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
Last Answer : Answer: D
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 : My (soon-to-be-replaced) air conditioner is frequently tripping the circuit breaker in my apartment. What can I do to prevent this?
Last Answer : answer:A mini-split AC unit will use less power than a regular square version and should help with the problem. However if your problem resides in old wiring with a lower amperage/threshold you might ... every time you want to use it but this has cut my electric bill dramatically. Hope this helps
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 : In addition to testing the calibration of a circuit breaker, maintenance should include all of the following EXCEPT ______________. A. changing out of magnetic elements and thermal heaters yearly B. ... for loose or missing parts D. making sure foreign matter does not block tripping element
Last Answer : Answer: A
Description : The arc resulting from the tripping of a circuit breaker is prevented from damaging the contacts by _____________. A. designing the contacts to open slowly B. directing the arc into an ... an inverse timed thermal trip for short circuit currents D. instantaneous magnetic trip for overload currents
Last Answer : Answer: B
Description : Out of the following, the best material capable of withstanding shock & vibration without the danger of cracking is (A) Malleable iron (B) Grey cast iron (C) Chilled cast iron (D) White cast iron
Last Answer : Option A
Description : Write down the circuit breaker with their rating used in traction substation. Explain any one.
Last Answer : Circuit Breaker With Their Rating Used in Traction Substation: Rated capacity of a circuit breaker is 750Amps at 25 kV, 500MVA. Its overall tripping time is 0.14 seconds composed of 0.04 ... but in case of traction substation application, mostly Minimum Oil Circuit Breaker (MOCB) is preferred.
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 : 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 : 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 : Why does our GFCI breaker keep tripping?
Last Answer : More details, please. What appliances are connected to the outlet(s) on this circuit?
Description : Component F in the illustrated device is for _________. EL-0033 A. short circut protection B. latching the trip unit closed after resetting the breaker C. overload protection D. providing a flexible connection between the input terminal G and the tripping unit E
Description : Why breaker tripping is prohibited on very low pressure?
Last Answer : The efficiency with which the arc quenching is taking place in the breaker depends on the air pressure. So if the air pressure is low effective arc quenching will not take place which will result in damage of CB. Hence the tripping of the breaker at very low air pressure is prevented.
Description : Draw a neat labeled diagram to show protective system for AC traction and give the function of each relay used in it.
Last Answer : Protective system for AC traction: Function Of Each Relay: For transformer - Inverse time over current relay- as back up protection on primary (HV side) over current ... against faults near substation Under voltage relay - protection against faults far away from substation
Description : The timer element of a reverse power relay cannot be energized unless _____________. A. the power flow is the same as the tripping direction B. the power flow is the opposite to the tripping direction C. the movement of the disk is damped by a permanent magnet D. one generator is motorized
Description : The timer element of a reverse power relay cannot be energized unless _____________. A. one generator is fully motorized B. the movement of the disk is damped by a permanent magnet C. the power flow is the same as the tripping direction D. the power flow is the opposite to the tripping direction
Description : In the illustration, the purpose of part B is to _________. EL-0033 A. increase resistance in series with the contacts as they close to prevent arcing B. create a magnetic field in the steel ... event of an overload D. provide ventilation to the contact when the breaker is close to rated capacity
Description : Write any four points that state how a traction transformer is different from ordinary transformer.
Last Answer : Ans: 1) Specially designed to withstand severe operating conditions. 2) Are required to have high short time peak capacity. 3) Class A insulation , specially reinforced to withstand frequent short circuits. 4) Can ... effect of SC impedance not less than 8.5 % for 10 MVA and 10 % for 12.5 MVA.
Description : State use of any four relays for the protection of traction transformer.
Last Answer : Relays for the protection of traction transformers: Inverse time over current relay as back up protection on primary (HV side) - over current protection of transformer and other equipment. ... . Buchholz relay - protection from incipient earth or inter winding faults inside the transformer
Description : Define the following terms related to circuit breaker. 1) Breaking Capacity 2) Making Capacity 3) Short time rating and 4) Normal current rating
Last Answer : 1) Breaking Capacity: It is current (r.m.s) that a circuit breaker is capable of breaking at given recovery voltage under specified conditions (e.g. power factor, rate of rise of ... under specified conditions. The only limitation in this case is the temperature rise of current-carrying parts.
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 : 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 : Action carried out by the relay and circuit breaker during fault condition?
Last Answer : Answer: After the relay sensing the fault condition, relay operates and close the trip coils. The effect of this will be circuit breaker operate to open the contacts.
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 : Why circuit breaker connect b)w two transformer (same rating
Last Answer : Because two transformers connection is in parallel to share the load if any transformer is receives the surge current because of the fault so to protect the other transformer from the fault.
Description : Keeping in view the cost and overall effectiveness, the following circuit breaker is best suited for capacitor bank switching. A) Vacuum B) Air blast C) SF6 D) Oil
Last Answer : Keeping in view the cost and overall effectiveness, the following circuit breaker is best suited for capacitor bank switching. A) Vacuum B) Air blast C) SF6 D) Oil
Description : In the illustrated motor controller circuit, which statment is true? EL-0023 A. The high and low speed lights operate at less than line voltage with a resistor in series. B. This controller can be ... . The wattage of the high speed light must be greater than the wattage of the low speed light.
Description : Breaking capacity of a circuit breaker is usually expressed in terms of (1) Ampere (2) Volts (3) MW (4) MVA
Last Answer : Breaking capacity of a circuit breaker is usually expressed in terms of MVA
Description : Mention the various tests carried out in a circuit breaker at HV labs.
Last Answer : Short circuit tests, Synthetic tests& direct tests.
Description : List four special features of traction transformer.
Last Answer : Ans: 1. Specially designed to withstand severe operating conditions. 2. Have high short time peak capacity. 3. Class A insulation specially reinforced to withstand stresses of frequent short circuits. 4. Can take ... SC , impedance not less than 8.5 % for 10 MVA and 10 % for 12.5 MVA.
Description : Mention the withstanding current in our human body.
Last Answer : 9mA
Description : As shown in the illustrations of console schematic diagrams, each circuit card and component, such as a relay or indicating lamp, has an identifier attached. This identifier, which is composed of ... where the item may actually be found on the console by section, surface and possible subassembly
Description : Based on temperature withstanding ability, classify insulating material.
Last Answer : class Temperature withstanding ability in 0C Materials Y 90 Cotton, silk paper and similar organic materials neither impregnated nor immersed in any oil, rubber, PVC. A 105 ... rubber compounds C Above 180 Mica, ceramics, glass, Teflon, quartz, etc.
Description : The purpose of a short circuit forcing module (short time trip) installed in a branch line is to provide ____________. A. high speed clearance of low impedance short circuits in the branch B. ... C. isolation of short circuits by selective tripping of branch circuit breakers D. all of the above
Description : . If the power distribution system shown in figure 2-22 uses selective tripping, what is the time delay rating for each of the circuit breakers shown?
Last Answer : CB1-long time delay; CB2, CB3-short time delay; CB4 through
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 : Making capacity of the circuit breaker depends on (A) operating voltage (B) short circuit MVA (C) fault current (D) All of the above
Last Answer : Making capacity of the circuit breaker depends on (A) operating voltage (B) short circuit MVA (C) fault current (D) All of the above
Description : Why the open circuit test on a transformer is conducted at rated voltage?
Last Answer : A:The open circuit on a transformer is conducted at a rated voltage because core loss depends upon the voltage. This open circuit test gives only core loss or iron loss of the transformer.
Description : A circuit is protected from overheating by a/an ___________. A. pyrometer B. thermal overload relay C. magnetic contactor D. overload transformer
Description : Which of the following precautions should be taken when a blown fuse, rated at 10 amperes, is replaced? A. Short out the fuse before removing it from the circuit. B. Use needle-nose pliers to ... D. Fuses of 10 ampere rating and less are virtually harmless when energized and may be handled freely.
Description : Periodic testing of circuit breakers is necessary to assure that a correctly rated and properly installed unit _________________. A. can trip faster as it increases in age B. will continue to provide ... not exceed its interrupting capacity D. be able to withstand at least 125% of applied voltage
Description : According to the lesson what does Nelson Mandela mean by ―defies the imagination‖? (a) Men and women risking and giving their lives (b) Patriots withstanding so much oppression and brutality without being broken. (c) Both a and b
Last Answer : (b) Patriots withstanding so much oppression and brutality without being broken.
Description : Steel pipe are (A) Suitable for withstanding high internal pressure (B) Connected by riveted or welded joints (C) Generally laid underground and no expansion joint is required (D) Likely to last 100 years under ordinary conditions
Last Answer : (D) Likely to last 100 years under ordinary conditions
Description : Explain about the open and short circuit tests on transformer?
Last Answer : A. Open circuit test (No load test) and short circuit test (full load test) are performed on a transformer to determine (i) Equivalent circuit of transformer (ii) Voltage ... determine copper loss in transformer at full load and parameters of approximate equivalent circuit of transformer.
Description : Purpose of Local breaker back-up relay; type -CTIG
Last Answer : To safe guard against the drastic consequences of failure to clear faults rapidly, many power supply authorities install 2 independent systems of protection for major transmission lines. There remains however the ... reset, which enables the time delay to be set closer to the breaker trip-time.
Description : What is the making current capacity of a 3-phase breaker as derived from its symmetrical breaker capacity?
Last Answer : Making capacity = 2.55 times symmetrical breaking capacity.
Description : If the centrifugal switch or relay used for cutting out the starting winding of a split-phase induction motor fails to open once the motor is in operation, the _____________. A. motor will overspeed B ... C. motor will immediately stall under load D. motor torque will be above normal at rated speed
Description : When troubleshooting a motor controller, all indications are that a relay coil should be energized. If there were no magnetic pull, with rated voltage measured across the coil, the most probable cause ... open C. auxiliary contact in series with the coil is defective D. relay armature is stuck
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'