1. Write a program to determine the efficiency and regulation of a 250 km, 3-phase, 50 Hz,
transmission line delivering 20 MW at 0.8 lagging pf to a balanced load at 132 kV. The line
resistance is 0.11 ohm/km, line inductance is 1.24 mH/km and capacitance is 0.0094 µF/km.
Repeat the experiment by considering 0.8 leading p.f. and compare the results.
2. For the data given below obtain i) primitive admittance matrix ii) bus incidence matrix.
Line num.
Bus code
Admittance in p.u.
1
1-4
1.4
2
1-2
1.6
3
2-3
2.4
4
3-4
2.0
5
2-4
1.8
3. The figure shows the single line diagram of a simple 3 bus power system with generator at bus-1.
The magnitude at bus 1 is adjusted to 1.05pu. The scheduled loads at buses 2 and 3 are marked on
the diagram. Line impedances are marked in p.u. The base value is 100MVA. The line charging
susceptances are neglected. Determine the phasor values of the voltage at the load bus 2 and 3.
(i) Find the slack bus real and reactive power.
(ii) Verify the result using MATLAB.
4.
A 60Hz synchronous generator having inertia constant H = 5 MJ/MVA and a direct axis transient reactance
Xd1 = 0.3 per unit is connected to an infinite bus through a purely reactive circuit as shown in figure.
Reactances are marked on the diagram on a common system base. The generator is delivering real power Pe
= 0.8 per unit and Q = 0.074 per unit to the infinite bus at a voltage of V = 1 per unit.
a.
b.
A temporary three-phase fault occurs at the sending end of the line at point F. When the fault is
cleared, both lines are intact. Determine the critical clearing angle and the critical fault clearing
time.
Verify the result using MATLAB program.
5. The one line diagram of a simple power system is shown in figure. The neutral of each
generator is grounded through a current limiting reactor of 0.25/3 per unit on a 100MVA
base. The system data expressed in per unit on a common 100 MVA base is tabulated
below. The generators are running on no load at their rated voltage and rated frequency
with their emf in phase.
Determine the fault current for balanced three phase fault at bus 3 through a fault impedance, Zf =
j0.1 per unit. Verify the result using MATLAB program.
Item
Base MVA
G1
G2
T1
T2
L12
L13
L23
100
100
100
100
100
100
100
Voltage Rating
kV
20
20
20/220
20/220
220
220
220
X1
X2
X0
0.15
0.15
0.10
0.10
0.125
0.15
0.25
0.15
0.15
0.10
0.10
0.125
0.15
0.25
0.05
0.05
0.10
0.10
0.30
0.35
0.7125
6. An isolated power station has the following parameters
Turbine time constant, T = 0.5sec
Governor time constant, g = 0.2sec
Generator inertia constant, H = 5sec
Governor speed regulation = R per unit
The load varies by 0.8 percent for a 1 percent change in frequency, i.e, D = 0.8
The governor speed regulation is set to R = 0.05 per unit. The turbine rated output is 250MW at
nominal frequency of 60Hz. A sudden load change of 50 MW (ΔPL = 0.2 per unit) occurs.
(i)
Find the steady state frequency deviation in Hz.
(ii)
Use MATLAB to obtain the time domain performance specifications and the frequency
deviation step response.
7. For the data given below obtain Z Bus using zbus building algorithm.
Line num.
Bus code
Admittance in p.u.
1
2
3
4
5
8.
1-0
2-1
3-1
2-0
2-3
4
10
10
4
10
9. Consider the system given below and assume that there is a DLG fault at bus 2, involving
phases b and c. Assume that Zf is j0.1 pu and Zg is j0.2 pu (where Zg is the neutral-toground impedance) both based on 50 VA. Consider the system shown below and the
following data:
Generator G1: 15 kV, 50 MVA, X1 = X2 = 0.10 pu and X0 = 0.05 pu based on its own
rating
Synchronous motor G2: 15 kV, 20 MVA, X1 = X2 = 0.20 pu and X0 = 0.07 pu based on
its own rating
Transformer T1: 15/115 kV, 30 MVA, X1 = X2 = X0 = 0.06 pu based on its own rating
Transformer T2: 115/15 kV, 25 MVA, X1 = X2 = X0 = 0.07 pu based on its own rating
Transmission line TL23: X1 = X2 = 0.03 pu and X0 = 0.10 pu based on its own rating
Assume a DLG fault at bus 2, involving phases b and c, and determine the fault current in per
units and amperes. Use 50 MVA as the megavolt-ampere base and assume that Zf is j0.1 pu
and Zg is j0.2 pu (where Zg is the neutral-to-ground impedance) both based on 50 MVA.
10. The single line diagram of a sample 3-bus power system is shown below. Data for this
system are given in Table 1 and Table 2.
a) Determine the phasor values of the voltages at buses 2 and 3 using the Gauss-Seidel
method. Perform only one iteration)
b) Determine the line flows and line losses after first iteration.
Neglect line charging admittance.
Table 2. Line Impedances
Table 1 Bus Data
11. (i) Determine Z bus matrix for the power system network shown in fig.
(ii) The line between buses 1 and 3 with impedance Z13 = j0.56 is removed by the
simultaneous opening of breakers at both ends of the line. Determine the new bus
impedance matrix.
12. Determine the critical clearing angle and critical clearing time for the power system
shown in Figure below for a three-phase fault at the point F. Generator having inertia
constant H = 5 MJ/MVA is supplying 1.0 p.u. MW power under prefault condition.
16) Write a program to determine the efficiency and regulation of a 250 Km transmission line having
resistance of 0.133 ohm/km/phase, inductance of 0.398mH/km/phase and shunt capacitance of
31.83μF/km/phase. The receiving end load is 50MW at 220kV with 0.8 lagging power factor.