EEE 6156
CAT 1
[30 MARKS]
13/05/2023 @ 1pm
1. Draw the per-unit impedance diagram of the system shown in Fig below.
Assumed base values are 100MVA and 100kV.
[10 Marks]
2. A synchronous generator of reactance 1.20 pu is connected to an infinite bus
(V = 1.0p.u) through transformers and a line of total reactance of 0.60pu. The
generator no load voltage is 1.20 pu and its inertia constant is H = 4MWs/MVA. The resistance and machine damping may be assumed negligible.
The system frequency is 50Hz. Calculate the frequency of natural oscillations
if the generator is loaded to
[10 Marks]
(i) 50 % and
(ii) 80 % of its maximum power limit
3. A 50Hz, synchronous generator capable of supplying 400MW of power is
connected to a large power system and is delivering 80MW when a threephase fault occurs at its terminals. Determine, the time in which the fault
must be cleared if the maximum power angle is to be 85o. Assume H = 7
MJ/MVA on a 100 MVA base. Also, calculate the critical clearing angle. [10
Marks]