1、Designation: G165 99 (Reapproved 2012)Standard Practice forDetermining Rail-to-Earth Resistance1This standard is issued under the fixed designation G165; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A
2、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 practice covers the procedures necessary to followfor measuring resistance-to-earth of the running rails which areused as the cond
3、uctors for returning the train operating currentto the substation in electric mass transit systems.1.2 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are for informationonly.1.3 This standard does not purport to address all of thesafety concerns, if
4、any, associated with 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.2. Referenced Documents2.1 ASTM Standards:2G15 Terminology Relating to Corrosion and Corros
5、ionTesting33. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 cross bondinsulated copper cables that connectedbetween adjacent sections of track to ensure electrical conti-nuity between them.3.1.2 direct fixation fastenera device for fastening run-ning rails to their support stru
6、ctures.3.1.3 impedance bonda device connected to running railsfor automatic train operations.3.1.4 The terminology used herein, if not specifically de-fined otherwise, shall be in accordance with Terminology G15.Definitions provided herein, and not given in TerminologyG15, are limited to this practi
7、ce.4. Significance and Use4.1 Low resistance between the rails and earth could resultin large magnitudes of stray earth currents with the attendantcorrosion damage to underground metallic structures.4.2 These measurements are of a low voltage type and arenot designed to evaluate the high voltage die
8、lectric character-istics of the rail insulating elements.4.3 Sections of track with rail-to-earth resistances less thanacceptable minimums must be tested in greater detail todetermine the reason(s) for this condition. Determination of thereason(s) for any low rail-to-earth resistance may require the
9、use of special testing techniques or special instruments, orboth, beyond the scope of this practice.4.4 The electrical tests call for the use of electric meters thathave varying characteristics depending on cost, manufacture,and generic type. It is assumed that any person employing thetest procedure
10、s contained herein will know how to determineand apply proper correction factors and that they will havesufficient knowledge to ensure reasonable accuracy in the dataobtained.4.5 This practice does not encompass all possible fieldconditions to obtain rail-to-earth resistance characteristics. Nogener
11、al set of test procedures will be applicable to all situa-tions.5. Equipment5.1 Indicating dc; high impedance (minimum ten megohm)voltmeter (two required); multi-scale, capable of reading posi-tive and negative values without removing test leads; andcovering at least the following full scale ranges:
12、5.1.1 0 to 10 mV,5.1.2 0 to 100 mV,5.1.3 0 to 1 V,5.1.4 0 to 10 V, and5.1.5 0 to 100 V.5.1.6 Meters shall be accurate within 1 % of full scale.5.2 Direct current ammeter, multi-scale, covering the fol-lowing full scale ranges:5.2.1 0 to 1 A,1This practice is under the jurisdiction of ASTM Committee
13、G01 on Corrosionof Metals and is the direct responsibility of Subcommittee G01.10 on Corrosion inSoils.Current edition approved May 1, 2012. Published June 2012. Originallyapproved in 1999. Last previous edition approved in 2005 as G16599(2005). DOI:10.1520/G0165-99R12.2For referenced ASTM standards
14、, 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 onthe ASTM website.3Withdrawn. The last approved version of this historical standard is referencedon www.astm.
15、org.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5.2.2 0 to 10 A, and5.2.3 0 to 100 A.5.3 Direct current milliammeter, multi-scale, covering thefollowing full scale ranges:5.3.1 0 to 15 mA,5.3.2 0 to 150 mA, and5.3.3 0 to 1500 mA,
16、5.4 An alternative to the ammeter and milliammeter is amillivolt meter and external shunts covering the listed currentranges. Meters (and shunt combinations if used) shall beaccurate to within 1 % of full scale.5.5 Direct current power source with control circuits. Gen-erally, 6 or 12 V automotive t
17、ype wet cell batteries will suffice.5.6 Test wires, assorted lengths and sizes, to suit fieldconditions. Wires should have minimum 600 V insulation inperfect condition (no visible cuts or abrasions) and be multi-strand copper conductors for flexibility.5.7 Miscellaneous tools as required for making
18、wire con-nections, splicing, and so forth.5.8 Vehicle to transport equipment and personnel alongtrack to facilitate testing.6. Visual Inspection6.1 The track section to be tested should be visuallyexamined to ensure the insulating components have beeninstalled and there is no debris, water, or other
19、 conductivematerial in electrical contact with the metallic track compo-nents that could result in the lowering of the effective track-to-earth resistance thus producing incorrect data.7. Electrical Tests7.1 Electrically isolate sections of track (see typical arrange-ments in Figs. 1 and 2). Length
20、of track section to be tested isdependent upon the locations of rail insulators. Rail insulatorsare found at the ends of turnouts and single and doublecrossovers. The lengths of the track sections will vary withinthe general range of 60 to 2750 m (200 to 9000 ft).7.1.1 Remove cable connections from
21、across rail insulators.7.1.2 Disconnect cross bonds within section of track beingtested and other track.7.1.3 Disconnect power traction substation negative feedercables from track section being tested.NOTE 1Switches within substation can be opened.7.2 Ensure electrical continuity between the rails w
22、ithin theinsulated track section being tested by the use of the existingcables at impedance bonds or by installing temporary wireconnections between the rails.7.3 Track-to-earth resistance measurements will be obtainedas shown on Fig. 3 for main track sections and as shown onFig. 4 for main track se
23、ctions containing double crossovers.Measurements on track sections containing turnouts and singlecrossovers will be similar to that shown on Fig. 4 with thenumber of test points being determined by the electricalconfiguration of insulating joints and bonding cables.7.4 The track-to-earth resistance
24、measurements for the trackin the train storage yards will require special consideration foreach section to be tested because of the number and location ofinsulating joints resulting from the type of signal system beingused within the yard area and because of the number of crossbonds and other bondin
25、g cables used within the yard.7.5 All data shall be recorded.7.6 A sketch showing location of the test and the electricaltest set-up used shall be included.7.7 The number of readings taken to determine an electricalconstant or property must be sufficient to ensure that randomfactors due to human err
26、or in reading the instruments andtransient disturbances in the electrical network have negligibleinfluence on final results. A minimum of three readings shouldbe obtained but additional readings may be required dependingupon the exact circumstances of the test. The adequacy of datagenerally can be e
27、stablished by the tester. Once the specifiedminimum number of readings have been obtained, data shouldbe examined to see that removal of neither the highest nor thelowest value will alter the arithmetic average of group by morethan 3 %. If the average is altered by more than 3 %, one morecomplete se
28、t of data should be taken and the results combinedwith the first set. If the test of the data still produces a changein the average value greater than 3 %, it may indicate anunstable condition in the system.FIG. 1 Schematic Diagram Typical Mainline Track SectionG165 99 (2012)27.8 Measurements Proced
29、ure(Fig. 3 for main tracksection, Fig. 4 for crossovers and turnouts).7.8.1 Establish current circuit (I1).7.8.2 Establish rail-to-earth voltage (E1) measuring circuit.7.8.3 Obtain change in (E1) per ampere of test current (I1)(number of readings obtained to be in accordance with 7.7).7.8.4 Calculat
30、e the effective track-to-earth resistance, R1.1,(ohms) as change in (E1(volts) per ampere of (I1):R1.15delta E1delta I1(1)7.8.4.1 With R1.1expressed in ohms, E1expressed in volts,and I1expressed in amperes.7.8.5 Obtain similar data for:R2.15delta E2delta I1(2)R3.15delta E3delta I1(3)R4.15delta E4del
31、ta I1(4)R4A.15delta E4Adelta I1crossovers and turnouts only! (5)7.8.6 Main Track Sections Only:7.8.6.1 Compare R2.1with R1.1. R2.1should be equal to or nomore than 3 % less than R1.1. Greater variation could indicatethe test rail section is not effectively insulated from theadjacent section.7.8.6.2
32、Compare R4.1with R1.1. These values should beequal within about 3 %, with R4.1being less than R1.1. Morevariation than about 3 % could be indicative of attenuationresulting from the relationship of the resistance of the rail andthe track-to-earth resistance. A significant variation betweenR1.1and R4
33、.1would be expected only in the event thetrack-to-earth resistance was much less than anticipated values.7.8.6.3 Compare R3.1and R4.1. A variation of more thanabout 3 % could indicate that the track section under test is noteffectively insulated from the adjacent section.7.8.7 Crossovers and Turnout
34、s OnlyCompare values ob-tained. All values should be within 3 % of each other becauseof the relatively short lengths of track involved. Any variationFIG. 2 Schematic Diagram Typical Double Crossover Track SectionNOTE 1All cable connections removed for measurements as shown on Fig. 1.NOTE 2Ground res
35、istance to be on the order of 1/100 (or less) of the track-to-earth resistance for the section being tested.FIG. 3 Schematic Diagram Mainline Test ArrangementG165 99 (2012)3in the values obtained of greater than 3 % should be evaluated,to determine the reason(s) and what, if any, further action isre
36、quired.NOTE 2Measurement of change in potentials across the insulatingjoints at all extremities are not required because these measurements willbe obtained during tests on the adjacent track section.7.8.8 Compute the average resistance-to-earth of the testsection for 305 m (1000 ft) of track. The le
37、ngth (L) track mustinclude both main tracks plus crossover. (Thus a doublecrossover on 36 ft to 10 in. track centers would contain in theorder of 366 m (1200 ft) of track.)RT5 R4.1x L305(6)where:RT= average resistance for 305 m (1000 ft)R4.1= track-to-earth resistance, V, andL = length of track with
38、in section, m.7.8.9 Record data.8. Acceptance Criteria8.1 Direct Fixation Track Construction:8.1.1 The track-to-earth resistance for direct fixation track isgoverned by the electrical resistance associated with the directfixation rail fasteners and the number of fasteners.8.1.2 Under ideal condition
39、s where there are no conductivematerials in electrical contact with the metallic rail or fastenercomponents, or both, that contact the minimum electricalresistance through a direct fixation rail fastener is typicallyspecified as 100 megohms (108V).8.1.3 Spacing of the direct fixation rail fasteners
40、on maintrack is typically 762 mm (30 in.). At this spacing there will be800 direct fixation rail fasteners in 305 m (1000 ft) of maintrack.8.1.4 The minimum track-to-earth resistance for 305 m can,therefore, be calculated by assuming each direct fixation railfastener has the minimum specified resist
41、ance (Rp) and usingthe number (N) of these fasteners in parallel between the railsand earth.RT5RpN100 3 1068005 1.25 3 1055 125 000 V (7)where:RT= track to earth resistance for 305 m,Rp= resistance of one fastener, andN = number of fasteners in 305 m of track.8.1.4.1 It is anticipated the actual res
42、istances will be lessthan their specified minimum under actual installed conditions.Acceptance criteria will, therefore, have to be based on anengineering evaluation of what can reasonably be anticipated.8.1.5 Any type of track that is constructed with dielectricisolators may be evaluated in a simil
43、ar manner as describedabove with adjustment for the expected electrical resistance ofthe fastener.8.2 Wooden Tie Track Constructions:8.2.1 The track-to-earth resistances for wooden tie construc-tion depends on several factors, the major ones being theresistivity of the wooden ties, the drainage char
44、acteristics ofthe road bed, and the spacing of the ties.8.2.2 The resistivity of the wooden ties depends on themoisture content of the wood. At low moisture content (lessthan 10 %) the wood is a moderately good insulator, butdecreases rapidly in effectiveness as the moisture content rises.8.2.3 The
45、condition of the ballast and the road bed ingeneral to provide good water drainage and prevent theaccumulation of dirt, debris, and other materials that canprovide an electrically conductive path between the rails andground.8.2.4 The spacing between ties is typically 686 mm (27 in.)on the main track
46、 and 762 mm (30 in.) on yard and secondarytrack.8.2.5 The acceptable criteria for track-to-earth resistancesmust be based on an engineering evaluation of what isreasonable for the specified construction and an evaluation ofwhat can be expected in magnitudes of stray earth currentsunder these conditi
47、ons.8.3 Wooden Tie and Direct Fixation Construction in OneTest Section:NOTE 1All cable connections removed for measurements as shown on Fig. 2.NOTE 2Ground resistance to be on the order of 1/100 (or less) of the track-to-earth resistance for the section being tested.FIG. 4 Schematic Diagram Double C
48、rossover Test ArrangementG165 99 (2012)48.3.1 The track-to-earth resistance for each type of construc-tion within the test section can be calculated from the length oftrack of each type. These resistances can then be combined bylaws of parallel resistances to determine the theoretical value orcompar
49、ison with the measured value.1R51RA11RB11RC1.(8)where:R = combined resistance of all parallel com-ponents, V, andRA,RB,RC. = resistances of the individual resistance tobe put in parallel, V.8.3.2 The anticipated resistances for direct fixation andwooden tie construction must be based on an engineeringevaluation of what is reasonable for the specified constructionand an evaluation of what can be expected in magnitudes ofstray earth currents under these conditions.8.4 Embedded Track ConstructionThe track-to-earth re-sistance for embedded track is governed by th
