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Unformatted text preview: School of Electrical & Information Engineering ELEC5203 Topics in Power Engineering
1st Semester 2009
Tutorial Questions Set 2
____________________________________ Question 1
A balanced threephase wyeconnected load is connected to a balanced threephase wyeconnected supply source. The impedance in each phase of wyeconnected
load is 25 ∠ 30° Ω and the linetoline voltage at load terminal is 4.16 kV. The
impedance in each of the three lines connecting the load and supply source is
1.6 ∠ 65° Ω . Using phase voltage Van as a reference, find the linetoline voltages at
the supply source and also find the linetoline voltages at source in per unit values
using the linetoline voltage at load terminal and line current as base values Question 2
The Thevenin equivalent circuit model of a singlephase power system is shown
in Figure 1. The opencircuit voltage is VS and shortcircuit impedance is Z S = j 0.1 Ω .
The load impedance is Z load = 1 Ω but the power factor can be unity, 0.8 lagging or 0.8
leading. For all the three power factor conditions mentioned above, the supply
voltage VS must be adjusted to keep the load terminal voltage Vload = 100 ∠ 0 V . For
all three power factor conditions
(i)
(ii)
(iii)
(iv)
(v)
(vi) Determine the supply voltage VS .
Determine the power factor angle φ .
Determine the transmission angle δ .
Determine the active power P at the source and the load.
Determine the reactive power Q at the source and the load.
Determine the apparent power S at the source and the load. ________________________________________________________________________________________________________
VGA, The University of Sydney 24 March 2009 Page 1 of 2 ELEC5203 Topics in Power Engineering
Tutorial Questions Set 2
________________________________________________________________________________________________________ i ZS vload vS Z load Figure 1. Thevenin’s equivalent circuit model of a singlephase AC power system. Question 3
A balanced threephase wyeconnected inductive load is supplied at 4.16kV,
50Hz and takes 1200kW of real power and 500kVAr of reactive power. The supply
source impedance is Z s = j1.2 Ω .
(i) Calculate the line current.
(ii) Calculate the power factor angle φ .
(iii) Calculate the linetoneutral voltage at supply source bus if the linetoline
voltage at the load bus is 4.16 kV.
(iv) Calculate the ratio of the linetoneutral voltage at supply source bus to the
linetoneutral voltage at the load bus.
(v) Calculate the transmission angle δ . ________________________________________________________________________________________________________
VGA, The University of Sydney 24 March 2009 Page 2 of 2 ...
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This note was uploaded on 04/25/2010 for the course ELEC 5203 taught by Professor Hashimamla during the Spring '10 term at Birla Institute of Technology & Science.
 Spring '10
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