TDMM Chapter 8

Question 1

ac

Answer 1

Alternating Current
A current flow that alternates periodically (usually sinusoidal) in magnitude and direction

Question 2

BBC

Answer 2

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

Question 3

Bonding

Answer 3

The connection intended to safely and effectively equalize the potential differences between two metallic items

Question 4

dc

Answer 4

Direct Current
Current flow that has a constant direction. The letters dc are also used generically to refer to any constant waveform.

Question 5

EMC

Answer 5

Electromagnetic Compatibility
The ability of equipment to function in a manner that makes them immune to certain amounts of electromagnetic interference (EMC) while keeping the interference generated within specific limits

Question 6

EMI

Answer 6

Electromagnetic Interference
Radiated of conducted electromagnetic energy that has an undesirable effect on electronic equipment or signal transmissions

Question 7

GEC

Answer 7

Grounding Earthing Conductor
The conductor used to connect to grounding (earthing) electrode to either the equipment grounding conductor or grounded conductor of the circuit at the service equioment

Question 8

GPR

Answer 8

Ground Potential Rise
A voltage difference between a grounding electrode system and the earth return currents produced by a lighting strike or a power fault current

Question 9

Grounding

Answer 9

The establishment of a reference for the electrical power source, the electrical equipment or both

Question 10

IG

Answer 10

Isolated Ground
An equipment grounding topology that presumably reduces the effects of EMI or RFI on the equipment grounding system

Question 11

Impedance

Answer 11

The total opposition of electrical current in ac circuits or an ac waveform up a dc or ac circuit or conductor

Question 12

Lightning Exposure

Answer 12

An outdoor telecom cables susceptibility to electrical power system faults or to lighting or other transients

Question 13

PBB

Answer 13

Primary Bonding Busbar
The dedicated extension of the building ac grounding electrode system for the telecom infrastructure

Question 14

RFI

Answer 14

Radio Frequency Interference
Electromagnetic interference in the radio frequency spectrum

Question 15

SBB

Answer 15

Secondary Bonding Busbar
The grounding connection point for telecom infrastructure systems and telecom equipment in the area being served by an ER or TR

Question 16

SBG

Answer 16

Supplementary Bonding Grid

Question 17

TBC

Answer 17

Telecom Bonding Conductor
A conductor that connects the telecom bonding infrastructure to the buildings service equipment ground

Question 18

Zone of Protection

Answer 18

Area under a lightning protection system

Question 19

What term describes the establishment of a reference for the electrical power source, the electrical equipment of both?

Answer 19

Grounding

Question 20

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

Answer 20

Bonding

Question 21

What is a foreign electrical voltage or current?

Answer 21

Electrical voltages or currents not normally carried by or expected in telecom systems

Question 22

Name four potential negative consequences of having a foreign voltage or current travel through a telecom system

Answer 22

• Electrical shock
• Destruction of equipment, fire
• Component malfunction
• Work or process distruption

Question 23

Name six factors the ICT designer must consider in designing the telecom bonding infrastructure

Answer 23

• Lightning
• Ground potential rise (GPR)
• Contact with electrical power circuits
• EMI
• RFI
• EMC

Question 24

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

Answer 24

True

Question 25

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

Answer 25

Initial planning and construction phases of a project

Question 26

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

Answer 26

Ask the AHJ to resolve

Question 27

Name the three subsystems that constitute a bonding and grounding system

Answer 27

- ac grounding electrode systems - Equipment grounding system - Telecom bonding infrastructure

Question 28

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

Answer 28

- Establishes a 0V reference for ac electrical power systems

Question 29

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

Answer 29

- Grounding electrode conductor (GEC) - Grounding (earthing) electrode

Question 30

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

Answer 30

The Grounding Electrode Conductor (GEC)

Question 31

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

Answer 31

Grounding Electrode

Question 32

Why does the ICT designer need to identify the type grounding electrode system used?

Answer 32

To make an effective connection

Question 33

Where are telecom busbars installed when when building steel is used as a grounding electrode?

Answer 33

On a steel member within the ER, TR or EF

Question 34

True or False The ICT designer should bond the telecom infrastructure to the buildings metallic pipes

Answer 34

False It is permissable but not recommended

Question 35

Typically, who is responsible for specifying the test criteria for the grounding system?

Answer 35

Qualified Electrical Designer

Question 36

When should the ac grounding electrode system be tested?

Answer 36

After the grounding infrastructure is installed but before final approval of it

Question 37

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

Answer 37

0 A

Question 38

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

Answer 38

Less than 1 A

Question 39

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

Answer 39

Less than 500 mA

Question 40

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

Answer 40

Electrical main individual should be contacted immediately

Question 41

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

Answer 41

Earth grounding resistance tester that is configured for a continuity test

Question 42

What is the recommended bonding resistance between grounding electrode and busbar in the EF?

Answer 42

0.1 ohms

Question 43

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

Answer 43

Less than 0.1 ohms

Question 44

What is the primary purpose of the telecom equipment grounding system?

Answer 44

To keep people safe and reduce fire hazards

Question 45

What is the main component of the telecom equipment grounding system?

Answer 45

Equipment grounding conductor

Question 46

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?

Answer 46

Impedance

Question 47

Name two forces that influence the impedance of an electrically conductive path

Answer 47

- Inductive reactance - Capacitance reactance

Question 48

What are the recommended maximum impedance values for telecom euipment grounding conductors?

Answer 48

1 ohm for 120v and 0.8 ohms for 277v

Question 49

Name three negative consequences that may occur if the impedance exceeds its maximum value

Answer 49

- Equipment operator shock - Equipment or structure fire - Equipment malfunction

Question 50

What instrument is used to measure impedance?

Answer 50

Ground impedance tester

Question 51

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

Answer 51

True

Question 52

What is the benefit of using an isolated ground?

Answer 52

Reduces EM and RFI

Question 53

Name two ways that isolation ground receptacles can be identified

Answer 53

- Solid orange receptacle coloring - Marked with an orange triangle

Question 54

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

Answer 54

May defeat the purpose of an equipotential plane that is desirable in all EF, ER and TRs

Question 55

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

Answer 55

To provide a low impedance path between many cabinets or racks of telecom equipment

Question 56

What is the overall purpose of the telecom bonding infrastructure?

Answer 56

To equalize potentials between metallic surfaces in the event of electrical system faults

Question 57

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

Answer 57

At the PBB

Question 58

Which component serves as the central attachement point for all telecom bonding and grounding connections in a small system?

Answer 58

PBB

Question 59

What are the minimum dimensions for a PBB?

Answer 59

0.25 in thick by 4 in wide

Question 60

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

Answer 60

Surge currents need to be equalized before they penetrate the telecom infrastructure

Question 61

What is the intended purpose of a TBC?

Answer 61

To bond the PBB to the ac grounding electrode system via the ac main service entrance panelboard

Question 62

What is the purpose of an SBB?

Answer 62

To serve the grounding connection point for telecom infrastructure systems

Question 63

What are the minimum dimensions of an SBB?

Answer 63

.025 in thick by 2 in wide

Question 64

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

Answer 64

To equalize the potentials during lighting, electrostatic discharge and EMI conditions

Question 65

What is a TBB?

Answer 65

The TBB is a TBC that is intended to equalize potentials between TRs on mulitple floors or multipe TRs on the same floor

Question 66

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

Answer 66

Impedance increases with the length, which reduces the TBBs ability to equalize potentials between ERs, TRs and EFs

Question 67

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

Answer 67

Specify the SBB in each TR be bonded to the structural steel if present and to the nearest ac electrical panelboard

Question 68

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

Answer 68

Backbone Bonding Conductor (BBC)

Question 69

What is the minimum recommended size for a bonding conductor if its run will not exceed 100ft?

Answer 69

6 AWG

Question 70

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

Answer 70

Divide 40V by the short time rating of the ac GEC

Question 71

Name two typical methods for making bonding connections

Answer 71

- Bolts of crimps - Exothermic welding

Question 72

Name three factors that make it difficult to determine the integrity of a telecom bonding connection

Answer 72

- Distance - Access - Existance of other parallel bonding connections

Question 73

Name four types of problems that can be revealed by visually inspecting a telecom bonding connection

Answer 73

- Loose connections - Corrosion - Physical damage - System modifications

Question 74

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

Answer 74

The conventionable method of bonding across sectional and angle brackets

Question 75

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

Answer 75

Prevents different lengths of conductors within the cable trays become a source of voltage and ultimately amperage due to impedance differences

Question 76

True or False Using direct buried cable eliminates risk of lightning exposure

Answer 76

False

Question 77

Why is electrical power cable routed above aerial cable?

Answer 77

To intercept and divert direct lightning strikes

Question 78

What term is used to describe an outdoor telecom cables susceptibility to electrical power system faults or to lightning or other transients?

Answer 78

Exposure

Question 79

When is telecom cable considered electrically exposed?

Answer 79

When any of its branches or individual circuits are exposed?

Question 80

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

Answer 80

Zone of Protection

Question 81

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

Answer 81

Cone of Protection

Question 82

Name the five factors used to estimate loss due to lightning

Answer 82

- Type of structure - Relative location - Lightning strike consequences - Occupancy - Lightning frequency

Question 83

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

Answer 83

- Consider it exposed - Note as exposed in request for quote response