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Timestamp: 2019-04-23 02:37:09+00:00

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differentiation among similar materials with respect to their containing organic, and some inorganic, filler.
are described in the following paragraphs and in Section 5.
should be used, and their development is encouraged.
tion of a conductive path.
of environmental conditions, especially dirt and moisture.
Subcommittee D09.12 on Electrical Tests. 39.
Current edition approved March 10, 1999. Published June 1999. Originally Annual Book of ASTM Standards, Vol 10.01.
published as D 495 – 38 T. Last previous edition D 495 – 94. Annual Book of ASTM Standards, Vol 10.02.
deleterious effect on the performance of the arc.1 Changes in both the timing of the intermittent arc and certain materials using inverted orientation. after the specimen has cooled.1 For definitions of terms used in this test method. the use of the tungsten rod electrodes is recommended duration.2. steel strip electrodes as the preferred technique. taken from a group of dissimilar materials.1 The apparatus (see Fig. method of re- 3. When testing materials with ditions as exist in alternating current circuits operating at high poor to moderate arc resistance (up to 180 s).2. A recommended circuit arrangement and Section 14). with the electrodes undisturbed from their 3. but at currents limited to units and tens of milliam. Any of these 3. 4. Thus.2 IEC Standard: 4. and then either (1) measuring the 3. and does not include the stainless steel electrodes.3. a thin specified to maximize data reproducibility among different test wiry line is formed between the electrodes. 3.3. the specimen to cool to room temperature.1 Definitions: NOTE 3—Some investigators have reported attempts to characterize the 3. n—a test condition in which the evaluating the damaged area after failure is to repeat the arc resistance test electrodes are located on the upper surface of the specimen. occurs intermittently between two electrodes resting on the It is permissible to make additional tests with rod electrodes. However. use the stainless voltage. however.” that is. The as to provide a basis for comparison with other data obtained severity is increased in the early stages by successively with such electrodes. rather than the crackly blue spark characteristic of a condenser discharge. test procedure for carrying out the second of these two means of 3. have low arc resistance. For values of arc resistance greater than decreasing to zero the interval between flashes of uniform 180 s. so surface of the specimen. decreases the variability often associated with the use of rod 4. D 495 2.2 In order to distinguish more easily among materials that electrodes on materials having poor or moderate arc resistance. because the corners of the stainless steel strip electrodes erode 4. The arc obtained will be relatively quiet.4. and in later stages by increasing the current.4 inverted orientation.3.2 Some organic compounds burst into flame without the 6. low-current type of arc resistance test 5. less steel strip and tungsten rod. Results obtained with the 4.s. use data obtained by this test method to infer that the materials examined occupy an unchanging quality relationship to each 4.4 The fourth type occurs by carbonization of the surface IEC 61621 Dry Solid Insulating Materials—Resistance Test until sufficient carbon is present to carry the current.3 Four general types of failure have been observed: appreciably under such conditions. be universally applicable because of the severe physical damage to the test area in many instances. NY 10036..2 This test method describes two electrode systems: stain- is intended to simulate only approximately such service con. Regardless of the conditions of anticipated use.1 arc resistance. Terminology resistance between 178 and 182 s than between 174 and 178 s. n—the end-point of the test procedure em. 3. tion. and the later stages are successively more severe. To High-Voltage.s. and obvious. use of the tungsten rod electrode system may be different from whereupon they are capable of conducting the current. sets. and is directly based upon Test Method D 495.3 normal orientation. 5.1 The stainless steel strip electrodes are referred to as rank. as well as other changes affecting the nature of the rials.2. the early stages of this test method are All of the factors that affect the disparate behavior of rod mild. Apparatus formation of a visible conducting path in the substance. electrodes.3 Others are seen to fail by “tracking. in normal or inverted orientation. characterizing the remaining insulating value of the damaged area is ployed in this test method (see Section 14).1 Discussion— Tests made with inverted orientation are more severe than tests made with normal orientation. increased data dispersion may be encountered. With other mate- the current. This technique peres. there is a much greater difference in arc 3.1 Many inorganic dielectrics become incandescent. refer remaining insulating value of the damaged area after failure by allowing to Terminology D 1711. can affect the duration of a test of most specimens with materials that evolve considerable gas during test. 4. much more weight should be given to a few electrodes. Interferences Reduced data dispersion has been encountered when testing 5. described in Appendix X1. Upon those obtained with the use of the stainless steel strip electrode cooling. they return to their earlier insulating condi. n—the total elapsed time in seconds insulation resistance between the electrodes or (2) determining the from the start of this test procedure until failure occurs (see percentage of breakdown voltage remaining relative to that obtained on an undamaged area of the specimen. Significance and Use other. Primary voltage control is made by a variable transformer 5 Available from American National Standards Institute. n—a test condition in which the original positions.1. The arc electrodes on such materials have not yet been fully reported.2 Definitions of Terms Specific to This Standard: original position of the electrodes.3 Abbreviations: changes can drastically alter a material’s position in order of 3.2 failure.1 The high-voltage. without disturbance of the 3. New rather than by a variable inductance because of its proved York.2. 11 W 42nd St. system. 1 for electrical circuit) is closely 4. seconds that overlap two stages than to the same elapsed time within a stage. especially discharge. 2 . 6. keep in mind that none of these methods will electrodes are located on the under surface of the specimen.4 Materials often fail within the first few seconds after a change in the severity stage. Still another. Low-Current Arc Discharges5 4. do not s.3.3. When comparing the arc resis- NOTE 2—IEC 61621 is technically equivalent to D 495. IEC 61621 describes only the tungsten tance of materials.2.
NOTE 5—Although provision has been made for the suppression of radio-frequency components of current in the arc. TT—A stop watch or electric interval timer 6 Jefferson Electric Type 721-411 luminous tube transformers have been found to operating at 115 V ac. R20 is about 50 V with FIG. s ⁄ 10 18 10 ⁄ s on. These resistors must be adjustable. WI. readable to 1 V in the satisfactory.3 Voltmeter.060 A.1. This resistor. Com- opening and closing the primary circuit according to the mercially available line voltage stabilizers that do not distort the voltage wave form are suitable. and a rated secondary current (on short circuit) of used to suppress parasitic high frequency in the arc circuit. with associated current ratings of 2 and 5 A. schedule in Table 1. A—An ac milliammeter capable of reading from 10 to 40 mA with an error of not over 65 %.. 6.7 Air Core Inductors—Inductance totaling from 1.1.1. TABLE 1 Sequence of 1-min Current Steps Step Current. will provide a 20 mA arc current. mA Time CycleA Total Time. during a test. R3 0 and R40 have values of about 30 V and 15V respectively. 1⁄4s off 180 10 10 continuous 240 20 20 continuous 300 30 30 continuous 360 40 40 continuous 420 A In the earlier steps an interrupted arc is used to obtain a less severe condition than the continuous arc. 1 Arc-Resistance Test Circuit a current rating of at least 13⁄4 A.1 Transformer. is permanently connected across the output wound or insulating nonmetallic cores of about 1⁄2 in. 13⁄4s off 14 60 1⁄4 10 10 1⁄4 s on. Similarly. The interruptor can be a synchronous motor driving three appro- priate sets of cams which actuate the contactor switches. to permit exact settings of the currents during calibration. provide arc currents of 30 mA and 40 mA respectively. R30.1. Before use. I—This motor-driven device is used to give the required cycles for the three lower steps of the test by NOTE 4—A constant primary voltage supply is recommended. Coils may be obtained from Cutler-Hammer. Closing switch S2 0.1 may be used if it can be demonstrated that equivalent data are obtained.2 is satisfactory. This is done by use of a suitable thermocouple-type r-f milliammeter temporarily inserted in series with the milliammeter.7.1. and nominally adjustable up to 135 V. with an accuracy of 61⁄120 s or better.1.7 of the autotransformer to indicate the voltage supplied to the mm) diameter and 5⁄8 in. An autotransformer 1. Other makes 8 of the same general construction will probably also be adequate.1. power factor corrected) with a rated primary potential of 115 V 6. A single coil of this inductance is not 6.) with equal or greater current-carrying capacity than listed in 6. Milwaukee. from bottom to top. (15. Inc. it may be shorted out by a by-pass switch when not in use. R 3—Rated at 15 000 V and at at 60 Hz ac. 30 cotton.5 Current Control Resistors. R10 is always in the circuit to provide a 10 mA current. with a current rating of at least 11⁄4 A.1. 6. 7 The Powerstatt (Superior Electric Co.6 Suppressing Resistor.or rated at 7 A or more.7 Ta.1. a rated secondary potential (on open circuit) of least 24 W.1. it may be desirable to check for their presence when the apparatus is first constructed.9 Timer. a current of less than 10 mA produces an unsteady (flaring) arc. enamel-covered wire. 3 . 6. to some extent. These resistors. along with the inductors in 6. D 495 6. when switched in.1. Since this milliammeter is used only when setting up or making changes in the circuit. R20. R10. Any other type or make meeting the requirements of 6. R40—Four resistors are required in series with the primary of Tv but in parallel with each other.8 Interruptor. 0. V1—An ac voltmeter.8 primary circuit. to make certain of its readings. Its value is approximately 60 V. (12.6 Tv—A self-regulating transformer (non. Each coil consists of 3000 to 5000 turns of wire range 90 to 130 V. be satisfactory.1. R10.5 H is obtained from about 8 coils of No. accurate to 1 s. to add R20 in parallel with NOTE 1—Switches SM to S40 are aligned in the sequence of their closing.2 to 6.9) inside length.4 Milliammeter.2 Variable Autotransformer. 6. 3⁄4s off 120 1⁄2 10 10 1⁄4 s on. this meter should be calibrated in a test circuit containing no arc gap. is 15 000 V. 6.) or the Variact (GenRad Co.
Use rods about 13⁄4 in. 6. In either type of rod electrode. isolated from the operator by a suitable enclosure through (19 mm). IL—A 6 W. throw switch insulated for 15 000 V ac. or rough spots. C S—Rated at 10 A mm) thick stainless steel into 1⁄2 by 1 in. to prevent cracking or chipping.4 mm) diameter tungsten These contactors are operated by the interrupted cams. and must be so disposed cycle being used and permits the operator to start the first cycle that it and any circuit components are not readily accessible of each test in a uniform manner by closing S ⁄ just after the 18 when energized.1.2).006 in.1. (The edges must be free of burrs.1. pits. R1. lis Honeywell Regulator Co.18 Tungsten Rod Electrodes (see 5. (12. except finishing the pointed tips to the proper geometry (see Fig. C ⁄ .12 Safety Interlocking Contactor. 4) by swaging.7 by 25.2 for restrictions)— open spring contactors.10 Indicator Lamp. have been found satisfactory. 2).4 mm) and 110 to 125 V ac. The shank ensures correct orientation of the electrode which projects an insulating handle of sufficient length to point after sharpening (see 9.11 Control Switches—Toggle switches are convenient. 3). leaving an exposed length of about 3⁄4 in.9 mm) long in the electrode assembly. S1 and S4 0. of the simple rod electrode may be obtained by adjustment of the rod in the electrode assembly. which require 10 A ratings. grind the end of the rod at a 30° angle to the axis (see Fig. or use shorter rod lengths 6. steel jig for securing the electrodes during sharpening to ensure All may be of the size rated at 3 A and 110 to 125 V ac.2. (45 intermittent arc cycles listed in Table 1.1. of approximately 160° (see Fig.17 Stainless Steel Strip Electrodes— Cut 0. 4) to achieve a flat elliptical face. This lamp indicates the interrupting ignition wire rated at 15 kV or higher. C ⁄ . rated at 11⁄4A (or better) and 125 V ac. IL. lamp is extinguished.1.13 Interruptor Contactors. thus rod (tungsten welding rod has been found suitable) which is closing and opening the primary circuit and providing the free of cracks. 115 V lamp with a 2000 6. Exercise care in grinding 9 Microswitch contactors available from Micro Switch. in series. a Division of Minneapo. This switch must be or silver soldering. C ⁄ —Normally- 18 14 12 6.16 Sharpening Jig for Tungsten Rod Electrodes—A 6.. 2 Grinding and Polishing Block with Tungsten Rod Electrode in Place 4 . Make the electrodes from 3⁄32 in. FIG. fastened into a square shank (see Fig. (2.15 6. D 495 6. (0. single. brazing.1.1.14 High Voltage Switch. S 4—A single-pole.) Bend each strip open the contactor and thus remove high voltage from the slightly in the middle of the long dimension to form an angle electrodes. 6. this interlocking contactor is installed so that raising the draft shield around the electrode assembly will strips. 6.1.15 Wiring—All wiring in the arc circuit must be of V resistor. although correct orientation ensure operator safety.1. Freeport.
men from air drafts.1 Stainless Steel Strip Electrode Assembly (see Fig. and provide a clear view of the arc from a position may be suffıcient to result in fire. ( c) electrodes are mounted in square shanks and sharpened in a correctly made jig. (b) support rods are required to track. ing factors are controlled: (a) axis of tungsten rod is perpen. The deemed most significant. Provide test. Solidly ground all electrically specimen is at the same level height. 8.19 Electrode Assemblies—These assemblies provide a 7.1. If electrodes are not mounted in square shanks. (6. may a transparent shield around the assembly to protect the speci. specimens so as to minimize the possibility of such occurrences 3. Make all comparison tests of parts in proper orientation will automatically be obtained if the follow. 6. and 8. moisture. Provide means for use at the completion of any test area. explosion.003 in.250 6 0. Either use an electrode holder such as the one in Fig. (6. Specimens and Number of Tests and at angles of 45° to a line joining the corners. 8. similar locations. test at least five use the rod electrode assembly with the rods separated and specimens 0. electrodes on the top of the specimen surface with the corners down and spaced 0.08 mm) apart. (6. D 495 FIG.19.25 mm) in thickness. obtain FIG.1 For standard comparison of materials. Construct each essential that the test apparatus. Fig.1 Lethal voltages may be present during this test.1. It is the arc to the top surface of the specimen. (12. or finger marks can affect the time dicular to the axis of the support rod.35 6 0. 7)—Place two stainless steel strip and to eliminate the possibility of personal injury. whether for stainless steel strip electrodes or for that may be electrically connected to it. Make each test on a flat surface of the specimen. or 8. 8)—Position the electrodes so that they lie in the same closer than 1⁄2in.4 mm) to the specimen edge nor Fig. test chambers. Design test equipment. test chamber. Fig. particularly in the test. and Fig. and all associated equipment assembly. 4 Top and Side Views of Tungsten Rod Electrode proper orientation by adjusting and rotating the electrodes after they are inserted in the appropriate electrode assembly.125 6 0. Test vertical plane and are both inclined 35° from the horizontal thin materials by first clamping them together tightly to form a (thus inclined 110° between their axes). resting on the stainless steel strip electrodes. Provide ample air space conductive parts that any person might come in contact with below the specimen. Protect the operator from inadvertent contact with the compressed gas or in oil.2 When testing molded parts. (3.1. 3 Strip Electrodes and Holders gripped in the pivot blocks in a position such that the axis of each electrode is inclined at 35° when the support rods are horizontal. 3. When making high voltage tests. so that the top surface of each and installed for safe operation. If affected.250 6 0. retain a charge even after disconnection of the voltage source. Check to see that the specimen as close as possible to the recommended thickness.35 6 0.010 in. or rupture of the slightly above the plane of the specimen. Adjust each electrode so that it rests independently test to ground any parts which: were at high voltage during the with a force of 50 6 5 g on the top of the specimen.7 mm) to a previously tested area. 5. 4 and area not closer than 1⁄4 in. clean specimens or parts with a 5 . and test 6.19. apply the arc to a location space the tips 0. be properly designed tungsten rod electrodes.3 Dust. Fig. especially in the region directly below the during the test. and (d) the spacing between electrode tips is adjusted with the support rods in a horizontal position. with each test 6. the energy released at breakdown electrodes.2 Tungsten Rod Electrode Assembly (see Fig.003 in. 7. may have acquired an induced charge during the test.08 mm) apart. and Fig. Safety Precautions means of holding the electrodes and specimen and of applying 7. and allow venting of combustion products Thoroughly instruct all operators in the proper way to conduct in cases where specimens give off toxic smoke or gases during tests safely. 6. 6. minor axes of the elliptical tip surfaces are horizontal.17 6 0.
2) with its elliptical tioning. static voltmeter across the secondary of Tv.2 Sharpen the tungsten rod electrodes when examination S10 and S1 closed. Ta.1 With the circuit connected as shown in Fig. S4.1. state the successive cuts.2 Tungsten Rod Electrodes: 10. 1 to 000) held between the fingers. Calibration be sure that they are free of burrs.2.08 mm).3 Adjustment of Secondary Current— With the cor- observable at 153 magnification. comes into contact with the high voltage wiring of the tion occur. Cleaning and Sharpening Electrodes when no burrs or rough edges are observable at 153 magni- 9.1. polish the rod surface rectly spaced electrodes resting on a lava or ceramic block and by rotating it on its axis using successive grades of emery paper with the draft shield closed.1 Stainless Steel Electrodes—Use two new corners of the fication. stainless steel strip electrodes for each test. First. Hold the surface against before testing. 1. close switches S 1. to of the tip edge shows that it has been rounded to a diameter of provide an open circuit operating voltage of 12 500 V. Then mount the Adjust R1 0 to give the required current of 10 mA as indicated 6 . proves to be the most effective technique of cleaning the 10. electrode in the sharpening jig (see Fig. or when burrs or rough edges are 10. The application of a continuous 40 mA arc for de-energized by opening S1 before each change in connection approximately 1 min (without a specimen in place) often is made. no cleaning or sharpening is 10. However. these instructions may be disregarded. calibrate required. the operator necessarily 9. using No. a rotating polishing disk or rub against a stationary machinist’s flat. The resulting elliptical face should be a highly nature and quantity of contaminant present (if known) in the report. (0.2 Open Circuit Operating Voltage— Attach an electro- electrodes. 5 Strip Electrodes in Place cloth containing water or other suitable solvent before condi. the test apparatus for correct voltage and current as follows: 9. initially adjust the autotransformed.1 If excessive accumulations of products of decomposi. polished surface inclined at 30 6 1° to the axis of the electrode.1.030 in. With S 4 open and 9. Wipe such specimens with a dry cloth immediately face flush with the surface of the jig. clean the rod electrodes gently with laboratory secondary circuit. Other than inspecting the electrode corners to 10. and S10. 1 to No. (from No. D 495 FIG.1 In making these calibrations. Replace electrodes after four tests.2. It is therefore imperative that the circuit be tissues. 000 emery or emery paper to make NOTE 6—If the purpose of the test is to ascertain the effect of contamination. The electrodes are considered properly sharpened and polished 9. 0.
1. 13.7 11⁄2 38 13⁄4 44. to provide comparison with previous information procedure until no further adjustment is necessary to obtain 10 obtained with rods). D 495 in. 7 .s.3 0. the obtained with the s. tungsten rod voltage (typically around 110 to 115 V) for all subsequent electrodes may be used to test materials having arc resistance calibration and testing.s. close S40 and adjust R40 to give a 40 mA current.500 12.2 If specimens have been kept at a temperature close to or below the dew point of the surroundings in which the test will be run. to obtain the required voltage across voltmeter V as that the omission of this step has no effect.s. placing R20 in parallel with R10. if with Procedure A of Practice D 6054. finally.s. Repeat this example. 13.254 0.1 Stainless steel strip (s. If the s. 11. use the 10 mA to indicate proper suppression of r-f. 6 Holder Detail the effect of exposure to humid atmosphere is of interest. 12. prevent condensation on the specimens by warm- ing the specimens in a dry atmosphere.1 This test method describes two electrode systems: FIG.4 0. Choice of Electrodes 12. electrode system.s. by the milliammeter A. thus times greater than 180 s when tested using s. and 12.s. Note the reading on the voltmeter V at this 12.1 Condition specimens prior to testing in accordance 13.2 The choice of electrode system depends upon the result current in the secondary when the equipment is first set up. close S2 0 along with S10. In such cases the rod readjust Ta to give an open circuit secondary voltage of 12 500 electrodes may be used to give additional information. (for V as indicated by an electrostatic voltmeter.650 16.) electrodes.1 Since the corners of s.025 ⁄ 9 16 14.010 0.s. mA and 12 500 V.2 Lower the draft shield.4 NOTE 1—The 0. Close S30 and adjust R30 for a 30 mA current.010-in.8 1 25. mm in. If the apparatus is checked for r-f 12.001 0.s. electrodes.1 Place the specimen in the appropriate electrode assem- 11.5 1⁄16 4. Conditioning bly (see Section 12) and check the spacing. 7 Strip Electrode Holder Assembly 12. 11.2.s.s. electrode r-f thermocouple milliammeter (see Note 5) should also read system yields an arc resistance time less than 180 s.2 Tungsten rod electrodes. For some insulation. Next. mm 0. electrode system for that material.s. FIG. slot and the corresponding angled corner must be made to provide a left and a right holder. Maintain this appreciably at testing times exceeding 180 s. electrodes can erode time while the arc is continuous at 10 mA. Open S4 again and s.1.s. close S1 and adjust T a. Adjust R20 to give an arc current of 20 mA. Procedure for Determination of Arc Resistance Time and. in which case the use of Procedure C of Practice D 6054 is recommended. unless it can be shown necessary. established in the calibration procedure. NOTE 7—Warming the specimens in a 50°C oven for about 30 min is suitable in most cases.
report an arc resistance value. D 495 FIG.1.1. and 15. lava. 14. after a tracking path 13. If the arc should “climb” or flare voltage is applied. formation of conducting paths across the entire surface of the 15.2. Report 14.3 Begin the test by first closing S1.1 Failure of materials for which this test method has the 15.2 Conditions of fabrication. Observe 14. or ceramic.1. In such instances. a persistent scintillation S1. simul.4 Particulates suspended in gases generated from burn- ing of the material obscure the arc and make it impossible to NOTE 8—Gases are expelled forcibly from some insulators. the disappearance of the arc into the specimen. The trend toward failure occurs over a broad interval of time taneously close ST and S ⁄ to begin the timer and the first level 18 before all parts of the arc disappear. the indicator lamp. immediately is no visible arc. thus causing the arc to flutter. The definite end-point occurs with the 15. interrupt the arc current and stop the interval timer by opening 14. Just after the lamp is extinguished. a noticeable change in sound.4 While the test is in progress.6 mm) lift at its middle) and to observe current only in the later part of the time during which the the progression of tracking.1 In testing some materials. The time of the appearance of the first of irregularly. it is an indication that the circuit constants are these intervals is designated as the end-point. and SM. (1. determine if the arc is “normal” (lying close to the specimen 14.4 Thickness of specimen. Do not include the persistence of this position nearly on a level with the surface of the specimen to remaining scintillation as part of the arc resistance time. 8 .3 In successive arc intervals the track conducts the with not over 1⁄16 in. incorrect. At the end of each the end-point reached only when every part of the specimen minute increase the arc severity in sequence as shown in Table surface between the electrodes is carrying the current and there 1 until failure occurs as defined in 3. In these instances. consider of arc severity in accordance with Table 1.1 Report the following information: most meaning and significance will have an end-point that is 15. usually quite definite.2. S4. check the equipment for determine the end-point.3 Conditioning prior to test. will be observed. a description of the part. Record the seconds to failure.1 Type and trade name of material. specimen. 14.2 Failure of other materials is more difficult to describe. 8 Tungsten Rod Electrode Assembly 13. watch the arc from a obviously is completed. or if not a standard specimen.1. close to the electrodes. Interpretation of Results 15. It may be preferable in such cases to proper operation by examining the arc for quietness and maintenance of a report simply that failure occurred by burning rather than to position close to an inert surface such as glass. At failure.
1) with switch S4 open.3.7 Median and minimum arc resistance times. This can be met by a voltage ratio.2. The ratio of this additional voltmeters.1 This test method is intended to determine the frac. Continue these steps general. X1. preferably of the serious physical damage to the specimen that the performance electrostatic type. and arced insulating materials in particular. is known up to about 1000 V. E. for situations in which arc currents are not limited to a low tion of breakdown voltage remaining after completion of the value such as 0. it is necessary to between the electrodes in an arc-resistance test. are required.1 The apparatus for this test is identical with that electrodes left undisturbed in their original position on the described in Section 6 of Test Method D 495 and the circuit specimen. Below 500 V it shall be relied upon in such cases. when X1. Plate glass. Exercise caution 7000 V. raise the voltage from zero by material may determine whether or not insulation will have to means of the autotransformer. VOLTS AFTER TRACKING TEST FOR DETERMINATION OF SURFACE BREAKDOWN VOLTAGE RATIO AFTER FAILURE OF SPECIMENS IN ARC-RESISTANCE X1. and take readings on the lowest be replaced following removal of the causes of a temporary or appropriate scales of V2 and V3 for each increase that gives a accidental arcing condition in service.1 arc resistance. It shall read at least 500 V.01 A or less.8 Special remarks. but will relate the readings of the primary voltmeter.1. root-mean- the arc-resistance Test Method D 495 has resulted in such square reading meter of very high resistance. as follows: breakdown voltage (“volts after tracking”) to the average X1.1. X1. and 125 V. No activity has been planned to mal or inverted. stainless steel electrodes.1 Scope in applying the results prior to a thorough analysis. are added.4 Calibration of V2 versus V3 cooling after surface failure under electrical arcing.1. Keywords 16. 16. and softening. Prepare a calibration curve from these data for use in 9 . This characteristic of a switches S1 and S1 0 closed. The degree to which a tion. track formed in a specimen of electrical insulating material X1.6 Number of tests. whichever is larger. if any. will melt and become conducting in the area specimens in the test for surface breakdown. and 15. a statement of precision. 1 is also identical.3. but after the specimen has cooled to room tempera. replace the electrode assembly. The judgment of the operator shall be higher. X1. between X1.1. develop such information. A breakdown voltage test is performed between the arc X1. 17. multi-scale meter with full-scale readings of about 25. It is used only occasionally to calibrate the of a voltage breakdown test at the damaged area would have circuit. high-voltage low-current dry arc resistance is determined 15.1.1. D 495 15. tungsten rod electrodes information has been presented to ASTM upon which to base APPENDIX (Nonmandatory Information) X1. It is to be connected.5 Electrode system used and orientation.2. dry arc resistance.3 Apparatus when failure has occurred as described in Test Method D 495. for instance burning.3. Precision and Bias 17.2 Voltmeter V3 shall be a high-voltage. with an accuracy of 65 %.4.1 In order to determine the breakdown voltage for for example. if necessary.2 This test method has no bias because the value for 15.1 This test method has been in use for many years. when necessary. 1). With to the designer of electrical equipment. but no current. after arcing is stopped. V2 and V3. except that two ture following failure in the arc-resistance test.2 The breakdown voltage of insulating materials in connected to X and then to Y.1 Certain insulating materials are known to recover a substantial measure of their original insulating value upon X1.1.1. 15. accurately readable to 610 V by means of a low-range scale.2 Significance and Use ground and position X or Y (Fig. arrangement shown in Fig. whether nor. total increment of about 100 V when the readings of V3. solely in terms of this test method. 75. with the V3 voltmeter. preferably to 6000 V or little or no significance. low 16. especially X1.2 This test method should not be used when failure in X1. It shall be accurately readable to 61⁄2 V or to6 5 % areas of the specimen shall be known as the surface breakdown of the reading.9 Kind and amount of contaminant. from the “failure” by opening S4 and attaching the ungrounded side of V3 to some that may exist under arcing conditions is of great significance convenient point electrically equivalent to X or Y (Fig. V2. to the actual recover its insulating value completely upon stoppage of the high voltage applied to the electrodes. then take steps of about 500 V up to about to decrease as the available current increases.1 Voltmeter V2 shall be connected directly across the breakdown voltage (“volts before tracking”) obtained in a terminals H and F of the primary of the high-voltage trans- similar manner with the arc electrodes resting on undamaged former Tv.1. high voltage. material will recover. To obtain this calibra- arc and subsequent re-solidification.
11.7. 610-832-9555 (fax). at the address shown below. Continue raising the electrode voltage in steps of 100 and surface breakdown voltage ratio. This standard is copyrighted by ASTM.1.7 Procedure for Determination of Arc-Resistance X1.1.7 Special remarks. X1.5.11.11 Report path has been formed between the electrodes. if not the action of the arc.astm.8 Kind and amount of contaminant.1 Use specimens as specified in Test Method D 495. Your comments will receive careful consideration at a meeting of the responsible technical committee. 10 . are entirely their own responsibility. to a reading equivalent to a voltage of 200 at the electrodes.1 The procedure for the determination of arc.1. open S 4 and with S10 closed raise V2 by means of Ta men. X1.11.9 Number of Tests X1. their positions during the procedure described in X1. permit them and the tested area to cool approximately to room X1.5 Number of tests. for instance burning.11.5 Test Specimens X1. If you feel that your comments have not received a fair hearing you should make your views known to the ASTM Committee on Standards.3 Conditioning prior to test.org).1 Test at least five specimens for arc-resistance time D 495.1.1. United States. The American Society for Testing and Materials takes no position respecting the validity of any patent rights asserted in connection with any item mentioned in this standard.1. if any.2 Without moving the electrodes or specimen from X1.1.org (e-mail).1.10 Calculation Breakdown Voltage X1. D 495 describing the breakdown voltage of arc paths on specimens by at the electrodes for which this last step was set is the converting from the reading of V2. temperature. watching V2 for a noticeable X1. X1. X1.11. as follows: conducting an equal number of similar tests of breakdown X1. X1.8. if not a standard speci- to zero.6 Conditioning X1. assisted. 3 s (estimated) before stopping the arc by opening all of S ⁄ to 18 S40 that may have been closed.8 Cleaning Electrodes X1. PA 19428-2959. Return Ta X1.1.6 Averages and minimums of arc resistance times decrease. either reapproved or withdrawn.7.11.2 Conditions of fabrication.1 When failure occurs in the arc resistance test.7.4 Thickness of specimen. This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years and if not revised. or through the ASTM website (www. Your comments are invited either for revision of this standard or for additional standards and should be addressed to ASTM Headquarters. Close S4 for an estimated 1 s. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the above address or at 610-832-9585 (phone). which you may attend. breakdown voltage of the arc path. close S10 to provide a steady arc for additional each of the values obtained for the exposed areas. 100 Barr Harbor Drive.1 Type and trade name of material. if desired. a description of the part. stop voltage on areas of the surface that have not been exposed to the interval timer immediately by opening ST.1 Condition the specimens as specified in Test Method X1. X1. X1.9. until a voltage is reached where closing this switch produces a and moderate but noticeable drop in the reading of V2.10.1.7. down voltage ratio) remaining after performing an arc test in resistance time is first carried out exactly as specified in Test accordance with Test Method D 495 shall be calculated by Method D 495. by means of Ta.1 Report the following information: X1. and the risk of infringement of such rights. keeping S4 open except for the 1-s test periods. Then. PO Box C700.11. West Conshohocken.6.1 The fraction of breakdown voltage (surface break- X1. by a mild air blast. or service@astm. Users of this standard are expressly advised that determination of the validity of any such patent rights. and dividing the average of these into already closed.1 Clean the electrodes in accordance with Test Method D 495.11.1.11.1. X1. The voltage X1. and breakdown voltage of the exposed areas. This is to ensure that a complete X1. soft-ening.

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