12-2. A simple three-phase power system is shown in Figure P12-1. Assume that the ratings...

12-2. A simple three-phase power system is shown in Figure P12-1. Assume that the ratings of the various devices in this system are as follows:

Assume that the power system is initially unloaded, and that the voltage at Bus 4 is 250 kV, and that all resistances may be neglected.

(a) Convert this power system to per-unit on a base of 500 MVA at 20 kV at generator G₂.

(b) Calculate Y_bus and Z_bus for this power system using the generator subtransient reactances.

(c) Suppose that a three-phase symmetrical fault occurs at Bus 4. What is the subtransient fault current? What is the voltage on each bus in the power system? What is the subtransient current flowing in each of the three transmission lines?

(d) Which circuit breaker in the power system sees the highest instantaneous current when a fault occurs at Bus 4?

(e) What is the transient fault current when a fault occurs at Bus 4? What is the voltage on each bus in the power system? What is the transient current flowing in each of the three transmission lines?

(f) What is the steady-state fault current when a fault occurs at Bus 4? What is the voltage on each bus in the power system? What is the steady-state current flowing in each of the three transmission lines?

(g) Determine the subtransient short-circuit MVA of this power system at Bus 4.

Figure P12-1 The simple power system of Problem 12-2.