DGVCL Exam Paper (11-12-2011) In the protection of transformers, harmonic restraint is used to guard against Unbalanced protection Lightning Switching over voltages Magnetizing inrush current Unbalanced protection Lightning 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
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 60 MVA 50 MVA 10 MVA 20 MVA 60 MVA 50 MVA 10 MVA 20 MVA ANSWER EXPLANATION DOWNLOAD EXAMIANS APP Short circuit kVA = Base kVA/%X
DGVCL Exam Paper (11-12-2011) First zone distance relay protects the transmission line section upto Its full length 50 % of its full length 25 % of its full length 80 % of its full length Its full length 50 % of its full length 25 % of its full length 80 % of its full length ANSWER DOWNLOAD EXAMIANS APP
DGVCL Exam Paper (11-12-2011) Ybus used in power flow studies and Zbus used in short circuit studies Have no inter relation Are inverse of each other Are transpose of each other Are the same Have no inter relation Are inverse of each other Are transpose of each other Are the same ANSWER DOWNLOAD EXAMIANS APP
DGVCL Exam Paper (11-12-2011) Due to skin effect Current flows through the half cross section of the conductor Portion of the conductor near the surface carries more current and the core of the conductor carries less current Portion of the conductor near the surface carries less current and the core of the conductor carries more current Uniform current flows through the conductor Current flows through the half cross section of the conductor Portion of the conductor near the surface carries more current and the core of the conductor carries less current Portion of the conductor near the surface carries less current and the core of the conductor carries more current Uniform current flows through the conductor ANSWER EXPLANATION DOWNLOAD EXAMIANS APP Skin Effect:tendency of the current to crowd near the conductor surface.Skin effect is proportional to frequency, conductor diameter and permiability. Skin effect increases effective resistance of conductor.In DC, no skin effect.
DGVCL Exam Paper (11-12-2011) The positive and negative sequence impedance of a transmission line are Infinite Zero Equal Different Infinite Zero Equal Different ANSWER DOWNLOAD EXAMIANS APP
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