What FCN was implemented to avoid reactor trip on 220V-DC failure of PHT and PPP breakers?

1 Answer

Answer :

The breaker close position supervision relay VAA 21 is changed by VAJC type, contacts position do not change if 220V-DC is lost now.

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Description : When 220V dc shunt alternator generating the voltage at rated value. If direction of rotation is reversed, then alternator will a) Build up its voltage with same polarity b) Build up its voltage with opposite polarity c) No build up of voltage d) None

Last Answer : Ans: No build up of voltage

Description : A dc shunt generator has a speed of 800 rpm when delivering 20 A to the load at the terminal voltage of 220V. If the same machine is run as a motor it takes a line current of 20A from 220V supply. The speed of ... . (B) more than 800 rpm. (C) less than 800 rpm. (D) both higher or lower than 800 rpm.

Last Answer : (C) less than 800 rpm.

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

Last Answer : Answer: D

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

Last Answer : Answer: B

Description : The purpose of a main switchboard circuit breaker's reverse-power trip is to _____________. A. prevent main circuit overload B. protect the circuit breaker blowout coil C. prevent alternator motorization D. prevent low voltage tripout

Last Answer : Answer: C

Description : Protection against sustained overloads occurring in molded-case circuit breakers is provided by a/an __________. A. overvoltage release B. thermal acting trip C. thermal overload relay D. current overload relay

Last Answer : Answer: B

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

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Description : What is the 2 stage stalling protection for PHT motor?

Last Answer : Because locked rotors withstand time of motor is less than starting time of motor under reduced voltage conditions. Stage 1 = 350% 6 sec for starting at rated voltage (Because starting time = 6 ... time under reduced voltage condition (Since starting current is less, stage 1 will not operate) 

Description : Why differential protection for PHT motors?

Last Answer : For more than 2500 kW motors it is required to provide differential protection. It is biased Relay against internal phase fault or earth fault very fast. Insensitive to starting current and stalling current. 

Description : Why bi-directional flow is chosen for PHT system?

Last Answer : Bi-directional flow is chosen for PHT system because, a. Uniform temperature gradient is facilitated so there will be no differential thermal expansion. b. It facilitates fuelling even when the ... , which facilitates uniform neutron flux and this intern gives rise to maximum fuel burns up. 

Description : What are the main futures of PHT system?  

Last Answer : a. Impeller – To reduce the water flow. b. Self-injection Hx – Cools the water in case of leakage. c. Gland supply – Cools the seals. d. Primary and secondary seals – sealing the pump. e. Thrust bearing – To take the axial thrust. 

Description : What are the materials in contact with PHT system?

Last Answer : Piping – carbon steel. Pressure tubes – zircalloy-2 Fuel cladding – zircalloy-2 End shield – stainless steel. Etc. 

Description : How coolant flow is maintained in the event of loss of power to the PHT system?

Last Answer : When the PHT power fails, it takes two minutes for DG to come to full power. The circulation is maintained by flywheel, which increases the de-acceleration and maintains the flow for two minutes. If ... which more denser cold water comes down and less denser hot water goes up by convection method. 

Description : In three pin plug 6 Amp. 220v AC rating. why earth pin diameter is higher than ohter two pin? what its purpose ?

Last Answer : Because Current flow in the conductor is inversely proportional to the conductor diameter. So if any short circuits occur in the system first high currents bypassed in the Earthling terminal.( R=Pl/a area of the conductor increases resistance value decreases)

Description : A 220/440 V, 50 Hz, 5 KVA, single phase transformer operates on 220V, 40Hz supply with secondary winding open circuited. Then (A) Both eddy current and hysteresis losses decreases. (B) Both ... same but hysteresis loss increases. (D) Eddy current loss increases but hysteresis loss remains the same.

Last Answer : (A) Both eddy current and hysteresis losses decreases.

Description : When power is restored after a complete power failure, a steering gear pump motor will ____________. A. have to be restarted B. have to be reset C. restart automatically D. trip its overload relays

Last Answer : Answer: C

Description : A saturable reactor uses relatively small DC currents to control _______________. A. high frequency low power loads B. low frequency low power loads C. high frequency high power loads D. low frequency high power loads

Last Answer : Answer: D

Description : An electrical device which employs a stationary armature and a rotating electromagnetic field is used aboard ship as a ____________. A. magnetic amplifier B. ship's service alternator C. three-wire DC generator D. saturable core reactor

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Description : The 24 volt DC bus on the emergency switchboard is used to supply power to the _____________. A. general alarm system B. gyrocompass power failure alarm system C. smoke detection system D. all of the above

Last Answer : Answer: D

Description : To avoid damaging the components of a printed circuit board when testing it with a DC volt-ohmmeter, you should _______. A. ground the board B. avoid reversing the polarity of the leads C. isolate sensitive components with heat sinks D. all of the above

Last Answer : Answer: B

Description : Accidental grounds in a shipboard electrical system must be repaired as soon as possible as they will ____________. A. result in immediate power outages B. damage circuit breakers C. appear on the ground detection system D. damage insulation and may cause outages

Last Answer : Answer: D

Description : A ground is indicated by the ground-detecting system on the main electrical switchboard. The FIRST step in locating the actual ground is to _____________. A. close all circuit breakers in ... ground detection system indicates normal C. change over generators D. check each circuit with a megohmmeter

Last Answer : Answer: B

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 : You can determine if a circuit breaker has tripped by ________________. A. examining the position of the handle B. checking for which of the breakers is warm C. looking for a burned-out link D. all of the above

Last Answer : Answer: A

Description : A 'dead front' switchboard is one _____________. A. without switches on it B. with insulated switches and no exposed terminals C. without circuit breakers D. without safety hand rails nor rubber mats

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Description : What are different types of circuit breakers employed in thermal power plant?

Last Answer : Answer: For low voltage operation 415/220V vacuum circuit breakers or air break circuit breakers are employed. For voltage ratings about 6.6kV and beyond SF6 circuit breakers are employed.

Description : What are different types of circuit breakers employed in thermal power plant?

Last Answer : For low voltage operation 415/220V vacuum circuit breakers or air break circuit breakers are employed. For voltage ratings about 6.6kV and beyond SF6 circuit breakers are employed.

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 : 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 : Why we need isolation transformers in power circuit ? why cant we use breakers to isolate?

Last Answer : In Isolation transformer is used, if there is change in parameter values of any side, the other side parameters will remain unchanged.

Description : How direct tests are conducted in circuit breakers?

Last Answer : Using a short circuit generator as the source. Using the power utility system or network as the source.

Description : State the different types of circuit breakers.

Last Answer : Air ,oil,vacuum circuit breakers.

Description : Write the classifications of test conducted on circuit breakers.

Last Answer : Type test Routine test Reliability test Commissioning test

Description : Write the classification of circuit breakers based on the medium used for arc extinction?

Last Answer : Air break circuit breaker Oil circuit breaker Minimum oil circuit breaker Air blast circuit breaker SF6 circuit breaker Vacuum circuit breaker

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 : What are the protections provided in PMCC circuit breakers?

Last Answer : 1. IDMT O/C (CDG 34). 2. IDMT E/F (CDG 11).  3. Under voltage (40% of 110V). 

Description : Why under voltage tripping of motor is incorporated in motor feeder breakers? 

Last Answer : The under voltage can occur in case of bus fault. If the motors are kept connected they will feed the fault which may cause the damage. Due to the back feeding from the motor the motor will slow down ... case pht motor will not rotate for the designed 3 minute period in case of bus under voltage).  

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 type breakers are provided in 6.6 kV buses?

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Description : Can I use this electrical AC cord in Europe where its 220V?

Last Answer : The plugs are a different shape in Europe. If you go to Radio Shack, they will sell you a plug adaptor kit and and a voltage converter.

Description : What happens if I plug a surge protector into a 220V outlet?

Last Answer : I think you should read this first: http://www.gson.org/stepdown/

Description : What is PPP ?

Last Answer : PPP means public-private partnership.

Description : What does PPP mean in economics ?

Last Answer : : PPP (Purchasing Power Parity) is a popular indicator or theoretical method of measuring the actual purchasing power of a currency in different countries. According to this theory, the long-term fixed exchange rate of two currencies is basically the purchasing power of these two currencies.

Description : What is the full form of PPP ?

Last Answer : The full form of PPP Popularization Of The People's Program.

Last Answer : Public Private Partnership / Purchasing Power Parity

Description : Will a 220v air conditioner raise my electric bill more than a 110v?

Last Answer : Yes. The 220 volt AC unit pulls more energy then a 110 volt. It basically draws double the power. It needs more elctricity to power it's internal componants.