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 : 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 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 : For interrupting capacitive currents which Circuit Breaker (CB) is used a) SF6 CB b) Oil CB c) Vacuum CB d) Air blast CB
Last Answer : Ans: Vacuum CB
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 : 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 : 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 : SF6 gas (a) is yellow in colour (b) is lighter than air (c) is nontoxic (d) has pungent small (e) none of the above
Last Answer : (c) is nontoxic
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 : 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 : Which of the following circuit breakers has high reliability & minimum maintenance? (A) Bulk oil type CB (B) Air blast CB (C) Vacuum CB (D) Sulphur hexafluoride CB
Last Answer : Which of the following circuit breakers has high reliability & minimum maintenance? (A) Bulk oil type CB (B) Air blast CB (C) Vacuum CB (D) Sulphur hexafluoride CB
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 : 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 : 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 : Fault diverters are basically (a) fuses (b) relays (c) fast switches (d) circuit breakers
Last Answer : (c) fast switches
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 : 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 : 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 : 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 : 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 : 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 : 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 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 : An efficient and a well designed protective relaying should have (a) good selectivity and reliability (b) economy and simplicity (c) high speed and selectivity (d) all of the above
Description : During maintenance of circuit breakers, _______________. A. always smooth roughened contact surfaces with a file B. never pass more than rated breaker current through the overload heater element C. ... wear and misalignment of main contacts D. assume heater elements installed are of correct size
Last Answer : Answer: C
Description : The current zero interruption, in oil and air blast circuit breakers, is achieved by?
Last Answer : The current zero interruption, in oil and air blast circuit breakers, is achieved by lengthening of the gap, cooling and blast effect.
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
Description : The following is/are the characteristics of SF6 circuit breakers: (A) It does not need an auxiliary breaking chamber (B) Short break time of 2 to 2.5 cycles (C) All of the above (D) None of the above
Last Answer : The following is/are the characteristics of SF6 circuit breakers: (A) It does not need an auxiliary breaking chamber (B) Short break time of 2 to 2.5 cycles (C) All of the above (D) None of the above
Description : What are the advantages of air blast circuit breaker over oil circuit breaker?
Last Answer : o The risk of fire is diminished o The arcing time is very small due to rapid buildup of dielectric strength between contacts o The arcing products are completely removed by the blast whereas oil deteriorates with successive operations
Description : What is the significance of SF6 gas pressure in 6.6kV breakers?
Last Answer : Density gauge Green – correct SF6 pressure (3 –3.5bar) Yellow – pressure for breaking system fault current (refilling should be done) Red – SF6 pressure less than 2 bar, which indicates leak in the system.
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
Last Answer : Air blast circuit breakers for 400 kV power system are designed to operate in 50 millisecond.
Description : What Is Sf6 Circuit Breaker?
Last Answer : SF6 is Sulpher hexa Flouride gas.. if this gas is used as arc quenching medium in a Circuitbreaker me SF6 CB.
Description : Describe the construction of SF6 circuit breaker with neat diagram.
Last Answer : Construction of SF6 Circuit Breaker : A sulphur hexafluoride (SF6) circuit breaker consists of fixed and moving contacts enclosed in a chamber. The chamber is called arc interruption ... contact, moving contact and arcing horn are coated with a copper-tungsten arc-resistant material.
Description : Explain construction and working of SF6 circuit breaker.
Last Answer : Construction: A sulphur hexafluoride (SF6) circuit breaker consists of fixed and moving contacts enclosed in a chamber. The chamber is called arc interruption chamber, which contains the ... arc being extinguished. Finally the gas enters the contact space increasing the dielectric strength.
Description : what is SF6 circuit breaker?
Last Answer : SF6 is Sulpher hexa Fluoride gas. If this gas is used as arc quenching medium in a Circuit breaker means SF6 CB.
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 : 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 : 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 : 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
Last Answer : (d) load flow, short-circuit and stability
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
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