1、Designation: D6097 01a (Reapproved 2008)1D6097 16Standard Test Method forRelative Resistance to Vented Water-Tree Growth in SolidDielectric Insulating Materials1This standard is issued under the fixed designation D6097; the number immediately following the designation indicates the year oforiginal a
2、doption 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 NOTEThe units statement in subsection 1.2 was corrected and the warning in old
3、Note 2 was moved into the text of8.2 editorially in July 2008.1. Scope1.1 This test method covers the relative resistance to vented water-tree growth in solid translucent thermoplastic or cross-linkedelectrical insulating materials. This test method is especially applicable to extruded polymeric ins
4、ulation materials used inmedium-voltage cables.1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibi
5、lityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitation prior to use. For specific hazard statements see 8.1.1.4 There is no similar or equivalent IEC standard.2. Referenced Documents2.1 ASTM Standards:2D1711 Termi
6、nology Relating to Electrical InsulationD1898 Practice for Sampling of Plastics (Withdrawn 1998)3D1928 Practice for Preparation of Compression-Molded Polyethylene Test Sheets and Test Specimens (Withdrawn 2001)3D2275 Test Method for Voltage Endurance of Solid Electrical Insulating Materials Subjecte
7、d to Partial Discharges (Corona) onthe SurfaceD3756 Test Method for Evaluation of Resistance to Electrical Breakdown by Treeing in Solid Dielectric Materials UsingDiverging Fields3. Terminology3.1 Definitions:3.1.1 Use Terminology D1711 for definitions of terms used in this test method and associate
8、d with electrical insulationmaterials.3.2 Definitions of Terms Specific to This Standard:3.2.1 water tree length (WTL), nthe maximum length of a stained tree-like micro-channel path in millimetres,millimeters,measured from the tip of the conical defect in the direction of the conical axis.3.2.2 resi
9、stance to water-tree growth (RWTG)(RWTG), na dimensionless value which is L divided by the WTL.3.2.3 thickness of point-to-plane specimen (L), nthe vertical distance in millimetresmillimeters from the tip of the conicaldefect to the opposite surface of the solid dielectric material.3.2.4 semiconduct
10、ive shield, npolymer/carbon black composite material used in medium voltage cables with volumeresistivity between 104 and 105 ohm-cm.1 This test method is under the jurisdiction of ASTM Committee D09 on Electrical and Electronic Insulating Materials and is the direct responsibility of SubcommitteeD0
11、9.12 on Electrical Tests.Current edition approved May 1, 2008Nov. 1, 2016. Published July 2008December 2016. Originally approved in 1997. Last previous edition approved in 20012008 asD6097 01a.D6097 01a (2008)1. DOI: 10.1520/D6097-01AR08E01.10.1520/D6097-16.2 For referencedASTM standards, visit theA
12、STM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.3 The last approved version of this historical standard is referenced on www.astm.org.This document is
13、not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropri
14、ate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States14. Summary of Test Method4.1 Ten compression-molded disk specimen
15、s, each containing a conical-shaped defect, are subjected to an applied voltage of5 kV at 1 kHz and 23 6 2C in an aqueous conductive solution of 1.0 N NaCl sodium chloride (NaCl) for 30 days. This controlledconical defect is created by a sharp needle with an included angle of 60 and a tip radius of
16、3 m. The electrical stress at the defecttip is enhanced and can be is estimated by the Masons Hyperbolic point-to-plane stress enhancement equation.4 This enhancedelectrical stress initiates the formation of a vented water-tree grown from the defect tip. Each treed specimen is stained and sliced.The
17、 water-tree length and point-to-plane specimen thickness measured under microscope are used to calculate a ratio that is definedas the resistance to water-tree growth.5. Significance and Use5.1 This is a laboratory test designed to simulate the growth of vented water-trees in the solid dielectric in
18、sulating materialinitiated by a sharp protrusion at the insulating and conductive interface under a wet environment in a high electrical field.Water-treeing is the phenomenon which describes the appearance of tree-like growth in organic dielectrics under an ac field whenexposed to moist environments
19、. Two types of water-trees are formed. Bow tie trees (within the dielectric) and vented water-treesformed from conductive/insulating material interface into the insulating material. The water-trees referred to in this test methodare the vented type.The insulating material is the solid dielectric org
20、anic material.The conductive material is the salt solution.Thissalt solution is used on both sides of the insulating material to simulate the same inner and outer semiconductive shields saturatedwith moisture between the insulation layer used in a medium-voltage underground power cable.5.2 This test
21、 method provides comparative data. The degree of correlation with the performance in service has not beenestablished.5.3 The standard test conditions are designed to grow a sufficient water-tree length for most solid dielectric insulating materialsof interest before electrical breakdown occurs. Mate
22、rials with a very high resistance to water-tree growth may require a longer timeunder test conditions (such as 180 days) or higher voltage (such as 10 or 15 kV) in order to differentiate their performance. For4 The sole source of supply of the base, Dow Corning 3110RTV, the catalyst, Dow Corning RTV
23、 Catalyst S, and the sealant, Dow Corning Multipurpose Silicone Sealant732, known to the committee at this time is Dow Corning, Inc., Midland, MI 48686. If you are aware of alternative suppliers, please provide this information to ASTMInternational Headquarters. Your comments will receive careful co
24、nsideration at a meeting of the responsible technical committe,committee, which you may attend.FIG. 1 TestTest Specimen Mold CavityD6097 162materials with a very low resistance to water-tree growth, electrical breakdown maywill occur during the 30-day testing time. timein most instances. A shorter t
25、esting time (such as one or ten days) is recommended to prevent electrical breakdown during testingfor those low water-tree resistant materials.5.4 Other voltages, frequencies, temperatures, aqueous solutions, and defects can are able to be used to evaluate specificmaterials for specific application
26、s.Temperatures shouldshall not exceed the softening or melting point of the material or 10 to 15Cbelow the boiling point of the salt solution. Any nonstandard conditions shouldshall be reported along with the results.5.5 Tree-growth rates generally increase with the test frequency. An acceleration f
27、actor due to frequency is given by (f/60)kwhere f is the test frequency and k is between 0.6 and 0.7. The test frequency of 1 kHz is selected to accelerate the water-treegrowth. However, the there is the possibility that the chemical nature of oxidized products from water-treeing may be different at
28、different frequency ranges.5.6 Two assumptions for this test method are: (1) all tested materials grow trees in the same power law kinetic manner and (2)the time under test conditions of 30 days is long enough to establish the difference in water-tree growth. If there is a doubt, at leastthree diffe
29、rent testing times (such as 30, 90, and 180 days) shouldshall be used to verify their comparative performance and disclosetheir kinetic nature of water-tree growth. Of course, it is also assumed that all water-treed regions are oxidized regions that canare able to be stained for optical observation.
30、 Different materials may also have different temperaturesThe softening temperatureof different materials will require different temperature and times to stain the oxidized (treed) regions due to their differentsoftening temperature.regions6. Apparatus6.1 Power SupplyAhigh-voltage supply with a sinus
31、oidal voltage output of at least 5 kVat a frequency of 1 kHz and an outputpower of 3 kVA.6.2 Conical NeedlesConical needles are made from steel or tungsten carbide. Their dimensions are 14.5 6 0.5 mm long, 46 0.2 mm in diameter, point radius of 3 6 1 m for the needle tip radius, and 60 6 1 point ang
32、le.6.3 Test Specimen MoldThe test specimen mold is a three-layer metal mold. The top metal plate is flat. The center plate hasat least ten holes to make ten test specimens for each material. Each hole has a 25.4-mm diameter and at least 31.75-mm spacingfrom center to center of each hole. The center
33、plate also has the guide holes about 8 mm in diameter at two corners to mate withpins in the bottom plate section. The bottom plate section consists of two metal plates bolted together. The first bottom plate hasthe same number of holes as the center plate. Each hole has the inside diameter of 4 mm
34、to accommodate needles. The secondbottom plate has the holes with an inside diameter of 10 mm. The center points of all the holes in the bottom and center platesare matched and aligned. These holes at the second bottom plate are threaded to accommodate the needle support member. Theneedle support me
35、mber is fabricated from threaded stainless steel rod drilled at one end to provide a snug fit for needles, and atthe other end to accommodate an hexagonal head driver. Needles are threaded into the support member. The needle and needlesupport assembly is carefully screwed into the base until the nee
36、dle point extends 3.2 6 0.1 mm above the surface. Fig. 1 is anexample of the mold cavity.6.4 Specimen HolderThe specimen holder, designed to hold at least ten specimens, is made from a solid block of clearpolymethyl methacrylate (PMMA). The PMMA is used because of the ease of machining and its good
37、electrical properties. Theinside is machined to a depth of 50.8 mm with a 12.7-mm wall thickness. The outside bottom has the same number of holes withan inside diameter of 25.4 mm with a depth of 6.35 mm, 6.35 mm, drilled with a spacing of 38.1 mm from center to center of theholes. The inside bottom
38、 has the same holes with an inside diameter of 12.7 mm and a depth of 6.35 mm 6.35 mm in line withthe centers of the holes drilled at the outside bottom. Fig. 2 is an example of the specimen holder.6.5 ElectrodesThe electrode is made from a 1-m length of 24 AWG nickel-chromium wire or other suitable
39、 conductive,noncorrosive metal wire formed, on one end, into a closed loop about 50 mm smaller in diameter than the inside diameter of thespecimen holder with the remainder bent perpendicular to the loop so that it can be is able to connected to the transformer toconduct the voltage into the electro
40、lyte (the salt solution).6.6 Water BathA circulating water bath; provided with heaters and temperature controls if tests are to be made at elevatedtemperatures.NOTE 1Circulation of the solution in the bath even at room temperature is necessary to remove gas bubbles formed at the interface of the sol
41、utionand the test specimens caused by electrolysis.6.7 MicroscopeA microscope equipped for 20 and 100 magnification.7. Reagents7.1 SaltReagent-grade sodium chloride.7.2 SealantsThe material used for sealing in this test method is a two-part silicone rubber sealant consisting of a base4 anda catalyst
42、. 47.3 Multipurpose Silicone Sealant SealantOne-part silicone4 rubber sealant.D6097 1637.4 Staining DyeThe staining dye is a mixture of the methylene blue and sodium hydroxide.7.5 Deionized Water, or distilled water.8. Hazards8.1 WarningLethal voltages are a potential hazard during the performance o
43、f this test method. It is essential that the testapparatus and all associated equipment that may be electrically connected to it be properly designed and installed for safeoperation.8.2 Solidly ground all electrically conductive parts that may be are possible for a person to contact during the test.
44、 Providemeans for use at the completion of any test to ground any parts which were at high voltage during the test or have the potentialfor acquiring an induced charge during the test or retaining a charge even after disconnection of the voltage source. Thoroughlyinstruct all operators as to the cor
45、rect procedures for performing tests safely. When making high-voltage tests, particularly incompressed gas, oil, water, or aqueous solution, it is possible for the energy released at breakdown to be sufficient to result in fire,explosion, or rupture of the test chamber. Design test equipment, test c
46、hambers, and test specimens so as to minimize the possibilityof such occurrences and to eliminate the possibility of personal injury. If the potential for fire exists, have fire suppressionequipment available.WarningWater in the test tank is gradually evaporated. Keeping the water level constant is
47、important to prevent an electricalhazard.9. Sampling9.1 Sample in accordance with Practice D1898.10. Test Specimen10.1 Geometry of Test Specimens SpecimensThe test specimen is a disk containing a conical defect at the center of one side.The disk has a diameter of 25.4 mm and a thickness of 6.35 mm.
48、This conical defect has a diameter of 3.2 mm 3.2 mm and heightof 3.2 mm 3.2 mm with an included angle of 60. The radius of the cone tip is 3 6 1 m. 1 m. Fig. 3 is the geometry of the testspecimen.10.2 Preparation of Test Specimens SpecimensCompression mold ten specimens for each solid dielectric mat
49、erial using thepreparation method described in Practice D1928. Use a pre-drilled polyethylene terephthalate sheet over needles to cover the metalsurface of the bottom section of the test specimen mold to prevent cross contamination from the previous material residue. ApplyFIG. 2 PMMAPMMA Specimen HolderD6097 164a colorless mold release agent to all surfaces of the center section of the mold, to prevent cross contamination from the previousmaterial residue. The mold release agent shouldshall not contain grease, wax, or silicone oil. Weig
