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

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
by

1 Answer

Answer :

(c) slow
by

Related questions

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

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

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

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

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

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

Discrimination between main and backup protection is provided by the use of relays which are?

Last Answer : Discrimination between main and back up protection is provided by the use of relays which are slow.

For which of the following protection from negative sequence currents is provided ? (a) Generators (b) Motors (c) Transmission line (d) Transformers

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

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

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

Distance relays are generally (a) split-phase relays (b) reactance relays (c) impedance relays (d) 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

relays are used for phase faults on long line. (a) Impedance (b) Reactance (c) Either of the above (d) None of the above

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

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 : 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

Last Answer : (c) both (a) and (b)

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

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

Directional relays are based on flow of (a) power (b) current (c) voltage wave (d) all of the above

Description : Directional relays are based on flow of (a) power (b) current (c) voltage wave (d) all of the above

Last Answer : (a) power

D.C. shunt relays are made of (a) few turns of thin wire (b) few turns of thick wire (c) many turns of thin wire (d) many turns of thick wire

Description : D.C. shunt relays are made of (a) few turns of thin wire (b) few turns of thick wire (c) many turns of thin wire (d) many turns of thick wire

Last Answer : (c) many turns of thin wire

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

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

Overload relays are of...... type. (a) induction (b) solid state (c) thermal (d) electromagnetic (e) all above

Description : Overload relays are of...... type. (a) induction (b) solid state (c) thermal (d) electromagnetic (e) all above

Last Answer : (e) all above

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

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

Fault diverters are basically (a) fuses (b) relays (c) fast switches (d) circuit breakers

Description : Fault diverters are basically (a) fuses (b) relays (c) fast switches (d) circuit breakers

Last Answer : (c) fast switches

Overheating of relay contacts or contact born out is due to (a) slow making and breaking of load circuit contacts (b) foreign matter on the contact surface (c) too low contact pressure (d) all of the above

Description : Overheating of relay contacts or contact born out is due to (a) slow making and breaking of load circuit contacts (b) foreign matter on the contact surface (c) too low contact pressure (d) all of the above

Last Answer : (d) all of the above

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

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

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 : 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

Last Answer : (d) all of the above

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

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

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

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

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

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

The delay fuses are used for the protection of ________ . (a) motors (b) power outlet circuits (c) fluorescent lamps (d) light circuits

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

H.R.C. fuses provide best protection against (a) overload (b) reverse current (c) open-circuits (d) short-circuits

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

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

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)

A thermal protection switch can protect against (a) short-circuit (b) temperature (c) overload (d) over voltage

Description : A thermal protection switch can protect against (a) short-circuit (b) temperature (c) overload (d) over voltage

Last Answer : (c) overload

Why Isolation switches are provided along with the circuit breakers?

Description : Why Isolation switches are provided along with the circuit breakers?

Last Answer : Isolation switches are provided for separating the disconnected element from the live portion of the system for the purpose of safety

Bus coupler is very essential in arrangement (a) single bus (b) double bus, double breaker (c) main and transfer bus (d) all of the above

Description : Bus coupler is very essential in arrangement (a) single bus (b) double bus, double breaker (c) main and transfer bus (d) all of the above

Last Answer : (c) main and transfer bus

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

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

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

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

The relay operating speed depends upon (a) the spring tension (b) the rate of flux built up (c) armature core air gap (d) all of the above

Description : The relay operating speed depends upon (a) the spring tension (b) the rate of flux built up (c) armature core air gap (d) all of the above

Last Answer : (d) all of the above

For an Resistive Load and Inductive load considered for switching operation of circuit breaker, Switching of which load is difficult and Why?

Description : For an Resistive Load and Inductive load considered for switching operation of circuit breaker, Switching of which load is difficult and Why?

Last Answer : In case of switching resistive load, current and voltage will be in phase i.e,when during current zero voltage also will be zero in case of resistive load. Hence the voltage at the ... maximum. This results in re-striking of arc once again. Therefore switching inductive load will be difficult

What is re-striking voltage?

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

When does an arc extincts?

Description : When does an arc extincts?

Last Answer : If the rate of rise of re-striking voltage (RRRV) is less than rate of rise of dielectric strength between the breaker contacts arc will not sustain and extincts

What is recovery voltage in circuit breaker?

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

Why asymmetrical breaking current is higher than the symmetrical breaking current in a circuit breaker?

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.

What is meant by Current Chopping?

Description : What is meant by Current Chopping?

Last Answer : Current Chopping is a phenomenon of current interruption before the natural current zero is reached.

Air Blast Circuit Breakers Advantages Disadvantages

Description : Air Blast Circuit Breakers Advantages Disadvantages

Last Answer : Air Blast Circuit Breakers Advantages Disadvantages In air blast circuit breakers, compressed air at a pressure of 20-30 kg/cm2 is employed as an arc quenching medium. Air blast circuit breakers ... air blast circuit breaker current chopping problem exists There is a problem of re-striking voltage

The material used for fuse must have (a) low melting point and high specific resistance (b) low melting point and -low specific resistance (c) high melting point and low specific resistance (d) low melting point and any specific resistance

Description : The material used for fuse must have (a) low melting point and high specific resistance (b) low melting point and -low specific resistance (c) high melting point and low specific resistance (d) low melting point and any specific resistance

Last Answer : (a) low melting point and high specific resistance

Admittance relay is _______ relay. (a) impedance (b) directional (c) non-directional (d) none of the above

Description : Admittance relay is _______ relay. (a) impedance (b) directional (c) non-directional (d) none of the above

Last Answer : (b) directional

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

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

Air blast circuit breakers for 400 kV power system are designed to operate in (a) 100 microsecond (b) 50 millisecond (c) 0.5 sec (d) 0.1 sec

Description : Air blast circuit breakers for 400 kV power system are designed to operate in (a) 100 microsecond (b) 50 millisecond (c) 0.5 sec (d) 0.1 sec

Last Answer : (b) 50 millisecond

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

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

transmission line has reflection coefficient as one. (a) Open circuit (b) Short-circuit (e) Long (d) None of the above

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

Arc in a circuit breaker is interrupted at (a) zero current (b) maximum current (c) minimum voltage (d) maximum voltage

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

Which of the following circuit breakers has high reliability and minimum maintenance ? (a) Air blast circuit breakers (b) Circuit breaker with SF6 gas (c) Vacuum circuit breakers (d) Oil circuit breakers

Description : Which of the following circuit breakers has high reliability and minimum maintenance ? (a) Air blast circuit breakers (b) Circuit breaker with SF6 gas (c) Vacuum circuit breakers (d) Oil circuit breakers

Last Answer : (b) Circuit breaker with SF6 gas

Series reactors should have (a) low resistance (b) high resistance (c) low impedance (d) high impedance

Description : Series reactors should have (a) low resistance (b) high resistance (c) low impedance (d) high impedance

Last Answer : (a) low resistance

Which of the following parameter can be neglected for a short line ? (a) Inductance (b) Capacitance (c) Resistance (d) 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

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

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

The under voltage relay can be used for (a) generators (b) busbars (c) transformers (d) motors (e) all 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