International Telecommunication Union
Technical Session, ProtectionBuenos Aires, 12/04/2010
ITU-T Study Group 05
EarthingEarthing and bondingand bonding
Claude Monney
Switzerland
ITU-TStudy Group 05
Introduction
Earthing and especially bonding are the pre-
requisite for the protection of equipments. It
insures that no dangerous voltages (both for the
equipment and for people) appear between ports.
TECHNICAL SESSION – PROTECTION - BUENOS AIRES 12.04.2010
ITU-TStudy Group 05
Relationship between earthing, bonding and surges
ELP: external lightning protection
Conducteddisturbances
Radiateddisturbances
Earthpotential rise
ELP
EN
MBN SPD
SPD: surge protection devices
EN: earthing network
MBN : Mesh bonding
network
TECHNICAL SESSION – PROTECTION - BUENOS AIRES 12.04.2010
ITU-TStudy Group 05
Relevant Recommendations
K.27: Bonding configurations and earthing
inside a telecommunication building
(1996)
K.35: Bonding configurations and earthing at
remote electronic sites (1996)
K.56: Protection of radio base stations against
lightning discharges (2010)
K.66: Protection of customer premises from
overvoltages (2004)
Earthing and Bonding handbook (2003)
IEC 60364-4-44: Protection against voltage
disturbances and electromagnetic
disturbances (2007)TECHNICAL SESSION – PROTECTION - BUENOS AIRES 12.04.2010
ITU-TStudy Group 05
Differences between earthing and bonding
Though both terms are commonly used together,
a clear distinction should be done
Bonding: Electrical connection putting
various exposed conductive parts and extraneous
conductive parts at a substantially equal potential.
Earthing: Connecting the bonding network
or bonding conductor to an earth electrode to
provide a defined path for the current flow and
reduce potential differences
TECHNICAL SESSION – PROTECTION - BUENOS AIRES 12.04.2010
ITU-TStudy Group 05
PE
T0506060-92/d05
L1 L2 L3 N PE
PE
Floor
Support column of the building
Reinforcement
Bonding ring conductorSystem block 1
Mesh-BN equipment
Interconnection
Bonding mat
Interconnected
reinforcement
Mesh-BN
equipment
48 V dc
service panel
Frame of dc
powerplant
Plumbing
Aircon
AC distribution
System block 2
mesh-BN equipment
Main earthing terminal
To foundation
reinforcement/ring
conductor
To earth
electrode
Telecom
cables
Basement
Lower floor
Floor n
Floor n+1
DC return conductor (+48 V)
Interconnected reinforcement
and building steel
Intra-system cabling
Shielded inter-system cabling
Bonding conductor
FIGURE B.1/K.27
Mesh-BN installation inside a telecommunication building
Bonding ring conductor
(recommended)
Connection of cable shield
to the rack is recommendedDifferences between earthing and bonding Bonding network
Bonding conductor
Earthing conductor
TECHNICAL SESSION – PROTECTION - BUENOS AIRES 12.04.2010
ITU-TStudy Group 05
Bonding networks
• Bonding is key to survive to overvoltages and overcurrents
• As shown in the film, earthing is secondary.
There are mainly 2 bonding networks’ families
oIn addition, one can either link all connections together or
isolate them from the structure
T0506760-95/d01
Star topology Mesh topology
Rack, equipment, module
Bonding conductor
FIGURE 1/K.27
Bonding network configurations forming a system block
TECHNICAL SESSION – PROTECTION - BUENOS AIRES 12.04.2010
ITU-TStudy Group 05
Bonding networks
Not applicable
Star -IBN Mesh-IBNSPCWSPCW
may be ofzero length
Mesh-BN
BN
CBN
IBN
SPCW
Bonding Network
Common Bonding Network
Isolated Bonding Network
Single Point Connection Window
Multip
le p
oin
tS
ingle
poin
t
Star configuration Mesh configuration
Rack, equipment, module, etc.
Bonding conductor
Nearby elements of CBN
Connection to CBN
Inte
gra
tion o
f th
e B
N into
the C
BN
FIGURE 2/K.27
Connection of system block to the CBN
Preferred
solution
TECHNICAL SESSION – PROTECTION - BUENOS AIRES 12.04.2010
ITU-TStudy Group 05
Maintenance of bonding networks
o Small changes that occur in the CBN generally have only
a small effect on its shielding capability.
o Additional shielding may be obtained by introduction of
additional conductors (e.g. bonding conductors, cable
trays, and conduit). Such modifications are usually
straightforward.
o IBN systems are more difficult to maintain, because
craft-person activity is liable to result in inadvertent
interconnections between IBN and CBN, violating the
desired single point connection, and introducing surge
currents into the IBN.
o It is recommended that systematic verification be
performed on all bonding configurations and earthing
connections inside a telecommunications building.
TECHNICAL SESSION – PROTECTION - BUENOS AIRES 12.04.2010
ITU-TStudy Group 05
AC power distribution
o From an EMC perspective, TN-S systems should
be preferred
T0506990-96/d01
PE DC-return
Main earthing terminal
Earthing network
PEPE
PEN
N
Output to indoor
mains installation (TN-S)
N
N
PEPE
PE DC-return
Main earthing terminal
Earthing network
N
N
PEPE
PE DC-return
Main earthing terminal
Earthing network
PE
Mode 1: TN-S/TN-S
ring conductor
Input from outdoor
mains distribution (TN-S)
NOTE – Mode 1 is obligatory if a separation transformer is dedicated to the building and the
TN-S system consequently originates at the transformer load side.
Mode 2: TN-C/TN-S
Output to indoor
mains installation (TN-S)
Input from outdoormains distribution (TN-C)
ring conductor
Mode 3: IT/IT or TT/TT
Output to indoor
mains installation (IT or TT)
Input from outdoor
mains distribution (IT or TT)
ring conductor
Outd
oor
main
s d
istr
ibution
Outd
oor
main
s d
istr
ibutio
nO
utd
oor
main
s d
istr
ibution
FIGURE 1/K.35
Arrangements for the transition from the outdoor mains distributionnetwork to the indoor mains
TECHNICAL SESSION – PROTECTION - BUENOS AIRES 12.04.2010
ITU-TStudy Group 05
TN-S inside the building
TECHNICAL SESSION – PROTECTION - BUENOS AIRES 12.04.2010
Bonding at
floor level
reduces
potential differences
ITU-TStudy Group 05
Earthing
The main functions of earthing are:
• Provide a safe path to the flow of surge current to
earth (e.g., from lightning)
• Reduce the current and voltage propagating along a
transmission line (e.g., a telecom cable)
• Reduce the voltage between the telecom line and
local earth
• Provide sufficient current for the tripping of circuit
breakers in case of a power to earth fault.
TECHNICAL SESSION – PROTECTION - BUENOS AIRES 12.04.2010
ITU-TStudy Group 05
Earthing
2) Ring electrode
3) Vertical rod
1) Armoured concrete
In the preference order
TECHNICAL SESSION – PROTECTION - BUENOS AIRES 12.04.2010
ITU-TStudy Group 05
Example for a small telecom center
2
3
T0507380-96/d02
1 1
Ring
bonding- bus
Equipment
frame
To earthing network
a.c. service
enclosure
Main
earthing
terminal
Earthing network
Supplementary
bonding-bus
1 Earthing conductor
2 Equipment bonding conductor
3 Protective conductor
FIGURE I.1/K.35
Example of bonding configurations and earthing of EEEs by use of ring bonding-bus12.04.2010 TECHNICAL SESSION – PROTECTION - BUENOS AIRES
ITU-TStudy Group 05
Example for a base station
12.04.2010 TECHNICAL SESSION – PROTECTION - BUENOS AIRES
ITU-TStudy Group 05
Example for a base station
12.04.2010 TECHNICAL SESSION – PROTECTION - BUENOS AIRES
ITU-TStudy Group 05
Example for a base station
12.04.2010 TECHNICAL SESSION – PROTECTION - BUENOS AIRES
ITU-TStudy Group 05
Overvoltage protection
o It isn’t possible to integrate live
conductors into the bonding network
o In order to limit the overvoltage to a
defined level, surge protection
devices are required
TECHNICAL SESSION – PROTECTION - BUENOS AIRES 12.04.2010