i v got a quiz and i m unable to find answers for these ,, i will appreciate it if u would assist me gents
q1-Which of the following is NOT an approved transformer configuration by ANSI in regard to voltage phase shift between primary and secondary windings?
a-Delta-Wye with thirty degrees lagging shift at the secondary
b-Wye-Wye with zero phase shift
c-Wye-Delta with thirty degrees lagging shift at the primary
d-Delta-Delta with zero phase shift
q2-What components of the fault current shall be considered during the first half cycle of the short circuit and for what purpose?
a-Transient asymmetrical fault for interrupting rating of the circuit breakers.
b-Sub-transient asymmetrical fault for Close and Latch rating of the circuit breakers.
c-Transient symmetrical fault for Close and Latch rating of the circuit breakers.
d-Sub-transient asymmetrical fault for interrupting rating of the circuit breakers.
q3-Which of the following is NOT true in regard to fault levels in balanced three phase powewr systems?
a-Arcing faults are higher than three phase bolted faults.
b-Ground fault equals approximately the ground resistor current rating fault in resistive grounded systems.
c-Phase to phase fault equals 0.867 of the three phase bolted fault.
d-Ground fault equals approximately three phase bolted fault in solidly grounded systems.
q4-An unbalanced wye with grounded neutral load consists of a 4 + j3 Ohm impedance connected to phase A, a 3 + j3 Ohm impedance connected to phase B, and a 4 + j5 Ohm impedance connected to phase C. The power source is balanced and the sequence is ABC with VAB = 208 at an angle of 0°. Assuming all currents are flowing from the source to the load, calculate the value of I(B) [where I(B) is the phase B current].??
A~ 28.3 A at an angle of 165°
B~ 49.0 A at an angle of -175°
C ~28.3 A at an angle of -145°
D ~28.3 A at an angle of -175°
q5-which of the following statements is incorrect?
a-Normal capacitive currents of the three phases of an ungrounded power system are unequal and hence they do not sum to zero.
b-Phase reversal is a fundamental negative sequence harmonic.
c-Phase to ground fault in an ungrounded balanced system will result in three times the single phase normal capacitive current.
d-Harmonics of triple multiples of the fundamental are zero sequence while harmonics of double multiples of the fundamental are negative sequence.
q1-Which of the following is NOT an approved transformer configuration by ANSI in regard to voltage phase shift between primary and secondary windings?
a-Delta-Wye with thirty degrees lagging shift at the secondary
b-Wye-Wye with zero phase shift
c-Wye-Delta with thirty degrees lagging shift at the primary
d-Delta-Delta with zero phase shift
q2-What components of the fault current shall be considered during the first half cycle of the short circuit and for what purpose?
a-Transient asymmetrical fault for interrupting rating of the circuit breakers.
b-Sub-transient asymmetrical fault for Close and Latch rating of the circuit breakers.
c-Transient symmetrical fault for Close and Latch rating of the circuit breakers.
d-Sub-transient asymmetrical fault for interrupting rating of the circuit breakers.
q3-Which of the following is NOT true in regard to fault levels in balanced three phase powewr systems?
a-Arcing faults are higher than three phase bolted faults.
b-Ground fault equals approximately the ground resistor current rating fault in resistive grounded systems.
c-Phase to phase fault equals 0.867 of the three phase bolted fault.
d-Ground fault equals approximately three phase bolted fault in solidly grounded systems.
q4-An unbalanced wye with grounded neutral load consists of a 4 + j3 Ohm impedance connected to phase A, a 3 + j3 Ohm impedance connected to phase B, and a 4 + j5 Ohm impedance connected to phase C. The power source is balanced and the sequence is ABC with VAB = 208 at an angle of 0°. Assuming all currents are flowing from the source to the load, calculate the value of I(B) [where I(B) is the phase B current].??
A~ 28.3 A at an angle of 165°
B~ 49.0 A at an angle of -175°
C ~28.3 A at an angle of -145°
D ~28.3 A at an angle of -175°
q5-which of the following statements is incorrect?
a-Normal capacitive currents of the three phases of an ungrounded power system are unequal and hence they do not sum to zero.
b-Phase reversal is a fundamental negative sequence harmonic.
c-Phase to ground fault in an ungrounded balanced system will result in three times the single phase normal capacitive current.
d-Harmonics of triple multiples of the fundamental are zero sequence while harmonics of double multiples of the fundamental are negative sequence.
