1、Designation: F 2676 09Standard Test Method forDetermining the Protective Performance of an ArcProtective Blanket for Electric Arc Hazards1This standard is issued under the fixed designation F 2676; the number immediately following the designation indicates the year oforiginal adoption or, in the cas
2、e 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. Scope1.1 This test method is used to evaluate the ability of the arcprotective blankets to withstand
3、 the effects of arc flash and arcblast in a configuration in which the blanket is hung oranchored near energized equipment. Specifically, this testmethod is used to determine the arc protective blankets (1)resistance to breakopen, (2) mechanical strength, and (3)ability to self-extinguish flames fol
4、lowing a controlled arcexposure.1.2 This method is used to determine the performance ofarc protective blankets in terms of: maximum arc current levelexpressed in kAand BTP(BTP) expressed as the product of arccurrent in kA and arc duration in number of cycles to causebreakopen (kA*cycles). Cycles are
5、 on the basis of 60 Hz.1.3 Blanket test specimens used in this test method are testsize blankets of 152 6 5cm(606 2 in.) by 122 6 5cm(486 2 in.). The test specimen size is for testing purposes only.Commercially available arc protective blankets either larger orsmaller than the test specimen size are
6、 covered by thisstandard.1.4 The arc protective blankets described in this test methodare made of flame-resistant materials and are available invarying sizes and configurations based on the application.1.5 This test method shall be used to measure and describethe properties of materials, products, o
7、r assemblies in responseto incident thermal (convective and radiant) and pressureenergies generated by an electric arc under controlled labora-tory conditions.1.6 The values stated in SI units shall be regarded asstandard. The values given in parentheses are mathematicalconversion to inch-pound or o
8、ther units commonly used for arctesting.1.7 This standard shall not be used to describe or appraisethe fire hazard or fire risk of materials, products, or assembliesunder actual fire conditions. However, results of this test maybe used as elements of a fire assessment, which takes intoaccount all of
9、 the factors, which are pertinent to an assessmentof the fire hazard of a particular end use.1.8 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 prac
10、tices and determine the applica-bility of regulatory limitations prior to use. For specificprecautions, see Section 7.2. Referenced Documents2.1 ASTM Standards:2D 4391 Terminology Relating to The Burning Behavior ofTextilesF 819 Terminology Relating to Electrical Protective Equip-ment for Workers3.
11、Terminology3.1 Definitions:3.1.1 arc, nconductive path in air for the electric currentcaused by ionization of air between two electrodes.3.1.2 arc induced fragmentation, nmolten metal frag-ments or other fragments emitted from an electric arc.3.1.3 arc protective blanket, na flat assembly of fabric(
12、s)with locations for attachment used to protect workers from theeffects of arc flash and arc blast.3.1.4 arc protective blanket maximum arc current Imax,nmaximum value of RMS arc current that blanket canwithstand without breakopen for no less than ten cycles of 60Hz.3.1.4.1 DiscussionStandard values
13、 of the maximum arccurrent for this test method are 15 kA, 25 kA, or 40 kA.3.1.5 arc protective blanket breakopen threshold perfor-mance (BTP), nthe product of the arc current I, kA and arcduration in cycles required for breakopen to occur at this samearc current level.3.1.6 breakopen, nin electrica
14、l arc testing, a materialresponse evidenced by the formation of one or more holes inthe material which may allow thermal energy to pass throughthe material.3.1.6.1 DiscussionThe instant of breakopen will only bevisible with a high-speed (HS) camera. The size of the1This test method is under the juri
15、sdiction of ASTM Committee F18 onElectrical Protective Equipment for Workers and is the direct responsibility ofSubcommittee F18.65 on Wearing Apparel.Current edition approved May 1, 2009. Published June 2009.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Custom
16、er Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.breakopen will quickly expand as the
17、arc blows through theblanket and burns back the edges of the materials. The finalsize of the breakopen hole is not significant, as it will dependto a great extent on the duration of the arc once the breakopenpoint is reached. The important measure using the HS camerais the time from arc initiation t
18、o the first evidence of arc plasmathrough the blanket.3.1.7 charring, nthe formation of carbonaceous residue asthe result of pyrolysis or incomplete combustion.3.1.8 directional arc, nin arc protective blanket testing,an arc expanding in direction of the blanket perpendicular toand centered to the b
19、lanket plane.3.1.9 dripping, nin arc testing, a material response evi-denced by flowing of a specimens material of composition anddroplets separation from the material.3.1.10 embrittlement, nthe formation of a brittle residueas the result of pyrolysis or incomplete combustion.3.1.11 ignition, nthe i
20、nitiation of combustion.3.1.12 ignitability, n (ignitable, adj)in electric arc expo-sure, the property of a material involving ignition accompaniedby heat and light, and continued burning resulting in consump-tion of at least 25 % of the exposed area of the test specimen.3.1.13 mechanical strength,
21、nfor an arc protective blan-ket, the ability to remain attached to its support(s) in essentiallyits original configuration.3.1.14 peak arc current, nmaximum value of the AC arccurrent, A.3.1.15 pressure wave, na certain force over an areacreated by air movement caused by an electric arc.3.1.16 RMS a
22、rc current, nroot mean square of the AC arccurrent, A.3.1.17 shrinkage, na decrease in one or more dimensionsof an object or material.3.2 For definitions of other terms see Terminologies D 4391or F 819.4. Summary of Test Method4.1 This test method determines resistance to breakopen andmechanical str
23、ength under directional arc exposure, ability toself-extinguish flames and the afterflame time of the exposedarc protective blankets. This test method simulates a conditionin a vault or substation or energy center where arc protectiveblanket may be attached to provide protection from the thermaleffe
24、cts and the pressure wave experienced during an electricalarc fault. This test method replicates most severe conditionswhen the arc is directed and focused on the blanket.4.2 This test method determines two ratings for arc protec-tive blanket: Maximum Arc Current, Imax, and BTP.4.3 Three nominal val
25、ues of Imaxare established in this testmethod: 15 kA, 25 kA and 40 kA. In this test method each arcprotective blanket test specimen is intentionally forced to breakopen. To be considered arc rated, blanket shall withstand threetimes at least one of the nominal values of Imaxwithoutbreakopen during a
26、t least 10 cycles.NOTE 1Additional testing at a higher Imaxthan 40 kA is permitted butthe arc protective blanket shall be rated at one of the three nominal valuesof Imaxwhich shall be the official rating.4.4 BTP is determined as the product of arc current and arcduration causing breakopen. Arc durat
27、ion is the number of 60Hz cycles between arc initiation and breakopen of the blanket.4.5 BTP is determined for at least three different arc currentlevels. A minimum value of BTP is assigned as arc rating to anarc protective blanket.4.6 In this test method the arc electrodes configuration isdesigned
28、so that the arc blast projects directionally towards thetest specimen.4.7 This test method involves observing HS video record-ings to determine test specimen breakopen and afterflame time.Each trial is recorded with a HS video camera.5. Significance and Use5.1 This test method determines the effecti
29、veness of arcprotective blankets in suprressing the combined effects of anarc flash and arc blast.5.2 The arc exposure energy is produced from controlledphase-to-ground arc fault. The resulting arc flash and blastenergy are intentionally directed onto the test specimen tosimulate worst case conditio
30、ns.5.3 Test results will describe the maximum arc current andproduct of arc current and cycles at which test specimens blockthe energy without breakopen, ability to self-extinguish after-flaming, afterflame time and the detection of mechanicalattachment failures during testing. Mechanical attachment
31、failure and afterflame time are obtained from visual observa-tions and video recording after each arc exposure.5.4 This test method maintains the arc protective blanket ina vertical position and does not involve movement except thatresulting from the arc exposure.5.5 In this test method, test specim
32、ens are exposed at threearc current levels to determine the test specimens perfor-mance.NOTE 2In experimental testing, some blankets increase in protection(in value of kA*cycles to cause breakopen) as the arc current increasesand some decrease as shown in Fig. 1. This test method is designed torecog
33、nize this behavior and to specify testing over the range of arc currentlevels including lower levels of 5 kA or 10 kA, or both.5.6 This test method specifies a standard set of exposureconditions. Different exposure conditions may produce differ-ent results.NOTE 3In addition to the standard set of ex
34、posure conditions, it ispermitted to test using other conditions representative of the expectedhazard, reported all non-standard test conditions that are used.6. Apparatus6.1 General Arrangement for Testing of Arc ProtectiveBlanketsThe test apparatus shall consist of a vault containingan electrode s
35、ystem and a blanket test specimen holdingstructure and a HS camera positioned outside the vault. A topview of the test apparatus in Fig. 2 shows the suggestedelectrode mounting supports.6.2 Arrangement of the Vault:6.2.1 Internal dimensions of the vault shall be 2.2 6 0.3 m(7 6 1 ft) wide, 2.2 6 0.3
36、m(76 1 ft) high and 2.2 6 0.3 m(7 6 1 ft) deep.F26760926.2.2 The vault shall have three solid walls (back and twosides), floor and roof and be capable of withstanding the entirerange of test conditions.6.2.3 The front is open for access to electrode system andblanket-holding structure and for provid
37、ing a view for the HScamera.6.2.4 The roof, floor and walls of the vault shall have noopening.6.2.5 The vault may be constructed of concrete or framedplywood finished with non-conductive heat-resistant material.6.3 Arrangement of Arc Electrodes and Supply BusArcelectrodes shall be arranged pointing
38、at the center of the testspecimen.6.3.1 Two arc electrodes shall penetrate into the vaultthrough a side wall.6.3.2 Material and diameter of the arc electrodes shall bestainless steel rod with 18-mm (0.75-in.) diameter.6.3.3 The arc electrodes shall be positioned horizontally,parallel to each other,
39、equidistant from the floor and the roof invertical plane and equidistant from back wall and front openingin horizontal plane.NOTE 4Electromagnetic forces generated by arc current can bend ormove parallel electrodes. In order to keep electrodes parallel, it isrecommended to use spacers made of insula
40、ting materials.6.3.4 The spacing between parallel arc electrodes shall be10 6 0.6 cm (4 6 0.25 in.). This spacing is equal to arc gap inthis test method.6.3.5 The arc electrodes shall protrude into the vault for thedistance of approximately 30 cm (12 in.) and be terminated toa supply bus outside the
41、 vault. The electrode distance to theblanket is 6 in.; this requires to be adjusted before every test.6.3.6 Care must be taken in the position and configuration ofthe supply bus or feeding cables to the arc electrodes as not toadversely affect the direction or motion of the arc. For testingpurposes,
42、 the arc is directed towards the blanket test specimenproviding a controlled test exposure. The general arrangementof supply buses and arc electrodes is shown in Fig. 2.6.4 Arrangement of Blanket Test SpecimenThe test speci-men of the arc protective blanket shall be arranged perpendicu-lar to arc el
43、ectrodes and at the distance of 15 6 1cm(66 0.5in.), from the tips of the arc electrodes.6.4.1 The test specimen shall be attached to the blanketholding structure.6.4.2 The blanket holding structure shall have the dimen-sions of 183 6 2.5 cm (72 6 1 in.) by 152 6 2.5 cm (6061in.).6.4.3 The blanket h
44、olding structure shall be mounded ver-tically and parallel to the side wall of the vault and at thedistance of 46 cm (18 in.) from the side wall.6.4.4 The blanket holding structure shall be equidistantfrom the floor and the roof in a vertical plane and equidistantfrom back wall and front opening in
45、a horizontal plane.6.4.5 The center of the test specimen shall be aligned withthe midpoint of the arc gap.6.5 Fuse WireA fuse wire, connecting the ends of elec-trodes tips, is used to initiate the arc. This wire is consumedduring the test. The fuse wire shall be a copper 16 gauge wire.6.6 Electric S
46、upplyThe electric supply shall be sufficientto allow for the discharge of an electric arc with a gap of up to10 cm (4 in.), with alternating arc current from 5 kA up to 50kA and with arc duration from 0.05 s (3 cycles at 60 Hz) up to2.5 s (150 cycles at 60 Hz). The arc shall not self extinguishdurin
47、g the test. The X/R ratio fo the test circuit shall be suchthat the test current contains a DC component resulting in thefirst peak of the test current having a magnitude of 2.3 timesthe symmetrical RMS value.6.7 Test Circuit ControlRepeat exposures of the arc cur-rents shall be within the tolerance
48、 of the selected test level. TheFIG. 1 Example of Performance Trend for Different BlanketsF2676093make switch shall be capable of point on wave closing within0.2 cycles from test to test, such that the closing angle willproduce maximum asymmetrical current with an X/R ratio ofthe test circuit as sta
49、ted in 6.6. The arc current, arc duration,and arc voltage shall be measured. The arc current, duration,arc voltage and arc energy shall be displayed on a test controlmonitor in graph form and stored in digital format.6.8 Data Acquisition SystemThe system shall be capableof recording voltage and current outputs with a resolution of 1% of the applied voltage and current.6.8.1 The current and voltage data shall be acquired at aminimum rate of 2000 samples per second.6.8.2 The arc voltage shall be measured as close as practicalto the electrodes.6.9 High-Sp
