POWER SYSTEMS

POWER SYSTEMS

Q.A wave will not experience any reflection when impedance of line is equal to

a surge impedance
b load impedance
c >surge impedance
d
Ans: surge impedance

Q.if the length of a wire is increased what happens to its resistance

a increases linearly
b increases exponentially

Q.for a current carrying coil if the current is doubled then the field strength is

a doubled
b halved
c increased 4 times

Q.a capacitor of 10 micro farads is charged thruogh a resistor of 10 ohms and a 6 V battery. Calculate the time taken by the capacitor to charge to its maxm value.

a 1 sec
b 100 sec
c 0.1 sec
d 10 sec

Q.what current is drawn by a 10 W lamp connected to a 220 V,60 Hz source.

a 1 A
b 0.5 A
c 0.045 A
d 0.01 A

Ans: 0.045

Q.At present how many HVDC lines are there in india?

a none
b one
c two
d more than two

Q.What is the distance between the EHV lines and earth?

a 8m
b 11m
c 18m
d 15m

Q.On no load in EHV lines what is the relation between receinving and sending end voltage?

a receiving end voltage > sending end voltage
b receiving end voltage < sending end voltage
c receiving end voltage = sending end voltage
d none

Ans: receiving end voltage > sending end voltage

Q.What is the surge impedance loading of 400kv line?

a 400 MW
b 400 KW
c 1600 MW
d 1600 KW

Ans: 400 MW

Q.What is the surge impedance loading of 400kv line with surge impedance given as 160 ohms

a 1000 MW
b 1000 KW
c 256 MW
d 256 KW

Ans: 1000 MW

Q.Where is the hydel power plant located in following places?

a Raamagundam
b Tarapur
c Kalpakam
d Srisailam

Ans: Raamagundam

Q.self GMD is used in the calculation of_______

a inductance only
b inductance and capacitance
c capacitance only
d none

Ans: inductance only

Q.What is the GMD if the distance between the lines are 6m,6m,12m?

a 7.55m
b 6m
c 12m
d 8.56m

Ans: 7.55m

Q.Zero sequence currents doesn't exist in the following fault

a L-G
b L-L
c L-L-G
d L-L-L-G

Ans: L-L


Q.To avoid arcing connect sutable value of ________ in earthing.

a capacitance
b indunctance
c resistance
d susceptance

Ans: indunctance

Q.In the following type of conductors the corona is minimum

a circular
b stranded
c helical
d rectamgular

Ans:circular

Q.At what frequency corona loss is more?

a 50Hz
b 60Hz
c 25Hz
d 100Hz

Ans: 100HZ

Q.What is the line current of a circuit when the current transformer of 1000:5 rating measures 4Amperes?

a 5000 A
b 1000 A
c 400 A
d 800A

Ans: 800A

Q.If the time delay of relay with TMS setting 0.1 is 10 sec, then what is the time delaty when the TMS setting is changed to 0.5

a 2 sec
b 20 sec
c 100 sec
d 5 sec

Ans: 5 sec

Q.In distribution lines_____

a X/R<0.1
b X/R>10
c X/R<1
d X/R<0.01

Ans: X/R<1

Q.In EHV lines _____

a X/R=10
b X/R=100
c X/R>3
d X/R<3

Ans: X/R>3

Q.In wind mills the frequent problems occur in______

a mechanical system
b blades
c electrodynamic system
d electric system

Q.The machine used in windmills is______

a Alternator
b Induction generator
c Synchronous generator
d All

Ans: Induction generator

Q.Insulators in EHV lines are designed based on_____

a switching voltages
b peak voltages
c corona
d lightning voltages

Ans: switching voltages

Q.The value of restriking voltage depends on______

a inductance of line
b capacitance of line
c both
d none

Ans: both

Q.HRC fuse and circuit-breaker combination is used CB operates for

a low over-load currents
b high over-load currents
c combination is never used

Ans: low over-load currents

Q. SIL of 400 KV lines is

a 400 MW
b 400 KW
c 1600 MW
d 1600 KW

Ans: 400 MW

Q. SIL of 100 KV cable is

a 400 MW
b 400 KW
c 250 MW
d 250 KW

Ans: 250 MW

Q.reflection coefficent of current of an open ended line.

a 1
b -1
c 2
d -2

Ans: -1

Q.Positive sequence terminal voltage is zero in

a L-L
b L-L-G
c L-G
d L-L-L

Ans: L-L-L

Q.Most economical load in underground cable is

a less than surge impedance
b equal to surge impdance
c more than surge impedence
d any load

Ans: less than surge impedance

Q.The impedance of a lossless transmission line is

a v(L/C)
b L/C
c 1/vLC
d 1/LC

Q.Zsc =100? Zoc =1? then Zo is

a 1
b 10
c 100
d 0.1

Ans: 10

Q.Normal PH value of water used in thermal power station is

a 7
b 2
c 5
d Slightly >7

Ans: Slightly >7

Q.Maximum power transfer through line V1= 110 kv, V2= 100kv, X=22 ohm is

a 500 MW
b 500 KW
c 250 MW
d 250 KW

Ans: 500 MW

Q.Which type of power plant requires maximum expenditure

a Hydel power plants
b Nuclear power plants
c Thermal power plants
d Gas based power plants

Q.Base load of a power station stands for

a 2-4 hours/day
b 4-8 hours/day
c 8-12 hours/day
d 12-24hours/day

Ans: 12-24hours/day

Q.A wire is placed on the top of a transmission line to protect from

a surge high voltage
b Direct lightning strocks
c indirect lightnin strocks
d Switching over voltages

Ans: Direct lightning strocks

Q.A wire is placed on the top of a transmission line acts as

a acts as a phase wire
b acts as neutral
c acts as a transmission wire
d acts as ground wire

Ans: acts as ground wire