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
Last Answer : When a transmission line is energized, the wave that propagates on it is current wave and voltage wave.
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 : 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 : A transmission line is protected by (a) inrush protection (b) distance protection (c) time graded and current graded over current protection (d) both (b) and (c) (e) none of the above
Last Answer : (d) both (b) and (c)
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 : 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 : 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
Last Answer : (d) all of the above
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 : Wave trap is used to trap waves of (a) power frequencies (b) higher frequencies entering generator or transformer units (c) either of the above (d) none of the above
Last Answer : (b) higher frequencies entering generator or transformer units
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 : 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 : Induction cup relay is operated due to changes in (a) current (b) voltage (c) impedance (d) all of the above
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 : 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 : 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
Last Answer : When a wave propagates on a transmission line, it suffers reflection several times at sending and other end.
Description : The contacts of high voltage switches used in power system are submerged in oil. The main purpose of the oil is to (a) lubricate the contacts (b) insulate the contacts from switch body (c) extinguish the arc (d) all of the above (e) none of the above
Last Answer : (c) extinguish the arc
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
Description : What is re-striking voltage?
Last Answer : The Re-striking voltage may be defined as the resultant transient voltage which appears across the breaker contacts at the instant of arc extinction
Description : What is recovery voltage in circuit breaker?
Last Answer : Recovery voltage in circuit breakers is defined as the power frequency rms voltage which appears across the breaker contacts after the transient oscillations die out and the final extinction of the arc ... poles of the circuit breaker. It is the voltage developed after the arc extinction is competed
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 : The under voltage relay can be used for (a) generators (b) busbars (c) transformers (d) motors (e) all of the above
Last Answer : (e) all of the above
Description : The short circuit in any winding of the transformer is the result of (a) mechanical vibration (b) insulation failure (c) loose connection (d) impulse voltage
Last Answer : (d) impulse voltage
Description : Resistance grounding is used for voltage between (a) 33kVto66kV (b) HkVto33kV (c) 3.3kVandllkV (d) none of the above
Last Answer : (c) 3.3kVandllkV
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 : Insulation resistance of high voltage circuit breakers is more than (a) 1 mega ohms (b) 10 mega ohms (c) 100 mega ohms (d) 500 mega ohms
Last Answer : (c) 100 mega ohms
Description : The voltage appearing across the contacts after opening of the circuit breaker is called______voltage. (a) recovery (b) surge (c) operating (d) arc (e) none of the above
Last Answer : (a) recovery
Description : Arc in a circuit behaves as (a) a capackive reactance (b) an inductive reactance (c) a resistance increasing with voltage rise across the arc (d) a resistance decreasing with voltage rise across the arc
Last Answer : (d) a resistance decreasing with voltage rise across the arc
Description : A thermal protection switch can protect against (a) short-circuit (b) temperature (c) overload (d) over voltage
Last Answer : (c) overload
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 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
Last Answer : (c) both (a) and (b)
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 : 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 : 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 : 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 : 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 : 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 : 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 : 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 : 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 : 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 : 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