A.C. network analyser is used to
solve problems of
(a) load flow
(b) load flow and short-circuit
(c) load flow and stability
(d) load flow, short-circuit and stability
(e) none of the above

1 Answer

Answer :

(d) load flow, short-circuit and stability

Related questions

Last Answer : A.C. network analyser is used to solve problems of load flow, short-circuit and stability.

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 : Short-circuit currents are due to (a) single phase to ground faults (b) phase to phase faults (c) two phase to ground faults (d) three phase faults (e) any of these

Last Answer : (e) any of these

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 : To reduce short circuit fault currents are used. (a) reactors (b) resistors (c) capacitors (d) none of the above

Last Answer : (a) reactors

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

Last Answer : (c) overload

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

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

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 : 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 : 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

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 : 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 : 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 : With which of the following, a circuit breaker must be equipped for remote operation ? (a) Inverse time trip (b) Time-delay trip (c) Shunt trip (d) None of the above (e) All of the above

Last Answer : (c) Shunt trip

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 : 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 parameter can be neglected for a short line ? (a) Inductance (b) Capacitance (c) Resistance (d) Reactance

Last Answer : (b) Capacitance

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

Last Answer : (a) power

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 : 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 : 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 : 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

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

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

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 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

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 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 : In a circuit breaker the basic problem is to (a) maintain the arc (b) extinguish the arc (c) transmit large power (d) emit the ionizing electrons

Last Answer : (c) transmit large power

Description : Ionization in circuit breaker is facilitated by (a) high temperature (b) increase of mean free path (c) increasing field strength (d) all of the above

Last Answer : (d) all of the above

Description : Burden of a protective relay is the power (a) required to operate the circuit breaker (b) absorbed by the circuit of relay (c) developed by the relay circuit (d) none of the above

Last Answer : (b) absorbed by the circuit of relay

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

Last Answer : (c) fast switches

Description : Which of the following medium is employed for extinction of arc in air circuit breaker ? (a) Water (b) Oil (c) Air (d) SF6

Last Answer : (c) Air

Description : The arcing contacts in a circuit breaker are made of (a) copper tungsten alloy (b) porcelain (c) electrolytic copper (d) aluminium alloy

Last Answer : (a) copper tungsten alloy

Description : On which of the following routine tests are conducted ? (a) Oil circuit breakers (b) Air blast circuit breakers (c) Minimum oil circuit breakers (d) All of the above

Last Answer : (d) All 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

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 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