DGVCL Exam Paper (11-12-2011) If the percentage reactance of the system upto the point of fault is 20% and the base kVA is 10,000 the short ciruit kVA is 50 MVA 60 MVA 10 MVA 20 MVA 50 MVA 60 MVA 10 MVA 20 MVA ANSWER EXPLANATION DOWNLOAD EXAMIANS APP Short circuit kVA = Base kVA/%X
DGVCL Exam Paper (11-12-2011) In the protection of transformers, harmonic restraint is used to guard against Unbalanced protection Magnetizing inrush current Switching over voltages Lightning Unbalanced protection Magnetizing inrush current Switching over voltages Lightning ANSWER EXPLANATION DOWNLOAD EXAMIANS APP Initial inrush of magnetizing currents have high component of even and odd harmonics.2nd - 63%3rd -26.8%4th- 5.1%5th- 4.1%6th- 3.77th-2.4
DGVCL Exam Paper (11-12-2011) Bulk power transmission over long HVDC lines are preferred on account of No harmonic problems Simple protection Minimum line power losses Low cost of HVDC terminals No harmonic problems Simple protection Minimum line power losses Low cost of HVDC terminals ANSWER DOWNLOAD EXAMIANS APP
DGVCL Exam Paper (11-12-2011) The transient stability of a power system can be improved by Excitation control Single pole switching of circuit breakers Phase shifting transformer Increasing the turbine valve opening Excitation control Single pole switching of circuit breakers Phase shifting transformer Increasing the turbine valve opening ANSWER DOWNLOAD EXAMIANS APP
DGVCL Exam Paper (11-12-2011) The purpose of providing a choke in a tube light is To improve the power factor To avoid radio interference To limit the current to an appropriate value To eliminate corona effect To improve the power factor To avoid radio interference To limit the current to an appropriate value To eliminate corona effect ANSWER DOWNLOAD EXAMIANS APP
DGVCL Exam Paper (11-12-2011) Which motor is used to start heavy loads? Differentially compounded motor Shunt motor Cumulatively compounded motor Series motor Differentially compounded motor Shunt motor Cumulatively compounded motor Series motor ANSWER EXPLANATION DOWNLOAD EXAMIANS APP Torque in d.c motor = k* φ * IaIn series motor φ α IaTα I²starting torque of dc series motor is high
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