For the system of Problem 9.12, compute the fault current and voltages at the fault for the following faults at bus 3:

(a) a bolted single line-toground fault,

(b) a bolted line-to-line fault,

(c) a bolted double line-toground fault. Also, for the single line-to-ground fault at bus 3, determine the currents and voltages at the terminals of generators G1 and G2.

Problem 9.12

Equipment ratings and per-unit reactances for the system shown in Figure 9.19 are given as follows:

Synchronous generators:

\(\begin{array}{lllll}\text { G1 } & 100 \text { MVA } & 25 \mathrm{kV} & \mathrm{X}_{1}=\mathrm{X}_{2}=0.2 & \mathrm{X}_{0}=0.05 \\ \text { G2 } & 100 \mathrm{MVA} & 13.8 \mathrm{kV} & \mathrm{X}_{1}=\mathrm{X}_{2}=0.2 &  \mathrm{X}_{0}=0.05\end{array}\)

Transformers: 

\(\begin{array}{llll}\text { T1 } & 100 \text { MVA } & 25 / 230 \mathrm{kV} & \mathrm{X}_{1}=\mathrm{X}_{2}=\mathrm{X}_{0}=0.05 \\ \text { T2 } & 100 \mathrm{MVA} & 13.8 / 230 \mathrm{kV} & \mathrm{X}_{1}=\mathrm{X}_{2}=\mathrm{X}_{0}=0.05\end{array}\)

Transmission lines:

Using a 100-MVA, \(230-\mathrm{kV}\) base for the transmission lines, draw the perunit sequence networks and reduce them to their Thévenin equivalents, "looking in" at bus 3. Neglect \(\Delta-Y\) phase shifts. Compute the fault currents for a bolted three-phase fault at bus 3 .

Transcribed Image Text:

4 T1 OH G1 j0.03 1 TL13 2 3 TL12 TL23 2 4 T2 b O j0.03 G2