Description : Why cannot we have cables instead of bus duct in main generator?
Last Answer : Very large number of cables in parallel required problems of sealing the terminations.
Description : Which is better, whether a) Phase segregated bus duct or b) Common bus duct?
Last Answer : Phase segregated bus duct is better, since phase to phase faults are avoided.
Description : Where fault level is more, whether in generator bus duct or UT bus duct? Why?
Last Answer : Fault level is more in UT bus duct. Because the fault currents fed by the both generator and GT adds up within UT bus duct in case there is a fault in UT bus duct.
Description : How moisture entry is prevented into bus duct?
Last Answer : Silicagel breathers at either end.
Description : What is the design basis of 6.6 kV aluminium bus bars?
Last Answer : a) Temperature rises not exceed 90 ºC. b) Withstand short ckt stresses. c) Take care of thermal expansion.
Description : Why aluminium bus bars are silver-plated in IPBD?
Last Answer : Aluminium bus bars are silver-plated at flexible connection to prevent the galvanic corrosion ant also for low contact resistance.
Description : Which of the listed safety features should be provided in small rooms or lockers where batteries are stored? A. Installation of a fixed CO2 system. B. An exhaust duct is to be provided and led from within ... An exhaust duct is to be provided and led from the top of the locker to the open air.
Last Answer : Answer: D
Description : Earth wire or ground wire is made of: a) copper b) aluminium c) iron d) galvanized steel
Last Answer : Ans: D
Description : Why bimetallic washers provided in aluminium copper transition joints?
Last Answer : To avoid galvanic corrosion failure.
Description : Why cast aluminium tri-foil clamp is used in single core cables laying?
Last Answer : When three conductors are clamped together the fluxes around the conductors are get cancelled
Description : What is resistance of copper compare to the aluminium?
Last Answer : Copper is less resistive than aluminium.
Description : hy aluminium armouring for single core 1000 mm2 is used?
Last Answer : Aluminium armouring for single core 1000 mm2 is used so that heating will not take place due to the flux around the conductor, as the aluminium is a non-magnetic material.
Description : ACSR (Aluminium Conductor Steel Reinforced) are used as (A) over head transmission lines. (B) super conductors. (C) fuse (D) underground cables.
Last Answer : (A) over head transmission lines.
Description : Which of the following is/are true concerning electric power operated watertight door systems? A. Each motor driven door must use the main bus as its source of power. B. Each distribution panel for ... to permit quick activation of the system. D. Each system must have a separate branch circuit.
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.
Last Answer : Answer: C
Description : In the schematic diagram of the DC compound generator shown in the illustration, the positive ammeter reading is 500 amps and the negative ammeter reading is 475 amps. What is the current flow through the neutral bus? EL-0037 A. 0 amp B. 12.5 amp C. 25 amp D. 975 amp
Description : Upon failure of the normal power supply, the emergency generator is placed on the line by the _____________. A. bus tie feeder B. automatic bus transfer device C. line connection feeder D. power failure alarm bus
Last Answer : Answer: B
Description : The purpose of the automatic bus transfer shown in the illustration is to ___________. EL-0014 A. stepdown voltage to the lighting distribution panel B. provide emergency power to ... emergency switchboard from the main switchboard D. provide overcurrent protection to the lighting distribution panel
Description : An alternator switchboard has a synchroscope and synchronizing lamps. If the synchroscope is broken, which of the steps listed is the most essential before an alternator can be paralleled with the bus? ... D. A portable phase sequence indicator must be used to verify the information from the lamps.
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 : As shown in the illustration, the function of the switch labeled 'PFSW' is to determine the ______________. EL-0003 A. bus frequency B. reactive volt amperes of the bus C. frequency of either generator D. power factor of either generator
Description : Motorization of an alternator is undesirable because _____________. A. the alternator will be damaged B. it puts an additional load on the bus C. high voltage pulses are induced in the bus D. all of the above
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 bus bar is 3 inches wide and 0.375 inches thick. What size of round conductor (in circular mils) is necessary to carry the same current as the bus bar? A. 1,125,000 circular mils B. 1,250,000 circular mils C. 1,432,000 circular mils D. 1,547,000 circular mils
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 : Attempting to parallel an AC generator which is out of phase with the bus will result in which of the following problems? A. The breaker should trip. B. The KVA will decrease. C. The synchronizing lamps will burn out. D. The power factor will be unitized.
Description : If field excitation is suddenly lost to an alternator operating in parallel, that alternator will _____________. A. supply excessive current to the bus B. operate at the same load, but with reduced voltage C. lose its load and tend to overspeed D. become overloaded and slow down
Description : Two paralleled alternators are operating near rated load. If one trips out mechanically, which of the listed actions should be taken FIRST? A. Restart the tripped machine immediately. B. Strip the board ... circuits. C. Start the emergency generator. D. Transfer all vital loads to the emergency bus.
Description : Multiple grounds have developed and were initialy indicated by the grounddetecting system as one ground. The FIRST step in locating the grounds is to _____________. A. examine the main bus bars ... no longer indicates any grounds C. change over generators D. check each circuit with a megohmmeter
Description : When paralleling two AC generators, the frequency of the machine coming online, immediately prior to closing its breaker, should be ____________. A. slightly less than the oncoming generator frequency B. the ... bus frequency C. slightly greater than the bus frequency D. the same as the bus voltage
Description : When paralleling two AC generators, the frequency of the incoming machine immediately prior to closing its breaker should be ____________. A. controlled by placing the governor switch in the automatic ... regulator C. slightly greater than the bus frequency D. slightly less than the bus frequency
Description : In the illustrated 450 VAC system, what should be provided between the bus and the device labeled 'F'? EL-0003 A. a potential transformer B. a current transformer C. an emergency disconnect device D. an audible alarm and indicating light
Description : What do the arrow-like symbols at coordinate '33J' shown in the illustration represent? EL-0099 A. Connection to ground. B. Connection to the analog common bus. C. Plug-in connection. D. Screw connection on a terminal board.
Description : When paralleling two alternators the synchronizing lamps grow dim and are totally darkened as the synchroscope pointer approaches the 0° position. This indicates the ____________. A. alternator voltages ... alternator is in phase with the bus voltage D. synchroscope pointer is defective or broken
Description : When paralleling two AC generators, the synchroscope selector switch and frequency meter switch should be set up to sense the frequency of the _____________. A. bus B. generator on the line C. oncoming generator D. bus transfer relay
Description : When paralleling two alternators using three synchronizing lamps, the flickering of all three lamps becomes progressively slower and slower. This means the ______________. A. frequency of the incoming ... the bus D. terminal voltage of the incoming alternator is approaching that of the bus
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 : The circuit illustrated represents a 2 wire DC ground detecting system. If the positive bus is grounded and the test button is pushed, which of the lamps will be brightest? EL-0008 A. X B. Y C. both will be equal brightness. D. both will go out.
Description : In the illustrated one line diagram, if the turbo generator fails, the diesel generator_________. EL-0014 A. will automaticly start and supply power to the emergency power switchboard, the power ... be manually started but once running will supply power to the lighting main through the ABT.
Description : The operating torque of the upper induction disc-type element, or timer element, of an AC reverse power relay is obtained from ____________. A. the main bus B. a separate battery source C. line voltage D. electromagnets
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
Description : The devices labeled 'L' in the illustration are _________. EL-0003 A. load lights indicating that the generator breaker is closed and the generator is supplying power to the main bus B. ... o'clock position the lights are at their dimmest or out indicating the the generators are in phase
Description : You are attempting to parallel two AC generators and the synchroscope pointer stops at a position other than 0°. If you close the circuit breaker at this moment _____________. A. the incoming ... hazardous condition will be created by the incoming machine being at a higher frequency than the bus
Description : You are attempting to parallel two AC generators, and the synchroscope pointer is revolving in the fast direction. This indicates that the frequency of the incoming machine is _____________. A. higher ... the same as the bus frequency and the circuit breaker may be closed at any pointer position
Description : The heaters for the winch circuit shown in the illustration are powered from _____________. EL-0102 A. a separate source B. the winch main bus C. the master switch power circuit D. the contactor control circuit
Description : You are attempting to parallel two AC generators and the synchroscope pointer is revolving slowly in the fast direction. You should _____________. A. use the governor control switch to adjust the incoming ... the 0° position D. use the field rheostat to adjust the speed of the incoming machine
Description : You are attempting to parallel two AC generators and the synchroscope pointer stops at a position other than 0° prior to closing the circuit breaker. This indicates ___________. A. the frequency of ... be closed after breaker has been reset D. there is an existing cross current between generators
Description : Periodic testing by a shoreside support technician using a special camera which can detect potentially dangerous loose or corroded bus bar and controller connections is termed ______________. A. heat sensitive thermography B. visual pyrotronics C. corrosion electrolysis D. electric vibroanalysis
Description : You are attempting to parallel two AC generators and the synchroscope pointer is revolving in the slow direction. This indicates that the frequency of the incoming machine is _____________. A. higher than ... same as the bus frequency, and the circuit breaker may be closed at any pointer position