ASTM F2249-24
(Specification)Standard Specification for In-Service Test Methods for Temporary Grounding Jumper Assemblies Used on De-Energized Electric Power Lines and Equipment
Standard Specification for In-Service Test Methods for Temporary Grounding Jumper Assemblies Used on De-Energized Electric Power Lines and Equipment
ABSTRACT
This specification covers the in-service inspection and electrical testing of temporary protective grounding jumper assemblies used by electrical workers in the field on de-energized electric power lines, circuits, and equipment. These assemblies consist of flexible cables, ferrules, clamps, and connectors. The test procedures detailed here provide an objective means of determining if a grounding jumper assembly meets minimum electrical specifications. The application, care, use, and maintenance of this equipment are not addressed in this specification.
SCOPE
1.1 This specification covers the in-service inspection and electrical testing of temporary protective grounding jumper assemblies which have been used by electrical workers in the field.
1.2 This specification discusses methods for testing grounding jumper assemblies, which consist of the flexible cables, ferrules, clamps and connectors used in the temporary protective grounding of de-energized circuits.
1.3 Manufacturing specifications for these grounding jumper assemblies are in Specifications F855.
1.4 The application, care, use, and maintenance of this equipment are beyond the scope of this specification.
1.5 The values stated in SI units are to be regarded as standard. The values given in parentheses after SI units are provided for information only and are not considered standard.
1.6 The following safety hazards caveat pertains only to the test portions of this specification. 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.7 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
General Information
Relations
Standards Content (Sample)
This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: F2249 − 24
Standard Specification for
In-Service Test Methods for Temporary Grounding Jumper
Assemblies Used on De-Energized Electric Power Lines and
Equipment
This standard is issued under the fixed designation F2249; 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 (´) indicates an editorial change since the last revision or reapproval.
1. Scope mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee.
1.1 This specification covers the in-service inspection and
electrical testing of temporary protective grounding jumper
2. Referenced Documents
assemblies which have been used by electrical workers in the
2.1 ASTM Standards:
field.
B172 Specification for Rope-Lay-Stranded Copper Conduc-
1.2 This specification discusses methods for testing ground-
tors Having Bunch-Stranded Members, for Electrical Con-
ing jumper assemblies, which consist of the flexible cables,
ductors
ferrules, clamps and connectors used in the temporary protec-
B173 Specification for Rope-Lay-Stranded Copper Conduc-
tive grounding of de-energized circuits.
tors Having Concentric-Stranded Members, for Electrical
1.3 Manufacturing specifications for these grounding
Conductors
jumper assemblies are in Specifications F855.
F855 Specifications for Temporary Protective Grounds to Be
Used on De-energized Electric Power Lines and Equip-
1.4 The application, care, use, and maintenance of this
ment
equipment are beyond the scope of this specification.
2.2 IEEE Standards:
1.5 The values stated in SI units are to be regarded as
IEEE Standard 80–2013 IEEE Guide for Safety in AC
standard. The values given in parentheses after SI units are
Substation Grounding
provided for information only and are not considered standard.
IEEE Standard 1048–2016 IEEE Guide for the Protective
1.6 The following safety hazards caveat pertains only to the
Grounding of Power Lines
test portions of this specification. This standard does not
IEEE Standard 1246–2011 IEEE Guide for Temporary Pro-
purport to address all of the safety concerns, if any, associated
tective Grounding Systems Used in Substations
with its use. It is the responsibility of the user of this standard
to establish appropriate safety, health, and environmental
3. Terminology
practices and determine the applicability of regulatory limita-
3.1 Definitions of Terms Specific to This Standard:
tions prior to use.
3.1.1 grounding jumper assembly, n—grounding cable with
1.7 This international standard was developed in accor-
connectors and ground clamps attached, also called a ground-
dance with internationally recognized principles on standard-
ing jumper or a protective ground assembly installed tempo-
ization established in the Decision on Principles for the
rarily on de-energized electric power circuits for the purpose of
Development of International Standards, Guides and Recom-
1 2
This specification is under the jurisdiction of ASTM Committee F18 on For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Electrical Protective Equipment for Workers and is the direct responsibility of contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Subcommittee F18.45 on Mechanical Apparatus. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved Jan. 1, 2024. Published January 2024. Originally the ASTM website.
approved in 2003. Last previous edition approved in 2023 as F2249 – 23. DOI: Available from the Institute of Electrical and Electronics Engineers, Inc. (IEEE)
10.1520/F2249-24. 1828 L St., NW, Suite 1202, Washington, DC 20036–5104.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F2249 − 24
potential equalization and to conduct a short circuit current for
a specified duration (time).
4. Significance and Use
4.1 Grounding jumper assemblies can be damaged by rough
handling, long term usage, weathering, corrosion, or a combi-
nation thereof. This deterioration may be both physical and
FIG. 1 Resistance and Impedance of Copper Grounding Jumper
electrical.
Assemblies
4.2 The test procedures in this specification provide an
Y = resistance of clamps, ferrule and portions of the cable
objective means of determining if a grounding jumper assem-
inside the ferrule, mΩ,
bly meets minimum electrical specifications. These methods
L = cable length expressed in feet (ferrule to ferrule mea-
permit testing of grounding jumper assemblies under con-
surement to the nearest inch, not including shrouded
trolled conditions.
portion of some ferrules which cover the cable
4.3 Each responsible entity must determine the required
insulation), and
safety margin for their workers during electrical fault condi- R = cable resistance from Table 1, mΩ/ft.
tions. Guidelines for use in the determination of these condi-
tions are beyond the scope of this specification and can be
found in such standards as IEEE Standard 80–2013 and IEEE
Standard 1048–2016, and IEEE Standard 1246–2011.
6.2 Thoroughly clean the jaws of the clamps with a stiff
4.4 Mechanical damage, other than broken strands, may not wire brush.
significantly affect the cable resistance. Close manual and
6.3 Attach the grounding jumper assembly clamps firmly to
visual inspection is required to detect some types of mechani-
the test set.
cal damage.
7. Electrical Requirements
4.5 The test procedures in this specification should be
performed at a time interval established by the user to ensure
7.1 The user must select the test method with the desired
that defective grounding jumper assemblies are detected and
precision and repeatability. The test instrument should be
removed from service in a timely manner.
sufficiently accurate to detect at least a one foot or less change
4.6 Retest the grounding jumper assembly after performing in cable length to ensure that the cable meets requirements.
any maintenance, in order to ensure its integrity.
7.2 Each method must take into account a precise cable
resistance per foot and the length of the cable being tested.
5. Inspection of Grounding Jumper Assemblies
7.3 Electrical tests relative to this standard are:
5.1 Visual inspection shall be made of all grounding jumper
7.3.1 DC resistance measurements,
assemblies prior to testing.
7.3.2 AC impedance measurements, and
5.1.1 If the following defects are evident, the grounding
7.3.3 Temperature rise measurements (supplementary
jumpers may be rejected without electrical testing:
method).
5.1.1.1 Cracked or broken ferrules and clamps,
5.1.1.2 Exposed broken strands,
7.4 DC Resistance or AC Impedance Method—Equipment
5.1.1.3 Cut or badly mashed or flattened cable,
required includes:
5.1.1.4 Extensively damaged cable-covering material,
7.4.1 A minimum 10 A dc source controllable to 5 % of
5.1.1.5 Swollen cable jacket or soft spots, indicating inter-
output current, short circuit protected, or
nal corrosion, and
7.4.2 A minimum 10 A ac source controllable to 5 % of
5.1.1.6 Cable strands with a black deposit on them.
output current, short circuit protected.
5.1.2 Grounding jumper assemblies which are visually de-
7.4.3 Measuring method for measurements of cable length
fective shall be removed from service and permanently
calibrated in inches or centimeters.
marked, tagged or destroyed (if beyond repair) to prevent
7.5 In-Service Electrical Resistance Pass/Fail Criteria—
re-use.
The pass/fail criterion of a grounding jumper assembly is based
5.2 All physical connections should be checked for tight-
on the resistance value of the assembly (cable, ferrules and
ness with manufacturer’s specified torque values.
clamps) which is higher than the established resistance value
for new assemblies. This increase in resistance accounts for
5.3 Before the grounding jumper assembly can be placed
manufacturing tolerance and the expected normal deterioration
back in service, it must pass the inspection requirements in 5.1,
of the assembly due to aging, contamination and corrosion,
be assembled per 5.2, and must pass the electrical requirements
particularly in the contact areas of the cable ferrules and
in Section 7.
clamps. The allowable increase in resistance is such as to
6. Cleaning and Measuring of Grounding Jumper
permit the grounding jumper assembly to perform safely
Assembly Prior to Electrical Testing
during electrical faults. The grounding jumper assembly, when
6.1 Identify the cable gauge (AWG) and a make a precise subjected to its rated maximum fault current and duration, must
measurement of the cable length. See Fig. 1. withstand the fault without its components separating, but
F2249 − 24
some heat damage and discoloration is acceptable. The elec- 7.5.2.2 Maximum Impedance of the Grounding Jumper
trical resistance value for the pass/fail criterion is made up of Assembly (Zm):
two parts (Fig. 1), the cable resistance and the resistance of the
2 2
Zm 5 = 1.05RL12Y 1 XL mΩ (3)
~ ! ~ !
two ends containing short cable sections, ferrules and clamps.
When the grounding jumper assemblies are tested with a dc
where:
source, the dc resistance of the assembly is used for the pass or
X = reactance of the cable in mΩ/ft.
fail purposes. With an ac source, the impedance of the cable
NOTE 1—Values of X can be found in data books such as the Standard
and the impedance of the ends (ferrules and clamps) are used Handbook of Electrical Engineers.
to determine if the grounding jumper fails or passes the test.
7.5.3 Testing with a DC Source—A dc source can be used to
determine the pass/fail value for a given grounding jumper
A
assembly. The resistance value (R) obtained from such a
TABLE 1 Class K Copper Cable Nominal Resistance, mΩ/ft
measurement should be compared with the calculated limiting
Grounding Resistance, mΩ/ft Resistance, mΩ/ft Resistance, mΩ/ft
Cable Size at 5 °C (41 °F) at 20 °C (68 °F) at 35 °C (95 °F)
maximum resistance (Rm) using Eq 2 or it can be compared to
#2 0.15433 0.16400 0.17367
the resistance values in Tables X1.2, or X2.2. The calculated
1/0 0.09693 0.10300 0.10907
criterion for pass/fail is based on 2/0 cable fault tests. The
2/0 0.07773 0.08260 0.08747
resistance of Y in the Rm (Eq 2) has been determined by
4/0 0.04893 0.05200 0.05507
A conservative analysis of the data to be 0.16 mΩ. This value is
20 °C Resistance values are taken from Table 2, B172 – 10.
below the “fusing range” of cables that passed the fault tests.
The value of Y = 0.16 mΩ or 2Y = 0.32 mΩ for all cable sizes.
Therefore, the pass/fail resistance value is:
7.5.1 Cable Resistance—Copper cables used as part of a
Rm 5 1.05 RL10.32 mΩ (4)
grounding jumper assembly must be constructed in accordance
NOTE 2—Tables X1.2 and X2.2 were derived from Eq 4.
with Specifications B172 or B173 as specified in Specification
F855. Two cable classes are identified in Specification F855 as 7.5.4 Testing with an AC Source—When an ac source is
being acceptable cables for use in ground cable assemblies.
used, it will determine the grounding jumper assembly imped-
They are Class K and Class M. Class K cable has proven to be ance (Z). This impedance is a function of the cable and the test
a very popular cable class for use in ground cable assemblies.
electrode spacing. For cable spacing of 12 in. or less, the cable
Table 1 provides the nominal resistance values for typical sizes reactance can be very low and the impedance value can
of Class K cables used in grounding jumper assemblies. If the
approach that of the cable resistance. The impedance (Z)
user is unable to determine the specific class of cable used in obtained from such a measurement should be compared with
a ground cable assembly, the resistance values in Table 1 are a
the calculated limiting maximum impedance (Zm) using Eq 3
reasonable approximation for both cable classes. Cable resis- to determine if the grounding jumper assembly has passed or
tance values for both cable classes are located in Appendix X1
failed the test. The pass/fail impedance value based on 2/0
through Appendix X2. cable fault tests is:
7.5.1.1 The cable resistance can change with ambient tem-
2 2
=
Zm 5 ~1.05 RL10.32! 1~XL! mΩ (5)
peratures. A 65.09 °C (69.16 °F) change in ambient tempera-
tures will cause a 62 % change in the measurement of
If multiple spacing of the cable is utilized in the test setup,
resistance values. Table 1 and Tables X1.1 and X2.1 give cable
the above equation becomes:
resistance values for a practical range of temperatures 5 °C,
2 2
=
Zm 5 ~1.05 RL10.32! 1~X L 1X L …1X L ! mΩ (6)
1 1 2 2 N N
20 °C, and 35 °C (41 °F, 68 °F, and 95 °F). Resistance values
NOTE 3—AC testing measurements of grounding jumper assemblies are
for different temperature values can be computed using Eq 1,
susceptible to errors and inconsistent results due to induction in the cable
where R is the cable resistance per foot in mΩ/ft at 20 °C, R
20 T2
if the cable is not laid out per the test method instructions. Different
is the cable resistance at the desired temperature T , and T is
instruments require different configurations (see Fig. 2).
2 2
the desired temperature in °C. NOTE 4—AC testing measurements of grounding jumper assemblies are
susceptible to errors if metal is laid across the cable or the cable is laid
R 5 R * @1 1 0.00393 * ~T 2 20!# mΩ⁄ft (1)
T2 20 2
across a metal object, even if the metal object is buried, such as a
reinforcing bar embedded in a concrete floor.
7.5.1.2 Results from the ASTM Round Robin Tests have
shown that an increase in cable resistance at a given tempera-
8. Cleaning/Reconditioning of Grounding Jumper
ture due to a combination of manufacturing tolerance and aging
Assembly after Electrical Testing
effects should not exceed 5 %. Therefore, the maximum
8.1 For the readings which are high, additional cleaning and
acceptable resistance in cables used in temporary protective
tightening of the assembly may restore its electrical integrity.
grounding jumpers should be equal to or less than 1.05 RL,
when R = cable resistance in mΩ/ft from Table 1, and L = cable
8.2 Disassemble the grounding jumper assembly and thor-
length in feet.
oughly clean the ferrule and clamp interface with isopropyl
7.5.2 Resistance and Impedance of Copper Grounding
alcohol and a stiff wire brush.
Jumper Assemblies—See Table 1, X1.1, or X2.1.
7.5.2.1 Maximum Resistance of the Grounding Jumper As-
sembly (Rm):
Standard Handbook for Electrical Enginee
...
This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: F2249 − 23 F2249 − 24
Standard Specification for
In-Service Test Methods for Temporary Grounding Jumper
Assemblies Used on De-Energized Electric Power Lines and
Equipment
This standard is issued under the fixed designation F2249; 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 (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This specification covers the in-service inspection and electrical testing of temporary protective grounding jumper assemblies
which have been used by electrical workers in the field.
1.2 This specification discusses methods for testing grounding jumper assemblies, which consist of the flexible cables, ferrules,
clamps and connectors used in the temporary protective grounding of de-energized circuits.
1.3 Manufacturing specifications for these grounding jumper assemblies are in Specifications F855.
1.4 The application, care, use, and maintenance of this equipment are beyond the scope of this specification.
1.5 The values stated in SI units are to be regarded as standard. The values given in parentheses after SI units are provided for
information only and are not considered standard.
1.6 The following safety hazards caveat pertains only to the test portions of this specification. 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.7 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
B172 Specification for Rope-Lay-Stranded Copper Conductors Having Bunch-Stranded Members, for Electrical Conductors
B173 Specification for Rope-Lay-Stranded Copper Conductors Having Concentric-Stranded Members, for Electrical Conduc-
tors
F855 Specifications for Temporary Protective Grounds to Be Used on De-energized Electric Power Lines and Equipment
This specification is under the jurisdiction of ASTM Committee F18 on Electrical Protective Equipment for Workers and is the direct responsibility of Subcommittee
F18.45 on Mechanical Apparatus.
Current edition approved Feb. 1, 2023Jan. 1, 2024. Published February 2023January 2024. Originally approved in 2003. Last previous edition approved in 20202023 as
ɛ1
F2249 – 20F2249 – 23. . DOI: 10.1520/F2249-23.10.1520/F2249-24.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F2249 − 24
2.2 IEEE Standards:
IEEE Standard 80–2013 IEEE Guide for Safety in AC Substation Grounding
IEEE Standard 1048–2016 IEEE Guide for the Protective Grounding of Power Lines
IEEE Standard 1246–2011 IEEE Guide for Temporary Protective Grounding Systems Used in Substations
3. Terminology
3.1 Definitions of Terms Specific to This Standard:
3.1.1 grounding jumper assembly—assembly, n—grounding cable with connectors and ground clamps attached, also called a
grounding jumper or a protective ground assembly installed temporarily on de-energized electric power circuits for the purpose of
potential equalization and to conduct a short circuit current for a specified duration (time).
4. Significance and Use
4.1 Grounding jumper assemblies can be damaged by rough handling, long term usage, weathering, corrosion, or a combination
thereof. This deterioration may be both physical and electrical.
4.2 The test procedures in this specification provide an objective means of determining if a grounding jumper assembly meets
minimum electrical specifications. These methods permit testing of grounding jumper assemblies under controlled conditions.
4.3 Each responsible entity must determine the required safety margin for their workers during electrical fault conditions.
Guidelines for use in the determination of these conditions are beyond the scope of this specification and can be found in such
standards as IEEE Standard 80–2013 and IEEE Standard 1048–2016, and IEEE Standard 1246–2011.
4.4 Mechanical damage, other than broken strands, may not significantly affect the cable resistance. Close manual and visual
inspection is required to detect some types of mechanical damage.
4.5 The test procedures in this specification should be performed at a time interval established by the user to ensure that defective
grounding jumper assemblies are detected and removed from service in a timely manner.
4.6 Retest the grounding jumper assembly after performing any maintenance, in order to ensure its integrity.
5. Inspection of Grounding Jumper Assemblies
5.1 Visual inspection shall be made of all grounding jumper assemblies prior to testing.
5.1.1 If the following defects are evident, the grounding jumpers may be rejected without electrical testing:
5.1.1.1 Cracked or broken ferrules and clamps,
5.1.1.2 Exposed broken strands,
5.1.1.3 Cut or badly mashed or flattened cable,
5.1.1.4 Extensively damaged cable-covering material,
5.1.1.5 Swollen cable jacket or soft spots, indicating internal corrosion, and
5.1.1.6 Cable strands with a black deposit on them.
5.1.2 Grounding jumper assemblies which are visually defective shall be removed from service and permanently marked, tagged
or destroyed (if beyond repair) to prevent re-use.
5.1.3 Before the grounding jumper assembly can be placed back in service, it must pass the inspection requirements in 5.1.1, and
the electrical requirements in Section 7.
Available from the Institute of Electrical and Electronics Engineers, Inc. (IEEE) 1828 L St., NW, Suite 1202, Washington, DC 20036–5104.
F2249 − 24
5.1.4 All physical connections should be checked for tightness with specified torque values.
5.2 All physical connections should be checked for tightness with manufacturer’s specified torque values.
5.3 Before the grounding jumper assembly can be placed back in service, it must pass the inspection requirements in 5.1, be
assembled per 5.2, and must pass the electrical requirements in Section 7.
6. Cleaning and Measuring of Grounding Jumper Assembly Prior to Electrical Testing
6.1 Identify the cable gagegauge (AWG) and a make a precise measurement of the cable length. See Fig. 1.
6.2 Thoroughly clean the jaws of the clamps with a stiff wire brush.
6.3 Attach the grounding jumper assembly clamps firmly to the test set.
7. Electrical Requirements
7.1 The user must select the test method with the desired precision and repeatability. The test instrument should be sufficiently
accurate to detect at least a one foot or less change in cable length to ensure that the cable meets requirements.
7.2 Each method must take into account a precise cable resistance per foot and the length of the cable being tested.
7.3 Electrical tests relative to this standard are:
7.3.1 DC resistance measurements,
7.3.2 AC impedance measurements, and
7.3.3 Temperature rise measurements (supplementary method).
7.4 DC Resistance or AC Impedance Method—Equipment required includes:
7.4.1 A minimum 10 A dc source controllable to 5 % of output current, short circuit protected, or
7.4.2 A minimum 10 A ac source controllable to 5 % of output current, short circuit protected.
7.4.3 Measuring method for measurements of cable length calibrated in inches or centimeters.
FIG. 1 Resistance and Impedance of Copper Grounding Jumper Assemblies
Y = resistance of clamps, ferrule and portions of the cable inside the ferrule, mΩ,
L = cable length expressed in feet (ferrule to ferrule measurement to the nearest inch, not including shrouded portion of some
ferrules which cover the cable insulation), and
R = cable resistance from Table 1, mΩ/ft.
F2249 − 24
7.5 In-Service Electrical Resistance Pass/Fail Criteria—The pass/fail criterion of a grounding jumper assembly is based on the
resistance value of the assembly (cable, ferrules and clamps) which is higher than the established resistance value for new
assemblies. This increase in resistance accounts for manufacturing tolerance and the expected normal deterioration of the assembly
due to aging, contamination and corrosion, particularly in the contact areas of the cable ferrules and clamps. The allowable increase
in resistance is such as to permit the grounding jumper assembly to perform safely during electrical faults. The grounding jumper
assembly, when subjected to its rated maximum fault current and duration, must withstand the fault without its components
separating, but some heat damage and discoloration is acceptable. The electrical resistance value for the pass/fail criterion is made
up of two parts (Fig. 1), the cable resistance and the resistance of the two ends containing short cable sections, ferrules and clamps.
When the grounding jumper assemblies are tested with a dc source, the dc resistance of the assembly is used for the pass or fail
purposes. With an ac source, the impedance of the cable and the impedance of the ends (ferrules and clamps) are used to determine
if the grounding jumper fails or passes the test.
A
TABLE 1 Class K Copper Cable Nominal Resistance, mΩ/ft
Grounding Resistance, mΩ/ft Resistance, mΩ/ft Resistance, mΩ/ft
Cable Size at 5 °C (41 °F) at 20 °C (68 °F) at 35 °C (95 °F)
#2 0.15433 0.16400 0.17367
1/0 0.09693 0.10300 0.10907
2/0 0.07773 0.08260 0.08747
4/0 0.04893 0.05200 0.05507
A
20 °C Resistance values are taken from Table 2, B172 – 10.
7.5.1 Cable Resistance—Copper cables used as part of a grounding jumper assembly must be constructed in accordance with
Specifications B172 or B173 as specified in Specification F855. Two cable classes are identified in Specification F855 as being
acceptable cables for use in ground cable assemblies. They are Class K and Class M. Class K cable has proven to be a very popular
cable class for use in ground cable assemblies. Table 1 provides the nominal resistance values for typical sizes of Class K cables
used in grounding jumper assemblies. If the user is unable to determine the specific class of cable used in a ground cable assembly,
the resistance values in Table 1 are a reasonable approximation for both cable classes. Cable resistance values for both cable classes
are located in Appendix X1 through Appendix X2.
7.5.1.1 The cable resistance can change with ambient temperatures. A 65.09 °C (69.16 °F) change in ambient temperatures will
cause a 62 % change in the measurement of resistance values. Table 1 and Tables X1.1 and X2.1 give cable resistance values for
a practical range of temperatures 5 °C, 20 °C, and 35 °C (41 °F, 68 °F, and 95 °F). Resistance values for different temperature
values can be computed using Eq 1, where R is the cable resistance per foot in mΩ/ft at 20 °C, R is the cable resistance at the
20 T2
desired temperature T , and T is the desired temperature in °C.
2 2
R 5 R * 1 1 0.00393 * T 2 20 mΩ⁄ft (1)
@ ~ !#
T2 20 2
7.5.1.2 Results from the ASTM Round Robin Tests have shown that an increase in cable resistance at a given temperature due to
a combination of manufacturing tolerance and aging effects should not exceed 5 %. Therefore, the maximum acceptable resistance
in cables used in temporary protective grounding jumpers should be equal to or less than 1.05 RL, when R = cable resistance in
mΩ/ft from Table 1, and L = cable length in feet.
7.5.2 Resistance and Impedance of Copper Grounding Jumper Assemblies—See Table 1, X1.1, or X2.1.
7.5.2.1 Maximum Resistance of the Grounding Jumper Assembly (Rm):
Rm 5 1.05 RL12YmΩ (2)
7.5.2.2 Maximum Impedance of the Grounding Jumper Assembly (Zm):
2 2
Zm 5= 1.05RL12Y 1 XL mΩ (3)
~ ! ~ !
where:
X = reactance of the cable in mΩ/ft.
F2249 − 24
NOTE 1—Values of X can be found in data books such as the Standard Handbook of Electrical Engineers.
7.5.3 Testing with a DC Source—A dc source can be used to determine the pass/fail value for a given grounding jumper assembly.
The resistance value (R) obtained from such a measurement should be compared with the calculated limiting maximum resistance
(Rm) using Eq 2 or it can be compared to the resistance values in Tables X1.2, or X2.2. The calculated criterion for pass/fail is
based on 2/0 cable fault tests. The resistance of Y in the Rm (Eq 2) has been determined by conservative analysis of the data to
be 0.16 mΩ. This value is below the “fusing range” of cables that passed the fault tests. The value of Y = 0.16 mΩ or 2Y = 0.32
mΩ for all cable sizes. Therefore, the pass/fail resistance value is:
Rm 5 1.05 RL10.32 mΩ (4)
NOTE 2—Tables X1.2 and X2.2 were derived from Eq 4.
7.5.4 Testing with an AC Source—When an ac source is used, it will determine the grounding jumper assembly impedance (Z).
This impedance is a function of the cable and the test electrode spacing. For cable spacing of 12 in. or less, the cable reactance
can be very low and the impedance value can approach that of the cable resistance. The impedance (Z) obtained from such a
measurement should be compared with the calculated limiting maximum impedance (Zm) using Eq 3 to determine if the grounding
jumper assembly has passed or failed the test. The pass/fail impedance value based on 2/0 cable fault tests is:
2 2
Zm 5= 1.05RL10.32 1 XL mΩ (5)
~ ! ~ !
If multiple spacing of the cable is utilized in the test setup, the above equation becomes:
2 2
Zm 5=~1.05RL10.32! 1~X L 1X L …1X L ! mΩ (6)
1 1 2 2 N N
NOTE 3—AC testing measurements of grounding jumper assemblies are susceptible to errors and inconsistent results due to induction in the cable if the
cable is not laid out per the test method instructions. Different instruments require different configurations (see Fig. 2).
NOTE 1—The cable configuration may have a dramatic effect on the readings. Sho
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