Transcript Grounding and Bonding

Guide to Network Cabling
Fundamentals
Chapter 2
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Chapter 2 - Grounding and Bonding
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Discuss how grounding and bonding work
Differentiate between “grounding and bonding
systems” and “grounding and bonding equipment”
Understand cable protection and equipmentgrounding practices
Identify the three types of telecommunications circuit
protectors
Understand how documentation helps you and your
network
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A Closer Look at
Grounding and Bonding
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Standards from the following organizations are the
four main sources for information about grounding
and bonding codes and practices
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National Electrical Code (NEC)
ANSI/EIA/TIA-607: Commercial Building Grounding and
Bonding for Telecommunications
Underwriters Laboratories UL-497: Protectors for Paired
Conductor Communication Circuits
IEEE Standard 142-1991: Grounding of Industrial and
Commercial Power Systems
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A Closer Look at
Grounding and Bonding
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Grounding, Bonding, and Effective Ground:
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A ground is a conducting connection between an
electrical circuit and the earth, or a conducting body
Bonding is the permanent joining of metallic parts to
form a conductive path that ensures electrical continuity
and safely conducts current
An effective ground is an intentional connection to a lowresistance earth ground that permits current to discharge
into the earth without buildup of hazardous voltages on
the cable, equipment, or people
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A Closer Look at
Grounding and Bonding
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Grounding and bonding network components:
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When designed and installed following the appropriate
codes, specifications, and safety practices, the
grounding and bonding network components create a
system that effectively safeguards personnel, property,
and equipment
The most common hazard in grounding and bonding
networks is electric shock, which occurs from accidental
contact with energized devices
The effects of electrical shock are determined by the
magnitude of current and duration of the shock
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A Closer Look at
Grounding and Bonding
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Grounding and bonding network components:
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Every building has a grounding electrode, a conductor
that provides a direct, low-resistance connection to the
earth
A grounding conductor connects the electrical equipment
to the grounding electrode and the building's main
grounding busbar
The main grounding busbar is a conductor that serves
as a common connection point for two or more circuits;
the busbar is solid copper with insulated standoffs
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A Closer Look at
Grounding and Bonding
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Grounding and bonding network components:
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Conductors used specifically for bonding are called
bonding conductors; the conductor that connects the
building’s service equipment ground to the
telecommunications grounding system is called the
bonding conductor for telecommunications (BCT)
The BCT is a No. 6 AWG (American Wire Gauge) or
larger insulated copper conductor that connects the
equipment ground to the telecommunications main
grounding busbar
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A Closer Look at
Grounding and Bonding
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Grounding and bonding network components:
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The telecommunications main grounding busbar (TMGB)
is the foundation of the grounding system and it serves
as an interface to the building’s power
The TMGB also serves as a central connection point for
the telecommunications bonding backbone (TBB) and
equipment
Usually there is one TMGB per building; it is typically in
the entrance room (facility), the building entrance for
both public and private network service cables, or in the
main telecommunications room
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A Closer Look at
Grounding and Bonding
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Grounding and bonding network components:
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In each telecommunications room the
telecommunications grounding busbar (TGB) provides a
common access point of connection for systems and
equipment bonding to ground
The TGB is built in a similar fashion to the TMGB and it
should be installed as close as possible to the panel
board in the telecommunications room
If a backboard (a panel for mounting system hardware
and equipment) is located in the same room as a TGB, it
should be bonded to the TGB
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A Closer Look at
Grounding and Bonding
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Grounding and bonding network components:
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The TMGB and all TGBs are interconnected by a No. 6
AWG or larger insulated conductor, the TBB
The TBB’s primary function is to reduce or equalize
differences in the telecommunications systems bonded
to it; it is considered part of the grounding and bonding
infrastructure, but it is independent of all equipment and
cable
The TBB begins at the TMGB and extends throughout
the building, using the telecommunications backbone
pathways
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A Closer Look at
Grounding and Bonding
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When planning TBB installation, the following
design considerations are important:
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Be consistent with the design of the telecommunications
backbone cabling system
Use multiple TBBs if the building size permits it, but they
must be bonded together at the top floor
Bonding conductors between a TBB and TGB must be
continuous and routed as directly as possible
Don’t use interior water pipe systems or metallic cable
shields as a TBB
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Grounding and Bonding
System vs. Equipment
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A building has six types of grounding and bonding
systems designed to provide overall protection for
the building and its occupants:
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Lightning protection system
Grounding electrode system
Electrical bonding and grounding system
Electrical power protection system
Telecommunications bonding and grounding system
Telecommunications circuit protector system
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Grounding and Bonding
System vs. Equipment
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Grounding systems:
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Lightning protection systems provide a designed path for
lightning current to travel
Lightning protection systems are made up of several
components: air terminals (lightning rods); conductors;
ground terminations (ground rods); surge arresters; and
surge protectors
The telecommunications ground must be bonded to the
lightning protection system within 3.7 meters of the base of
the building
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Grounding and Bonding
System vs. Equipment
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Grounding systems (cont.):
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Grounding electrode systems are the end product of
bonding together all metal underground water pipes, the
metal frame of the building, any electrode that is encased
in concrete, any ground ring, and any made or other
electrodes
Other electrodes include rod and pipe electrodes, plate
electrodes, and metal underground systems
Grounding electrode system forms a single, reliable ground
for a building
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Grounding and Bonding
System vs. Equipment
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Grounding systems (cont.):
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Both the electrical bonding and grounding systems and the
electrical power protection system refer to the
requirements for all electrical installations, such as types,
sizes, methods and locations of conductors and
connections
Three scientific principles guide bonding conductors:
equalization, diversion, and coupling
The type of bonding conductors used in most commercial
buildings depends on the application and the fault-currentcarrying capacity needed
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Grounding and Bonding
System vs. Equipment
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Equipment grounding:
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Each type of grounding equipment has its own set of
grounding and bonding specifications
The primary purpose of equipment grounding is to remove
potentially dangerous voltages; it also protects against
electrical shock and prevents heat building up in the
equipment
Earth grounding is an intentional connection from a circuit
conductor to a ground electrode placed in the earth and it
provides a safe path for the dissipation of fault currents
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Grounding and Bonding
System vs. Equipment
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Equipment grounding (cont.):
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The grounding conductor should be bonded to the nearest
accessible earth-ground
The bonding jumper must be no smaller than AWG 6
copper, it must be connected between the communications
system grounding electrode and the building’s power
grounding electrode system
Termination is the connection of a cable to connecting
hardware; the earth ground must terminate to the
grounding electrode using either exothermic welding, listed
lugs or clamps, or listed pressure connector
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Grounding and Bonding
System vs. Equipment
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Equipment grounding (cont.):
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An intrinsically safe system operates by preventing ignition
of flammable or combustible material under normal or
abnormal conditions
The primary advantage of intrinsically safe systems is that
ordinary wiring is allowed
Intrinsically safe systems are composed of safe
interconnecting cables, cable shields, enclosures, cable
trays, and raceways; all items must be grounded with an
equipment grounding electrode, and bonded with an
approved method
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Cable Protection and EquipmentGrounding Practices
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Inside cable and wire is that which runs from
communications equipment to the protector
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All types of inside communication cables and wires must
be rated for resistance to the spread of fire, be suitable for
the installation site, and have a voltage rating of at least
300 volts; the conductors in these cables, other than fiber,
must be copper
Specific installation requirements include: the separation of
communications cables and electrical power cabling; using
approved firestopping methods; proper conduit use
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Cable Protection and EquipmentGrounding Practices
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Inside cable and wire (cont.)
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When using an unshielded backbone cable, a TBB
conductor should be used with it; the TBB must be bonded
to the grounding using the grounding busbar nearest the
termination point of the cable
The shields of shielded cable are usually grounded at each
end to a connector panel, which must be bonded to the
closest approved ground
In smaller equipment rooms, equipment is usually
grounded via the closest ground; larger buildings with
multiple equipment rooms require multiple TGBs
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Telecommunications Circuit
Protectors
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A telecommunications circuit protector is a device
that protects telecommunications facilities and
equipment from abnormally high voltages and
current
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High voltage and currents are usually caused by exposure
to lightning, accidental contact with electrical light, or power
conductors operating at over 300 volts to ground
There are three types of telecommunications circuit
protectors: primary; secondary; and data and fire alarm
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Telecommunications Circuit
Protectors
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Primary protectors are most typically made from
carbon blocks, glass tubes, or solid state
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When ready to install, follow these installation practices:
they should be installed immediately adjacent to the
exposed cable’s point of entrance; for long-term reliability,
ensure that the installation is in a noncorrosive
atmosphere; adequate lighting is very important; when
installed in a metal box, bond the box with a grounding
conductor directly to the protector’s ground; when installed
outside, use cabinets, boxes and mounting hardware
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Telecommunications Circuit
Protectors
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Secondary protectors are typically made from heat
coil, sneak-current fuse, or PTC resistors
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Secondary protectors must coordinate with the lightning
transient and power-fault requirements of primary
protection
For this reason, secondary protectors often include primary
protection device materials, and secondary protection is
usually available as an option on primary protectors
Secondary protectors must handle sneak current
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How Documentation Helps You and
Your Network
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The advantages of keeping documentation:
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It serves as a comprehensive reference
It allows for easier additions, moves, and changes to
equipment and workstations
It can be a valuable source when troubleshooting
It can provide the necessary justification for adding staff or
equipment
It provides proof that the installation meets a
manufacturer’s hardware or software requirements
It makes security management more effective
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Chapter Summary
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All telecommunications systems require grounding and
bonding systems. Several associations provide codes,
standards, and minimum requirements for installing these
systems. ANSI/EIA/TIA-607, “Commercial Building
Grounding and Bonding Requirements for
Telecommunications,” is the primary source of installation
information. The second most important source is the
NEC
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Chapter Summary
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A grounding and bonding network is made up of insulated
copper conductors. These conductors are run in parallel
with the telecommunications cables, and link rooms
containing telecommunications equipment to a common
ground. The recommended size for these conductors
range from No. 6 to No. 3 /0 AWG insulated copper
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Chapter Summary
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These conductors are bonded to solid copper grounding
busbars, which are installed in the entrance facility, the
main telecommunications room, and all other
telecommunications rooms. In addition to the conductors
that run throughout the building, telecommunications
equipment, frames, cabinets, raceways, and protectors
are grounded to the busbars
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Chapter Summary
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The busbars throughout the building are bonded together
with a backbone cable of at least No. 6 AWG insulated
copper. This backbone cable is also connected to the
main grounding busbar, which is bonded to the electrical
service (power) ground and an earth ground
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Chapter Summary
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Telecommunications circuit protectors are used to protect
telecommunications facilities and equipment from
abnormally high voltages and currents. This protection is
in addition to the requirements and recommendations for
grounding and bonding telecommunications systems
Documentation makes your job easier and helps you and
your networks work more efficiently
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