PowerWorld Simulator case in this Problem duplicates the system from Problem 1, except the...

PowerWorld Simulator case in this Problem duplicates the system from Problem 1, except the generators are modeled using a two-axis model, with the same and H parameters are in Problem 1. Compare the critical clearing time between this case and the problem 1 case.

Problem 1

Open PowerWorld Simulator case in this Problem, which models the Example 1 with transient stability data added for the generators. Determine the critical clearing time (to the nearest 0.01 second) for a fault on the line between buses 2 and 5 at the bus 5 end which is cleared by opening the line.

EXAMPLE 1

Power-flow input data and Ybus

Figure 1 shows a single-line diagram of a five-bus power system. Input data are given in Tables 1, 2, and 3. As shown in Table 1, bus 1, to which a generator is connected, is the swing bus. Bus 3, to which a generator and a load are connected, is a voltage-controlled bus. Buses 2, 4, and 5 are load buses. Note that the loads at buses 2 and 3 are inductive since Q2 = −QL2 = −2.8 and −QL3 = −0.4 are negative.

For each bus k, determine which of the variables Vk, dk, Pk, and Qk are input data and which are unknowns. Also, compute the elements of the second row of Ybus.

SOLUTION

The input data and unknowns are listed in Table 4. For bus 1, the swing bus, P1 and Q1 are unknowns. For bus 3, a voltage-controlled bus, Q3 and δ3 are unknowns. For buses 2, 4, and 5, load buses, V2, V4, V5 and δ2, δ4, δ5 are unknowns.

The elements of Ybus are computed from (6.4.2). Since buses 1 and 3 are not directly connected to bus 2,

 Y21 = Y23 = 0

Using (6.4.2),

Figure 1

Single-line diagram

Figure 2

Table 1

Bus input data*

*Sbase = 100 MVA, Vbase = 15 kV at buses 1, 3, and 345 kV at buses 2, 4, 5

Table 2

Line input data

Table 3

Transformer input data

Table 4

Input data and unknowns

Equation