Shivaji University 2010-6th Sem B.E Electrical Engineering T.E(Electrical)- (New), Power System Stability and Control - Question Paper
This is power system stability and control for third year electrical engg. students.
Seat
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No. | _
T.E. (Electrical) (Semester - VI) Examination, 2010 POWER SYSTEM STABILITY AND CONTROL (New Course)
Day and Date : Thursday, 18-11-2010 Total Marks : 100
Time : 10.00 a.m. to 1.00 p.m.
Instructions: 1) Answer any three questions from each Section.
2) Suitable diagrams should be drawn wherever necessary.
3) Figures to right indicate full marks.
4) Assume suitable data wherever necessary.
SECTION -1
1, a) Derive sequence components for three phase system of voltages. 8
b) A30MVA, 11KV generator has Zj = z2 = j0 2PU, Zq=j 0,05 PUa) Aline to ground fault occurs on the generator terminals. Find the fault current and line to line voltage during fauli conditions. Assume that the generator neutral is solidly grounded and that the generator is operating ai no load and at rated voltage at the occurrence of fault b) Find the current for a 3 phase fault. 8
2. a) Develop an equivalent network showing the interconnection of sequence
network to simulate single line to ground fault. 8
b) A 50 MVA, 11 KV, 3-phase alternator was subjected to different types of
faults. The fault currents were: 3 phase fault 1870A. line to line fault 2590A,
single line to ground fault 4130 A, The alternator neutral is solidly grounded,
Find the per unit values of the three-sequence reactances of the alternator. 10
p.tjo.
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3. a) Ex p 1 ain workin g of an auiom ali c vol la ge reg ul aior for an al cemator. 8 b) A s ingle area cons ists of two generating units with the fol lowing characteristics.
-2-
Speed regulation SR
Unit Rating (PU on unit MVA base)
1 600 MVA 6%
2 500 MVA 4%
The uniLs arc operating in parallel, sharing 900 MW al the nominal frcqucncy. Unit 1 supplies 500 MW and uniL 2 supplies 400 MW at 60 Hz. The load is increased by 90 MW.
Assume there is no frequency dependant load i.e. D = 0. Find the steady-staie frcqucncy deviation and the new generation on each unit. 8
4. a) Explain with diagram load frequency control of an isolated power system. 8
b) The symmetrical components of a set of unbalanced three phase currents are la0 = 3 < - 30, la1 = 5 < 90 and la" = 4 < 30 obtain the original unbalanced phasors. 8
SECTION - II
5. a) Derive the condition of economic load dispatch neglecting transmission line
losses. 8
b) The incremental costs in Rs/MWh of two Lurboakemators is as follows :
- 0.2P, + 60;- = 0.3P2 + 40 dPi dP2
The rating of units are 150 MW and 250 MW. How will the load of 200 MW be shared between two units for most economic operation ? Determine the saving in cost in Rs/h for economic load allocation compared to the loading in proportion to the rating of the units. 8
6. a) Explain the step by step solution of swing equation. 8
b) Explain equal area criterion to determine stability of the system for sudden change in mechanical input. 8
7. a) A 200 MVA. 11KV, 50 Hz 4 pole turbo generator has an inertia constant of
6 MJ/MVA.
a) Find the stored energy in the rotor al synchronous speed.
b) The machine is operating at a load of 120 MW. when the load suddenly increases to 160 MW. Find the rotor retardation
c) The retardation calculated above is maintained for 5 cycles. Find the change in power angle and rotor speed in rpm at the end of this period, 10
b) Explain d ifferent meih ods o f improvin g s tabi I ity. 8
8. a) Explain following terms with respect to power system security.
i) System monitoring
ii) Contingency analysis
iii) C o rrec tive ac tio n analys is. 8
b) A 4 pole 50 Hz turbo alternator is rated at 45 MWT 0,8 Pf lag and has an inertia of 25000 kg.m2> It is connected through a transmission line to another set whose corresponding data is 2 pole, 60 MW, 50Hz, 0,75 Pf lag 9000 kg.m2, Find inertia constant of each machine on its own rating and that of single equivalent set connected to an infinite bus on a base of 100 MVA. 8
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| Earning: Approval pending. |
