POWER SYSTEM ANALYSIS
SEM-VI, 2010
B.TECH EXAMINATION
UTTARAKHAND TECHNICAL UNIVERSITY
(UTU)
Time: 3 hours
Total
Marks:100
Attempt any four of
the following:
- One conductor of a three phase line is open. The
current flowing to the connected load through a line is 10A. With the
current in line a as reference and assuming that line c is open, find the
symmetrical components of the line currents.
- The line to ground voltages on the high voltage sides
of a step up transformer are 100 kV, 33 kV and 38 kV on phases a, b and c
respectively. The voltage of phase a leads that of phase b by 100o and
lags that of phase c by 176.5o. Determine analytically the
symmetrical components of voltage.
- The line currents in amperes in phase a, b and c
respectively is 500+j150, 100-j600 and -300+j600 referred to the same
reference vector. Find the symmetrical components of the currents.
- Three identical Y connected resistors from a load bank
with a three phase rating of 2300 V and 500 kVA. If the load bank has
applied voltages |Vab| = 1840 V, |Vbc| = 2760 V and |Vca| = 2300 V, find
the line voltages and currents in per unit into the load. Assume that the
neutral system and select a base of 2300 V, 500 kVA.
- A 25 MVA, 13.2 kV alternators with solidly grounded
neutral has a sub transient reactance of 0.25 pu. The negative and zero
sequence reactance are 0.35 and 0.1 pu. A single line to ground fault
occurs at the terminals of an unloaded alternator, determine the fault
current.
- Draw the zero sequence equivalent circuit of 3 phase
transformer for various possible combinations.
Attempt any four of
the following:
- Find out the average three phase power in terms of
symmetrical components.
- A 500 kV 2μ sec rectangular of 350 ohms approaches a
station at which the concentrated earth capacitance is 3000 pF. Determine
the maximum value of the transmitted wave.
- Explain the variation of current and voltage on an
overheated line when one end of the line is
(a) short circuited and (b) open circuited and at the other end a source of constant e.m.f V is switched on. - Differentiate between steady state stability and
transient stability and transient stability of a power system. Discuss the
factors that affect
(a) Steady state stability and
(b) Transient state stability of the system. - What is the load flow solution? Explain its
significance in power system analysis.
- Explain the principle of operation of Ferranti surge
absorber.
Attempt any two of
the following:
- Classes the various types of buses in power system for
load flow studies. Justify the classification.
- What is equal area criterion? Discuss its applications
and limitations in the study of power system stability.
- Show that a travelling wave moves with a velocity of
light on the overhead line and its speed is proportional to 1 /√εr on
a cable with dielectric material of permittivity εr.
Attempt any two of
the following:
- Derive an expression for the maximum power transfer
between two nodes. Show that this power is maximum when X =
√3R, where X is the reactance and R is the resistance of the system.
- Develop load flow equations suitable for solution by
(i) Gauss Seideal method
(ii) Newton-Raphson method using nodal admittance approach. - Explain the point by point method of solving the swing
equation. Compare this method with the equal area criterion method.
Attempt any two of
the following:
- A 50 Hz four pole turbo generator rated 20 MVA, 13.2 kV
has an inertia constant of H = 9.0 kW-sec/kVA. Determine the K.E stored in
the rotor at the synchronous speed. Determine the acceleration if the
input less the rotational losses is 2500 HP and the electric power
developed is 15000 kW. If the acceleration computed for the generated is
constant for a period of 15 cycles. Determine the change in torque angle
in that period and the rpm at the end of 15 cycles. Assume that the
generator is synchronized with a large system and has no accelerating
torque before the 15 cycle period.
- Two generating stations having short circuit capacities
of 1200 MVA and 800 MVA respectively and operating at 11kV are linked by
an interconnected cable having a reactance of 0.5 Ohm per phase. Determine
the short circuit capacity of each station.
- The following is the system data for a load flow
solution:
Determine the voltage at the end of first iteration using Gauss-Seidel method. Take α = 1.6.
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