4D 3638 Test Method for Compar
8、ative Tracking Index ofElectrical Insulating Materials2.2 IEC Publication:IEC 112, Recommended Method for Determining the Com-parative Track Index of Solid Insulating Materials UnderMoist Conditions, 1971 Second Edition53. Terminology3.1 In addition to the definitions listed below, terminologyas def
9、ined in Terminology D 1711 is assumed.3.2 Definitions:3.2.1 track, na partially conducting path of localizeddeterioration on the surface of an insulating material.3.2.2 tracking, nthe process that produces tracks as aresult of the action of electric discharges on or close to aninsulation surface.3.2
10、.3 tracking, contamination, ntracking caused by scin-tillations that result from the increased surface conduction dueto contamination.3.2.4 tracking index, TI, nan index for electrical insulat-ing materials which is arbitrarily defined as the numerical valueof that voltage which will cause failure b
11、y tracking when thenumber of drops of contaminant required to cause failure isequal to 50.3.2.4.1 DiscussionThis value is obtained from a plot ofthe number of drops required to cause failure by trackingversus the applied voltage.3.2.5 tracking indexcopper electrodes, TI-Cu, na track-ing index test u
12、sing copper electrodes.3.2.5.1 DiscussionThis test is comparable to comparativetracking index, Test Method D 3638, with the followingexceptions: (1) copper electrodes are used instead of platinum,and (2) the electrodes may have to be re-ground after every testbecause of the softness of copper.1This
13、test method is under the jurisdiction of ASTM Committee D09 onElectrical and Electronic Insulating Materials and is the direct responsibility ofSubcommittee D09.12 on Electrical Tests.Current edition approved March 1, 2004. Published March 2004. Originallyapproved in 1992. Last previous edition appr
14、oved in 1997 as D 5288 97.2Mathes, K. N., Chapter 4, “Surface Failure Measurements,” EngineeringDielectrics, Vol IIB, Electrical Properties of Solid Insulating Materials, Measure-ment Techniques, R. Bartnikas, Editor, ASTM STP 926, ASTM, Philadelphia, 1987.3For referenced ASTM standards, visit the A
15、STM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.4Withdrawn.5Available from the International Electrotechnical Commission, Geneva, Swit-zerland.1Copyrigh
16、t ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.2.6 tracking resistance, nthe quantitative expression ofthe voltage and the time required to develop a track underspecified conditions.4. Summary of Test Method4.1 The surface of a specimen of
17、 electrical insulatingmaterial is subjected to a low-voltage alternating stress com-bined with a low current which results from an aqueouscontaminant (electrolyte) which is dropped between two op-posing copper electrodes every 30 s.The voltage applied acrossthese electrodes is maintained until the c
18、urrent flow betweenthem exceeds a predetermined value which constitutes failure.Additional specimens are tested at other voltages so that arelationship between applied voltage and number of drops tofailure can be established through graphical means. Thenumerical value of the voltage which causes fai
19、lure with theapplication of 50 drops of the electrolyte is arbitrarily calledthe tracking index. This value provides an indication of therelative track resistance of the material.5. Significance and Use5.1 Electrical equipment may fail as a result of electricaltracking of insulating material that is
20、 exposed to variouscontaminating environments and surface conditions. There area number of ASTM and other tests designed to quantifybehavior of materials, especially at relatively high voltages.This method is an accelerated test which at relatively low testvoltages, provides a comparison of the perf
21、ormance of insu-lating materials under wet and contaminated conditions. TheTracking IndexCopper Electrodes test is not related directlyto the suitable operating voltage in service.5.2 When organic electrical insulating materials are sub-jected to conduction currents between electrodes on theirsurfac
22、es, many minute tree-like carbonaceous paths or tracksare developed near the electrodes. These tracks are orientedrandomly, but generally propagate between the electrodesunder the influence of the applied potential difference. Even-tually a series of tracks spans the electrode gap, and failureoccurs
23、 by shorting of the electrodes.5.3 As in other tracking test methods, for example, IEC 112and Test Method D 3638, this test method specifies testprocedures that are intended to promote the formation ofsurface discharges which will produce carbon tracks in areproducible manner. Since these conditions
24、 rarely reproducethe actual conditions encountered in service, the results oftracking tests cannot be used to infer either direct or relativeservice behavior of a material in a specific design application.Tracking tests can be used for screening purposes only.Suitability is verified through testing
25、of the material in actualend use or under conditions that closely simulate actual enduse.5.4 The use of copper electrodes in this type of test wasdeveloped at the University of Cincinnati, NEMAlaboratory. Itis felt by the members of the Industrial Laminates Section ofNEMA that using copper electrode
26、s gives a more realisticvalue for a tracking index, related to the resin system used toreinforce the substrate of a laminate. In general, tracking testsmade with copper electrodes tend to give lower values thanplatinum electrodes in the same type of test. It is a fact thatcopper is more widely used
27、than platinum for electricalconductors.66. Apparatus6.1 The simplified electrical circuitry used in this test isillustrated in Fig. 1. For necessary information on the cleanli-ness of apparatus, see Annex A1. The essential componentsare:6.1.1 Variable Power Source, consisting of a transformertype su
28、pply, such as the combination T1and T2in Fig. 1, witha variable output of 0 to 1000 V, 60 Hz capable of maintaininga current of 1 A (1 kVA).6.1.2 Voltmeter (V1), capable of measuring the varying acoutput of the power source. A 0 to 600-V voltmeter with anaccuracy of at least 60.5 % of full scale.6.1
29、.3 Ammeter (A1), with a range of 0 to 1 A ac and anaccuracy of at least 610 % of full scale.6.1.4 Current Limiting Resistor (R1), continuously vari-able, wire wound, rated at greater than 1 A.6.1.5 Shorting Switch (S1), single-pole single-throw ratedat 1000 V and greater than 1 A.NOTE 2The need for
30、a shorting switch is optional. It is possible tocouple the variable resistor with the autotransformer which gives anautomatic setting of the current throughout the range of the instrument.Then whenever it is necessary to check the calibration of the instrument,the shorting action can be accomplished
31、 by a jumper wire placed acrossthe electrodes. This coupling of the autotransformer with the variableresistor is another option.6.1.6 Over-Current Relay (R0), shall not trip at currents upto 0.1 A and the tripping time on short circuit shall be aminimum of 0.5 s (the current shall be limited on shor
32、t circuitto 1 A with a tolerance of 610 % at a power factor of 0.9 to1.0).NOTE 3Some instruments have used a Heinemann breaker, which isprobably the closest standard commercial breaker to that described in theIEC Method.7Also the tripping action can be accomplished with elec-tronic circuitry.6Midden
33、dorf, W. H. and Vemuri, R., “Report on Copper vs. Platinum Elec-trodes,” 1990, Available from National Electrical Manufacturers Association, 2101L St. N.W., Suite 300, Washington, D.C. 20037-8400.7Heinemann Model Series JA, Curve 2.FIG. 1 Electrical Circuit ComponentsD 5288 97 (2004)26.1.7 Testing F
34、ixture (J1)adjustable platform which sup-ports the specimen and electrode setup.6.1.8 Copper Electrodes, of electrolytic copper having arectangular cross section measuring 5 by 2 mm (0.2 by 0.08in.), extending 20 mm (0.8 in.) minimum from suitablemounting shanks (Fig. 2). The end of each electrode i
35、smachined to form a 30 chisel-point edge, having a radius from0.05 to 0.10 mm, extending along the 5-mm (0.2-in.) side ofthe electrode. This is the radius that generally results frompolishing a “0 mm” radius electrode. Since the direction ofpolish may influence the results, polish all electrodes in
36、adirection perpendicular to the long dimension of the electrodeface.6.1.9 Dropping Apparatus, which should drop the electro-lyte precisely as specified. Included should also be a means ofelectrically starting and stopping the dropping of the electrolyteas well as a counting device for monitoring the
37、 numberofdrops. The orifice diameter of the drop mechanism is approxi-mately 1.5 mm. However, it may be necessary to adjust thisdiameter somewhat so as to obtain the proper drop size inaccordance with 9.2.7. Reagents7.1 Electrolyte Solution of Ammonium Chloride in Water:7.1.1 Prepare a solution of a
38、mmonium chloride at an ap-proximate concentration of 0.1 % by dissolving1gofreagentgrade ammonium chloride in 1 Lof water. The water used shallhave a volume resistivity of no less than 0.5 MV-cm at 23C.Allow the solution to stand overnight in a covered, but notsealed, container.7.1.2 Measure the res
39、istivity of the solution using a conduc-tivity cell and an ac bridge, or meter, following the manufac-turers instructions. If the resistivity is 385 6 5 V-cm at 23 612 C, the solution is suitable for use in the test. If theresistivity is outside the above limits, adjust the concentrationuntil these
40、limits are observed. Adjustment is accomplished byadding water or NH4Cl.7.1.3 Calibrate the conductivity cell with 0.01 N potassiumchloride calibrating solution which is available from the cellmanufacturer.8. Test Specimens8.1 Samples should be selected in accordance with PracticeD 1898.8.2 Typical
41、test specimens are 50 mm (2 in.) or 100 mm (4in.) diameter disks or any other similar shape. The minimumthickness is 2.5 mm (0.100 in.). Test five specimens of eachsample.8.3 Variations in values can result from a lack of uniformityof dispersion of the material throughout the molded specimenor from
42、surface imperfections. Take care to prepare specimensthat are as uniform as possible, both within the particularspecimen and from one specimen to another.8.4 Conditioning should be in accordance with Procedure Aof Practice D 618.8.5 Specimens must be clean of dust, dirt, oil, or othercontaminants. T
43、he molded surface must be smooth andscratch-free.9. Calibration and Standardization9.1 Partially support the electrodes by adjustable pivot armsand rest on the test specimen as shown in Fig. 2, exerting aforce of 100 g (3.5 oz).9.2 The drop height for the electrolyte is a maximum of 40mm (1.6 in.) a
44、bove the electrode gap. The holding device isdesigned to store an aqueous solution and deliver periodicallya measured drop to the specimen. The drop size is 20+50mm3(0.0015 in.3) and the drop rate is 1 drop/30 6 5 s. (Thedrop size can be measured by using a small calibrated graduateto accumulate a n
45、umber of drops to obtain an accuratereading.)9.3 Allow approximately 15 drops of electrolyte to dropfrom the apparatus into a beaker or other container so as toremove any solution with a high concentration of ammoniumchloride.9.4 Reform the electrodes after every test. Replace theelectrodes when sha
46、rpening or machining reduces the length tocause instability of the electrode in the holder.9.5 Reproducibility of results is improved by reforming,polishing and washing the electrodes after each test. Washusing a stream of distilled water and dry with a clean paperbased industrial towel.10. Procedur
47、e10.1 Conduct the test in a draft-free, clean environment at atemperature of 20 6 5C.10.2 Fill the dropping assembly with solution and set thecounter to 0.10.3 Set the power source to a voltage expected to begreater than the TI-Cu value and adjust in accordance with10.6.10.4 Place the test specimen
48、on the supporting platform sothat the electrodes can be placed on the specimen.10.5 Position the electrodes as shown in Fig. 2 so that thechisel edges contact the specimen at a 60 angle betweenelectrodes and so that the chisel faces are parallel in the verticalplane and are separated by 4 6 0.2 mm (
49、0.16 in.).NOTE 4Contact of the electrodes with the specimen shall be such thatwhen a light source is so placed that the light reaches the eye along theFIG. 2 Electrodes (Radius 0.05 to 0.1 mm)D 5288 97 (2004)3surface of the specimen, no light is visible between the specimen and theelectrodes. If light is visible due to the electrode edges becoming rounded,re-grind the edges.10.6 Open the shorting switch and begin the sequence ofdrops with the time interval between drops set at 30 6 5s.10.7 Continue until tracking occurs. This condition is usu-ally well defin
