B.Tech-B.Tech Electrical Engineering 7th Sem EEE 7EE5 Power System Engineering 7E4175(Rajasthan Technical University-2011)

7E4175
B.Tech. VII Semester (Main/Back) Examination, Nov-Dec - 2011
Electrical Engineering
7EE5 Power System Engineering

Time: 3 Hours
Maximum Marks: 80
Min. Passing Marks : 24

 

 

Unit - I

 

 

Q.1. a) Draw and explain Heat Rate Curve and Incremental Cost Curves of thermal generating units. Prove that Incremental Cost Curve cuts the Heat Rate curve
at its minimum value. [8]

b) Derive transmission loss formula in terms of real power generations. [8]

OR

Q.1. a) Explain "dynamic programming method" of unit commitment. [8]

b) Three plants of a total capacity of 500 MW are scheduled for operating to supply a total system load of3l 0 MW. Evaluate the optimum load scheduling if the plants have the following cost characteristics and the limitation. [8]

 

 

 

 

 

 

 

 

 

 

Unit - II

 

Q.2. a) Write the causes of instability. What conditions are to be satisfied for stable operation of a generator? What are the limits of steady state stability? [8]

b) A 50 Hz, 20 pole hydro electric generator rated at 500 MVA, 20 KV has H = 2MJ/MVA.

i) Determine its W_s and W_sm

ii) Write the swing equation for this generator.

iii) Generator is initially working at P_m = P_e = 1.0 p.u. with δo = 10° when a 3 - phase short circuit occurs at its terminals which results in its electrical output reducing to 0 for t > 0. Determine its power angle δ, 3 cycles after the short circuit. Assume the mechanical input power Pm remains constant at 1.0 p.u. during this time. [8]

OR

Q.2. a) Find the Swing Equation for "Coherent group of machines".    [8]

b) A 50 Hz synchronous generator having inertia constant H = 5 MJ/MVA and a transient reactance X_d ' = 0.2 pu is connected to an infinite bus througha purely reactive circuit as shown. Reactance values are marked on the diagram on a common system base. The generator is delivering real power of

i) 0.6 pu

ii) 2.0 pu at 0.8 power factor lagging to the infinite bus at a voltage of V = 1 p.u. Calculate - transferreactance, apparent power, current, excitation emf and synchronizing power coefficient.     [8]

 

 

 

 

 

 

 

 

 

Unit - III

 

Q.3. a) Explain large signal stability using equal area criteria. [8]

b) Find out the equation for critical clearing angle and critical clearing time, if sudden short circuit occurs on one of the two parallel transmission lines, fault near the generator bus. [8]

OR

Q.3. a) Find out equation for critical clearing angle if an.auto reclose circuit breaker is used in a system having two transmission lines in parallel and a fault occurs at the mid point of one of the parallel lines. [8]

b) For the system shown in fig, both the terminal voltage and infinite bus voltage are 1.0 p.u. and the generator is delivering 1.0 p.u. Power. Calculate the critical clearing"angle and the critical clearing time when the system is subjected to a 3 - phase fault at point p (middle of the line) as shown in fig. Let H = 5 MJ/MVA. [8]

 

 

 

 

 

 

 

 

 

 

Unit - IV

 

Q.4. a) Describe about basic elements of an excitation system of the synchronous generator. [8]

b) Explain the DC excitation system with amplidyne voltage regulator. [8]

OR

Q.4. a) Explain about power system interconnections in India.

b) Write advantages and problems of inter connected power systems.

c) Explain reserve capacity of power stations.                                            [4+6+6]

 

 

Unit - V

 

 

Q.5. a) Explain working of Tap changing Transformer and its uses.

b) What are the advantages and problems of series compensation. How these problems can be eliminated?           [8+8]

OR

Q.5. a) Explain "Power System Security". Draw static security level diagram.

b) What are the situations which may cause voltage instability? How the voltage collapse can be prevented?         [8+8]

Earning:  ₹ 7.80/-