What are the main sources of power supply to 6.6 kV buses? 

1 Answer

Answer :

a. Unit transformer which steps down the generated voltage to 6.6 kV from the generator. b. Start up transformer, which steps down the grid voltage to 6.6 kV. 

Related questions

Description : What type breakers are provided in 6.6 kV buses?

Last Answer : ABB. Make, SF6 gas, 1250A and 2000A capacity circuit breakers are provided in 6.6 kV buses. 

Description : List some important loads to 6.6 kV buses. 

Last Answer : a. Auxiliary transformers. b. PHT motors. c. BFP motors.  d. CEP motors. e. CCW motors. f. Chiller motors. g. Pressuring pump motors. 

Description : What is the distribution of DC control supply in CL IV, III, II- 415V and 6.6 kV?

Last Answer : Closing coil and Trip coil 2 supply from one source. Trip coil 1 supply from one source. Protections supply from one source. 

Description : How 6.6 kV-bus supply was chosen?

Last Answer : 11 kV was rejected in view of the high insulation cost with 11 kV motors. 3.3 kV was rejected, since max motor size with 3.3 kV bus is limited to 2 MW. But we are having the motors having rating more than 2 MW, which cannot suit to 3.3 kV bus. 6.6 kV bus we can start upto 5 mw size motor. 

Description : What are the sources of power supply to class I bus? 

Last Answer : a. Through control UPS 240 V AC. b. Through control UPS 220 V DC backed by 220 V batteries. c. Through control UPS 48 V DC backed by 48 V batteries. 

Description : What are the different types of buses in a power system?

Last Answer : The buses of a power system can be classified into three types based on the quantities being specified for the buses, which are as follows: a. Load bus or PQ bus (P and Q are specified) b. Generator bus ... P and V are specified) c. Slack bus or swing bus or reference bus (|V| and δ are specified)

Description : What are the main parts of 220 kV Circuit Breaker? 

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Description : Why the earthing transformer primary voltage is 16.5 kV rated in main generator even though actual voltage during the E/F is root 3 times less?

Last Answer : The transformer should not saturate during E/F otherwise it will cause ferroresonance with the GT winding capacitance. Dangerous O/V and neutral shifting will occur. During loss of load or field ... saturation. Saturation can also occur due to point on wave of application causing flux doubling. 

Description : What are the sources of 240 V AC class I supply? What are the functions of each part of UPS? 

Last Answer : Six sources. Three 20 kVA UPS for safety related loads. Two 60 kVA UPS for non-safety related loads. One 60 kVA UPS as a standby to safety related loads. These all UPS are back up by ... UPS into service. Manual bypass To take main UPS to maintenance by putting stand by UPS into service. 

Description : What are the types of cables used in 6.6 kV and 415 V system voltages? 

Last Answer : In 6.6 kV system AC (unearthed) grade having stranded aluminium conductors cables are used. Their insulation's are as follows. 1. XLPE - Crossed linked polyethylene insulation. 2. FRLS PVC - Fire ... V grade copper or aluminium stranded cables are used. Their insulations are HR PVC and FS type. 

Description : What are the interlocks between 415 V and 6.6 kV switch gear? 

Last Answer : 6.6 kV Breaker closed cannot rack in or out. Service lever cannot move while breaker closed. Breaker cannot be closed in in-between position. 415 V Breaker door cannot be opened when breaker is ... . Breaker cannot be closed in in-between position. Breaker closed cannot be rack in or out. 

Description : What is the difference between lockout of 6.6 kV and 415 V CB’s?

Last Answer : Voltage levels. Manual / auto reset. Lockout relays of 415 V breakers are all Electro-magnetic type. There is no mechanical latch. But in 6.6 kV it is of mechanical latch type relays.

Description : Why core balance CT is preferred over residual connected CT’s to sense earth fault in 6.6 kV feeders?

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Description : Why 2 types of earth fault relays in 6.6 kV side of transformers?

Last Answer : I – Trips 6.6 kV breakers only. It gives primary protection for 6.6 kV bus bars. I1 – Trips the both HT and LT breakers. It acts as a backup to ref and also acts as backup to bus bar earthfault relay. 

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

Last Answer : No, logically prevented.  

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 : 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 is the minimum voltage required for starting of 6.6 kV motors?

Last Answer : Minimum 80% of rated voltage.

Description : The voltage at the two ends of a transmission line are 132 KV and its reactance is 40 ohm. The Capacity of the line is (A) 435.6 MW (B) 217.8 MW (C) 251.5 MW (D) 500 MW

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Description : A bus disconnect link is used to isolate _____________. A. one bus bar from another B. the generator circuit breaker from the bus C. different phases from the equalizer connection D. positive and negative buses from the neutral

Last Answer : Answer: B

Description : When the generator buses are treated as load bus.

Last Answer : If the reactive power constraints of a generator bus violates the specified limits then the generator is treated as load bus.

Description : Why parallel operations of classIII buses are not permitted? 

Last Answer : Fault on one side affects the other buses, switchgear fault level rating is exceeded.  

Description : As per chart on energy consumption the supply unit of furnace oil is ……… a. kWh c. kV b. kg. d. Watts

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Description : 95. As per pie chart on energy consumption the supply unit of the electricity is……….. a. kWh c. kV b. kg. d. Watts

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Description : The source of emergency lighting and power at loss of normal ship's power on a cargo vessel should be obtained from the ______________. A. emergency generator supply to the emergency ... switchboard C. battery supply to the main switchboard D. turbogenerator supply to the emergency switchboard

Last Answer : Answer: A

Description : Upon failure of the normal power supply, the emergency generator is placed on the line by the _____________. A. main bus tie feeder B. automatic bus transfer device C. line connection feeder D. power failure alarm bus

Last Answer : Answer: B

Description : Which of the following statements represents an application of a silicon controlled rectifier? A. To provide DC power for a main propulsion motor. B. For use as a voltage reference diode. C. For sensing flame in an automated burner. D. To eliminate power supply hum.

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Description : The dielectric strength of a vacuum or dry air is approximately ________________. A. 450 volts/inch B. 1000 volts/inch C. 20-kv/inch D. 50-kv/inch

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Description : If we give 2334 A, 540V on Primary side of 1.125 MVA step up transformer, then what will be the Secondary Current, If Secondary Voltage=11 KV?

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Description : Why 1.1 kV grade cables used for 415V?

Last Answer : To take care of the both earthed / unearthed systems.  

Description : What are the levels of SF6 gas in 220 kV breaker and their significance?

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Description : What is the type of 220 kV circuit breaker? 

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Description : Give the details of switchyard 220 kV CB, Isolator, CT, CVT and lightning arrestor.  

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Description : Why resistance grounding preferred for less than 33 kV and more than 415 V?

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Description : What are the protections provided for 220 kV lines and bus bars? 

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Description : Why earth switches are provided in 220 kV bays?  

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Description : If we give 2334 A, 540V on Primary side of 1.125 MVA step up transformer, then what will be the Secondary Current, If Secondary Voltage=11 KV?

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Description : Oil-filled cable has a working stress of __________ kV/mm (A) 10 (B) 12 (C) 13 (D) 15

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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.

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Description : Mention the various types of buses in power system with specified quantities for each bus.

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Description : A power system has 100 buses including 10 generator buses. For the load flow analysis using Newton-Raphson method in polar coordinates, the size of the Jacobian is a) 189x189 b) 100x100 c) 90x90 d) 180x180

Last Answer : a) 189x189

Description : In power system, the maximum number of buses are a) Generator buses b) Load buses c) Slack buses d) P-V buses

Last Answer : b) Load buses