Q:Why temperature rise is conducted in bus bars and isolators?
Ans: Bus bars and isolators are rated for continuous power flow.Due to handling of heavy currents rise in temperature occurs.So it is necessary to test these devices for temperature rise within permissible limit.
Q:How to calculate capacitor bank value to maintain unity power factor with some suitable example?
Ans: Tan(theta)=KVAR/KW
KVAR= KW(Tan(Cos-1(1)e)- Tan(Cos-1(1)d) )
e= Existing P.F
d= Desired P.F
Q.Why all transmission and distribution systems are 3 phase systems?
Ans: A 3 phase a.c circuit using the same conductor size can carry three times the power which can be carried by a 1 phase circuit and 3 conductors for the phases and one conductor for the neutral is used for 3 phase 4 wire system.Thus a 3 phase circuit is more economical than single phase circuit in terms of initial cost as well as the losses.Therefore all transmission and distribution systems are 3 phase systems.
Q.Why the transmission systems are mostly overhead systems?
Ans:Because of the cost consideration, the transmission systems are mostly overhead systems.
Q.Why all overhead lines use ACSR conductors?
Ans: ACSR conductors comprises of hard drawn aluminum wires stranded around a core of single or multiple strand galvanized steel wire. Aluminum provides the necessary conductivity while the steel provides the necessary mechanical strength. Has less corona loss.The breaking load is high and has less weight.
Q.Why transmission lines are 3 phase 3 wire circuits while distribution lines are 3 phase 4 wire circuits?
Ans:A Balanced 3 phase circuit does not require the neutral conductor, as the instantaneous sum of the 3 line currents are zero.Therefore the transmission lines and feeders are 3 phase 3 wire circuits.
The distributors are 3 phase 4 wire circuits because a neutral wire is necessary to supply the 1 phase loads of domestic and commercial consumers.
Q.Why overhead line conductors are invariably stranded?
Ans:They are stranded to make them flexible during erection and while in service.
Q.Stat the advantages of interconnected systems.
Ans:Any area fed from one generating station during overload hours/ fault condition can be fed from another power station and thus reserved capacity required is reduced,reliability of supply is increased and efficiency is increased.
Q.What is a ring distributor?
Ans:A ring distributor is a distributor which is arranged to form a closed circuit and is fed at one or more than one point.
Q.State any two advantages of ring main system.
Ans:Less voltage fluctuations at consumer’s terminals. Less copper is required as each part of the ring carries less current than in radial system.
Q.Mention the disadvantages of a 3 wire system.
Ans:The safety is partially reduced .A balancer is required and therefore cost is increased.
Q. What are the advantages of a 3 wire dc distribution system over a 2 wire dc distribution system?
Ans:If 3 wire system is used to transmit the same amount of power over the same distance with same efficiency with same consumer voltage we require 0.3125 times copper as required in 2 wire system.
Ans: Bus bars and isolators are rated for continuous power flow.Due to handling of heavy currents rise in temperature occurs.So it is necessary to test these devices for temperature rise within permissible limit.
Q:How to calculate capacitor bank value to maintain unity power factor with some suitable example?
Ans: Tan(theta)=KVAR/KW
KVAR= KW(Tan(Cos-1(1)e)- Tan(Cos-1(1)d) )
e= Existing P.F
d= Desired P.F
Q.Why all transmission and distribution systems are 3 phase systems?
Ans: A 3 phase a.c circuit using the same conductor size can carry three times the power which can be carried by a 1 phase circuit and 3 conductors for the phases and one conductor for the neutral is used for 3 phase 4 wire system.Thus a 3 phase circuit is more economical than single phase circuit in terms of initial cost as well as the losses.Therefore all transmission and distribution systems are 3 phase systems.
Q.Why the transmission systems are mostly overhead systems?
Ans:Because of the cost consideration, the transmission systems are mostly overhead systems.
Q.Why all overhead lines use ACSR conductors?
Ans: ACSR conductors comprises of hard drawn aluminum wires stranded around a core of single or multiple strand galvanized steel wire. Aluminum provides the necessary conductivity while the steel provides the necessary mechanical strength. Has less corona loss.The breaking load is high and has less weight.
Q.Why transmission lines are 3 phase 3 wire circuits while distribution lines are 3 phase 4 wire circuits?
Ans:A Balanced 3 phase circuit does not require the neutral conductor, as the instantaneous sum of the 3 line currents are zero.Therefore the transmission lines and feeders are 3 phase 3 wire circuits.
The distributors are 3 phase 4 wire circuits because a neutral wire is necessary to supply the 1 phase loads of domestic and commercial consumers.
Q.Why overhead line conductors are invariably stranded?
Ans:They are stranded to make them flexible during erection and while in service.
Q.Stat the advantages of interconnected systems.
Ans:Any area fed from one generating station during overload hours/ fault condition can be fed from another power station and thus reserved capacity required is reduced,reliability of supply is increased and efficiency is increased.
Q.What is a ring distributor?
Ans:A ring distributor is a distributor which is arranged to form a closed circuit and is fed at one or more than one point.
Q.State any two advantages of ring main system.
Ans:Less voltage fluctuations at consumer’s terminals. Less copper is required as each part of the ring carries less current than in radial system.
Q.Mention the disadvantages of a 3 wire system.
Ans:The safety is partially reduced .A balancer is required and therefore cost is increased.
Q. What are the advantages of a 3 wire dc distribution system over a 2 wire dc distribution system?
Ans:If 3 wire system is used to transmit the same amount of power over the same distance with same efficiency with same consumer voltage we require 0.3125 times copper as required in 2 wire system.
ow do the various devices protect the penstock?
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