Download Faculty of Engineering - Pharos University in Alexandria

Pharos University
Faculty of Engineering
Department of Electrical Engineering
SEMESTER: 3rd level - 5th semester
Course Title:
Electrical Power Engineering 1
Instructor:
Dr. Sahar Abd El Moneim
Academic Year: Fall 2012/13
Course Code: EE272
Sheet-1
Three-Phase System
Three-Phase System
1- A balanced three-phase Y-connected generator with positive sequence has an
impedance of 0.2 +j0.5 / and an internal voltage of 120 V/. The generator
feeds a balanced three-phase Y-connected load having an impedance of
39 +j28 /. The impedance of the line connecting the generator to the load
is 0.78 +j1.5 /. The a-internal voltage of the generator is specified as the
reference phasor.
a)
b)
c)
d)
e)
f)
g)
h)
i)
j)
k)
l)
Construct the a-phase equivalent circuit of the system.
Calculate the three line currents IaA, IbB and IcC.
Calculate the three –phase voltages at the load VA, VB and VC.
Calculate the line voltages VAB , VBC and VCA at the terminals of the
load.
Calculate the phase voltages at the terminals of the generator Va , Vb
and Vc .
Calculate the line voltages Vab, Vbc and Vca at the terminals of the
generator.
Calculate the average power per phase delivered to the Y-connected
load.
Calculate the total average power delivered to the load.
Calculate the total average power lost in the line.
Calculate the total average power lost in the generator.
Calculate the total number of magnetizing Vars absorbed by the load.
Calculate the total complex power delivered by the source.
Assignment:
2- A balanced three-phase Y-connected generator with line Voltage = 800v and
an internal impedance of Zs=0.4+j1 / . The Transmission line impedance
connecting the generator with the loads Zl= 1+2j / , whereas the neutral
impedance Zn=5+12j / .
The generator is connected to unbalanced three-phase Y-connected load :
Z1=20+30j /
Z2=15-10j /
Z3=20+20j /
Find :
a) Calculate the three line currents .
b) Calculate the neutral Voltage Vn.
c) Calculate the neutral current In.
d) Calculate the three –phase voltages at the load VA, VB and VC.
e) Calculate the line voltages VAB , VBC and VCA at the terminals of the
load.
f) Calculate the generator complex power and apparent Power .
g) Calculate the total average power delivered to the load.
h) Calculate the total number of magnetizing Vars absorbed by the load.
i) Calculate the total average power lost in the line and source impedance.