Power System -III
QUESTION 2018
[Multiple Choice Type Questions]
1)The impedance of a transmission line is z=3+j4, its conductance is given by
a) 1/3 b) 3/5 c ) 3/25 d) 4/5
2)In a transmission line the voltage and current are given by v=(10+ j5) and i =(6+j4). The circuit is
a) Inductive b) Capacitive c) Resistive d) It could be any of the above
3) If the penalty factor of a plant is unity, its incremental transmission loss is
a) 1.0 b)-1.0 c) zero d) None of these
4) If X is the system reactance and R its resistance, the power transferred is maximum, when
a)X = R b)√ 2R c)= √ 3R d) X =2R
5)The injection of VAR is required to
a) compensate the line loss b) get a good voltage profile
c) increase of voltage at the receiving d) All of these
6)For economic measure in power system, the generators at a power plant should operate at
a) equal loads b) minimum loads c)load proportional to the rating d) equal incremental cost
7) A traveling wave 400x1x50 means crest value of
a) 400V with rise time of 1/50 sec
b) 400kV with rise time 1sec and fall time 50 sec
c) 400kV with rise time 1μsec and fall time for 1/2 the crest value 50μsec
d) 400mV with rise time 1μsec and fall time 50μsec
8) An O.H. transmission line having surge impedance Z is terminated to an underground cable of surge impedance Z2. The reflection coefficient for the traveling wave at the junction of the line and cable is
a)(Z1+Z2)/(Z1-Z2) b) Z2/(Z1 +Z2)
c)(Z2-Z1)/(Z1+Z2) d)(Z1-Z2)/(Z1+Z2)
9) The insulation strength of EHV lines is mainly governed by
a) switching over voltage b) lightning overvoltage
c)power frequency over voltage d) dynamic overvoltage
10)The surge impedance of a 3-phase, 400KV transmission line is 400 Ohms. The surge impedance loading (S/L) is
a) 400 MW b) 100 MW c) 1600 MVW d) 200 MW
11) If for a given alternator in economic operation mode, the incremental cost is given by (0.012P+8) Rs/MWh, dPL/dp = 0.2 and plant λ=25, then the power generation is (PL =Transmission loss),
a) 1000 MW b) 1250 MW c) 750 MWN d) 1500 MW
12) The impedance per phase of a 3-phase transmission line on a base of 100 MVA, 100 kV is 2 P.u. The value of this impedance on a base of 400 MVA and 400 kV would be
a) 1.5 p.u. b) 1.0 p.u. c) 0.5 p.u. d) 0.25 p.u.
POWER SYSTEM-III
QUESTION-2017
[Multiple Choice Type Questions]
1) Economic operation of power system is carried out on the basis of
a) equal incremental fuel cost b) equal area criterion
c) equal fuel cost d) all units sharing equal power
2) Permissible change in power frequency is
a) 0.5 Hz b) 1 Hz c)5 Hz d) 10 Hz
3) Lightning arrester should be located
a) near the circuit breaker b) away from the circuit breaker
c) near the transformer d) away from the transformer
4) Load compensation is used to improve
a) voltage profile and power factor b) voltage profile and active power
5) In AGC, the voltage and frequency is controlled by
a) excitation control b) turbine speed control
c) excitation control and turbine speed control d) None of these
6) Series compensation in transmission lines
a) increases stability limit b) decreases stability limit
c) has no effect on stability limit d) increases active power
7) A generating unit has an incremental production cost of Rs. 60/MWh. If the penalty factor for this unit is 1.2, the incremental cost of power delivered
a) Rs. 50/MWh b) Rs. 72/MWh c)Rs. 61.2/MWh d) Rs. 48/MWh
8) An uncompensated transmission line on open circuit lead to
a) Ferranti effect b) line charging current flowing into generators is more
c) both (a) and (b) d) none of these
9) For increasing the reactive power output of a synchronous generator
a) field current has to be reduced
b) field current has to be increased
c) generator speed has to be increased
d)generator speed has to be decreased
10)The capacitance and inductance per unit length of a line operating at 110 KV are 0.1 uF and 2mH. The surge impedance loading of the line is
a) 40 MVA b) 30 MVA C)27 MVA d) 20 MVA
11) An overhead transmission line is provided with earth wire for protection against
a) switching surge b) traveling wave
c) lightning surge d) Ferro-resonance
12) The transient phenomenon lasts in a power system for a period ranging from
a) few ms to 1s b) 1s to 2s c) 2s to 3s d) greater than 3s
POWER SYSTEM-III
QUESTION-2016
[Multiple Choice Type Questions]
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