a) Less transient over voltage due to arcing grounds.
b) Voltage of phases are limited to phase to ground voltage. (No neutral shifting)
c) Allows graded insulation of transformer (low cost)
d) Fast E/F protection.
Description : Why neutrals are solid grounded below 600v?
Last Answer : Human safety Permits enough E/F current because ground resistance is large in less than 415v, hence fast fault clearance, Equipment safety against over voltage.
Description : Why 6.6 kV transformer is resistance grounded by 10 ohms and current limited to 400 A?
Last Answer : a) To reduce burning and melting in faulted switchgear or machine. b) To reduce mechanical stresses in equipment. c) To reduce the electrical hazards by stray ground fault currents in the ground ... screen in 6.6 kV XLPE (cross-linked polyethylene). Therefore the cost of the cable decreases.
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 : Why resistance grounding preferred for less than 33 kV and more than 415 V?
Last Answer : a) To limit the earth fault current for equipment safety else, high short ckt forces dislocate in windings/bus bars etc, b) Over voltage due to arcing ground reduced c) Permits earth fault protection (not possible in ungrounded system)
Description : The generation voltage is usually (A) between 11 KV and 33 KV. (B) between 132 KV and 400 KV. (C) between 400 KV and 700 KV. (D) None of the above.
Last Answer : (A) between 11 KV and 33 KV.
Description : For more complete vessel protection when using an impressed current cathodic system _____________. A. all ship's service alternators have additional temperature sensing devices and a thermal recorder ... with the hull and the propeller shaft is grounded through a slip ring/brush arrangement
Last Answer : Answer: D
Description : For cost and safety, the outdoor substations are installed for voltages above (a) 11 kV (b) 33 kV (c) 60kV (d) 110kV
Last Answer : (b) 33 kV
Description : The operating voltage of extra high tension cables is upto (a) 6.6 kV (b) 11 kV (c) 33 kV (d) 66 kV (e) 132 kV
Last Answer : (d) 66 kV
Description : The operating voltage of supertension cables is up to (a) 3.3 kV (b) 6.6 kV (c) 11 kV (d) 33 kV
Last Answer : (d) 33 kV
Description : Overhead system can be designed for operation up to (a) 11 kV (b) 33 kV (c) 66 kV (d) 400 kV
Last Answer : (c) 66 kV
Description : The underground system cannot be operated above (a) 440 V (b) 11 kV (c) 33 kV (d) 66 kV
Description : Pressure cables are generally not used beyond (a) 11 kV (b) 33 kV (c) 66 kV (d) 132 kV
Description : For transmission of power over a distance of 200 km, the transmission voltage should be (a) 132 kV (b) 66 kV (c) 33 kV (d) 11 kV
Last Answer : (a) 132 kV
Description : Pin type insulators are generally not used for voltages beyond (a) 1 kV (b) 11 kV (c) 22 kV (d) 33 kV
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 : How many insulator disc used for 33 kV transmission voltage line?
Last Answer : 5,As 33kv is Vrms
Description : Solid type cables are considered unreliable beyond 66 kV because (a) insulation may melt due to higher temperature (b) skin effect dominates on the conductor (c) of corona loss between conductor and sheath material (d) there is a danger of breakdown of insulation due to the presence of voids
Last Answer : (d) there is a danger of breakdown of insulation due to the presence of voids
Description : Which of the following statements concerning electrical cables is correct? A. Where they pass through watertight bulkheads, they should be fitted with watertight stuffing boxes. B. Electric cable coverings should ... , or glued in place where nonmetallic insulation is used. D. All of the above.
Last Answer : Answer: A
Description : All electric cables passing through watertight bulkheads must be _____________. A. installed with watertight stuffing tubes B. grounded on both sides of the bulkhead C. fitted with unions on each side of the bulkhead D. welded on both sides of the bulkhead
Description : According to Coast Guard Regulations (46 CFR), the talking and calling circuits of a sound powered telephone system must be _____________. A. intrinsically safe B. independent of each other C. independently grounded D. connected to a common ground
Last Answer : Answer: B
Description : When using the test set-up shown in the illustration, the lighted lamp indicates the winding is ____________. EL-0027 A. grounded B. good C. open D. shorted
Description : When using a megohmmeter to determine which shunt field coil is grounded in a DC machine, you must ____________. A. insulate the field frame from the ship's hull B. disconnect each shunt ... C. use a motor driven high capacity megohmmeter D. remove all main line lead connections before testing
Description : In preparing to take insulation resistance readings on a main generator, the windings should be grounded for about 15 minutes prior to the test to _____________. A. allow accurate zeroing of the meter ... the windings D. help the windings to cool to the same temperature as the ground test connection
Last Answer : Answer: C
Description : Which of the listed conditions might contribute to very rapid wearing of a DC machine's commutator bars? A. A grounded commutator bar B. Using improper carbon brushes C. Aligning the front and rear mica V-rings improperly D. An open circuit in the armature
Description : An open armature connection in a DC propulsion motor could be caused by ____________. A. low-load operation B. clogged ventilation ducts C. sparking at the brushes D. a grounded shunt field coil
Description : When a megohmmeter is being used on a alternating current machine, the meter pointer will dip toward 'zero' and then gradually rise to the true resistance value if the motor insulation is _____________. A. grounded B. good C. shorted D. dirty
Description : A circuit that has one of two wires in contact with the hull of a ship, is called a _____________. A. grounded circuit B. short circuit C. series circuit D. closed circuit
Description : If all of the ground detection lamps burn with equal brilliance, whether the test button is depressed or released, then ___________. A. no grounds exist B. all phases are grounded C. all lamps show a ground D. all of the above
Description : A circuit with a blown fuse would be described as a/an _____________. A. short circuit B. open circuit C. bonded circuit D. grounded circuit
Description : In the illustrated test, if the lamp fails to light on any of the three windings then _________. EL-0027 A. all three windings are grounded and the motor should be sent out for repair B. ... the motor controller and the controller should be checked D. the test should be redone at a higher voltage
Description : In the illustration, the tan and white wires are connected to the solenoid valve. The solinoid valve is_________. EL-0043 A. in the liquid line before the TXV B. energized and open whenever the unit ... so the unit must be modified before using aboard ship D. the water inlet for the ice maker
Description : A voltmeter located on a control panel has been operating correctly for six months, suddenly burns out. After removing it, it is found that neither side of the meter has been grounded. When ... side and the ground C. installed exactly as the old installation D. grounded to the positive side
Description : In the illustration, the tan and white wires are connected to the solenoid valve. The solenoid valve is_________. EL-0042 A. in the liquid line before the TXV B. energized and open whenever the unit ... so the unit must be modified before using aboard ship D. the water inlet for the ice maker
Description : The ground indicating light on the main electrical switchboard is indicating a ground. The best procedure for locating the grounded circuit is to _____________. A. trace the circuit paths while looking for ... a time, until the lights no longer indicate a ground D. check all circuits for continuity
Description : In replacing a defective transformer with a new one, which of the following actions must be carried out to insure proper operation of the equipment it serves? A. The secondary leads must be grounded ... magnetize it. D. The iron core must be grounded for 10 minutes to remove any residual magnetism.
Description : If all three ground-detection lamps continue to burn at equal intensity after the test button is depressed and released, which of the listed conditions is indicated? A. No grounds exist B. All three phases are grounded C. The test switch is faulty D. The current transformers are shorted out
Description : If the illustrated test is being performed to determine which winding is grounded and the light does not come on then __________. EL-0027 A. winding is grounded and you should continue on to the ... the windings but probabily in the pecker head, you should check and retape the line lead connections
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 : The vertical dotted line connecting the small circular symbols at coordinates '05L', '09L', '13L', '21L', '25L', etc., shown in the illustration, indicate that all _______________. EL-0100 A. contacts are ... board 'TB2' C. wires are grounded at both ends of the line D. wires have a common shield
Description : Violent gassing developed by a lead-acid battery during charging indicates that the ____________. A. plate separators are grounded B. cell voltages are excessive C. specific gravity in insufficient D. charging rate is excessive
Description : Before servicing the device indicated as 'A' in panels #1 and #3 of the illustration, the device labeled 'CT' must __________. EL-0003 A. have the disconnected leads taped to prevent ... D. have one lead grounded to discharge static electricity for the prevention of damage to electronic components
Description : Which of the instruments listed could be use to locate a grounded field coil in a synchronous motor? A. Ammeter B. Voltmeter C. Megohmmeter D. Frequency meter
Description : In which of the situations listed will a megohmmeter give the most accurate readings? A. While the machine is in operation. B. While the machine is discharging static electricity. C. Immediately prior to ... machine. D. When the machine has been shut down and grounded for a period of 15 minutes.
Description : The leads from a megohmmeter are attached to the leads of an AC motor field coil. A reading of infinity is obtained indicating a/an ____________. A. open field coil B. shorted field coil C. grounded field coil D. shunted field coil
Description : While paralleling two (2) AC generators using synchronizing lamps only, both lamps will go dark when the generators are ____________. A. running at the same speed B. grounded C. of the same polarity D. in phase
Description : In the system shown in the illustration, the station at section I is unable to signal any other station nor is any other station able to signal the station in section I. The station can, however, ring ... only a single station to respond to itself. D. The switch at component 'C' is stuck open.
Description : As shown in the illustration, when the 'speed control' system is in 'SPLIT' _______________. EL-0096 A. Relays #1, #5 and #8 are not used B. the 'slew rated controller' is grounded through Relay ... E/P converters' are bypassed and air is fed directly to the governors via the 'load sharing valve'