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83 questions · page 4 of 5. Answer in your head first, then check the solution.

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TypeAll 83Problem solvingObjective 83
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#61📘 EE Pocket Reviewer RojasEasy
For high voltage ac circuit breakers, the rated short-time current is passed for about how many seconds?
AAbout 0.1 second
BAbout 10 seconds
CAbout 3 seconds
DAbout 30 seconds
#62📘 EE Pocket Reviewer RojasEasy
Which of the following circuit breakers does not use a pneumatic operating mechanism?
ABulk-oil circuit breaker
BAir break circuit breaker
CAir blast circuit breaker
DSF6 gas circuit breaker
#63📘 EE Pocket Reviewer RojasEasy
The current rating is not necessary in which of the following?
AIsolators
BLightning arresters
CLoad break switches
DCircuit breakers
#64📘 EE Pocket Reviewer RojasEasy
Directional relays are based on flow of which one?
APower
BVoltage
CCurrent
DAll of these
#65📘 EE Pocket Reviewer RojasEasy
Which of the following statements is true about SF6 (sulphur hexafluoride)?
AIt is a conductor
BIt is a dielectric
CIt is an inactive gas
DIt is a semi-conductor
#66📘 EE Pocket Reviewer RojasEasy
Which one is true regarding the air used in the air blast circuit breaker?
AIt must contain oil mist
BIt must be ionized
CIt must be free from any moisture
DAll of these
#67📘 EE Pocket Reviewer RojasEasy
HRC (high rupturing capacity) fuses provides best protection in which of the following conditions?
AOpen circuits
BShort circuits
COverloads
DAll of these
#68📘 EE Pocket Reviewer RojasEasy
In an SF6 circuit breaker, during arc extinction what happens to the SF6 gas?
AIt will reduce to SF3
BIt gets oxidized
CIt will combine with oxygen
DIt will decompose into S and F ions
#69📘 EE Pocket Reviewer RojasEasy
The pressure of SF6 gas in a circuit breaker is on what order?
AAbout 100 mm Hg
BAbout 3 to 5 kg/cm²
CAbout 1 kg/cm²
DAbout 30 to 50 kg/cm²
#70📘 EE Pocket Reviewer RojasEasy
Which of the following relays is used in transformers?
AMHO relay
BMerz-Price relay
CBuchholz relay
DReverse power relay
#71📘 EE Pocket Reviewer RojasEasy
What is the usual clearing time of a circuit breaker?
ABelow one minute
BMore than one minute
CAbout 2 seconds
DAbout few cycles of the supply voltage
#72📘 EE Pocket Reviewer RojasEasy
A fuse wire possesses which of the following characteristics?
AInverse-time characteristics
BDirect-time characteristics
CInverse-time squared characteristics
DDirect-time squared characteristics
#73📘 EE Pocket Reviewer RojasEasy
Time-delay fuses are used for the protection of which one?
AGenerators
BMotors
CSmall appliance outlets
DLighting outlets
#74📘 EE Pocket Reviewer RojasEasy
Which one is a method describing “oil immersion” of contacts?
AArc prevention
BDe-ionization
CArc dispersion
DIonization
#75📘 EE Pocket Reviewer RojasEasy
How is the SF6 gas transported?
AIn liquid form using cylinders
BIn gas form using cylinders
CIn solid form using boxes
DNone of these
#76📘 EE Pocket Reviewer RojasEasy
The contact resistance in a circuit breaker is least affected by which of the following?
AThe shape of the contact faces
BThe ambient temperature
CThe amount of surface contamination
DThe mechanical force applied to the contacts
#77📘 EE Pocket Reviewer RojasEasy
Magnetic circuit breakers have what type of trip mechanism?
ADelayed trip
BThermal trip
CInstantaneous trip
DBoth A and B
#78📘 EE Pocket Reviewer RojasEasy
Which one is a cause for the over voltage surges in power system?
ALightning
BSwitching
CResonance
DAll of these
#79📘 EE Pocket Reviewer RojasEasy
Low voltage circuit breakers have rated voltages less than how much?
A200 V
B500 V
C1 kV
D10 kV
#80📘 EE Pocket Reviewer RojasEasy
How do you call the current which exists at the instant of contact separation in a circuit breaker?
ARestriking current
BSurge current
CRecovery current
DBreaking current

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