Shivaji University 2010-6th Sem B.E Electrical Engineering T.E(Electrical)- (New), Power System Stability and Control - exam paper
This is 3rd year electrical engineering students 2nd semester paper (total sixth semester) of power system stability and control(PSAC).
N ~ 792
::No.
T.E. Electrical (Semester - VI) (New Course) Examination., 2010 POWER SYSTEM STABILITY AND CONTROL
Day and Date : Wednesday, i 9-5-2010
Total Marks; 100
Time: 2.30 p.tvto 5.30 p.m.
Instructions : I ) Solve any three, questions from Section I and any three
quesiums from Section SI.
2} Use of non-programmable calculator is permitted.
3) Assume suitable dma wherever necessary.
SECTION - I
L a) Explain the phenomenon of shmtoircuit on & synchronous machine with a neat skc?.ch of short-circuit current waveform. Draw short-circuit models of
a machine during
I) Sub-transient period U) Transient period
ill) Steady-state* 8
b) A generator is connected through a transformer to a synchronous motor. Reduced to the same base, the per unit sub-transient reactances of the generator and motor are 0.15 and 0.35, respectively, and leakage reactance of the transformer is 0J per unit. A three phase fault occurs at the terminals of the motor when, die terminal voltage of the generator is 0,9 per unit and the output current of the generator is 1.0 per unit at 0.8 power factor leading, rind the sab-transient current in per unit in the fault, In the generator, and in the motor. 8
a) One conductor of three phsse line is oper.. The current flowing to the delta connected ioad through phase a is 1GA. With the current in line a as reference and assuming that line c is open, find the symmetrical components of line eurrenis. 8
b) Obtain the expression for three phase power in terms of symmetrical components, 8
a) Gb&in sequence circuits for Y/Y transformer with both neutrals grounded. 10
b) For a siail power system shown in Fig. I7 obtain the zero seqiience diagram,
*fir Q &3C z
"Via.s.& '
f*yrso-
A ir
; yw
O
Fig. I : Single line diagram of a s ro all power system for Q. 3. b
a) Di sc us s Ihc mo thod of analy zin g s i n gle line to grours d fan Its. 8
b) Explain how the frequency of the power system varies with the load. 8
5. a) Discuss di Cerent c o n s Ira i nts on ec onomi c ge ner ati o n.
b) The incremental fuel cost in rupees per MWh for a plam consisting, of two units are:
dC;/d?Gj 0.20 PGI -i- 40 dC2/d?G:, - 0.20 PG2 *30
assume that both units are operating at all times, and total load varies from 40 MW to 250 MW, and the and minimum loads on each unit are
Co be 125 MW and 20 MW respectively, How will the load be shared between two units as the system load varies over the full range ? What are the corresponding values of the plant incremental cos is ?
{assume various values of % as 35n 44, 50, 55, 60, 61, 25, 65).
6. a) With suitable example explain optima] unit commitment
b) What are reliabi 1 ity consideraiions associated with optima; scheduling ?
7. a) A synchronous generator of reactance \ 20 per unit is connected to an infinite
bus bar (|V| ~ 1.0 per unit) through transformer and a transmission line having total reactance 0.60 per unit The generator no load voltage is 1,20 per unit and its Inertia constant is H - 4 MW-sec/MVA. The resistance and machine damping may be assumed negligible. The system frequency is 50 Hz. Calculate the natural frequency of oscillations if the generator is loaded to 50%.
b) What h equal area criterion for stability assessment ? Define critical clearing time and critical clearing angle.
8. a) With s ui table e xam p1 e explain voltage eo I lapse.
b) What is the need of contingency analysis of a power system ?
|
Attachment: |
| Earning: Approval pending. |
