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Electrical Power system – I
Assignment-1
1. The one-line diagram of a three-phase power system is shown below in the figure. Select
a common base of 1OOMVA and 22kV on the generator side and draw an impedance
diagram with all impedances marked in per-unit .The manufacturer's data for each device
is given as follow:
G:
90MVA
22kV
x"=18%
T1:
5OMVA
22/220kV x"=1O%
T2:
40MVA
220/11kV x"=6.0%
T3:
40MVA
22/110kV x"=6.4%
T4:
40MVA
11O/11kV x"=8.0%
M:
66.5MVA
lO.45kV
x"=18.5%
The tree phase load at bus 4 absorbs 57MVA, 0.6 power factor lagging at 10.54KV .Line 1
and 2 has reactance of 48.4 and 65.43Ω respectively.
2. In a single phase line conductors a and a’ in parallel form one circuit while conductors b
and b’ in parallel form the return path. Calculate the total inductance of the line per km
assuming that the current is equally shared by the two parallel conductors. Conductor
diameter is 1.8cm.
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3. A single phase, 25km long overhead line consists of two conductors 1.8m apart,
diameters of each conductor being 6mm. if the line voltage is 33km, 50Hz determine the
capacitance o neutral and charging current of the open circuited line.
4. Determine the efficiency and regulation of 3 phase, 100km, 50Hz transmission line
delivering 20MW at a p.f. of 0.8 lagging and 66Kv to a balanced load. The conductors
are copper, each having resistance 0.1Ω per km, 1.5cm outside diameter, spaced
equilaterally 2m between centers. Neglect leakance and use (i) nominal T-Model and (ii)
nominal Π- model.
5. A single circuit 50Hz, 3 phase transmission line has the following parameters per km.
R= 0.2Ω
L= 1.3mH and
C= 0.01X 10 F
-6
If the line is 120km long and delivers 40MW at132KV and 0.8 p.f lagging. Determine the
ABCD parameters for the line and calculate the sending and receiving end voltages using
the ABCD parameters.
Assignment due date Feb. 20, 2015
Assignment =15%
Mid = 35%
Final = 50%