DGVCL Exam Paper (11-12-2011) An over excited synchronous motor draws current at Depends on nature of load Leading power factor Lagging power factor Unity power factor Depends on nature of load Leading power factor Lagging power factor Unity power factor ANSWER EXPLANATION DOWNLOAD EXAMIANS APP Over excitation : leading currentUnder excitation : lagging currentNormal excitation : current with unity PF (in phase current)
DGVCL Exam Paper (11-12-2011) Which type of back up protection is widely used for the protection of transmission lines? Relay backup Control backup Remote backup Breaker backup Relay backup Control backup Remote backup Breaker backup ANSWER DOWNLOAD EXAMIANS APP
DGVCL Exam Paper (11-12-2011) Bulk power transmission over long HVDC lines are preferred on account of Low cost of HVDC terminals Simple protection Minimum line power losses No harmonic problems Low cost of HVDC terminals Simple protection Minimum line power losses No harmonic problems ANSWER DOWNLOAD EXAMIANS APP
DGVCL Exam Paper (11-12-2011) The bus bar zone faults are generally Phase to phase faults Double line to ground faults Single line to ground faults Three phase short ciruits Phase to phase faults Double line to ground faults Single line to ground faults Three phase short ciruits ANSWER DOWNLOAD EXAMIANS APP
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 10 MVA 50 MVA 60 MVA 20 MVA 10 MVA 50 MVA 60 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 Lightning Unbalanced protection Switching over voltages Magnetizing inrush current Lightning Unbalanced protection Switching over voltages Magnetizing inrush current 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
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