1、Designation: F2522 12Standard Test Method forDetermining the Protective Performance of a ShieldAttached on Live Line Tools or on Racking Rods for ElectricArc Hazards1This standard is issued under the fixed designation F2522; the number immediately following the designation indicates the year oforigi
2、nal 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. Scope1.1 This test method is used to determine the heat attenua-tion fact
3、or (HAF), the effective heat attenuation factor (EHAF),and the shields mechanical strength (SMS) of a shield attachedon live line tools or racking rods intended for protection ofworkers exposed to electric arcs.1.2 The materials used in this test method of workerprotection are in the form of a shiel
4、d attached on live line toolsor on the racking rods.1.3 The protective shield described in this test method shallbe transparent and shall be easily attached and removed fromlive line tools or from racking rods.1.4 The protective shield described in this test method has24-in. (0.61-m) diameter and ca
5、n be used for most applications,however for special cases, the shield can have different sizes tosuit the protective requirements of the application.1.5 This standard shall be used to measure and describe theproperties of materials, products, or assemblies in response toincident energies (thermal-co
6、nvective, and radiant and pressurewave) generated by an electric arc under controlled laboratoryconditions and does not purport to predict damage from light,resultant pressure impact other than the pressure and thermalaspects measured.1.6 The values stated in inch-pound units are to be regardedas st
7、andard. The values given in parentheses are mathematicalconversions to SI units that are provided for information onlyand are not considered standard.1.7 This standard shall not be used to describe or appraisethe fire hazard or fire risk of materials, products, or assembliesunder actual fire conditi
8、ons. However, results of this test maybe used as elements of a fire assessment, which takes intoaccount all of 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
9、its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use. For specificprecautions, see Section 7.2. Referenced Documents2.1 ASTM Standards:2D4391 Terminology Relating to
10、 The Burning Behavior ofTextilesF1959/F1959M Test Method for Determining theArc Ratingof Materials for Clothing3. 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 duration, ntime duration of the arc, s.
11、3.1.3 arc energy, vi dt, nsum of the instantaneous arcvoltage values multiplied by the instantaneous arc currentvalues multiplied by the incremental time values during thearc, J.3.1.4 arc gap, ndistance between the arc electrodes, cmin.3.1.5 arc voltage, nvoltage across the gap caused by thecurrent
12、flowing through the resistance created by the arc gap,V. See also Terminology D4391.3.1.6 asymmetrical arc current, nthe total arc currentproduced during closure; it includes a direct component and asymmetrical component, A.3.1.7 blowout, nthe extinguishing of the arc caused by amagnetic field.3.1.8
13、 closure, npoint on supply current wave form wherearc is initiated.1This test method is under the jurisdiction of ASTM Committee F18 onElectrical Protective Equipment for Workers and is the direct responsibility ofSubcommittee F18.35 on Tools therefore, its mass shall be verysmall to reduce the chan
14、ce of molten metal burns. The fusewire shall be a copper wire with a diameter no greater than 0.02in. (0.0005 m).6.7 Electric SupplyThe electric supply should be suffi-cient to allow for the discharge of an electric arc with a gap ofup to 12 in. (0.305 m), with alternating arc current from 4000up to
15、 25 000 A and with arc duration from 3 cycles (0.05 s) upto 90 cycles (1.5 s) from a 60 Hz supply. The X/R ratio of thetest circuit shall be such that the test current contains a DCcomponent resulting in the first peak of the test current havinga magnitude of 2.3 times the symmetrical RMS value.6.8
16、Test Circuit ControlRepeat exposures of the arc cur-rents shall not deviate more than 2 % per test from the selectedtest level. The make switch shall be capable of point on waveclosing within 0.2 cycles from test to test, such that the closingangle will produce maximum asymmetrical current with anX/
17、R ratio of the test circuit as stated in 6.7. The arc current,duration, and voltage shall be measured. The arc, current,duration, voltage and energy shall be displayed in graph formand stored in digital format.6.9 Data Acquisition SystemThe system shall be capableof recording voltage, current, and s
18、ufficient calorimeter outputsas required by the test. The sensitivity and accuracy of the dataacquisition system shall be as described in Test MethodF1959/F1959M.6.10 Data Acquisition System ProtectionDue to the natureof this type of testing, the use of isolating devices on thecalorimeter outputs to
19、 protect the acquisition system is recom-mended.6.11 SensorsRefer to the calorimeters as described in TestMethod F1959/F1959M.7. Precautions7.1 The test apparatus discharges large amounts of energy.In addition, the electric arc produces very intense light. Cared1 = 24 in. (0.61 m), distance from the
20、 wall (back plate) to the arc electrodesd2=6in.(0.15m)(gap) between electrodesd3 = 53 in. (1.35 m), parallel distance of the hot stick or the racking rod above the floord4 = 24 in. (0.61 m), distance of the shield from the electrodesd5=4in.(0.10m),vertical distance between centers of S1 and S2S1 and
21、 S2 = 24.5 in. (0.62 m), approximate horizontal distance of the sensors from the electrodesS1, S2, S3, S4, S5, and S6 are located vertically, and S1 is 5 ft (1.52 m) from the arc centerFIG. 3 Test Set-up for EHAF Measurement with Shield on a Live Line ToolF2522 124should be taken to protect personne
22、l working in the area.Workers should be behind protective barriers or at a safedistance to prevent electrocution and contact with moltenmetal. Workers wishing to directly view the test should usevery heavily tinted glasses such as ANSI/ASC Filter Shade 12welding glasses. If the test is conducted ind
23、oors, there shall bea means to ventilate the area to carry away combustionproducts, smoke, and fumes. Air currents can disturb the arc,reducing the heat flux at the surface of any of the calorimeters.The test apparatus should be shielded by non-combustiblematerials suitable for the test area. Outdoo
24、r tests shall beconducted in a manner appropriate to prevent exposure of thetest specimen to moisture and wind (the elements). The leads tothe test apparatus should be positioned to prevent blowout ofthe electric arc. The test apparatus should be insulated fromground for the appropriate test voltage
25、.7.2 The test apparatus, electrodes and calorimeter assem-blies become hot during testing. Use protective gloves whenhandling these hot objects.7.3 Use care when the specimen ignites or releases combus-tible gases. An appropriate fire extinguisher should be readilyavailable. Ensure all materials are
26、 fully extinguished.7.4 Immediately after each test, the electric supply shall beshut off from the test apparatus and all other laboratoryequipment used to generate the arc. The apparatus and otherlaboratory equipment shall be isolated and grounded. Afterdata acquisition has been completed, appropri
27、ate methods shallbe used to ventilate the test area before it is entered bypersonnel. No one should enter the test area prior to exhaustingall smoke and fumes.8. Sampling and Specimen Preparation8.1 Test Specimens for Shield TestFrom the shields to betested, select a new shield with a given size (sh
28、ield diameter).Shields of the same size should be replaced after each set oftests.9. Calibration and Standardization9.1 Data Collection System Pre-calibrationThe data col-lection system shall be calibrated by using a thermocouplecalibrator/simulator. This will allow calibrations to be made atmultipl
29、e points and at levels above 100C. Due to the nature ofthe tests frequent calibration checks are recommended.9.2 Calorimeter Calibration CheckCalorimeters shall bechecked to verify proper operation. Measure and graph thetemperature rise of each calorimeter and system response whenexposed to a foxed
30、radiant energy source for 30 s. At 30 s, noone calorimeter response shall vary by more than 4C from theaverage of all calorimeters. Any calorimeter not meeting thisrequirement shall be suspected of faulty connections and shallbe replaced or repaired.NOTE 2One acceptable method is to expose each calo
31、rimeter to afixed radiant energy source for 30 s. For example, place the front surfaceof a 500 W spot light 10.5 in. from the calorimeter. The spot shall becentered on and perpendicular to the calorimeter.39.3 Arc Exposure CalibrationPrior to each calibration,position the electrodes of the test appa
32、ratus to produce a 12-in.(0.305-m) gap. The face of the monitor sensors shall be parallel3A 500-W light source is available from the Strand Electric and Engineering Co.Ltd. as Part No. 83 (500 W, 120 V light source).d1 = 24 in. (0.61 m), distance from the wall (back plate) to the arc electrodesd2=6i
33、n.(0.15m)(gap) between electrodesd3 = 53 in. (1.35 m), parallel distance of the hot stick or the racking rod above the floord4 = 24 in. (0.61 m), distance of the shield from the electrodesd5=4in.(0.10m),vertical distance between centers of S1 and S2S1 and S2 = 24.5 in. (0.62 m), approximate horizont
34、al distance of the sensors from the electrodesS1, S2, S3, S4, S5, and S6 are located vertically, and S1 is 5 ft (1.52 m) from the arc centerFIG. 4 Test Set-up for EHAF Measurement with Shield on a Racking RodF2522 125and normal to, the centerline of the electrodes. The midpoint ofthe electrode gap s
35、hall be at the same elevation as the centerpoint of the monitor sensors (see Fig. 1). Connect the fuse wireto the end of one electrode by making several wraps and twistsand then to the end of the other electrode by the same method.The fuse wire shall be pulled tight and the excess trimmed. Thetest c
36、ontroller should be adjusted to produce the desired arccurrent and duration.9.4 Apparatus Calibration CheckPosition each monitorsensor so that the surface of each sensor is 12 in. (0.305 m)from, parallel and normal to the centerline of the electrodes.Set the symmetrical arc exposure current to the t
37、est amperagelevel and the arc duration at 10 cycles (0.167 s). Discharge thearc. Determine the maximum temperature rise for each of thesensors, and multiply by the sensor constant 0.135 (cal/cm2C)to obtain the incident energy (total heat) (cal/cm2) measured byeach sensor. Compare the highest sensor
38、reading and theaverage value obtained for all sensors, for example, with themeasured result of 10.1 cal/cm2for the calibration exposure of8000Afor 0.167 s. Compare the total heat value determined bythe sensors to the value shown. The average total heatcalculated for the sensors shall be at least 60
39、% of the valuedetermined by calculation or that shown. The highest measuredtotal heat of any one sensor shall be within 10 % of thecalculated value. If these values are not obtained, inspect thetest setup and correct any possible problems that could produceless than desired results. An arc exposure
40、calibration testshould be conducted at the desired test level after eachadjustment, and prior to the start and end of each days testingand after any equipment adjustment or failure. Detailed andmost recent procedure for calculation of heat flux from coppersensors is found in Test Method F1959/F1959M
41、.9.4.1 Because the arc does not follow a path that isequidistant from each sensor, the results will vary. At 8000 A,the highest total heat measured with a single sensor shall bebetween 9 and 11 cal/cm2and the average total heat for allsensors shall be at least 6 cal/cm2. If these values are notachie
42、ved, check the calibration of the sensor system, electricalconditions, and the physical setup of the apparatus and repeatthe calibration exposure until the required results are obtained.9.4.2 If during testing the exposure values specified in 9.4are not achieved in three consecutive tests, then susp
43、end testingand re-calibrate the system. If a change is made as a result ofthe re-calibration, then the data from the last three tests shall berejected.9.5 Confirmation of Test Apparatus SettingConfirm thetest apparatus setting for each test from the controller equip-ment. Values reported should be p
44、eak arc current, RMS arccurrent, arc duration, arc energy, and arc voltage. A graph ofthe arc current should be plotted to ensure proper wave form.In addition, the ambient temperature and relative humidityshall be recorded.10. Apparatus Care and Maintenance10.1 Initial TemperatureCool the sensors af
45、ter exposurewith a jet of air or by contact with a cold surface. Confirm thatthe sensors are at a temperature of 25 to 35C.10.2 Surface ReconditioningWhile the sensor is hot, wipethe sensor face immediately after each test, to remove anydecomposition products that condense and could be a source offu
46、ture error. If a deposit collects and appears to be thicker thana thin layer of paint, or the surface is irregular, the sensorsurface requires reconditioning. Carefully clean the cooledsensor with acetone or petroleum solvent, making certain tofollow safe handling practices. Repaint the surface with
47、 a thinlayer of flat black high temperature spray paint. Use the samepaint on all sensors and ensure that the paint is dry beforerunning the next test.10.3 The Shield and Incident Energy Monitoring SensorCareThe shield and monitoring sensors shall be kept dry. Foroutdoor tests the shield and monitor
48、ing sensors shall becovered during long periods between tests to prevent excesstemperature rise resulting from exposure to any heat source.Due to the destructive nature of the electric arc, the monitoringsensor holders should be covered with the same paint as thesensors. The sensor holders should be
49、 re-coated periodically toreduce deterioration.11. Procedure11.1 Heat Attenuation Factor (HAF)As shown in Figs. 1and 2, two heat sensors, (S1 and S2), shall be used to measureHAF. The approximate horizontal distance of sensors S1 andS2 shall be about 24.5 in. (0.62 m) from the arc electrodes,with sensor S2 behind the shield. The shield attached to an 8-ft(2.44-m) long hot stick ora5ft(1.52 m) long racking rod shallbe located 24 in. (0.61 m) from the center of the arc electrodes.The hot stick or the racking rod shall be placed parallel and 53in
