American Railway Engineering and Maintenance of Way Association

Letter Ballot 38 19-10

1. Committee and Subcommittee:

AREMA C&S Committee 38

2. Letter Ballot Number: 38 19-10

3. Assignment:

MP's revised at Fall '19 meeting.

4. Ballot Item:

Ballot 38 19-10: This ballot contains the MP approved at the Fall ‘19 meeting:

• 19.01.14 Recommended Practices for Installation and Maintenance of Grounds for

Communication Facilities

5. Rationale:

Revised Manual Parts

Draft

Not ye

t App

roved

AREMA® C&S Manual

202116 Part

19.1.14

________________________________________________________________

- 1 –

Recommended Practices for Installation and Maintenance of Grounds for Communication Facilities

Reaffirmed Revised 202116 (10 Pages) A-General A-1 Function: The function of a grounding system is to provide a path to ground for

currents resulting from lightning, induction and crosses with foreign circuits. A-2 General Requirements: A good grounding system is of great importance and

should be designed and installed in a manner that ensures optimum conductivity to ground in order to safeguard employees and the general public from injury caused by electrical potentials.

B-Definitions B-1 Approved: Acceptable to the authority having jurisdiction. Equipment is normally

considered acceptable if it is accepted, or certified, or listed, or labeled, or otherwise determined to be safe by a nationally recognized testing laboratory, such as, but not limited to, Underwriters Laboratories, Inc., Factory Mutual Engineering Corp. and the Canadian Standards Association.

B-2 Arrester: A device designed to limit transient voltages on equipment or

conductors. The normal arrester condition is in the open circuit mode, until its breakdown voltage is exceeded. After breakdown, the arrester discharges current to ground across its GAP. The arrester again assumes the open circuit condition after the passage of the surge.

B-3 Bond: A conductor providing a low impedance path between metallic parts

required to be electrically connected. B-4 Earth: The earth's potential is normally considered to be the reference electrical

potential. Due to the relatively high resistivity of soil, it is not possible to make a zero impedance connection to the reference earth potential.

B-5 Electrode: A metallic object used as a terminal to connect to the reference earth

potential. B-6 Existing Electrode: Direct buried metallic piping systems, metal building

frameworks, well casings, steel piling, and other underground metal structures installed for purposes other than grounding and having suitably low impedance to the reference earth potential, are classified as existing electrodes.

Draft

Not ye

t App

roved

AREMA® C&S Manual

Part 19.1.14

202116

________________________________________________________________

- 2 –

B-7 Exothermic Weld: A process in which a permanent electrical connection of copper to copper or copper to steel is made. An exothermic chemical reaction is utilized to produce molten copper that welds the desired metal components together. During the welding process, a ceramic or graphite mold is used to contain the molten copper around the objects being welded together.

B-8 Ground Conductor: The conductor that connects the protector or the

communication equipment ground point to the ground electrode. B-9 Grounded Conductor: The conductor of the utility electrical service that is

intentionally connected to a ground electrode (neutral conductor). B-10 Grounding System: The grounding system consists of the ground conductor,

electrode connection and the electrode. The purpose is to maintain the same impedance from any point connected to that system to ground.

B-11 Made Electrode: Metallic objects such as rods, pipes, plates, etc., specifically

installed to obtain a sufficiently low impedance connection to the reference earth potential.

B-12 Multi-Grounded Neutral: The neutral conductor of the utility electrical service

where the neutral conductor is connected to a made electrode at each transformer location and at a sufficient number of additional points to total not less than four electrode connections in each mile of line, not including electrode connections at the individual services.

B-13 Patina: A green or greenish-blue crust or film on bronze or copper formed by

oxidation. B-14 Protector: Similar to any arrestor, except it can fail in an open or closed circuit

condition as defined by its construction. B-15 Sectional Rods: Sectional rods are ground rods that are threaded at both ends

and can be joined together with threaded couplings to achieve whatever driven depth is required. Any sectional rod may be used as a top, intermediate, or bottom section.

B-16 Sphere of Influence: An electrode in soil of uniform resistivity radiates current in

all directs. The electrode can be considered to be surrounded by shells of soil, all of equal thickness. The shell nearest the electrode has the smallest surface area and so offers the greatest resistance. The next shell is somewhat larger in area and offers less resistance; and so on out. Finally, a distance from the electrode is reached where an additional shell of soil will not add significantly to the total resistance. This is the dimension of the sphere of influence of the

Draft

Not ye

t App

roved

AREMA® C&S Manual

202116 Part

19.1.14

________________________________________________________________

- 3 –

electrode. For a ground rod or pipe, the radius of the sphere of influence can usually be considered to be equal to the driven depth of the rod or pipe.

C-Choice of Electrodes C-1 Existing Electrodes: An extensive direct buried metallic cold water piping system

is the preferred electrode where it is readily accessible. Such systems normally have a resistance to earth within the maximum values given in Table 19114-3 and have been used extensively in the past. The existing electrode cannot be used as a primary electrode. National Electrical Code requires that the primary electrode can only be established by a driven ground rod. Existing electrode can be used only as a secondary electrode where practical.

C-2 A direct buried cold water piping system with nonmetallic pipe, corrosion

protected metallic pipe, or metallic pipe with insulated joints is not suitable for use as a grounding electrode.

C-3 Insulated or non-insulated underground cold water piping connected to a well

that has a measured resistance to earth within the maximum values given in Table 19114-3, may be used as a grounding electrode. Care must be exercised to assure that all parts of the piping system that may be disconnected at some time in the future are effectively bonded together.

C-4 Direct buried metallic piping systems other than for cold water (steam pipes, gas

pipes, sprinkler systems, air lines, etc.) shall not be used as a grounding electrode.

C-5 Made electrodes shall be of metal or combinations of metals that do not corrode

excessively under the existing conditions for the expected service life of the communication installation. All outer surfaces of a made electrode shall be conductive, that is, not having paint, enamel, or other insulating type covering.

C-6 Made electrodes shall, as far as practical, penetrate below the frost line and into

permanent moisture level. Failure to reach permanent moisture may not only result in high resistance to earth, but may also result in large variations in resistance during changes of the seasons.

C-7 Made electrodes may consist of driven rods, driven pipes, buried wire, buried

plates, or buried strips of metal. Driven rods are the most generally used and are the recommended type of made electrode.

C-8 Driven Rods: Driven rods shall have a minimum cross-sectional dimension of 1/2

inches, a total length of not less than 8 ft., and shall have a driven depth of not less than 8 ft. Where a rock bottom is encountered a different type of electrode

Draft

Not ye

t App

roved

AREMA® C&S Manual

Part 19.1.14

202116

________________________________________________________________

- 4 –

should be employed. Grinding wells constructed from ground rods and filled with ground enhancement material are the most effective.

C-9 Copper, copper-clad steel, galvanized steel, and stainless steel rods are the

most popular. Listed in Table 190114-1 are electrode life expectancy estimates based on NFPA field tests

Table 19114-1

Ground Rod Type Life Expectancy

Galvanized 10 to 15 years

Copper Bonded/Clad Steel 35 to 40 years

Solid Copper More than 40 years

Stainless Steel More than 40 years

C-10 In order to achieve a resistance to earth within the maximum values given in

Table 19114-3, multiple rods connected in parallel or sectional rods coupled together (to achieve a greater driven depth), or a combination of the two may be used. Other ground enhancement methods are also available including chemical ground rods and ground rods incased in ground enhancement material.

C-11 Multiple rods should be spaced a distance apart at least equal to the driven depth

of the rods and preferably twice the driven depth. . This will minimize the effect of overlapping of the spheres of influence of the rods. In general, sectional rods coupled together to achieve a driven depth down to the permanent moisture level of the soil is more efficient that the same total length of multiple single-length rods connected in parallel.

C-12 Electrical Service Grounding Electrodes: Where the electrical service to the

building has multiple-grounded neutrals, the communication ground connection should be made to the service grounding conductor, via an established main copper ground bar representing a principle ground point.

D-Ground Conductor D-1 Material: Grounding conductors shall be copper, solid or stranded and shall be

insulated in accordance with section 800 of the latest edition of the National Electrical Code.

D-2 Sizes: Grounding conductors shall not be smaller than the sizes listed in Table

19114-1.

Draft

Not ye

t App

roved

AREMA® C&S Manual

202116 Part

19.1.14

________________________________________________________________

- 5 –

Table 19114-2

Number of Arresters Size of Copper Ground Wire

1 to 80 No. 6 AWG

Over 80 No. 4 AWG

D-3 Splices: A grounding conductor shall be installed in one continuous length without a splice or joint and should be terminated at the main copper ground bar/principle grounding point. Where the grounding conductor is distributed to different locations, each conductor should initiate at the main ground bar to avoid splices and daisy chaining. See Paragraph E-3 for exception on splices.

D-4 Self Impedance: It is very important that the ground conductor is kept as short as

practical and with a minimum number of bends in order to keep the self-impedance of the ground conductor as low as possible. For the same reason, a ground conductor should not contain bends exceeding 60 degrees or coils.

E-Electrode Connection E-1 The connection of a ground or bond wire to an electrode shall be as accessible

as practical and shall withstand vibration and exposure to the elements while maintaining a permanently low resistance connection. Wherever possible, exothermic weld, silver soldering or brazing is recommended.

E-2 To Water Pipes: For connection to a water pipe, an approved pipe grounding

clamp or an exothermic type weld shall be used. Before connection is made check that path to ground is uninterrupted by plastic, rubber or other types of non-conducting materials. Refer to section C for more details).

E-3 To Driven Rod: For connection to a driven rod electrode, an approved ground

rod clamp or an exothermic type weld shall be used. If the rod electrode is equipped with a tail wire, the connection shall be made by means of exothermic weld or a compression sleeve to the tail wire.

E-4 To Other Electrodes: For connection to a steel members, an approved lugs or an

exothermic type welds shall be used.

Draft

Not ye

t App

roved

AREMA® C&S Manual

Part 19.1.14

202116

________________________________________________________________

- 6 –

E-5 Contact Surfaces: If any coating of non-conductive material, such as enamel, rust, or scale, is present on the electrode contact surface at the point of connection, the coating shall be thoroughly removed and clean to obtain a good connection. Conductive paste should be used between dissimilar materials on mechanical connections.

F-Installation F-1 Existing Electrodes: As stated in section C, an extensive direct buried cold water

metallic piping system forms a satisfactory ground electrode and shall be used whenever practical as a secondary grounding electrode. Connection of the ground wire shall be made on the street side of all fittings such as valves, meters, etc. when possible. When this is not possible, it is necessary to install properly sized bond wires around meters, valves or other fittings.

F-2 Made Electrodes: The preferable location for a made electrode is where the

surrounding earth will be moist throughout most of the year. Abundant vegetation usually indicates underlying moisture and favorable conditions; however, if the soil is such that the surface water readily seeps away, the natural salts in the earth are dissolved and carried off, leaving the earth a relatively poor conducting medium without the presence of electrolytes. For this reason filled-in ground, gravelly or sandy soil and, in some cases, fresh water streams, are not desirable locations for made grounds with exception of chemical ground rods.

F-3 Bonding of Electrodes: A bond shall be of copper and shall not be smaller than

No. 6 AWG or its equivalent. The communication grounding electrode and the electrical power-grounding electrode where separate made electrodes are used in or on the same building or structure should be bonded together at the main copper ground bar/principle grounding point. Bonding together of all separate electrodes will limit the potential differences between them and between their associated wiring systems.

F-4 Run In Straight Line: The grounding conductor shall be run to the grounding

electrode in as straight a line as practical without any sharp bends, coils or kinks. Sufficient slack shall be left in the grounding conductor at the grounding electrode to insure against possible breakage of the conductor due to vibration (i.e., water pipe) or settlement (i.e. driven rod), etc. Under no circumstances shall the slack be taken up in the form of a coil.

F-5 Physical Damage: Where necessary, the grounding conductor shall be guarded

protected from physical damage with molding, etc. The protection from physical damage shall extend at least 8 ft. above ground.

Draft

Not ye

t App

roved

AREMA® C&S Manual

202116 Part

19.1.14

________________________________________________________________

- 7 –

F-6 Through Metallic Duct Or Conduit: If the grounding conductor is run through a metallic duct or conduit it must be bonded to each end of the duct or conduit.

F-7 Splices: See Paragraph D-3. G-Resistance to Earth G-1 The grounding electrode system may consist of one or more electrodes bonded

together. The resistance to earth of the grounding electrode system shall not exceed the values given in Table 19114-2 3 under ordinary conditions.

Table 19114-3

Plant for Which Ground is Provided Recommended Maximum

Allowable Resistance

Offices with power facilities. .

10 ohms

Offices with made ground and with protectors

for over 10 wires.

25 ohms

All other offices. 25 ohms

Booths and shelter boxes. 25 ohms

Cable terminals (except where cable sheath

ground is used) and grounds for messages.

25 ohms

Telecommunication towers 5 Ohms

H-Measurement of Electrode Resistance H-1 In general, experience in any given location will enable an installer to determine

whether or not an existing electrode will have a resistance within the limits given in Table 19114-3II or what type and configuration of made electrode will be required. It is recommended, however, that the resistance of an existing electrode, as well as a made electrode, should be measured before it is placed in service. Fall of Potential is the preferred measuring method. When using existing grounding systems it should be noted that low current DC measurement will not reveal extent of the corrosion of this system. Additional investigation including excavation of the system might be required.

Before designing or installing new grounding system, local soil resistivity

measurements should be obtained to various depths of the earth. The most common method used is the Wenner Four Point Method. Refer to Fig. 19144-1. For more details refer to IEEE Standard 81 (IEEE Guide for Measuring Earth

Draft

Not ye

t App

roved

AREMA® C&S Manual

Part 19.1.14

202116

________________________________________________________________

- 8 –

Resistivity, Ground Impedance and Earth Surface Potentials of Grounding Systems).

Figure 19114-1

H-2 The resistance to earth of a made electrode may vary considerably from time to

time due to the amount of moisture contained in the earth. Therefore, measurements of electrode resistance to ground should not be made during those times when the moisture content of the earth is greater than normal.

H-3 The resistance of an electrode to earth may be easily measured by using a direct

reading instrument specifically designed for this purpose. This type of instrument permits the resistance to be measured with a minimum amount of time and effort. It is strongly recommended that an instrument specifically designed for measurement of electrode resistance to earth should be used rather than using instruments designed for other purposes.

H-4 The electrode under test should be isolated from the grounded equipment during

the measurement procedure in order to obtain an accurate resistance measurement. Preferably, the ground conductor should be disconnected from the electrode. This temporary disconnection of the ground conductor shall be permitted only under competent supervision and for testing purposes only. There are commercially available instruments that allow for safety measurement of each electrode without disconnecting them from a grounding grid.

Draft

Not ye

t App

roved

AREMA® C&S Manual

202116 Part

19.1.14

________________________________________________________________

- 9 –

H-5 There are two methods generally used to measure the electrode resistance to earth. The two terminaltwo-terminal method, also known as the direct method, and the three- terminal method, also known as the fall-of-potential method.

H-6 Two Two-Terminal Method: This is the simplest method but it can be used only if

certain requirements are met. First, an existing electrode of known low resistance to earth (such as an extensive direct buried metallic cold water piping system) must be available. Second, the electrode under test must not be in the sphere of influence of the existing reference electrode. The instrument is connected to each electrode and measures the sum of the resistances to earth of the two electrodes. The resistance to ground of the electrode under test is obtained by subtracting the resistance to ground of the known electrode from the measured resistance.

H-7 Three Three-Terminal Method: Also known as Fall of Potential method is used to

measure resistance otf the existing or newly installed grounding system. In the three terminalthree-terminal method, two small test probes, which are part of the test instrument, are used in conjunction with the electrode under test. A reference electrode is, therefore, not required. Consult the instructions with the particular test instrument being used for information on performing this measurement. For more details refer to IEEE Standard 81 (IEEE Guide for Measuring Earth Resistivity, Ground Impedance and Earth Surface Potentials of Grounding Systems).

Figure 19114-2

Draft

Not ye

t App

roved

AREMA® C&S Manual

Part 19.1.14

202116

________________________________________________________________

- 10 –

H-8 When using either the two two-terminal method or the three terminalthree-

terminal method, care should be exercised to avoid influence of the test readings by any stray ground currents or buried metallic pipes, etc.

J-Reducing Resistance of Made Electrodes J-1 Chemical Soil Treatment: When deep driven rods are not possible due to hard

underlying rock, etc., and the number of multiple paralleled rods required make this approach impractical, then other approaches are required. The most effective methods in reducing soil resistivity is the use of vertical chemical ground rods or vertical ground rods encased in ground enhancement material. In both cases drilling vertical holes is required.

K-Maintenance K-1 Inspection and Tests: Inspections and tests should be made at regular intervals

typically once a year, as determined by past experience with grounding systems in a particular area, to insure that the grounding system meets the requirements of this specification. The testing should be conducted during the same season for each location. Records should be kept so that a general trend of increased ground resistance will be evident.

K-2 All joints and connections should be periodically inspected. If found faulty, repairs

shall be made as required. K-3 A green film called a patina (copper oxide) may form on copper ground

conductors and electrodes due to the unavoidable corrosion process. This patina should not be cleaned off because it slows down the process of corrosion, even though it was originally caused by corrosion.

L-References L-1Reference was made to the following codes and standards in the preparation of this recommend practice. National Electrical Safety Code, ANSI C2- National Electrical Code, NFPA 70-

Formatted: Indent: Left: 0", First line: 0", Tab stops: 3.25", Centered + Not at -0.5" + 0"

Formatted: Left, Tab stops: 3.25", Centered + Not at -0.5"

Formatted: Left, Indent: Left: 0", First line: 0", Tab stops: 3.25", Centered + Not at -0.5" + 0"

Formatted: Left, Tab stops: 3.25", Centered + Not at -0.5"

Formatted: Left, Indent: Left: 0", First line: 0", Tab stops: 3.25", Centered + Not at -0.5" + 0" + 0.5"

Draft

Not ye

t App

roved

AREMA® C&S Manual

202116 Part

19.1.14

________________________________________________________________

- 11 –

Canadian Electrical Code, C22.1 IEEE Standard 81

Draft

Not ye

t App

roved