Description : Ungrounded neutral transmission system is not recommended because of system (a) insulation being overstressed due to over voltages (b) insulation overstress may lead to failure and subsequent phase to phase faults (c) being inadequately protected against ground fault (d) all of the above
Last Answer : (d) all of the above
Description : Large internal faults are protected by (a) merz price percentage differential protection (b) mho and ohm relays (c) horn gaps and temperature relays (d) earth fault and positive sequence relays
Last Answer : (a) merz price percentage differential protection
Description : For which of the following protection from negative sequence currents is provided ? (a) Generators (b) Motors (c) Transmission line (d) Transformers
Last Answer : (a) Generators
Description : The interaction between a transmission line and communication line is minimized by (a) transposing transmission as well as communication lines (b) increasing the height of the transmission line tower (c) increasing the distance between the two lines (d) all of the above
Description : When a transmission line is energized, the wave that propagates on it is (a) current wave only (b) voltage wave only (c) both (a) and (b) (d) power factor wave only
Last Answer : (c) both (a) and (b)
Description : The inverse definite mean time relays are used for over current and earth fault protection of transformer against (a) heavy loads (b) internal short-circuits (c) external short-circuits (d) all of the above
Last Answer : (b) internal short-circuits
Description : Over voltage protection is recommended for (a) hydro-electric generators (b) steam turbine generators (c) gas turbine generators (d) all of the above (e) none of the above
Description : H.R.C. fuses provide best protection against (a) overload (b) reverse current (c) open-circuits (d) short-circuits
Last Answer : (d) short-circuits
Description : transmission line has reflection coefficient as one. (a) Open circuit (b) Short-circuit (e) Long (d) None of the above
Last Answer : (a) Open circuit
Description : When a wave propagates on a transmission line, it suffers reflection several times at (a) tapping (b) load end (c) sending end (d) sending and other end (e) all of the above
Last Answer : (d) sending and other end
Description : A thermal protection switch can protect against (a) short-circuit (b) temperature (c) overload (d) over voltage
Last Answer : (c) overload
Description : What will be the reflection coefficient of the wave of load connected to transmission line if surge impedance of the line is equal to load ? (a) Zero (b) Unity (c) Infinity (d) None of the above
Last Answer : (a) Zero
Description : Which of the following devices will receive voltage surge first travelling on the transmission line ? (a) Lightning arresters (b) Relays (c) Step-down transformer (d) Switchgear
Last Answer : (a) Lightning arresters
Description : relay is preferred for phase fault on short transmission line. (a) Induction type (b) Reactance (c) Impedance (d) None of the above
Last Answer : (b) Reactance
Description : The reflection co-efficient at the open circuited end of a transmission line. (a) zero (b) infinity (c) unity (d) none of the above
Last Answer : (c) unity
Description : Shunt capacitance is neglected while considering (a) short transmission line (b) medium transmission line (c) long transmission line (d) medium and long transmission lines
Last Answer : (a) short transmission line
Description : For the protection of power station buildings against direct strokes the requirements are (a) interception (b) interception and conduction (c) interception, conduction and dissipation (d) interception, conduction, dissipation and reflection (e) none of the above
Last Answer : (c) interception, conduction and dissipation
Description : Which of the following is the least expensive protection for overcurrent is low voltage system ? (a) Rewireable fuse (b) Isolator (c) Oil circuit breaker (d) Air break circuit breaker (e) None of the above
Last Answer : (a) Rewireable fuse
Description : Overfluxing protection is recommended for (a) distribution transformer (b) generator transformer of the power plant (c) auto-transformer of the power plant (d) station transformer of the power plant
Last Answer : (b) generator transformer of the power plant
Description : The single phasing relays are used for the protection of (a) single phase motors only (b) two phase motors only (c) two single phase motors running in parallel (d) three phase motors
Last Answer : (d) three phase motors
Description : For which of the following ratings of the transformer differential protection is recommended ? (a) above 30 kVA. (b) equal to and above 5 MVA (c) equal to and above 25 MVA (d) none of the above
Last Answer : (b) equal to and above 5 MVA
Description : Discrimination between main and back up protection is provided by the use of relays which are (a) fact (b) sensitive (c) slow (d) none of the above
Last Answer : (c) slow
Description : The delay fuses are used for the protection of ________ . (a) motors (b) power outlet circuits (c) fluorescent lamps (d) light circuits
Last Answer : (a) motors
Description : The current zero interruption, in oil and air blast circuit breakers, is achieved by (a) lengthening of the gap (b) cooling and blast effect (c) both (a) and (b) (d) deionizing the oil with forced air (e) none of the above
Description : Distance relays are generally (a) split-phase relays (b) reactance relays (c) impedance relays (d) none of the above
Last Answer : (d) none of the above
Description : Thermal overload relays are used to protect the motor against over current due to (a) short-circuits (b) heavy loads (c) grounds (d) all of the above
Last Answer : (b) heavy loads
Description : The line insulation is the insulation level of the station equipment. (a) less than (b) same as (c) more than (d) proportional to (e) not directly related with
Last Answer : (e) not directly related with
Description : The main function of a fuse is to (a) protect the line (b) open the circuit (c) protect the appliance (d) prevent excessive currents (e) none of the above
Last Answer : (d) prevent excessive currents
Description : Circuit breakers are essentially (a) current carrying contacts called electrodes (b) arc extinguishers (c) circuits to break the system (d) transformers to isolate the two systems (e) any of the above
Last Answer : (a) current carrying contacts called electrodes
Description : Relays can be designed to respond to changes in (a) resistance, reactance or impedance (b) voltage and current (c) light intensity (d) temperature (e) all above
Last Answer : (e) all above
Description : Series capacitors are used to (a) compensate for line inductive reactance (b) compensate for line capacitive reactance (c) improve line voltage (d) none of the above
Last Answer : (a) compensate for line inductive reactance
Description : Which of the following parameter can be neglected for a short line ? (a) Inductance (b) Capacitance (c) Resistance (d) Reactance
Last Answer : (b) Capacitance
Description : relays are used for phase faults on long line. (a) Impedance (b) Reactance (c) Either of the above (d) None of the above
Last Answer : (a) Impedance
Description : Why asymmetrical breaking current is higher than the symmetrical breaking current in a circuit breaker?
Last Answer : Asymmetrical breaking current is the rms value of the combined sum of the dc and ac components of the short circuit current at the instant of separation of the breaker contacts while ... the ac component alone. Thus asymmetrical breaking current is higher than the symmetrical breaking current.
Description : What is meant by Current Chopping?
Last Answer : Current Chopping is a phenomenon of current interruption before the natural current zero is reached.
Description : Arc in a circuit breaker is interrupted at (a) zero current (b) maximum current (c) minimum voltage (d) maximum voltage
Last Answer : (a) zero current
Description : Which of the following statements is incorrect ? (a) Lightning arrestors are used before the switchgear (b) Shunt reactors are used as compensation reactors (c) The peak short current is (1.8 xV2) ... component (d) The MVA at fault is equal to base MVA divided by per unit equivalent fault reactance
Last Answer : (a) Lightning arrestors are used before the switchgear
Description : Induction cup relay is operated due to changes in (a) current (b) voltage (c) impedance (d) all of the above
Description : Which of the following statements is incorrect? (a) Station batteries are used to operate relay only (b) The lightning arresters are basically surge diverters (c) An impedance relay has maximum fault current when fault occurs near the relay (d) A high speed relay has an operation of 1 to 2 cycles
Last Answer : (a) Station batteries are used to operate relay only
Description : The arc voltage produced in A.C. circuit breaker is always (a) in phase with the arc current (b) lagging the arc current by 90" (c) leading the arc current by 90° (d) none of the above
Last Answer : (a) in phase with the arc current
Description : Protective relays are devices that detect abnormal conditions in electrical circuits by measuring (a) current during abnormal condition (b) voltage during abnormal condition (c) constantly the electrical quantities which differ during normal and abnormal conditions (d) none of the above
Last Answer : (c) constantly the electrical quantities which differ during normal and abnormal conditions
Description : Directional relays are based on flow of (a) power (b) current (c) voltage wave (d) all of the above
Last Answer : (a) power
Description : Circuit breakers usually operate under (a) transient state of short-circuit current (b) sub-transient state of short-circuit current (c) steady state of short-circuit current (d) after D.C. component has ceased
Last Answer : (a) transient state of short-circuit current
Description : In order that current should flow without causing excessive heating or voltage drop, the relay contacts should (a) have low contact resistance (b) be clean and smooth (c) be of sufficient size and proper shape (d) have all above properties
Last Answer : (d) have all above properties
Description : Air blast circuit breaker is used for (a) over currents (b) short duty (c) intermittant duty (d) repeated duty
Last Answer : (d) repeated duty
Description : To protect most of the electrical equipment handling low power, the types of relays used are (a) thermocouple (b) electronic and bimetallic (c) both (a) and (b) (d) none of the above
Description : Magnetic circuit breaker has ______ trip action. (a) delayed (b) instantaneous (c) both of the above (d) none of the above
Last Answer : (b) instantaneous
Description : Thermal circuit breaker has (a) delayed trip action (b) instantaneous trip action (c) both of the above (d) none of the above
Last Answer : (a) delayed trip action
Description : The relay with inverse time characteristic will operate within (a) 1.5 sec (b) 5 to 10 sec (c) 5 to 20 sec (d) 20 to 30 sec (e) none of the above
Last Answer : (b) 5 to 10 sec
Description : The time of closing the cycle, in modern circuit breakers is (a) 0.003 sec (b) 0.001 sec (c) 0.01 sec (d) 0.10 sec (e) none of the above
Last Answer : (a) 0.003 sec