ASTM G165-99
(Practice)Standard Practice for Determining Rail-to-Earth Resistance
Standard Practice for Determining Rail-to-Earth Resistance
SCOPE
1.1 This practice covers the procedures necessary to follow for measuring resistance-to-earth of the running rails which are used as the conductors for returning the train operating current to the substation in electric mass transit systems.
This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation:G165–99
Standard Practice for
Determining Rail-to-Earth Resistance
This standard is issued under the fixed designation G 165; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope 4.3 Sections of track with rail-to-earth resistances less than
acceptable minimums must be tested in greater detail to
1.1 This practice covers the procedures necessary to follow
determinethereason(s)forthiscondition.Determinationofthe
for measuring resistance-to-earth of the running rails which are
reason(s) for any low rail-to-earth resistance may require the
used as the conductors for returning the train operating current
use of special testing techniques or special instruments, or
to the substation in electric mass transit systems.
both, beyond the scope of this practice.
1.2 This standard does not purport to address all of the
4.4 The electrical tests call for the use of electric meters that
safety concerns, if any, associated with its use. It is the
have varying characteristics depending on cost, manufacture,
responsibility of the user of this standard to establish appro-
and generic type. It is assumed that any person employing the
priate safety and health practices and determine the applica-
test procedures contained herein will know how to determine
bility of regulatory limitations prior to use.
and apply proper correction factors and that they will have
2. Referenced Documents sufficient knowledge to ensure reasonable accuracy in the data
obtained.
2.1 ASTM Standards:
4.5 This practice does not encompass all possible field
G 15 Terminology Relating to Corrosion and Corrosion
conditions to obtain rail-to-earth resistance characteristics. No
Testing
general set of test procedures will be applicable to all situa-
3. Terminology
tions.
3.1 Definitions of Terms Specific to This Standard:
5. Equipment
3.1.1 direct fixation fastener—a device for fastening run-
5.1 Indicating dc, high impedance (minimum ten megohm)
ning rails to their support structures.
voltmeter (two required), multi-scale, capable of reading posi-
3.1.2 cross bond—insulated copper cables that connected
tive and negative values without removing test leads and
between adjacent sections of track to ensure electrical conti-
covering at least the following full scale ranges:
nuity between them.
5.1.1 0 to 10 mV,
3.1.3 impedance bond—a device connected to running rails
5.1.2 0 to 100 mV,
for automatic train operations.
5.1.3 0 to 1 V,
3.1.4 The terminology used herein, if not specifically de-
5.1.4 0 to 10 V, and
finedotherwise,shallbeinaccordancewithTerminologyG 15.
5.1.5 0 to 100 V.
Definitions provided, herein, and not given in Terminology
5.1.6 Meters shall be accurate within 1 % of full scale.
G 15 are limited to this practice.
5.2 Direct current ammeter, multi-scale, covering the fol-
4. Significance and Use
lowing full scale ranges:
5.2.1 0 to 1 A,
4.1 Low resistance between the rails and earth could result
5.2.2 0 to 10 A, and
in large magnitudes of stray earth currents with the attendant
5.2.3 0 to 100 A.
corrosion damage to underground metallic structures.
5.3 Direct current milliammeter, multi-scale, covering the
4.2 These measurements are of a low voltage type and are
following full scale ranges:
not designed to evaluate the high voltage dielectric character-
5.3.1 0 to 15 mA,
istics of the rail insulating elements.
5.3.2 0 to 150 mA, and
5.3.3 0 to 1500 mA,
This practice is under the jurisdiction of ASTM Committee G-1 on Corrosion
5.4 An alternative to the ammeter and milliammeter is a
of Metals and is the direct responsibility of Subcommittee G01.10 on Corrosion in
millivolt meter and external shunts covering the listed current
Soils.
ranges. Meters (and shunt combinations if used) shall be
Current edition approved Dec. 10, 1999. Published February 2000.
Annual Book of ASTM Standards, Vol 03.02. accurate to within 1 % of full scale.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
G165
5.5 Direct current power source with control circuits. Gen- Measurements on track sections containing turnouts and single
erally, 6 or 12 V automotive type wet cell batteries will suffice. crossovers will be similar to that shown on Fig. 4 with the
5.6 Test wires, assorted lengths and sizes, to suit field number of test points being determined by the electrical
conditions. Wires should have minimum 600 V insulation in configuration of insulating joints and bonding cables.
perfect condition (no visible cuts or abrasions) and be multi-
7.4 The track-to-earth resistance measurements for the track
strand copper conductors for flexibility. in the train storage yards will require special consideration for
5.7 Miscellaneous tools as required for making wire con-
each section to be tested because of the number and location of
nections, splicing and so forth. insulating joints resulting from the type of signal system being
5.8 Vehicle to transport equipment and personnel along
used within the yard area and because of the number of cross
track to facilitate testing. bonds and other bonding cables used within the yard.
7.5 All data shall be recorded.
6. Visual Inspection
7.6 A sketch showing location of the test and the electrical
6.1 The track section to be tested should be visually
test set-up used shall be included.
examined to ensure the insulating components have been
7.7 The number of readings taken to determine an electrical
installed and there is no debris, water, or other conductive
constant or property must be sufficient to ensure that random
material in electrical contact with the metallic track compo-
factors due to human error in reading the instruments and
nents that could result in the lowering of the effective track-
transient disturbances in the electrical network have negligible
to-earth resistance thus producing incorrect data.
influence on final results.Aminimum of three readings should
be obtained but additional readings may be required depending
7. Electrical Tests
upon the exact circumstances of the test. The adequacy of data
7.1 Electricallyisolatesectionsoftrack(seetypicalarrange-
generally can be established by the tester. Once the specified
ments in Figs. 1 and 2). Length of track section to be tested is
minimum number of readings have been obtained, data should
dependent upon the locations of rail insulators. Rail insulators
be examined to see that removal of neither the highest nor the
are found at the ends of turnouts and single and double
lowest value will alter the arithmetic average of group by more
crossovers. The lengths of the track sections will vary within
than 3 %. If the average is altered by more than 3 %, one more
the general range of 60 to 2750 m (200 to 9000 ft).
complete set of data should be taken and the results combined
7.1.1 Remove cable connections from across rail insulators.
with the first set. If the test of the data still produces a change
7.1.2 Disconnect cross bonds within section of track being
in the average value greater than 3 %, it may indicate an
tested and other track.
unstable condition in the system.
7.1.3 Disconnect power traction substation negative feeder
7.8 Measurements Procedure— (Fig. 3 for main track
cables from track section being tested.
section, Fig. 4 for crossovers and turnouts).
7.8.1 Establish current circuit (I ).
NOTE 1—Switches within substation can be opened.
7.8.2 Establish rail-to-earth voltage (E ) measuring circuit.
7.2 Ensure electrical continuity between the rails within the
7.8.3 Obtain change in (E ) per ampere of test current (I )
1 1
insulated track section being tested by the use of the existing
(number of readings obtained to be in accordance with 7.7).
cables at impedance bonds or by installing temporary wire
7.8.4 Calculate the effective track-to-earth resistance, R ,
connections between the rails. 1.1
(ohms) as change in (E (volts) per ampere of (I ):
7.3 Track-to-earthresistancemeasurementswillbeobtained 1 1
as shown on Fig. 3 for main track sections and as sh
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