Re-determine the Example 9_8 fault currents, except with a second generator added at bus 3. The parameters for the new generator should be identical to those of the existing generator at bus 3. Are the fault currents larger or smaller than the Example 9_8 values?

Example 9_8

Consider the five-bus power system whose single-line diagram is shown in Figure 6.2. Machine, line, and transformer data are given in Tables 9.1, 9.2, and 9.3. Note that the neutrals of both transformers and generator 1 are solidly grounded, as indicated by a neutral reactance of zero for this equipment. However, a neutral reactance equal to 0.0025 per unit is connected to the generator 2 neutral. The prefault voltage is 1.05 per unit. Using PowerWorld Simulator, determine the fault currents and voltages for a bolted single line-to-ground fault at bus 1 , then bus 2 , and so on to bus 5 .

Figure 6.2

Tables (9.1, 9.2, 9.3)

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400 MVA 15 kV B1 1 400 MVA 15/345 kV 5 851 0 B52 345 kV 100 mi B21 2- Line 2 Line 3 345 kV 50 mi 280 Mvar Line 1 B41 B42 345 kV 200 mi B22 4 800 MW T2 800 MVA 345/15 kV B3 3 40 Mvar 80 MW 520 MW 800 MVA 15 kV