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MJ Class > Chapter 8 > Flashcards

Chapter 8 Flashcards

1
Q

ac

A

Alternating Current
A current flow that alternates
periodically (usually sinusoidal)
in magnitude and direction.
TDMM.* Page G-7

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2
Q

BBC

A

Backbone Bonding Conductor
A conductor that is intended to
equalize potentials between TRs
on the same floor of a structure
where multiple TBBs are used in
a multi-story building. Formerly
referred to as the grounding
equalizer (GE).
TDMM.* Page 8-20

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3
Q

Bonding

A

The connection intended to
safely and effectively equalize
the potential differences
between two metallic items.
TDMM.* Page 8-1

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4
Q

dc

A

Direct Current
Current flow that has a constant
direction. The letters dc are also
used generically to refer to any
constant waveform or signal
(e.g., a battery voltage of 3 volts
direct current [Vdc]).
TDMM.* Page G-58

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5
Q

EMC

A

Electromagnetic Compatibility
The ability of equipment to
function in a manner that makes
them immune to certain amounts
of electromagnetic interference
(EMI), while keeping the
interference generated by them
within specific limits.
TDMM.* Page G-67

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6
Q

EMI

A

Electromagnetic Interference
Radiated or conducted
electromagnetic energy that has
an undesirable effect on
electronic equipment or signal
transmissions.
TDMM: G-67

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7
Q

GEC

A

Grounding Electrode Conductor
The conductor used to connect the
grounding (earthing) electrode to
either the equipment grounding
(earthing) conductor, or to the
grounded conductor of the circuit
at the service equipment, or at the
source of a separately
derived system.
TDMM.* Page 8-5

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8
Q

GPR

A

Ground Potential Rise
A voltage difference between a
grounding electrode system and
the earth return currents
produced by a lightning strike or
a power fault current.
TDMM: Page G-87

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9
Q

Grounding

A

The establishment of a
reference for the electrical
power source (ac or dc), the
electrical equipment, or both.
TDMM.* Page 8-1

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10
Q

IG

A

Isolated Ground
An equipment grounding
(earthing) topology that
presumably reduces the effects
of EMI and RFI on the equipment
grounding (earthing) system.
TDMM.* Page 8-10

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11
Q

Impedance

A

The total opposition of electrical
current in ac circuits or an ac
waveform imposed upon a dc or
ac circuit or conductor.
TDMM.* Page 8-8

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12
Q

Lightning Exposure

A

An outdoor telecommunications
cable’s susceptibility to
electrical power system faults or
to lightning or other transients.
TDMM.* Page 8-26

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13
Q

PBB

A

Primary Bonding Busbar
The dedicated extension of the
building ac grounding (earthing)
electrode system for the
telecommunications
infrastructure. Formerly referred
to as the telecommunications
main grounding busbar (TMGB).
TDMM.* Page 8-17

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14
Q

RFI

A

Radio Frequency Interference
Electromagnetic interference
(EMI) in the radio frequency (RF)
spectrum. The source may be
any object (artificial or natural)
that carries rapidly changing
electrical currents or generates
RF, such as an electrical
circuit or the sun.
TDMM.* Page G-158

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15
Q

SBB

A

Secondary Bonding Busbar
The grounding (earthing)
connection point for
telecommunications
infrastructure systems and
telecommunications equipment
in the area being served by an
ER or TR. Formerly referred to as
the telecommunications
grounding busbar (TGB).
TDMM.* Page 8-18

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16
Q

SBG

A

Supplementary Bonding Grid
A set of conductors or conductive
elements formed into a grid or
provided as a conductive plate that
becomes part of the bonding
network to which it is
intentionally attached.
TDMM: Page G-788

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17
Q

TBC

A

Telecommunications Bonding
Conductor
A conductor that interconnects the
telecommunications bonding
infrastructure to the building s
service equipment (power) ground.
Formerly referred to as the bonding
conductor for telecommunications
(BCT).
TDMM.* Page G-792

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18
Q

Zone of Protection

A

Area under or nearly under a
lightning protection system.
TDMM.* Page 8-26

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19
Q

What term describes the
establishment of a
reference for the electrical
power source (ac or dc),
the electrical equipment,
or both?

A

Grounding
TDMM.* Page 8-1

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20
Q

What term describes the
connection intended to
safely and effectively
equalize the potential
differences between two
metallic items?

A

Bonding
TDMM.* Page 8-1

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21
Q

What is a “foreign”
electrical voltage
or current?

A

Electrical voltages or currents
that are not normally carried by,
or expected in,
the telecommunications
distribution system
TDMM.* Page 8-2

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22
Q

Name 4 potential negative
consequences of having a
foreign voltage or current
travel through the
telecommunications
distribution system.

A

1 .Death or injury due to electrical
shock
2.Destruction of electronic
equipment and property due to
electrical fire
3.Component malfunction or
degradation
4.Work or process disruption
TDMM.* Page 8-2

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23
Q

Name 6 factors the ICT
designer must consider
when designing the
bonding infrastructure for a
telecommunications
distribution system.

A

1.Lightning
2.Ground potential rise (GPR)
3.Contact with electrical power circuits
4.EMI
5.RFl
6.EMC
TDMM.* Page 8-2

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24
Q

True or False
The ICT designer is not
responsible for engineering
the portions of electrical
system related to ac
electrical ground faults, air
terminal lightning protection
systems, or surge protection.

A

True. The ICT designer is not
responsible for engineering the
portions of electrical system
related to ac electrical ground
faults, air terminal lightning
protection systems, or surge
protection.
TDMM: Page 8-3

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25
Q

When is the best time to
design a bonding,
grounding (earthing), and
protection scheme for
a structure?

A

During the initial planning and
construction phases of a project
TDMM.* Page 8-3

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26
Q

How should the ICT
designer seek to resolve a
conflict between a local
safety code and the
manufacturer’s
requirements?

A

Ask the AHJ to resolve the
conflict before proceeding.
TDMM.* Page 8-3

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27
Q

Name the 3 subsystems
that constitute a bonding
and grounding (earthing)
system.

A

1 .ac grounding electrode
systems
2.Equipment grounding
(earthing) system
3. Telecommunications bonding
infrastructure
TDMM.* Page 8-4

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28
Q

What is the purpose of the
ac grounding (earthing)
electrode system?

A

Establishes a 0 V reference for ac
electrical power systems, whether
utility-provided or customer-derived
Provides a path for the dissipation
of currents due to lightning or
accidental contact with higher-
voltage systems
Provides a path for the dissipation
of electrostatic discharge currents
TDMM.* Page 8-5

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29
Q

Name the 2 main
components of the ac
grounding (earthing)
electrode system.

A

1 .Grounding electrode
conductor (GEC)
2.Grounding (earthing) electrode
TDMM.* Page 8-5

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30
Q

Which component of the ac
system can be used to
connect the grounding
(earthing) electrode the
equipment grounding
(earthing) conductor?

A

The GEC, which can also be
used to connect to the grounded
conductor of the circuit at the
service equipment or at the
source of a separately
derived system
TDMM.* Page 8-5

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31
Q

What device within the ac
grounding (earthing)
electrode system is used to
establish an electrical
connection to the earth?

A

Grounding (earthing) electrode
TDMM.* Page 8-5

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32
Q

Why does the ICT
distribution designer need
to identify the type of ac
grounding (earthing)
electrode system used
for the building’s ac
electrical system?

A

To make an effective bonding
connection for the grounding
(earthing) busbars and other
telecommunications points
within the TRs
TDMM.* Page 8-6

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33
Q

Where are
telecommunications
busbars installed when
building steel is used as a
grounding (earthing)
electrode?

A

On or as close as practicable
to a structural steel member
within the ER, TR, or EF
TDMM.* Page 8-6

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34
Q

True or False
The ICT distribution
designer should bond the
telecommunications
bonding infrastructure to
the building’s metallic
water pipes whenever
possible.

A

False. While it is permissible to
use a building’s metallic water
pipes for bonding, they should
be used with caution.
Maintenance and upgrades are
generally performed with
nonconductive plastic pipes. For
this reason, if used, metallic
water pipes should never be a
single ground (earth) source.
TDMM.* Page 8-6

35
Q

Typically, who is
responsible for specifying
the test criteria for the
verification of the ac
grounding (earthing)
electrode

A

Qualified electrical designer
TDMM.* Page 8-7

36
Q

When should the ac
grounding electrode
be tested?

A

After the cabling and
telecommunications grounding
(earthing) infrastructure are
installed but prior to either the
final approval of the
telecommunications bonding
infrastructure or end-user
telecommunications equipment
installation
TDMM.* Page 8-7

37
Q

What is the best possible
reading for any bonding
conductor when measuring
ac current?

A

0 A
TDMM.* Page 8-7

38
Q

What is the recommended
maximum ac current value
on any bonding conductor?

A

Less than 1 A
TDMM.* Page 8-7

39
Q

What is the recommended
maximum dc current value
on any bonding conductor?

A

Less than 500 mA
TDMM.* Page 8-7

40
Q

What should be done if
testing reveals an
abnormally high ac current
level on a bonding
conductor?

A

A qualified electrical
maintenance individual should
be called immediately.
TDMM.* Page 8-7

41
Q

What type of tester is used
for two-point bonding
measurements?

A

Earth grounding (earthing)
resistance tester that is
configured for a continuity test
TDMM.* Page 8-7

42
Q

What is the recommended
bonding resistance
between the nearest
available grounding
(earthing) electrode and the
busbar in the EF?

A

0.1 ohms (100 milliohms)
TDMM.* Page 8-7

43
Q

What is the acceptable
bonding resistance
between the nearest
available grounding
(earthing) electrode and the
busbar in the EF of a
central office facility?

A

Less than 100 milliohms,
possibly 50 milliohms
TDMM.* Page 8-7

44
Q

What is the primary
purpose of the
telecommunications
equipment grounding
(earthing) system?

A

To enhance personnel safety
and reduce the likelihood of a
fire hazard by facilitating the
operation of overcurrent devices
(circuit breakers)
TDMM.* Page 8-8

45
Q

What is the main
component of the
telecommunications
equipment grounding
(earthing) system?

A

Equipment grounding
(earthing) conductor
TDMM.* Page 8-8

46
Q

What term is used to
describe the total
opposition of electrical
current in ac circuits or an
ac waveform imposed on a
dc or ac circuit or
conductor?

A

Impedance
TDMM: Page 8-8

47
Q

Name 2 forces that
influence the impedance
of an electrically
conductive path.

A

1 .lnductive reactance
2.Capacitive reactance
TDMM.* Page 8-8

48
Q

What are the
recommended maximum
impedance values for
telecommunications
equipment grounding
(earthing) conductors in the
United States?

A

1 ohm for ac circuits of 120 V
to ground and 0.8 ohms
for 277 V to ground
TDMM: Page 8-9

49
Q

Name 3 negative
consequences that may
occur if the impedance of
an ac electrical circuit
exceeds its recommended
maximum value.

A

1 .Equipment operator could be
exposed to a prolonged
electrical shock, which may be
fatal.
2. The equipment or structure
could catch on fire.
3.Equipment may malfunction
repeatedly.
TDMM: Page 8-9

50
Q

What instrument is used to
measure the impedance of
the telecommunications
equipment grounding
(earthing) conductor?

A

Ground impedance tester
TDMM: Page 8-9

51
Q

True or False
Most ground impedance
testers can be used to
uncover improper wiring
conditions.

A

True. Test personnel can use
most ground impedance testers
to uncover most improper
wiring conditions.
TDMM.* Page 8-9

52
Q

What is the presumed
benefit of using an
isolated ground?

A

Reduces the effects of EMI and
RFI on the equipment grounding
(earthing) system)
TDMM.* Page 8-10

53
Q

Name 2 ways that isolation
ground receptacles
can be identified.

A

1 .With a solid orange receptacle
coloring
2.With a beige receptacle
coloring marked with an orange
triangle on the face
TDMM.* Page 8-70

54
Q

An IG system is NOT
recommended for use for
in customer premises voice
and data systems. Why?

A

Because its use may defeat the
purpose of an equipotential
plane that is desired for all EFs,
ERs, and TRs
TDMM.* Page 8-10

55
Q

What is the purpose of a
supplementary bonding
grid (SBG)?

A

To provide a low-impedance
path between many cabinets or
racks of telecommunications
equipment
TDMM.* Page 8-70

56
Q

What is the overall purpose
of the telecommunications
bonding infrastructure?

A

To equalize potentials between
metallic surfaces predominantly
in the event of lightning, ac
electrical system faults,
electromagnetic induction, or
electrostatic discharge
TDMM.* Page 8-12

57
Q

Where do
telecommunications
bonding and grounding
begin in a small ER or EF?

A

At the PBB
TDMM.* Page 8-13

58
Q

Which component serves
as the central attachment
point for all
telecommunications
bonding and grounding
(earthing) connections in a
small system?

A

PBB
TDMM.* Page 8-13

59
Q

What are the minimum
dimensions of a PBB?

A

=6.3 mm (0.25 in) thick by
-101.6 mm (4 in) wide,
and variable in length
TDMM.* Page 8-17

60
Q

Why should the PBB be
located as near as possible
to the telecommunications
cable EF?

A

Because surge currents need
to be equalized before
they penetrate the
telecommunications
infrastructure
TDMM.* Page 8-17

61
Q

What is the intended
purpose of a TBC?

A

To bond the PBB to the ac
grounding (earthing) electrode
system via the ac main service
entrance panelboard
TDMM.* Page 8-17

62
Q

What is the purpose
of an SBB?

A

To serve as the grounding
(earthing) connection point for
telecommunications
infrastructure systems and
telecommunications equipment
in the area served by an ER or TR
TDMM.* Page 8-18

63
Q

What are the minimum
dimensions of an SBB?

A

=6.3 mm (0.25 in) thick by
mm (2 in) wide,
and variable in length
TDMM.* Page 8-18

64
Q

Why should the SBB be
referenced to the
telecommunications
ground terminal of the
nearest ac electrical
panelboard?

A

To equalize the potentials
during lightning, electrostatic
discharge, and EMI conditions
TDMM.* 8-19

65
Q

What is a TBB?

A

The TBB is a TBC that is
intended to equalize potentials
between TRs on multiple floors
or multiples TRs on the same
floor of a building with an
ultimate connection to
the EF’s PBB.
TDMM.* Page 8-79

66
Q

What is the relationship
between impedance and
length of a TBB?

A

Impedance increases with the
length, which reduces the TBB’s
ability to equalize potentials
between ERs, TRs, TEs, and EFs.
TDMM.* Page 8-79

67
Q

What is an alternative
method to using a TBB in
the system for a large site?

A

Specify that the SBB in each TR
be bonded to the structural steel
if present and to the nearest ac
electrical panelboard.
TDMM.* Page 8-79

68
Q

Which component is
intended to equalize
potentials between TRs
on the same floor
of a structure where
multiple TBBs are used?

A

Backbone bonding conductor
(BBC)
TDMM.* Page 8-20

69
Q

What is the minimum
recommended size for a
bonding conductor if its run
will not exceed
-30.5 m (100 ft)?

A

6 AWG
TDMM.* Page 8-20

70
Q

How is the maximum
resistance value for a
conductor length
calculated?

A

By dividing 40 V by the short-
time rating of the ac GEC
TDMM.* Page 8-21

71
Q

Name 2 typical methods
for making bonding
connections.

A

1 .Bolts or crimps
2.Exothermic welding
TDMM.* Page 8-22

72
Q

Name 3 factors that make
it difficult to determine
the integrity of a
telecommunications
bonding connection.

A

1 .Distance
2.Access
3.Existence of other parallel
bonding connections
TDMM.* Page 8-23

73
Q

Name 4 types of problems
that can be revealed by
visually inspecting a
telecommunications
bonding connection.

A

1 .Loose connections
2. Corrosion
3. Physical damage
4. System modifications
TDMM.* Page 8-23

74
Q

What type of bonding
method may be useful for
cable trays when the
mechanical integrity of the
connection is
questionable?

A

The conventional method of
bonding across sectional and
angle brackets
TDMM.* Page 8-25

75
Q

Why should the use of
home runs of
telecommunications
bonding conductors within
cable trays be avoided?

A

To prevent varying lengths of
telecommunications bonding
conductors within the cable
trays from becoming a source of
voltage and, ultimately,
amperage due to impedance
differences
TDMM.* Page 8-25

76
Q

True or False
Using direct-buried cable
eliminates risk of
(lightning) exposure.

A

False. In general, a choice of
direct-buried cable does not
eliminate exposure.
TDMM.* Page 8-26

77
Q

Why is electrical power
cable routed above
aerial cable?

A

To intercept and divert direct
lightning strikes
TDMM.* Page 8-26

78
Q

What term is used to
describe an outdoor
telecommunications
cable’s susceptibility to
electrical power system
faults or to lightning or
other transients?

A

Exposure
TDMM.* Page 8-26

79
Q

When is telecommunications
cable considered electrically
exposed?

A

When any of its branches or
individual circuits are exposed
TDMM.* Page 8-26

80
Q

What term is used to
describe the area under or
nearly under a lightning
protection system?

A

Zone of protection
TDMM.* Page 8-26

81
Q

What term is used to refer
to a simplified zone
of protection?

A

Cone of protection
TDMM.* Page 8-26

82
Q

Name the 5 factors used to
estimate loss due to lightning
(as listed in NFPA 780).

A

1 . Type of structure & construction
2.Relative location
3.Lightning strike consequences
4.Occupancy & contents
5.Lightning frequency
TDMM.* Page 8-27

83
Q

What steps should the ICT
distribution designer take
when cable exposure
is in question?

A

*Consider it exposed.
Note it as exposed in the
request for quote response.
TDMM. Page 8-28

MJ Class (22 decks)

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