An interconnection reactor system is shown in fig.. The base values for the given percent reactances are the ratings of the individual pieces of equipment. A three phase short circuit occurs at point F. Determine the fault current and fault KVA if the bus-bar line to line voltage is 11 kV. 10MVA 10%. G₁ 20MVA 15% G₂ X1 -0000 10MVA 5% 20MVA 15% G3 -0000 8MVA 4%

Q2. The single-line diagram of a simple three-bus power system is shown in Figure-2. Each generator is represented by an emf behind the sub-transient reactance. All impedances are expressed in per unit on a common MVA base. All resistances and shunt capacitances are neglected. The generators are operating on no load at their rated voltage with their emfs in phase. A three-phase fault occurs at bus 3 through a fault impedance of Zf = j0.19 per unit. (i) Using Th'evenin's theorem, obtain the impedance to the point of fault and the fault current in (ii) Determine the bus voltages per unit. ) j0.05 j0.075 j0.75 2 j0.30 j0.45 Figure-2: Single line diagram of the power system network for Q2 3

What are the hazards of phase failure and phase reversal?

Id is :  510221

A 60 Hz, 33 kV, 3-phase alternator with earthed neutral has a reactance of 7 ohms per phase and is connected to a bus-bar through a circuit breaker. The distributed capacitance upto circuit breaker between phase and neutral in 0.03 uF. Determine   (i) peak re-striking voltage across the contacts of the breaker   (ii) frequency of oscillations

Problem #2: A transformer is fed from a generator via a 5-cycle breaker. Generator reactance are: X"=18%, X'=25%, Xe=120%. A three-phase fault occurs at the load side of the breaker when the transformer was unloaded. Find: A)The sustained short circuit current in the breaker. B) Initial symmetrical rms current in the breaker. C) Maximum dc short circuit component in the breaker.

Describe the effects of harmonics on power distribution system.

Full calculation with any assumption needed. All sub questions please as it is all related.

Q5: A generator is connected through a transformer to a synchronous motor. Reduced to the same base, the per unit subtransient reactances of the generator and motor are 0.15 and 0.35, respectively, and the leakage reactance of the transformer is 0.1 per uint. A three-phase fault occurs at the terminals of the motor when the terminal voltage of the generator is 0.9 per uint and the output current of the generator is 1 per unit at 0.8 power factor leading. Find the subtransient current in per unit in the fault, in the generator, and in the motor. Use the terminal voltage of the generator as the reference phasor and obtain the solution (a) by using the internal voltages of the machines and (b) by using Thevenin's theorem.

5. Two 75 MVA 3-phase alternator are connected in parallel. The speed load characteristic of the first generator is 2% from no-load to full load while that of the second alternator is 3% from no-load to full load. The machines are fully loaded when the load is 150 MVA. If the load is reduced to 80 MVA. Calculate the load carried by each machines?