Week 19 Chapter 9 Part 2 - Pages 9-36 to 9-80

Question 1

In a _____ direct current (dc) distribution topology, power is directed from the switchboard to a secondary distribution bay before going to the load(s).

a. Centralized
b. Distributed
c. Decentralized
d. Structured

Answer 1

c. Decentralized

9-53

Under Switchboard Section: The two types of power board distribution are:
• Centralized (distribution goes to the loads directly from the power board)
• Decentralized (dc power is distributed to a secondary distribution bay and is distributed from the secondary bay to the loads)

Question 2

To fully recharge a lead-acid battery, because of chemical losses within the battery, ___ percent more energy (power) must be returned to the battery than has been removed during discharge.

a. 10
b. 20
c. 30
d. 40

Answer 2

a. 10

p 9-55

To fully recharge a lead-acid battery, because of chemical losses within the battery, 10 percent more energy (power) must be returned to the battery than has been removed during discharge. NiCd batteries require 40 percent more energy return.

Question 3

Gelled electrolyte cells are classified as ___

a. Alkaline
b. Flooded lead-acid
c. Valve-regulated lead-acid
d. Wet

Answer 3

c. Valve-regulated lead-acid

p 9-63

Battery cells used for telecommunications applications include:
• Alkaline
• Vented lead-acid (VLA), which is also known as flooded lead-acid (FLA)
• Valve regulated lead-acid (VRLA). Gelled electrolyte cells are part of this classification

Question 4

The use of more than _____ parallel cells in a battery plant is not recommended because of the possibility of unequal charging.

a. 3
b. 4
c. 5
d. 6

Answer 4

c. 5

p 9-69

The use of more than five parallel cells in a battery plant is not recommended. Imbalance problems that lead to unequal charging of the individual strings may be caused by:
• Differences in the resistance of the paralleling connectors.
• Different resistances of each string of cells (i.e., differing cell internal resistance and intercell connector resistance).

Question 5

The transfer time associated with a static transfer switch (STS) is typically one:

a. Millisecond
b. One cycle
c. Quarter cycle
d. Half of a cycle

Answer 5

c. Quarter cycle

p 9-50

STSs are devices that can transfer electrical loads between two synchronized power sources in a break before making (open transition) transfer in a fraction of a second, typically one quarter of a cycle.

Question 6

For telecommunications, the nominal (dc) operating voltage in the United States is negative ___ V. It is referred to as negative because the positive side of the system is intentionally grounded.

a. 2
b. 12
c. 24
d. 48

Answer 6

d. 48

p 9-52

It is referred to as negative because the positive side of the system is intentionally grounded. There are also numerous pieces of ICT equipment that operate at positive 12 VDC.

For cellular radio, the nominal operating voltage is positive 24 V. It is referred to as positive because the negative side is intentionally grounded.

Question 7

Battery protection devices should be capable of interrupting short circuit current, which is approximately _____ times the rated ampere-hour (AH) capacity of the battery.

a. 2
b. 7
c. 10
d. 11

Answer 7

c. 10

p 9-71

Protection devices should be capable of interrupting the battery’s short circuit current, which is approximately 10 times the rated AH capacity.

Question 8

___ are used to reduce voltage waveform distortion that affects sensitive electronic equipment.

a. Voltage regulators
b. Harmonic filters
c. Isolation transformers
d. Power line conditioners
e. Harmonic mitigating transformer

Answer 8

b. Harmonic filters

p 9-38

Harmonic filters are used to reduce voltage waveform distortion that affects sensitive electronic equipment. These filters screen out harmonics and high-frequency noise. Some of the better surge protecting devices, voltage regulators, and power line conditioners include harmonic filters.

Question 9

A ___ may be appropriate where harmonics are found to be a concern within the electrical system based on load make up or actual field measurements in an existing system.

a. Voltage regulators
b. Harmonic filters
c. Isolation transformers
d. Power line conditioners
e. Harmonic mitigating transformer

Answer 9

e. Harmonic mitigating transformer

p 9-37

Harmonic mitigating transformers come in a variety of configurations and are usually tailored to the application. They utilize winding connection and phase shifting techniques internal to the transformer to reduce harmonic content and their effects on the electrical system.

These transformers eliminate the need for 200 percent neutrals, K-rated transformers, and other costly oversizing design techniques built into the electrical system.

Question 10

The online double-conversion UPS is the most frequent type of UPS system used in ITS design and construction.

a. True
b. False

Answer 10

a. True

p 9-41

Online double-conversion UPS units exist in different designs, and each has its own unique advantages and disadvantages. The online double-conversion UPS is the most frequent type of UPS system used in ICT design and construction.

Question 11

___ or passive standby UPS units are devices that power the load directly from the utility and only provide backup power when the utility power goes below preset tolerances.

a. Off-line
b. Line-interactive
c. Online double-conversion

Answer 11

a. Off-line

p 9-40

Off-line or passive standby UPS units provide limited line conditioning. It is not recommended that standby power systems be used to support critical communications loads

Question 12

___ UPS units are basically off-line UPS units with line conditioning included. Electronic or magnetic energy storage is used to sustain the load during transfer to inverter.

a. Off-line
b. Line-interactive
c. Online double-conversion

Answer 12

b. Line-interactive

p 9-41

These units work well in most circumstances, but they have the following limitations:
• There is no frequency regulation.
• Battery reserve time and recharge time may be limited.
• Some may not be suitable for use with generators.
• The isolation of power source to load in a line- interactive UPS unit is not as good as in an online double conversion UPS unit.

Question 13

All lead-acid battery cells require the addition of water to the electrolyte at regular intervals in order to maintain a minimum level.

a. True
b. False

Answer 13

b. False

p 9-64

VRLA cells have vent or pressure-relief (regulator) valves, and addition of water to the electrolyte is not required.
The NEC states that “A sealed cell or battery is one that has no provision for the addition of water or electrolyte or for external measurement of electrolyte specific gravity.

Question 14

A remote power panel (RPP) has ___ at the desired voltage to a grouping of ___.

a. Multiple feeders; transformers
b. Multiple feeders; panelboards
c. A single feeder; transformers
d. A single feeder; panelboards

Answer 14

d. A single feeder; panelboards

p 9-27

RPPs are basically PDUs without transformers. An RPP has a single feeder at the desired voltage to a grouping of panelboards and also typically has the surge suppression to protect the equipment.

Question 15

Additional cost and space requirements are two disadvantages of a(n) _____ redundant multi-module UPS topology since the backup UPS is not normally used to power the critical load.

a. Isolated
b. Parallel
c. Distributed
d. Series

Answer 15

a. Isolated

p 9-45

Multiple isolated redundant UPS systems can be deployed together if necessary. One drawback of an isolated redundant system is that the backup UPS is not normally used to drive the critical load, so it is a costly and space-consuming system (see Figure 9.21).

Question 16

Valve-regulated lead-acid (VRLA) battery cells typically have capacities up to _____ ampere-hours (AH).

a. 1000
b. 2000
c. 3000
d. 4000

Answer 16

c. 3000

p 9-65

Valve-regulated cells are typically available with a 3-20 year life range with capacities up to about 3000 AH. The shorter life cells are somewhat limited in their capacities.

Question 17

___ generators are generally used with automatic transfer switches to provide power during extended outages.

a. Battery-powered
b. Online
c. Engine
d. Motor

Answer 17

c. Engine

p 9-39

Engine generators are generally used with automatic transfer switches to provide power during extended outages.

However, there is a time delay between the power failure and engine generator start-up. An engine generator does not provide any conditioning or protection when not running.

Question 18

For a lead-acid cell this is a nominal ___ V, and for an alkaline cell, ___ V.

a. 1.2, 2
b. 2, 12
c. 2, 1.2
d. 12, 2

Answer 18

c. 2, 1.2

p 9-62

The voltage depends on the plate material and type of electrolyte. For a lead-acid cell this is a nominal 2 V, and for an alkaline cell, 1.2 V

Question 19

In a battery plant, cells are connected in ___ to increase voltage.

a. Series
b. Parallel

Answer 19

a. Series

p 9-62

Cells are connected in series to increase voltage.

The capacity of a cell depends on the size and quantity of cell plates. Cells can be connected in PARALLEL to increase battery capacity.

Question 20

VRLA batteries will typically have a lifespan that is ___ of what is expected.

a. One quarter
b. One half
c. Three quarter

Answer 20

b. One half

p 9-65

It should be noted that expected battery life is based on ideal conditions. Since these seldom occur in real world applications, VRLA batteries will typically have a lifespan that is half of what is expected.

Therefore, a 10-year design will typically only last four or five years. Wet cell batteries will have a longer life expectancy than VRLA batteries.

Question 21

The life of a battery can be decreased by as much as ___ percent for each 10 °C (50 °F) above the optimum operating temperature.

a. 10
b. 20
c. 40
d. 50

Answer 21

d. 50

p 9-69

Question 22

Unlike a parallel redundant systems, the ___ UPS system contains its own static bypass transfer switches.

a. Isolated
b. Distributed
c. Communications link
d. Ring

Answer 22

c. Communications link

p 9-46

Also, unlike parallel redundant systems, each UPS unit contains its own static bypass transfer switches and control units so a unit failure cannot take down the entire system.

Question 23

When calculating the load on a UPS, the ICT distribution designer should prepare the calculations using kilo ___

a. Watts
b. Volt-amperes

Answer 23

a. Watts

p 9-47

When calculating the load on a UPS, the ICT distribution designer should prepare the calculations using kilowatts, not kilovolt-amperes. If it is not possible to determine kilowatts, the ICT distribution designer should assume that the load is in kilowatts.

Question 24

Battery cell sizing uses amperes as the unit of measure for reserve times that are:

a. Two hours or more
b. Less than two hours
c. One hour or more
d. Less than one hour

Answer 24

c. One hour or more

p 9-68

Sizing in amperes is usually done when reserve times of one hour and above are involved. Follow the steps below for battery cell sizing in amperes.

Sizing in watts uses the load kilowatt figure. This is typically used for reserve times of less than an hour since the manufacturer typically presents data for short reserve times in that format (e.g., watts per cell, at a certain temperature, discharged to a certain voltage).

Question 25

When designing the switchboard in a direct current (dc) power system, the grounded termination busbar (dc return busbar) _____ isolated from the metal frame of the switchboard.

a. Must never be
b. Should be

Answer 25

b. Should be

p 9-60

Isolate the grounded termination busbar (the dc return busbar) from the metal frame of the switchboard. In a negative 48 V system, this is the positive busbar; for a positive 24 V system, this is the negative busbar. However, this busbar must be grounded at the main grounding (earthing) busbar.

Question 26

A(n) _____ UPS topology consists of multiple single module, parallel redundant, or isolated redundant UPS systems connected to two or more distribution paths.

a. Ring bus
b. Communications link
c. Distributed redundant
d. Isolated redundant
e. Parallel redundant

Answer 26

c. Distributed redundant

p 9-46

Question 27

A single generator system (N) consists of one generator adequately sized to handle the critical load where redundancy is not a requirement. This configuration is typically found in ___ electrical systems and most commonly used as a backup for building emergency and standby loads.

a. Class 1, Class 2, and Class 3
b. Class 1 and Class 2
c. Class 2
d. Class 1

Answer 27

c. Class 2

p 9-40

A single generator system (N) consists of one generator adequately sized to handle the critical load where redundancy is not a requirement. This configuration is typically found in Class 2 electrical systems and most commonly used as a backup for building emergency and standby loads.

Question 28

A static transfer switch (STS) transfers an electrical load between two synchronized power sources in a _____ transfer.

a. Make before break (closed transition)
b. Break before make (open transition)

Answer 28

b. Break before make (open transition)

p 9-50

STSs are devices that can transfer electrical loads between two synchronized power sources in a break before making (open transition) transfer in a fraction of a second, typically one quarter of a cycle.

Question 29

“A protective device for limiting transient voltages by diverting or limiting surge current” is the definition found in the National Electrical Code (NEC) for a transient voltage surge:

a. Protector
b. Diverter
c. Suppressor
d. Arrester

Answer 29

c. Suppressor

p 9-37

SPDs (also called surge arresters and transient voltage surge suppressors) limit, clamp, or divert surges and transients. The NEC defines a surge arrester as “a protective device for limiting surge voltages by discharging or bypassing surge current.”

Question 30

Line-interactive UPS units work well in most circumstances, some may not be suitable for use with generators.

a. True
b. False

Answer 30

a. True

p 9-41

These units work well in most circumstances, but they have the following limitations:
• There is no frequency regulation.
• Battery reserve time and recharge time may be limited.
• Some may not be suitable for use with generators.
• The isolation of power source to load in a line-interactive UPS unit is not as good as in an online double conversion UPS unit.

Question 31

When designing cable runs for a direct current (dc) power system, the bending radius must not be less than _____ times the overall diameter for unshielded power cables.

a. Ten
b. Eight
c. Six
d. Four

Answer 31

b. Eight

p 9-62

Design the cable routes or bus ducts so that tight or excessive bends are avoided. The bending radius must not be less than eight times the overall diameter for unshielded power cable

Question 32

An isolation transformer has a limited ability to prevent _____ noise.

a. Differential mode
b. Line-to-ground
c. Normal mode
d. Common mode

Answer 32

c. Normal mode

p 9-36

This transformer is effective in rejecting common-mode (line-to-ground) noise when the secondary neutral is bonded to ground (earth), but it has a limited ability to prevent normal mode (line-to-line) noise.

Question 33

Isolation transformers are typically used for general purpose loads in cases where the non-linear load is less than _____ percent of the total connected

a. 50
b. 40
c. 30
d. 20

Answer 33

d. 20

p 9-36

Isolation transformers are typically used for general purpose loads where the nonlinear load is less than 20 percent of the total connected load.

Question 34

The _____ concept for the installation of surge suppressors places surge protective devices (SPDs) at the service entrance panel, distribution panelboard, branch circuit panelboard, and the outlet serving the load.

a. “Distributed”
b. “Tier”
c. “Level”
d. “Stage”

Answer 34

d. “Stage”

p 9-37

The “stage” concept for installation of surge suppressors is recommended. This involves installing an SPD at the:
• Service entrance panel as a service protector.
• Distribution panelboard level.
• Branch circuit panelboard level.

Question 35

With regards to redundancy or reliability, a paralleled generator system topology can be implemented in any one of the Class configurations.

a. True
b. False

Answer 35

a. True

p 9-40

Paralleled generator systems can be implemented in any one of the Class configurations. This method utilizes multiple smaller generators where the outputs of each are synchronized, allowing them to be connected to the electrical system in parallel.

Question 36

In order to calculate the direct current (dc) watts required to obtain battery cell sizing for an inverter, divide the alternating current (ac) watts by:

a. The average discharge current in amperes
b. 0.707 volts
c. The power factor
d. The inverter’s efficiency value

Answer 36

d. The inverter’s efficiency value

p 9-67

Question 37

In a direct current (dc) power system, the rectifier/chargers are primarily _____ voltage systems.

a. Variable
b. Constant

Answer 37

b. Constant

p 9-53

Rectifier/chargers are primarily constant voltage systems because they supply current on demand to the load and battery at a constant voltage

Question 38

Calculations for DC loads are generally expressed in:

a. Amperes
b. Volts
c. Voltage amperes (VA)
d. Watts

Answer 38

a. Amperes

p 9-55

Calculations for dc loads are typically expressed in dc amperes since rectifier/chargers are sized in amperes. If watts are provided, divide by the nominal operating voltage to obtain amperes.

Question 39

You have been asked to provide a N+1 level of power redundancy in the new equipment room (ER) being designed with a Class-II power supply. What should you do?

a. Provide a UPS that serves all of the equipment in the facility.
b. Provide two separate UPS units with an automatic power failure transfer to serve entire facility.
c. Provide two separate UPS units with each one serving half the equipment in the facility.
d. Provide two separate UPS systems with one serving the entire facility and the second on automatic power failure transfer to serve critical circuits only.

Answer 39

b. Provide two separate UPS units with an automatic power failure transfer to serve entire facility.

Question 40

You have discovered a common mode current on the metallic cable sheaths of your building riser cables. What is the MOST likely cause for you to investigate?

a. Lack of cable protection
b. Two separate and distinct ground references
c. Improper secondary protection
d. Improper physical protection of cable

Answer 40

b. Two separate and distinct ground references

Question 41

A common mode (CM) signal can be converted to a differential mode (DM) signal as a result of a(n):

a. Unbalanced circuit
b. Grounded circuit
c. Poorly timed signal
d. Improper dielectric material

Answer 41

a. Unbalanced circuit

Question 42

Many UPS are designed to accommodate only slightly ___ loads and, therefore, must be derated to drive ___ loads.

a. inductive, capacitive
b. capacitive, inductive

Answer 42

a. inductive, capacitive

p 9-48

Many UPS are designed to accommodate only slightly inductive loads and, therefore, must be derated to drive capacitive loads.