Description : What are the main parts of 220 kV Circuit Breaker?
Last Answer : Pole column filled with SF6 Pneumatic drive system with compressed air circuit Control cubicle unit
Description : What are the levels of SF6 gas in 220 kV breaker and their significance?
Last Answer : 7 kg/cm2 - normal pressure 5.2 bar - alarm 5.0 bar - closing/tripping operation blocked.
Description : Give the details of switchyard 220 kV CB, Isolator, CT, CVT and lightning arrestor.
Last Answer : 220 kV SF6 Circuit Breaker 1. Make - ABB 2. Air pressure blocking a. Close Block - 17.3 bar. b. Open block - 16.7 bar. c. Auto reclose block - 19 bar. 3. SF6 pressure block a. Alarm - 5. ... , storage and erection. Rated voltage : 216 kV rms. Operating voltage : 184 kV rms.
Description : In 220 kV switchyard why lightning arrestor should be properly grounded?
Last Answer : a. During lightning, surges should be discharged to ground, otherwise it will puncture the equipment insulation and it is possible only when lightning arrestor is grounded properly. b. In order to make it effective ... kV. Soil resistivity a should be minimum and may be it is 3.5 ohm per meter.
Description : What is the difference in action of lock out pressure signal on 6.6 kV and 220 kV breakers?
Last Answer : When lock out signal comes to 6.6 kV breakers the breaker will trip. Where as in case of 220 kV breakers the breaker will not trip. If the breaker is open it will be open only and can not be closed. If it is in closed condition it will be closed.
Description : What are the protections provided for 220 kV lines and bus bars?
Last Answer : a. Bus bar differential protection. b. Distance protection. c. Over current protection. d. Earth fault protection.
Description : Why earth switches are provided in 220 kV bays?
Last Answer : When bay CB trips, both end (station and grid) CB will trip. The earth switches are provided because the grid will always be alive so to prevent any shocks to the operator or maintenance personnel who is working on the line or bay due to accidental energizing of the bus.
Description : A three-phase, 33 kV oil circuit breaker is rated 1200 A, 2000 MVA, 3 s. The symmetrical breaking current is (A) 1200 A (B) 3600 A (C) 35 kA (D) 104.8 kA
Last Answer : A three-phase, 33 kV oil circuit breaker is rated 1200 A, 2000 MVA, 3 s. The symmetrical breaking current is 35 kA
Description : A 3-phase circuit breaker is rated at 1250 A, 2000 MVA, 33 kV, 4s. Its making current capacity will be (a) 35 kA (b) 89 kA (c) 79 kA (d) 69 kA
Last Answer : 89
Description : The minimum clearance between the ground and a 220 kV line is about (a) 4.3 m (b) 5.5 m (c) 7.0 m (d) 10.5 m
Last Answer : (c) 7.0 m
Description : Cables for 220 kV lines are invariably (a) mica insulated (b) paper insulated (c) compressed oil or compressed gas insulated (d) rubber insulated (e) none of the above
Last Answer : (c) compressed oil or compressed gas insulated
Description : For transmission of power over a distance of 500 km, the transmission voltage should be in the range (a) 150 to 220 kV (b) 100 to 120 kV (c) 60 to 100 kV (d) 20 to 50 kV
Last Answer : (a) 150 to 220 kV
Description : The spacing between phase conductors of a 220 kV line is approximately equal to (a) 2 m (b) 3.5 m (c) 6 m (d) 8.5 m
Last Answer : (c) 6 m
Description : A single core cable is designed to work for a single phase system with a peak voltage of 220 kV. The maximum permissible stress in the dielectric is not to exceed 20 kV/mm. For economical size, the overall core diameter of the cable is (A) 28.2 mm (B) 26.4 mm (C) 24.4 mm (D) 22.0 mm
Last Answer : A single core cable is designed to work for a single phase system with a peak voltage of 220 kV. The maximum permissible stress in the dielectric is not to exceed 20 kV/mm. For economical size, the overall core diameter of the cable is 22.0 mm
Description : The X:R ratio of 220 kV line as compared to 400 kV line is?
Last Answer : The X:R ratio of 220 kV line as compared to 400 kV line is smaller.
Description : If the line voltage to the controller shown in the illustration is 440 volts, what is applied across the control circuit? EL-0080 A. 110 volts B. 220 volts C. 440 volts D. 660 volts
Last Answer : Answer: C
Description : Fuses placed in series with a thermal trip-type circuit breaker are used for _____________. A. time-delay protection B. short-circuit protection C. short duration surge protection D. sustained overload protection
Last Answer : Answer: B
Description : In accordance with Coast Guard Regulations (46 CFR), a circuit breaker located in the machinery space and installed in a 440V AC system must _____________. A. be dependent upon mechanical ... the maximum asymmetrical shortcircuit current available at the point of application D. all of the above
Description : Coast Guard Regulations (46 CFR) require each switchboard to have ___________. A. non-conductive deck covering at the frount B. non-conductive deck coverings at the rear C. a name plate for each circuit breaker D. all the above
Last Answer : Answer: D
Description : Before any work on electrical or electronic equipment is performed, which of the following precautions should be carried out? A. De-energize the applicable switchboard bus. B. Bypass the interlocks. C. ... supply circuit breaker in the open position. D. Station a man at the circuit supply switch.
Description : Which of the synchroscope illustrations depicts the appropriate direction of rotation and position for closing the circuit breaker when paralleling AC generators? EL-0053 A. A B. B C. C D. D
Description : The schematic diagram shown in the illustration uses symbol 'A' to represent a/an _________. EL-0011 A. non-renewable fuse link B. circuit breaker coil C. overload relay coil D. thermal overload heater
Description : An AC generator operating in parallel loses its excitation without tripping the circuit breaker. This will __________. A. not affect the faulty generator due to the compensation of the other generators B. ... between the armature and the bus D. cause high currents to be induced in the field windings
Description : Voltage failure of an AC generator may be caused by ____________. A. failure of the exciter generator B. a tripped bus circuit breaker C. high mica segments on the stator bus bar D. excessive prime mover speed
Last Answer : Answer: A
Description : Which of the following problems will occur if the circuit breaker of the incoming alternator is closed and it is 180° out of phase with the loaded alternator when paralleling? A. The rotor of the ... The rotor of the incoming alternator will stop. D. Both alternators will parallel 180° out of phase.
Description : Which of the following actions must be carried out prior to closing the alternator circuit breaker according to the graph shown in the illustration? EL-0002 A. Increase the alternator voltage. B. Decrease the line voltage. C. Increase the line voltage. D. Decrease the line frequency.
Description : An alternator will fail to produce line voltage as a result of _____________. A. a closed circuit breaker B. oxidized slip rings C. improperly staggered brushes D. exciter generator failure
Description : In order to safely carry out repairs to a generator circuit breaker, it must be isolated from the bus. This is accomplished by opening the _____________. A. reverse power relay B. bus disconnect link C. generator bus fuse connections D. power directional relay
Description : A circuit breaker for a 300 KW alternator is rated at 470 amperes of full continuous load. The amount of overcurrent allowed is 125%. Which of the following conditions will trip the breaker? A. ... 10 minutes. C. Momentary starting load of 550 amperes. D. Sustained current flow of 590 amperes.
Description : As a result of a mechanical malfunction in one of the ship's service generators operating in parallel, you must secure that generator. In order to prevent a possible overload to the ... feeder circuit breakers, the malfunctioning prime mover turbine throttle trip, and the generator circuit breaker.
Description : As shown in the illustration, 'B' is a ____________. EL-0058 A. single-pole, double-throw switch B. double-pole, single-throw switch C. double-pole, double-throw switch D. circuit breaker
Description : If an electric motor fails to start, you should FIRST check the _____________. A. phase sequence B. ampere load C. fuse or circuit breaker D. line frequency
Description : To remove an alternator operating in parallel with another unit from the main electrical bus, you must FIRST _________. A. adjust the power factor on both units B. set the desired voltage on ... C. open the circuit breaker on the outgoing alternator D. remove the load from the outgoing alternator
Description : After closing the circuit breaker to place two similar alternators in parallel, the NEXT step is to balance the _____________. A. power factor B. voltage load C. kilowatt load D. ampere load
Description : When an AC or a DC motor fails to start, the FIRST step in troubleshooting should be to check the ____________. A. motor windings for obvious opens B. motor controller leads for continuity C. fuse or circuit breaker D. motor controller leads for grounds
Description : An alternator is being paralleled with one on the line. At the INSTANT the circuit breaker is closed, the frequency of the incoming alternator will normally _____________. A. increase B. not change C. decrease D. be exactly 60 hertz
Description : In the illustration, the contacts between terminals 26 and 27 should be closed when _________. EL-0046 A. using one generator in isochronous mode only B. using two or more generators in ... through varying loads in parallel or single operation D. the circuit breaker is closed for that generator
Description : When paralleling two AC generators, the frequency (cycles) of the incoming generator, just prior to closing the circuit breaker, should be _____________. A. slightly less than the frequency of the generator on ... C. slightly more than the frequency of the generator on the line D. all of the above
Description : If a circuit breaker that utilizes built-in, current limiting fuses (CLF's) cannot be closed, the problem may be traced to __________. A. a blown CLF plunger holding the trip bar in the open position B. a missing CLF C. a misaligned limiter housing assembly D. all of the above
Description : When a fluorescent lamp has reached the end of its useful life, it should be replaced immediately, or the resultant flashing may _____________. A. blow the lamp's circuit breaker B. explode, ... fly in all directions C. short circuit the ballast transformer D. damage the starter and the ballast
Description : How will a molded-case circuit breaker react after it has tripped, as a result of an overloaded circuit? A. The breaker will trip again if immediately reset. B. The breaker handle will lock in ... down. D. The breaker handle cannot be moved to the OFF position until the thermal element cools down.
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
Description : When the operating handle of a molded case circuit breaker is in the mid-position, it indicates the circuit breaker is _____________. A. in the 'opened' position B. in the 'closed' position C. tripped D. reset
Description : You can determine if a circuit breaker is tripped by ______. A. examining the position of the handle B. checking for the warm breaker C. looking for a burned-out link D. looking for the tripped breaker light
Description : A shore power circuit breaker should be closed only _____________. A. when the ship's generators have been directly paralleled to those on shore B. in a shipyard C. if a quick disconnect coupling is used D. when the ship's generators have been removed from the bus
Description : Undervoltage trips are frequently installed on switchboard circuit breakers to trip ____________. A. out generators in the event of severe arcing or sparking B. out generators when there is reversal of power ... , but continues to run D. out generators when there is low voltage in the main circuit
Description : A device which can be used to check the calibration of a circuit breaker is a _________________. A. 500 volt megohmmeter B. portable low voltage high current testing unit C. standard digital multimeter D. clamp-on voltmeter
Description : A reverse-current relay will prevent AC generator motorization by ____________. A. automatically redirecting the load B. automatically speeding up the prime mover C. tripping the panel board main switch D. tripping the generator circuit breaker
Description : You are attempting to parallel two AC generators, and the synchroscope pointer is revolving fast in the clockwise direction. This indicates that the frequency of the incoming machine is _____________. A. higher ... at any pointer position D. the same as the bus frequency but out of phase with it