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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 three-phase wye-connected load is connected to a balanced threephase wye-connected supply source. The impedance in each phase of wye-connected
load is 25 ∠ 30° Ω and the line-to-line 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 line-to-line voltages at
the supply source and also find the line-to-line voltages at source in per unit values
using the line-to-line voltage at load terminal and line current as base values Question 2
The Thevenin equivalent circuit model of a single-phase power system is shown
in Figure 1. The open-circuit voltage is VS and short-circuit 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
(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 single-phase AC power system. Question 3
A balanced three-phase wye-connected 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 line-to-neutral voltage at supply source bus if the line-to-line
voltage at the load bus is 4.16 kV.
(iv) Calculate the ratio of the line-to-neutral voltage at supply source bus to the
line-to-neutral 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