For which of the following equipment current rating is not necessary?
(A) Circuit breakers
(B) Isolators
(C) Load break switch
(D) Circuit breakers and load break switches
A circuit is disconnected by isolators when____________?
(A) line is energized
(B) there is no current in the line
(C) line is on full load
(D) circuit breaker is not open
By which of the following a bus-bar is rated?
(A) Current only
(B) Current and voltage
(C) Current, voltage and frequency
(D) Current, voltage, frequency and short time current
In aluminium conductors, steel core is provided to____________?
(A) compensate for skin effect
(B) neutralise proximity effect
(C) reduce line inductance
(D) increase the tensile strength
By which of the following methods string efficiency can be improved?
(A) Using a guard ring
(B) Grading the insulator
(C) Using long cross arm
(D) Any of the above
(D) None of the above
Owing to skin effect:
(A) current flows through the half cross-section of the conductor
(B) portion of the conductor near the surface carries more current and core of the conductor carries less current
(C) portion of the conductor near the surface carries less current and core of the conductor carries more cur¬rent
(D) any of the above
(D) none of the above
Which of the following bus-bar schemes has the lowest cost?
(A) Ring bus-bar scheme
(B) Single bus-bar scheme
(C) Breaker and a half scheme
(D) Main and transfer scheme
On which of the following factors skin effect depends?
(A) Frequency of the current
(B) Size of the conductor
(C) Resistivity of the conductor material
(D) All of the above
Constant voltage transmission entails the following disadvantage?
(A) large conductor area is required for same power transmission
(B) short-circuit current of the system is increased
(C) either of the above
(D) none of the above
In a tap changing transformer, the tappings are provided on__________?
(A) primary winding
(B) secondary winding
(C) high voltage winding
(D) any of the above