CSP, Lvl 6- Lessons 4,5,7,8

Question 1

The scope of Article 450 indicates that this article covers the installation of all transformers. There are ? exceptions that modify this Article 450 scope statement.

Answer 1

8

Question 2

why would Overcurrent protective devices on a transformer primary may require increased sizing?

Answer 2

due to the magnetizing inrush current.

Question 3

Primary inrush current characteristics can vary by?

Answer 3

transformer design

Question 4

What section of Article 450 details the basic ampere rating sizing requirements for overcurrent protection of transformers?

Answer 4

450.3

Question 5

The two tables of concern for transformer protection are ?

Answer 5

Table 450.3(A) for transformers over 1,000 volts, nominal and Table 450.3(B) for transformers 1,000 volts or less.

Question 6

When increased sizing of the overcurrent protective device is utilized on the primary side of a transformer, overcurrent protection on the secondary side, sized closer to the load, is typically?

Answer 6

Required

Question 7

When determining the overcurrent protection requirements for transformers in a circuit, other requirements from Article(s) ? may also need to be investigated.

Answer 7

230
240
408

Question 8

Table 450.3(A) provides provisions for both?

Answer 8

“any location” and “supervised locations only.”

Question 9

For the purposes of the application of Table 450.3(A), a “supervised location” is a location where?

Answer 9

conditions of maintenance and supervision ensure that only qualified persons monitor and service the transformer installation.

Question 10

Study math for questions 12-22, lesson 4

Answer 10

Study math for questions 12-22, lesson 4

Question 11

A transformer supplying a fire pump is not permitted to have?

Answer 11

secondary overcurrent protection.

Question 12

The transformer primary overcurrent protective device supplying a fire pump must be rated to carry the sum of the locked-rotor current of the fire and pressure pump motors plus ?

Answer 12

the full-load current of the accessory equipment.

Question 13

For transformers covered by the scope of Article 450, the nameplate must provide which of the following that are vital information for calculating the available fault current on the transformer secondary?

Answer 13

-Impedance of transformers 25 kVA and larger
-kVA
-Primary and secondary voltage

Question 14

NEC ? covers interrupting rating requirements for equipment.

Answer 14

110.9

Question 15

study questions 2, 8, 12- 20. lesson 5

Answer 15

study questions 2, 8, 12- 20. lesson 5

Question 16

A fully rated system is one in which all of the overcurrent protective devices have an individual interrupting rating at least as great as the ?

Answer 16

available fault current at their point of application.

Question 17

Only fully rated systems may be able to be?.

Answer 17

selectively coordinated.

Question 18

A series rated system consists of a ? that can be applied at a point in the system where the available fault current is greater than the interrupting rating of the load-side circuit breaker, but not greater than that of the main or line-side device.

Answer 18

circuit breaker and a circuit breaker

fuse and a circuit breaker

Question 19

If a series-rated fuse/circuit breaker combination indicates a maximum 400-ampere Class J fuse is required?

Answer 19

any manufacturer’s fuse that is listed as UL Class J with 400 amperes or less can be used.

Question 20

There are many requirements and limitations for series rated systems, but only one advantage:

Answer 20

lower installed cost.

Question 21

Series rated systems can cause problems or limitations with future ?

Answer 21

expansions, upgrades, or system integrity.

Question 22

The NEC defines ? as “localization of an overcurrent condition to restrict outages to the circuit or equipment affected, accomplished by the selection and installation of overcurrent protective devices and their ratings or settings for the full range of available overcurrents, from overload to the available fault current, and for the full range of overcurrent protective device opening times associated with those overcurrents.”

Answer 22

Coordination, Selective

Question 23

If a system is not selectively coordinated, unnecessary power loss can occur to loads that otherwise should be?

Answer 23

unaffected.

Question 24

The vertical axis of a time-current curve represents the ? .

Answer 24

time in seconds

Question 25

The horizontal axis of a time-current curve represents the ? .

Answer 25

current in amperes

Question 26

Both the ? and ? must be analyzed to determine if the circuit breakers are selectively coordinated.

Answer 26

unlatching time and clearing time

Question 27

For a fuse to selectively coordinate with an upstream fuse of a larger ampere rating,

Answer 27

the downstream fuse must clear before the upstream fuse melts.

Question 28

Fuses can be selectively coordinated for all levels of overcurrents by ?

Answer 28

following the fuse manufacturer’s selective coordination ratios.

Question 29

Circuit breakers with short-time delay and no instantaneous trip can be bought with an arc flash reduction maintenance switch which helps mitigate the

Answer 29

arc flash incident energy for occasions such as when an Electrical Worker must perform diagnostics on energized equipment.

Question 30

An emergency system overcurrent protective device is required to be selectively coordinated with all supply-side overcurrent protective devices per NEC Section ? .

Answer 30

700.32

Question 31

Selective coordination is an important consideration for reliability of ?

Answer 31

emergency systems to deliver power to vital loads.

Question 32

Selective coordination is required for?

Answer 32

multiple elevators supplied by the same source.

Question 33

study questions 15, 18 Lesson 6

Answer 33

study questions 15, 18 Lesson 6

Question 34

The NEC selective coordination requirements primarily are for systems or circuits in which the loads are vital for ? .

Answer 34

keeping continuous processing industrial plants operating

life safety

Question 35

Selective coordination is a benefit for any electrical distribution system and increases reliable power delivery to the loads. For most systems, it is a design consideration but.?

Answer 35

not mandatory.

Question 36

Study questions 1, 6-10, 19-21. Lesson 8

Answer 36

Study questions 1, 6-10, 19-21. Lesson 8

Question 37

For most circuits, phase OCPDs provide protection for all types of short-circuit conditions, including ?

Answer 37

ground faults.

Question 38

Lower-magnitude ground faults may be detected by the main OCPD but would not be cleared for a long period of time, during which ?

Answer 38

considerable damage could be incurred.

Question 39

Large ampere rated service-entrance overcurrent protective devices may not always sense and open ?

Answer 39

lower-level ground-fault conditions prior to extensive damage.

Question 40

The ? of ground-fault protection can depend not just upon the components, wiring, setting, and maintenance of the relay, but also upon the proper installation of the building wiring system.

Answer 40

reliability

Question 41

The two types of ground-fault sensing relays are ?

Answer 41

zero sequence and residual.

Question 42

The effective time-current curve for ground-fault protection consists of the ?

Answer 42

ground-fault relay and the phase overcurrent protective device.

Question 43

Residual ground-fault protection monitors ground fault currents in the ? .

Answer 43

grounding strap

Question 44

Zero sequence ground-fault protection monitors current in the ? .

Answer 44

neutral conductor

phase conductors

Question 45

Inappropriate GFPE settings are a common cause of?

Answer 45

main service nuisance power outages.

Question 46

Ground-fault protection can create selective coordination concerns depending upon?

Answer 46

the types and sizes of devices selected.

Question 47

The point where GFPE is most commonly required is at service disconnects of ?

Answer 47

1,000 amperes or more for 480/277-volt, 3-phase, 4-wire, solidly grounded wye electrical systems.

Question 48

For healthcare facilities, 517.17(B) requires the feeders to have ?

Answer 48

GFPE if the service has GFPE.

Question 49

The primary consideration for the protection of transformers is to accommodate the ? without sacrificing protection.

Answer 49

primary magnetizing inrush currents