1、Designation: D5288 10An 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 D5288; the number immediately following the designation
2、 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 () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This test method was developed using
3、 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 Association (NEMA) labora
4、tory 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 It is acceptable to consider other electrode materialsfor use with this test method depending upon
5、 the application ofthe insulating material.1.2 This test method is similar to Test Method D3638,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.The inch-po
6、und equivalents of the metric units are approxi-mate.1.4 This standard is used to measure and describe theresponse of materials, products, or assemblies to heat andflame under controlled conditions, but does not by itselfincorporate all factors required for fire hazard or fire riskassessment of the
7、materials, products, or assemblies underactual fire conditions.1.5 Fire testing is inherently hazardous. Adequate safe-guards for personnel and property shall be employed inconducting these tests.2. Referenced Documents2.1 ASTM Standards:3D618 Practice for Conditioning Plastics for TestingD1711 Term
8、inology Relating to Electrical InsulationD3636 Practice for Sampling and Judging Quality of SolidElectrical Insulating MaterialsD3638 Test Method for Comparative Tracking Index ofElectrical Insulating Materials2.2 IEC Publication:IEC 112 Recommended Method for Determining the Com-parative Track Inde
9、x of Solid Insulating Materials UnderMoist Conditions, 1971 Second Edition43. Terminology3.1 In addition to the definitions listed below, terminologyas defined in Terminology D1711 is assumed.3.2 Definitions:3.2.1 track, na partially conducting path of localizeddeterioration on the surface of an ins
10、ulating material.3.2.2 tracking, nthe process that produces tracks as aresult of the action of electric discharges on or close to aninsulation surface.3.2.3 tracking, contamination, ntracking caused by scin-tillations that result from the increased surface conduction dueto contamination.3.2.4 tracki
11、ng index, TI, nan index for electrical insulat-ing materials which is arbitrarily defined as the numerical valueof that voltage which will cause failure by 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 oft
12、he number of drops required to cause failure by trackingversus the applied voltage.1This 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 Ja
13、n. 15, 2010. Published February 2010. Originallyapproved in 1992. Last previous edition approved in 2004 as D5288 97(2004).DOI: 10.1520/D5288-10.2Mathes, K. N., Chapter 4, “Surface Failure Measurements,” EngineeringDielectrics, Vol IIB, Electrical Properties of Solid Insulating Materials, Measure-me
14、nt Techniques , R. Bartnikas, Editor, ASTM STP 926, ASTM, Philadelphia,1987.3For referenced ASTM standards, visit the ASTM 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 onth
15、e ASTM website.4Available from International Electrotechnical Commission (IEC), 3 rue deVaremb, Case postale 131, CH-1211, Geneva 20, Switzerland, http:/www.iec.ch.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, Wes
16、t Conshohocken, PA 19428-2959, United States.3.2.5 tracking indexcopper electrodes, TI-Cu, na track-ing index test using copper electrodes.3.2.5.1 DiscussionThis test is comparable to comparativetracking index, Test Method D3638, with the following excep-tions: (1) copper electrodes are used instead
17、 of platinum, and(2) the electrodes may have to be re-ground after every testbecause of the softness of copper.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 specim
18、en of 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
19、the current 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 cause
20、s failure 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 has the potential to fail as a resultof electrical tracking of insul
21、ating material that is exposed tovarious contaminating environments and surface conditions. Anumber of ASTM and other tests have been designed toquantify behavior of materials, especially at relatively highvoltages. This method is an accelerated test which at relativelylow test voltages, provides a
22、comparison of the performance ofinsulating materials under wet and contaminated conditions.The Tracking IndexCopper Electrodes test is not relateddirectly to the suitable operating voltage in service.5.2 When organic electrical insulating materials are sub-jected to conduction currents between elect
23、rodes on theirsurfaces, 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 ga
24、p, and failureoccurs by shorting of the electrodes.5.3 As in other tracking test methods, for example, IEC 112and Test Method D3638, this test method specifies test proce-dures that are intended to promote the formation of surfacedischarges which will produce carbon tracks in a reproduciblemanner. S
25、ince these conditions rarely reproduce the actualconditions encountered in service, the results of tracking testscannot be used to infer either direct or relative service behaviorof a material in a specific design application. Tracking tests canbe used for screening purposes only. Suitability is ver
26、ifiedthrough testing of the material in actual end use or underconditions that closely simulate actual end use.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
27、using copper electrodes 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 thatcoppe
28、r is more widely used than platinum for electricalconductors.56. 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 o
29、f a transformertype supply, 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. A0 to 600-V voltmeter with anaccuracy of at least 60.
30、5 % of full scale.6.1.3 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
31、A.NOTE 2The need for 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 actio
32、n can be accomplished 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 sha
33、ll be limited on short circuitto 1 A with a tolerance of 610 % at a power factor of 0.9 to1.0).5Middendorf, 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.FI
34、G. 1 Electrical Circuit ComponentsD5288 102NOTE 3Some instruments have used a Heinemann breaker, which isprobably the closest standard commercial breaker to that described in theIEC Method.6Also the tripping action can be accomplished with elec-tronic circuitry.6.1.7 Testing Fixture (J1)adjustable p
35、latform 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 ismachined to form a 30
36、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 has the potential to influence the results, polish allelectrodes in a direc
37、tion perpendicular to the long dimension ofthe electrode face.6.1.9 Dropping Apparatus, which shall drop the electrolyteprecisely as specified. It is important to also include a means ofelectrically starting and stopping the dropping of the electrolyteas well as a counting device for monitoring the
38、numberofdrops. The orifice diameter of the drop mechanism is approxi-mately 1.5 mm. However, if necessary, adjust this diametersomewhat so as to obtain the proper drop size in accordancewith 9.2.7. Reagents7.1 Electrolyte Solution of Ammonium Chloride in Water:7.1.1 Prepare a solution of ammonium ch
39、loride 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 resistivity o
40、f 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 limits are
41、 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 Select samples in accordance with Practice D3636.8.2 Typical test specimens are 50
42、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 surface imperfections.
43、 Take care to prepare specimensthat are as uniform as possible, both within the particularspecimen and from one specimen to another.8.4 Condition samples in accordance with Procedure A ofPractice D618.8.5 Specimens must be clean of dust, dirt, oil, or othercontaminants. The molded surface must be sm
44、ooth 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.) above the electrode gap. The
45、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 number of drops to obtain an
46、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 sharpening or machining reduces
47、 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. Procedure10.1 Conduct the test in a
48、draft-free, clean environment at atemperature of 20 6 5C.10.2 Fill the dropping assembly with solution and set thecounter to 0.6The sole source of supply of the apparatus known to the committee at this timeis the Heinemann Model Series JA, Curve 2. If you are aware of alternativesuppliers, please pr
49、ovide this information to ASTM International Headquarters.Your comments will receive careful consideration at a meeting of the responsibletechnical committee,1which you may attend.FIG. 2 Electrodes (Radius 0.05 to 0.1 mm)D5288 10310.3 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 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 b
