KUPPAM ENGINEERING COLLEGE, KUPPAMDEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERINGIII/II B.TECH ASUB: POWER SYSTEM ANALYSIS DATE: 20.02.15

1 A) Explain the symmetrical component method to analyze an unsymmetrical system? B) One conductor of 3- line is open. The current flowing to the delta connected load through a line a is 10A. With the current in line a as reference and assume that line c is open. Find the symmetrical components of the line currents? 2 A) Explain briefly power in terms of symmetrical components? B) A set of 3- unbalanced voltages & currents resolved into symmetrical components gives the following results. Va0 = 30 -30, Va1 = 450 0, Va2 = 225 40 & Ia0 = 10190, Ia1 = 620, Ia2 = 550. Determine the complex power represented by these voltages and currents by (i) symmetrical components (ii) unbalanced phase quantities3 A) What is the relation between impedance in phase frame and sequence frame? B) Explain briefly sequence impedance network of an unloaded generator?4 A) Derive the fault current equation for LG fault on an unloaded generator? B) A 11KV, 25MVA, synchronous generator has +ve, -ve & zero sequence reactances of 0.12, 0.12 & 0.08 p.u respectively. The generator neutral is grounded through a reactance of 0.03pu. A LG fault occurs at the generator terminals. Determine the line to line voltages. Assume that the generator was unloaded before the fault.5 A) Derive the fault current equation for LL fault on an unloaded generator? B) A salient pole generator without dampers is rated 20MVA, 13.8KV and has a direct axis sub transient reactance of 0.25p.u. The -ve & zero sequence reactances of 0.35 & 0.1p.u respectively. The generator neutral is solidly grounded. Determine the sub transient current in the generator and the line to line voltages for sub transient conditions when a line to line fault occurs at the generator terminals with the generator operating unloaded at the rated voltage. Neglect resistance.6 A) Derive the fault current equation for LLG fault on an unloaded generator? B) Explain briefly open conductor faults?7 A) Derive the swing equation? Also derive the equations for coherent & non- coherent swinging when the two machines are connected at same bus. B) Derive the power flow equation for an Alternator is directly connected to the load 8. A) Define Steady state Stability ? Also calculate the steady state stability limit when an Alternator is connected to infinite bus? B) Explain briefly methods of improving steady state stability?