Related MCQ Question

• Which portion of the transmission system is more prone to faults?
• Which portion of the power system is least prone to faults?
• The magnitude of fault current depends upon
• The most common type of fault is
• The maximum short-circuit current occurs in the case of  :
• Series reactors are used to
• Current limiting reactors may be 
• Symmetrical components are used in power system for the analysis of
• In a star-connected system without neutral grounding, zero sequence currents are
• A balanced 3-phase system consists of
• The Positive sequence current of a transmission line is  :
• For a fully transposed transmission line
• Zero sequence fault current is absent when fault is
• The current of a single-phase load drawn from a 3-phase system has  :
• Zero-sequence current can flow from a line to transformer bank if the windings are in
• The primary function of a fuse is to
• What is the advantage of HRC fuses over Rewirable fuses?
• In HRC fuse the time between cut-off and final current zero is called 
• If a combination of HRC fuse and a circuit breaker is employed, the circuit breaker operates for
• The least expensive protection for overcurrent in low-voltage system is
• A Circuit breaker normally operates
• When a fault occurs in a high voltage transmission line, first the 
• The initiation of electric arc at the instant of contact separation is caused by
• Arcing voltage will be the least in case of
• The heat produced at the contact point owing to flow of electric current is least affected by
• Which of the following should have low value for the contacts and their material?
• In a Circuit Breaker Contact wipe  is necessary 
• The fluids used in circuit breakers should be of 
• Sparking between contacts can be reduced by inserting 
• For magnetic blow out of arc the magnetic field is produced
• In a circuit breaker the contact space is ionized by
• Ionization In a circuit breaker is facilitated by
• The stability of arc in vacuum depends on
• The interrupting time of a circuit breaker is the period between the instant of
•  The total clearing time for a high speed circuit breaker is around
• The resistance of an electric arc can be increased by 
• The arc voltage in a circuit breaker is
• The active recovery voltage in a circuit breaker depends upon 
• In a circuit breaker the current that exists at the instant of contact separation is called the ________   current.
• The rate of rise of re-striking voltage (RRRV) is depends upon
• It is difficult to interrupt a capacitive circuit because 
• Main purpose of oil in OCB is to 
• The chances of arc interruption in subsequent current zeros
• In a minimum oil circuit breaker the oil is used 
• Air blast circuit breakers are suitable for
• Resistance switching is normally employed in
• The air-blast circuit breakers for  400 kV system are designed to operate in
• The minimum oil circuit breaker has less volume of oil because 
• Resistance switching is used In air-blast circuit breaker to 
• Air used in air blast circuit breaker must
• Sulphur hexafluoride gas is transported in
• A thermal protection switch provides protection against
• For remote operation, the circuit breaker must be equipped with 
• Which of the following circuit breakers produce the least arc energy?
• Which of the following circuit breakers take minimum time in installation?
• Circuit breakers usually operate under 
• The re-striking voltage is measured in
• Rated breaking capacity (MVA)  of a circuit breaker is equal to 
• The making to breaking current ratio  for an EHV  circuit breaker is 
• The making capacity of a circuit breaker is
• An isolator is installed 
• Current rating is not necessary in case of
• Isolators used in transmission lines are capable of breaking  :
• Purpose of backup protection is
• The actuating quantity for the relays may be 
• The protective relay is provided to 
• Plug setting of an electromagnetic relay can be altered by varying 
• The torque produced in shaded pole structure induction type relay is
• The most efficient torque-producing actuating structure for induction-type relays is 
• The Buchholz relay protects a transformer from 
• In an Overcurrent protection the setting of the earth fault relay is 
• Inverse time-current relays are used for the protection of
• IDMT relays are used to protect the power transformers against 
• Earth fault relays are 
• The domains of power system where directional overcurrent relay is indispensable are
• Directional overcurrent relays have two exciting coils connected across 
• In distance protection, the relay measures
• The structure used in reactance relays is
• A reactance relay is
• Reactance relay is normally used for protection against
• Admittance relay is
• A mho relay is a 
• A distance relay with inherent directional property is known as 
• The relay used for phase fault protection of short transmission lines is
• Mho relay is usually employed for the protection of
• Where severe synchronising swing occur, the relay employed is
• Which of the following relays has inherent directional characteristic?
• A differential relay response to 
• Difference relays are used for protection of equipment against 
• Undervoltage relays are mainly used for
• In a biased differential relay the bias is defined as a ratio of 
• Both voltage and current signals are required for 
• The relay used for feeder protection is
• Phase relays are used to provide protection against 
• In a static overcurrent relay, inverse time characteristics are obtained by
• Two-input phase comparator in a static relay is made up of a 
• The phase comparators in case of static relay and electromechanical relay normally are 
• Merz-Price protection is employed for protection of
• The short-circuit current of an alternator, in case of line to line fault, depends on its 
• We do not require any protection against prime mover failure in case of 
• Field failure in an alternator occurs due to
• The earth fault in stator causes 
• A negative sequence relay is commonly used to protect
• Earth fault protection for an electric motor is provided by
• Which relay is used to detect and protect internal faults of a transformer?
• The inrush current of a transformer at no load is maximum if the supply voltage is switched on
• Magnetizing inrush phenomena occur in
• For the protection of transformers, harmonic restraint is used to guard against
• For preventing the malfunction of Merz-Price protection scheme on inrush of magnetizing current
• Problems associated with differential protection  is/are 
• The material used for bus-bars should have 
• A bus-bar is rated by 
• Single bus-bar arrangement 
• A bus coupler circuit breaker is utilized in a substation for 
• Zero-sequence impedance of the transmission line is
• Which is the pilotless protection method for feeder line?
• A transmission line is protected by  :
• For complete protection of a 3-phase transmission line, we require
• How many relay are used to detect interphase fault of a three-line system?
• The transmission line distance production relay having the property of being inherently directional is 
• Time graded protection of a radial feeder can be achieved by using 
• The normal resistance of a pilot wire is
• For protection of parallel feeders fed from one end, the relays required are 
• Pilot-wire protection scheme is most economical and provides high speed relaying for
• Adjustable resistors are connected in the pilot wires in order to 
• Signal mixing transformers are used for 
• The frequency of carrier in the carrier current pilot scheme is in the range of
• The frequency of carrier transmitted by microwave pilot is in the range of
• A line trap in a long transmission line is used to 
• Lightning is a huge spark caused by electrical discharge taking place between 
• Switching over-voltages are more hazardous than lightning surges in case of 
• The over-voltage surges in power system may be caused by
• The protection against direct lightning strokes and high voltage steep waves is provided by 
• For protection of rotating machines against lightning surges  ___________  is used.
• Lighting arresters are used in power system to protect electrical equipment against
• Impulse ratios of insulators and lightning arresters should be
• Which of the following is the protective device against lightning over-voltages?
• Overhead ground wires are used to protect a transmission line against 
• An overhead transmission line is provided with earth wire for protection against 
• The resistance in a thyrite lightning arrester is
• A lightning arrester provides 
• Surge absorbers are used for protection against
• Surge modifiers are employed for 
• A thyrite type lightning arrester 
• A lightning arrester connected between the line earth in a power system 
• Which of the following is a non-linear diverter?
• A valve type lightning arrestor in a substation should be placed 
• Coupling factor of a ground wire can be increased by 
• When a transmission line is energized, the wave that propagates on it is
• Travelling voltage wave and current wave have the same waveforms and travel together along the transmission line at a velocity 
• For a transmission line the standing wave ratio is the ratio of 
• The steepness of the wave-front can be reduced by connecting 
• The insulation strength of an  EHV transmission line is mainly governed by 
• The size of the earth wire is determined on the basis of 
• The advantage of neutral earthing is
• Resistance earthing is employed for voltages between 
• Peterson coil is used for
• Tower footing resistance of a transmission tower should be 
• The earthing transformer is used to
• The voltage of a particular bus is regulated by controlling the 
• In ac distribution system the voltage can be controlled by using 
• Tap changing transformers are employed for 
• The best location for use of a booster transformer in a transmission line is
• Series capacitor is used in a transmission line to
• Shunt compensation in an  EHV line is used to improve
• What will happen if a short-circuit fault occurs in a switched capacitor controlled reactor?
• Which of the following is provided with arcing horns?
• Pole mounted substations are used in
• AC network analyzer is employed for solving the problem of 
• Power system stability is defined as
• The power transmission capacity of a transmission line is 
• The load carrying capability of a long ac transmission line is
• The power systems are operated with power angle around
• Series capacitors are used to