# BE Power System Analysis Fifth sem

Answer All the Questions
1. What is the relation between percentage value and per unit value?
2. Write the equation for per unit impedance.
3. Draw p model of a transmission line.
4. Distinguish between bus admittance matrix and bus impedance
matrix.
5. Distinguish between symmetrical and unsymmetrical short
circuits.
6. State the merit of using Zbus matrix in short circuit analysis.
7. What are the applications of load flow analysis?
8. Write any two assumptions made to simplify the transient
stability problem.
9. Write the power angle equation of an alternator connected to a
synchronous motor through pure reactance network.
10. What is meant by steady state limit?

PART – B (5 x 12 = 60)
Answer All the Questions
11. Obtain the reactance diagram of the power system given below:
(or)
12. Three motors rated 6.9 kV are connected to the same bus. The
motors are
No.1 5000 H.P., 0.8 p.f. synchronous motor, x” = 17%.
No.2 3000 H.P., u p.f. synchronous motor, x” = 15%.
No.3 3500 H.P., induction motor, x” = 20%.
Express the sub transient reactance of these motors in per unit on
a base of 10,000 kVA, 6.6 kV.
13. For the transmission system with the following line
specifications, determine the Bus admittance matrix.
Bus code p – q
ChargingY’ pq/2
Impedance Zpq Bus Code Line
1 – 2 0.06 + j0.18 1 j0.05
1 – 3 0.02 + j0.06 2 j0.06
2 – 3 0.04 + j0.12 3 j0.05
(or)

and lags that of phase c by 176.5°. Determine the symmetrical
components of voltage.
17. Derive the basic equation for the load flow study using gaussseidal
method. With respect to this method explain the following
(a) Acceleration factor.
(b) Convergence criteria.
(c) Handling of PV buses.
(or)
18. The bus admittance matrix of a 3 bus power system is
Bus No. Bus Type PG QG PL QL
1 P – V 2.9034 – – –
2 P – Q – – 4.0089 1.7915
3 Slack – – – –
The latest solution is
V1 = 1.05 6.96°
V2 = 0.9338 -8.8°
V3 = 1.0 0°
Determine the bus voltage at the end of the next iteration using
Newton Raphson method.
19. Derive Swing equation used for stability studies in power system.
(or)
20. The moment of inertia of a 4 pole, 100 MVA, 11 kV, 3 phase, 0.8
pf, 50 Hz turbo alternator is 10000 kg-m2. Calculate H and M.
YBus =
1 2 3
1 -j20 j10 j10
2 j10 -j15 j5
3 j10 j5 -j15