Finals Flashcards
(25 cards)
Factors affecting earth resistivity includes except
a. moisture content
b. Type of soil
c. Method of measurement
d. temperature
c. Method of measurement
The National Electrical Code recommends additional electrode if a resistance to ground greater than
a. 10 Ω
b. 25 Ω
c. 20 Ω
d.15 Ω
b. 25 Ω
British design of lightning protection system is based on
a. Rolling sphere method
b. all of the choices
c. Use of natural conductors
d. Protective angle or cone method
b. all of the choices
The recommended minimum protective margin for lightning and switching surges in insulation coordination is
a. 1.30 and 1.25
b. 1.15 and 1.20
c. 1.20 and 1.15
d. 1.25 and 1.30
c. 1.20 and 1.15
In the British standard, S1 refers to
a. Strike on the ground near the structure
b. Strike directly to the structure
c. Strike on the ground near a service connected to the structure
d. Strike to a service connected to the structure
b. Strike directly to the structure
A lightning flash is a constant source of
a. Heat
b. light
c. Voltage
d. Current
d. Current
Improving earth resistance include
a. treat the soil
b. all of the choices
c. lengthen the earth electrode in the earth
d. use of multiple rods
b. all of the choices
Most common form of lightning that account for 90% or more of the cloud-to-ground flashes worldwide is
a. Category 2
b. Category 3
c. Category 1
d. Category 4
c. Category 1
The vast majority of surge suppressors today use
a. Metal Oxide Varistors
b. Spark Gap arrester
c. Expulsion arrester
d. Valve arrester
a. Metal Oxide Varistors
Useful life of Metal Oxide Varistors is largely dependent on magnitude of
a. Current
b. Voltage
c. Time
d. Temperature
a. Current
This installation is unusual, because combined neutral and earth wiring is used in both the supply and within the installation itself
a. TN-C-S System
b. TN-S System
c. TT System
d. TN-C System
d. TN-C System
Electric shock severity is dependent on except
a. Length of time current flows
b. Amount of current through body
c. Temperature of body
d. Path of current through body
c. Temperature of body
A device that establishes an electrical connection to the earth
a. Neutral conductor
b. Grounded conductor
c. Grounding conductor
d. Grounding electrode
d. Grounding electrode
Insulation breakdown occurs because of the following except
a. Mechanical
b. Thermal
c. Electrical
d. Chemical
c. Electrical
Color of neutral conductor
a. Gray
b. Red
c. Black
d. Green
a. Gray
The selection of the insulation strength of equipment in relation to the voltages which can appear on the system
a. Insulation Coordination
b. Dielectric coordination
c. Dielectric strength testing
d. Insulation Protection
a. Insulation Coordination
The typical duration of a lightning flash is approximately
a. 0.15 sec
b. 0.35 sec
c. 0.50 sec
d. 0.25 Sec
c. 0.50 sec
This is probably the most usual earthing system in the world, with the Electricity Supply Company providing an earth terminal at the incoming mains position
a. TN-S System
b. TT System
c. TN-C System
d. TN-C-S System
a. TN-S System
Key design elements for static dissipators based on point discharge theory includes
a. Radius of the dissipator electrode
b. Number of dissipator electrodes
c. All of the choices
d. Dissipator construction material
c. All of the choices
Transient over-voltage is normally classified as one of the following types except
a. Medium front
b. Slow front
c. Very fast front
d. Fast front
a. Medium front
Color of equipment grounding conductor
a. Black
b. White
c. Green
d. Gray
c. Green
Level of current through a body that would cause possible suffocation
a. 10mA
b. 30mA
c. 20mA
d. 5mA
b. 30mA
The minimum recommended thickness of stainless steel sheet considered as part of LPS is
a. 0.70 mm
b. 2.00 mm
c. 0.65 mm
d. 0.50 mm
d. 0.50 mm
Use to reduce the steepness of wave fronts to protect turn to turn insulation from surges applied to or reflected within machine windings
a. High Voltage Surge Capacitors
b. Shunt Capacitor
c. Metal Enclosed Capacitor
d. Series Capacitor Compensation
a. High Voltage Surge Capacitors
