During unit operation, can we parallel 2 SUT?

During unit operation, can we parallel 2 SUT? 
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1 Answer

Answer :

No, due to switchgear limitation. 
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Related questions

During unit operation, can we parallel UT & SUT continuously?

Description : During unit operation, can we parallel UT & SUT continuously?

Last Answer : No, due to switchgear limitation.  

What are the protections for SUT?

Description : What are the protections for SUT? 

Last Answer : a) Over current protection for phase and earth fault b) Differential protection c) HV and LV restricted earthfault protection  d) HV side directional back up over current protection for phase ... protection f) Over fluxing protection g) Buchholz and high oil, winding temperature protection. 

Why vector group of SUT is chosen as Yn-Yo-Yo?

Description : Why vector group of SUT is chosen as Yn-Yo-Yo?

Last Answer : To facilitate momentary paralleling of SUT with UT on 6.6kV buses.  

Why UT, SUT secondary is rated for 6.9kV where as bus voltage is 6.6kV?

Description : Why UT, SUT secondary is rated for 6.9kV where as bus voltage is 6.6kV? 

Last Answer : The no load secondary 6.9kV voltage level adequately takes into account voltage drop during loaded condition to cater station buses at 6.6kV level. 

Why twin secondary SUT?

Description : Why twin secondary SUT? 

Last Answer : As per is, the rating single secondary power transformer is limited to 25MVA (6.6 kV) or 40 MVA (11 kV), in order to limit the 3 phase symmetrical fault level with in 26-40 kA (contribution from grid and local machines) 

Why REF is provided in the LV side of SUT and UT?

Description : Why REF is provided in the LV side of SUT and UT? 

Last Answer : The LV sides of the two transformers are earthed through the resistance. This will limit the flow of current in case of LV earth fault. Hence the differential protection may not act for a LV earth fault. Hence ref protection is provided. 

Why the neutral is earthed through earthing resistance in case of UT and SUT?

Description : Why the neutral is earthed through earthing resistance in case of UT and SUT? 

Last Answer : This is done to limit the earth fault current.  

What is the vector group of GT, UT, SUT?

Description : What is the vector group of GT, UT, SUT?

Last Answer : Yd11 Dy1 Yy0 

What is the coverage of differential protection for SUT?

Description : What is the coverage of differential protection for SUT?

Last Answer : Covers from 230 kV bushing to 6.6 kV breaker end.  

What is E/F current limit for SUT and UT?

Description : What is E/F current limit for SUT and UT?

Last Answer : 400a limited by 10 ohms resistor.  

Purpose of standby E/F protection in SUT/UT?

Description : Purpose of standby E/F protection in SUT/UT? 

Last Answer : Back up for LV winding, LV neutral CT- CDG 12 – resistance earthing – relay set high time delay to discriminate with LV feeder and trip transformer if sustained E/F, also protects neutral earthing resistor.

Why REF is now is used for HV side also in GT/SUT?

Description : Why REF is now is used for HV side also in GT/SUT?

Last Answer : The E/F setting of differential is poor.  

During unit operation can we have one UT feeding both unit 6.6 kV loads?

Description : During unit operation can we have one UT feeding both unit 6.6 kV loads? 

Last Answer : No, logically prevented.  

Can we trip GFB from control room during unit operation?

Description : Can we trip GFB from control room during unit operation?  

Last Answer : No only if generator breaker is off.  

A vessel is equipped with two ship's service generators. Generator #1 is rated at 900 kw and generator #2 is rated at 600 kw. During parallel operation, with a hotel load of 1,000 kw, what should be the kw load on generator #2? A. 100 kw B. 400 kw C. 500 kw D. 600 kw

Description : A vessel is equipped with two ship's service generators. Generator #1 is rated at 900 kw and generator #2 is rated at 600 kw. During parallel operation, with a hotel load of 1,000 kw, what should be the kw load on generator #2? A. 100 kw B. 400 kw C. 500 kw D. 600 kw

Last Answer : Answer: B

Coast Guard Regulations (46 CFR) require that each alternating current generator arranged for parallel operation shall be provided with _____________. A. more than one means of excitation B. individual circuit fuses C. a high back-pressure trip D. a reverse-power trip

Description : Coast Guard Regulations (46 CFR) require that each alternating current generator arranged for parallel operation shall be provided with _____________. A. more than one means of excitation B. individual circuit fuses C. a high back-pressure trip D. a reverse-power trip

Last Answer : Answer: D

Which of the following statements is true concerning the operation of two alternators in parallel? A. The cycles per second of each alternator are the same. B. Both alternator governors must be set with the same amount of speed droop. C. The number of field poles must be the same on each alternator. D. The load must always be divided equally between alternators.

Description : Which of the following statements is true concerning the operation of two alternators in parallel? A. The cycles per second of each alternator are the same. B. Both alternator governors must be set ... be the same on each alternator. D. The load must always be divided equally between alternators.

Last Answer : Answer: A

Which of the following should be the FIRST step in removing a generator from parallel operation? A. Trip the generator off the switchboard. B. Turn off all electrical equipment. C. Remove the load from the 'off going' generator. D. Increase the cycles of the generator staying on the line.

Description : Which of the following should be the FIRST step in removing a generator from parallel operation? A. Trip the generator off the switchboard. B. Turn off all electrical equipment. C. Remove the load from the 'off going' generator. D. Increase the cycles of the generator staying on the line.

Last Answer : Answer: C

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 parallel only C. the prime mover speed is to remain constant through varying loads in parallel or single operation D. the circuit breaker is closed for that generator

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

Last Answer : Answer: C

What are the conditions for parallel operation of two transformers ?

Description : What are the conditions for parallel operation of two transformers ?

Last Answer : Transformers which are to be operated parallel should have to satisfy the following conditions: Polarities of both the transformers should be same else lead to short circuit Voltage rating of ... Phase displacement of transformers should be same Phase sequence of two transformers should be same

What are the conditions for parallel operation of two transformers ?

Description : What are the conditions for parallel operation of two transformers ?

Last Answer : Transformers which are to be operated parallel should have to satisfy the following conditions: Polarities of both the transformers should be same else lead to short circuit Voltage rating of ... Phase displacement of transformers should be same Phase sequence of two transformers should be same

What are the Conditions for parallel operation of transformers?

Description : What are the Conditions for parallel operation of transformers?

Last Answer : A. a) Same voltage ratio of transformer: If two transformers of different voltage ratio, are connected in parallel with same primary supply voltage, there will be a difference in secondary voltages. If ... not in same phase sequence, during the cycle, each pair of phases will be short circuited.

What are the advantages of parallel operation of transformers?

Description : What are the advantages of parallel operation of transformers?

Last Answer : A. 1) To maximize electrical power system efficiency: Generally electrical power transformer gives the maximum efficiency at full load. If we run numbers of transformers in parallel, we can switch ... running in parallel can be removed from system to balance the capital investment and its return.

What Are The Conditions To Be Satisfied For Parallel Operation Of Dc Generators?

Description : What Are The Conditions To Be Satisfied For Parallel Operation Of Dc Generators?

Last Answer : The polarities of the generators must be same or the connections must be interchanged till they become same. The voltages of both the generators must be equal. The change of voltage with ... and negative terminals of generators must be connected properly to the positive and negative of busbar.

What steps are to be taken before disconnecting one Alternator from parallel operation?

Description : What steps are to be taken before disconnecting one Alternator from parallel operation?

Last Answer : The following steps are to be taken before disconnecting one Alternator from parallel operation · The prime-mover input of the outgoing generator has to be decreased and that of other generators ... delivered by the outgoing generator is zero, it has to be disconnected from parallel operation.

What is need of parallel operation of alternators?

Description : What is need of parallel operation of alternators?

Last Answer : 1. Optimum utilization of alternators as most of the power stations are interconnected by grid. 2. Reduced operating cost: number of alternators operating at a time can be changed depending on ... demands. 3. Easy maintenance: Alternator may be shut down for maintenance 4. Continuity and reliability

What are the conditions for parallel operation of transformer?

Description : What are the conditions for parallel operation of transformer?

Last Answer : -Equal polarity -Equal turn ratio -percentage impedance should be same -Equal X/R ratio -Equal KVA rating -Equal phase sequence

What is the need for parallel operation of transformer?

Description : What is the need for parallel operation of transformer?

Last Answer : -Non availability of single large transformer to meet the load -Increased power demand -To improve reliability -If many smaller transformer is used one can be used as spare -Transportation problem for large transformer.

Two transformers of identical voltages but different capacities are operated in parallel, for satisfactory load sharing: a) Impedances should be equal b) Per unit impedance must be equal c) per unit impedance and X/R ratio must be equal d) Impedance and X/R ratio must be equal

Description : Two transformers of identical voltages but different capacities are operated in parallel, for satisfactory load sharing: a) Impedances should be equal b) Per unit impedance must be equal c) per unit impedance and X/R ratio must be equal d) Impedance and X/R ratio must be equal

Last Answer : Ans: C

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 the outgoing alternator C. open the circuit breaker on the outgoing alternator D. remove the load from the outgoing alternator

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

Last Answer : Answer: D

Two AC generators of the same capacity are operating in parallel. One with a zero speed droop setting and the other with a 5% speed droop. If its capacity is not exceeded, the unit whose governor has the zero speed droop setting will _____________. A. assume the smaller share of the load B. maintain the frequency of the system C. have poor sensitivity characteristics D. have poor power response

Description : Two AC generators of the same capacity are operating in parallel. One with a zero speed droop setting and the other with a 5% speed droop. If its capacity is not exceeded, the unit whose ... B. maintain the frequency of the system C. have poor sensitivity characteristics D. have poor power response

Last Answer : Answer: B

Two transformers operating in parallel will share the load depending upon their (A) Rating. (B) Leakage reactance. (C) Efficiency. (D) Per-unit impedance.

Description : Two transformers operating in parallel will share the load depending upon their (A) Rating. (B) Leakage reactance. (C) Efficiency. (D) Per-unit impedance.

Last Answer : Ans: A Transformers having higher kVA rating will share more load.

For the parallel operation of two or more D.C. compound generators, we should ensure that?

Last Answer : For the parallel operation of two or more D.C. compound generators, we should ensure that series fields of all generators should be either on positive side or negative side of the armature.

The purpose of 'R6' in the winch circuit shown in the illustration is to _______________. EL-0102 A. maintain dry conditions within the winch brake box B. keep the series field current at a low value during 'fourth and fifth point lowering' C. act as the armature dynamic braking load to assist the winch in stopping D. limit the armature current during lowering operation with heavy loads

Description : The purpose of 'R6' in the winch circuit shown in the illustration is to _______________. EL-0102 A. maintain dry conditions within the winch brake box B. keep the series field current at ... to assist the winch in stopping D. limit the armature current during lowering operation with heavy loads

Last Answer : Answer: C

Magnetic controller contacts may become welded together during operation because of _____________. A. excessive magnetic gap B. low contact pressure C. an open coil D. excessive ambient temperature

Description : Magnetic controller contacts may become welded together during operation because of _____________. A. excessive magnetic gap B. low contact pressure C. an open coil D. excessive ambient temperature

Last Answer : Answer: B

During its operation, loud buzzing and resultant welding of contacts of a magnetic relay may be caused by __________. A. overheating of the contactor coil B. low voltage on the operating coil C. low insulation resistance to ground D. lubrication of the contact bearing points

Description : During its operation, loud buzzing and resultant welding of contacts of a magnetic relay may be caused by __________. A. overheating of the contactor coil B. low voltage on the operating coil C. low insulation resistance to ground D. lubrication of the contact bearing points

Last Answer : Answer: B

Magnetic controller contacts may become welded together during operation due to _____________. A. an open coil B. low contact pressure C. excessive ambient temperature D. excessive magnetic gap

Description : Magnetic controller contacts may become welded together during operation due to _____________. A. an open coil B. low contact pressure C. excessive ambient temperature D. excessive magnetic gap

Last Answer : Answer: B

Before testing insulation with a megohmmeter, the windings of large machines should be grounded for about 15 minutes just prior to the test as the ______________. A. insulation may be damaged B. insulation may be covered with moisture C. armature windings will have a greater number of leakage paths D. larger machines may acquire a charge of static electricity during operation

Description : Before testing insulation with a megohmmeter, the windings of large machines should be grounded for about 15 minutes just prior to the test as the ______________. A. insulation may be damaged ... number of leakage paths D. larger machines may acquire a charge of static electricity during operation

Last Answer : Answer: D

The arrow drawn through the component shown in the illustration means that the device's value _____________. EL-0015 A. is fixed and cannot be changed B. is variable between two limits C. has yet to be determined for the circuit application D. is not allowed to change during circuit operation

Description : The arrow drawn through the component shown in the illustration means that the device's value _____________. EL-0015 A. is fixed and cannot be changed B. is variable between two limits C. has yet to be determined for the circuit application D. is not allowed to change during circuit operation

Last Answer : Answer: B

What are V1 and V2? How they are connected? What is the harm in opening F/M vault door during reactor operation?

Description : What are V1 and V2? How they are connected? What is the harm in opening F/M vault door during reactor operation? 

Last Answer : The reactor building is divided into two areas. They are V1 and V2. V1 - Dry volume area. V2 - Wet volume area. V1 area includes F/M vault, boiler room, and entire dome area. ... directly goes to F/M maintenance area, which is a V2 area. Thus pressurizing the entire building. 

What is the cooling water used in moderator heat exchanger during normal operation? And during class IV failure?

Description : What is the cooling water used in moderator heat exchanger during normal operation? And during class IV failure?

Last Answer : During normal operation process LP water is used in moderator heat exchangers, which transfers heat to seawater. During class IV failure firewater is used for the moderator heat exchanger. 

Transformer Parallel Operation Why To do Is it

Last Answer : Transformer Rated Load Wait More Load Power For Supply To do Is.

The operation of revolving a plane table about its vertical axis so that all lines on the sheet become parallel to corresponding lines on the ground, is known (A) Levelling (B) Centering (C) Orientation (D) Setting

Description : The operation of revolving a plane table about its vertical axis so that all lines on the sheet become parallel to corresponding lines on the ground, is known (A) Levelling (B) Centering (C) Orientation (D) Setting

Last Answer : (C) Orientation

What generator characteristics must be considered when alternators are synchronized for parallel operation?

Description : What generator characteristics must be considered when alternators are synchronized for parallel operation?

Last Answer : Output voltage, frequency, and phase relationships.

Which of the following are the functions of operating system? i) recovering from errors ii) facilitating input/output iii) facilitating parallel operation iv) sharing hardware among users v) implementing user interface A) i, ii, ii, and v only B) i, ii, iii, and iv only C) ii, iii, iv and v only D) All i, ii, iii, iv and v

Description : Which of the following are the functions of operating system? i) recovering from errors ii) facilitating input/output iii) facilitating parallel operation iv) sharing hardware among users v) implementing user interface A) i, ii, ... only C) ii, iii, iv and v only D) All i, ii, iii, iv and v

Last Answer : D) All i, ii, iii, iv and v

Use the new system as the same time as the old system to compare the results. This is known as … A) Procedure Writing B) Simultaneous processing C) Parallel Operation D) File Conversion

Description : Use the new system as the same time as the old system to compare the results. This is known as … A) Procedure Writing B) Simultaneous processing C) Parallel Operation D) File Conversion

Last Answer : C) Parallel Operation

The ideal level of operation for a pure monopoly firm is the level where (a) TR and STC curve are parallel to each other ; (b) TR = TC ; (c) TR = Total variable cost; (d) TR is less than STC

Description : The ideal level of operation for a pure monopoly firm is the level where (a) TR and STC curve are parallel to each other ; (b) TR = TC ; (c) TR = Total variable cost; (d) TR is less than STC 

Last Answer : (a) TR and STC curve are parallel to each other ; 

State any two conditions for parallel operation of 3-phase transformer.

Description : State any two conditions for parallel operation of 3-phase transformer.

Last Answer : Conditions for Parallel operation of 3 phase transformer 1) Voltage ratings of both the transformers must be identical. 2) Percentage or p.u. impedance should be equal in magnitude. 3) X/R ratio ... between primary & secondary voltages must be same. 6) Phase sequence on both sides must be same.