CODE STANDARDS AND
PRACTICES LEVEL 3
PRACTICE TEST
Question 1: Which condition is classi�ed as an overcurrent rather than a normal load condition?
Choices:
1) A conductor carrying its calculated load continuously 2) A short circuit between two conductors of di�erent potential 3) A balanced three-phase load at rated current 4) A conductor operating below its ampacity Correct Answer: A short circuit between two conductors of di�erent potential Explanation: A short circuit is an overcurrent condition because current �ows at a magnitude above the normal current-carrying capacity of the circuit. Overcurrents include overloads and fault currents such as short circuits and ground faults.Page 1
Question 2: At the same point in an electrical system, why is arcing-fault current generally lower than bolted short-circuit current?
Choices:
1) The arc adds impedance to the fault path 2) The system voltage automatically drops to zero 3) The conductor ampacity increases during an arc 4) The upstream transformer stops contributing current
Correct Answer: The arc adds impedance to the fault path
Explanation: An electrical arc adds resistance and impedance to the fault path. That added impedance limits current, so an arcing fault generally produces less current than a low- impedance bolted fault at the same location.Question 3: What is the primary hazard created by a sustained overload that is not cleared in su�cient time?
Choices:
1) Improved conductor e�ciency 2) Lower conductor resistance 3) Overheating and deterioration of insulation 4) Automatic reduction of available fault current
Correct Answer: Overheating and deterioration of insulation
Explanation: A sustained overload produces excessive heating in conductors and equipment. If it continues, insulation can deteriorate and the condition can progress to equipment damage, a short circuit, or �re.Page 2
Question 4: Which type of device is intended to provide overcurrent protection for branch circuits over the full range of overcurrents for which it is listed?
Choices:
1) Supplementary overcurrent protective device 2) Branch-circuit overcurrent protective device 3) Grounding electrode conductor 4) Surge-protective device
Correct Answer: Branch-circuit overcurrent protective device
Explanation: A branch-circuit overcurrent protective device is evaluated for branch-circuit protection and can protect against the applicable overload and fault-current conditions.Supplementary protection has a more limited role and does not replace required branch-circuit protection.
Question 5: A manufacturer installs a supplementary fuse inside a piece of
utilization equipment. What is the correct general application of that fuse?
Choices:
1) It may replace the required branch-circuit OCPD in all cases 2) It is used only for service-entrance conductor protection 3) It provides added protection within the equipment but does not substitute for required branch-circuit protection 4) It is required to have the same ampere rating as the service disconnect Correct Answer: It provides added protection within the equipment but does not substitute for required branch-circuit protection Explanation: Supplementary overcurrent protection is used to provide additional protection within appliances or equipment. It is not a substitute for required branch-circuit overcurrent protection unless a speci�c listing or Code rule permits the application.Page 3