DGVCL Exam Paper (11-12-2011) Which type of back up protection is widely used for the protection of transmission lines? Breaker backup Remote backup Control backup Relay backup Breaker backup Remote backup Control backup Relay backup ANSWER DOWNLOAD EXAMIANS APP
DGVCL Exam Paper (11-12-2011) Under operating conditions, the secondary of a current transformer is always short ciruited because It is safe to human beings It avoids core saturation and high voltage induction It protects the primary ciruits It protects the secondary ciruits It is safe to human beings It avoids core saturation and high voltage induction It protects the primary ciruits It protects the secondary ciruits ANSWER DOWNLOAD EXAMIANS APP
DGVCL Exam Paper (11-12-2011) The efficiency of a transformer at full load, 0.8 p.f. lag is 90%. Its efficiency at full load, 0.8 p.f. lead will be More than 90% Less than 90% 80 % 90 % More than 90% Less than 90% 80 % 90 % ANSWER EXPLANATION DOWNLOAD EXAMIANS APP Efficiency= output power/input powerefficiency = (v*i*cosφ)/((v*i*cosφ)+(x² Pc)+(Pi)) x=fractional part of full load
DGVCL Exam Paper (11-12-2011) Which of the following correctly represents the sequence of operations of isolator, circiut breaker and earthing switch while opening a circuit? Open isolator close circuit breaker-open earthing switch Open circuit breaker-open isolator-close earthing switch Close earthing switch - open ciruit- breaker-open islotor Close circuit breaker-close isolator - open earthing switch Open isolator close circuit breaker-open earthing switch Open circuit breaker-open isolator-close earthing switch Close earthing switch - open ciruit- breaker-open islotor Close circuit breaker-close isolator - open earthing switch ANSWER DOWNLOAD EXAMIANS APP
DGVCL Exam Paper (11-12-2011) In the protection of transformers, harmonic restraint is used to guard against Switching over voltages Unbalanced protection Lightning Magnetizing inrush current Switching over voltages Unbalanced protection Lightning 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
DGVCL Exam Paper (11-12-2011) The transient stability of a power system can be improved by Phase shifting transformer Increasing the turbine valve opening Single pole switching of circuit breakers Excitation control Phase shifting transformer Increasing the turbine valve opening Single pole switching of circuit breakers Excitation control ANSWER DOWNLOAD EXAMIANS APP
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