6.29 In Example 6.9, double the impedance of the line from bus 2 to bus 4. Determine the

new values for the second row of Ybus. Verify your result using PowerWorld Simulator

case Example 6.9./nEXAMPLE 6.9 Power-flow input data and Yous

FIGURE 6.2

Single-line diagram for

Example 6.9

Figure 6.2 shows a single-line diagram of a five-bus power system. Input data

are given in Tables 6.1, 6.2, and 6.3. As shown in Table 6.1, 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 Q are

input data and which are unknowns. Also, compute the elements of the sec-

ond row of Yous-

SOLUTION The input data and unknowns are listed in Table 6.4. For bus 1,

the swing bus, P₁ and Q₁ are unknowns. For bus 3, a voltage-controlled bus,

400 MVA

15 KV

T1

38

A

400 MVA

15345 KV

851

10

852

345 KV

100 mi

821

2

280 Mv

Line 3

345 kV

50 mi

Line 1

□

841

0

B42

345 kV

200 mi

822

800 MW

T2

800 MVA

345/15 KV

40 Mvar 80 MW

520 MW

800 MVA

15 kV/nTABLE 6.1

Bus input data for

Example 6.9*

801 4

5

TABLE 6.2

Line input data for

Example 6.9

Bus

1

2

3

TABLE 6.3

Transformer input data

for Example 6.9

2-4

2-5

4-5

Type

Swing

Load

1-5

3-4

Constant

voltage

Bus-to-Bus

TABLE 6.4 Bus

Input data and

1

unknowns for Example 2

6.9

Load

Load

Bus-to-Bus

PG

QG

V

per

PL

Q

8

per

per

per per

unit degrees unit unit unit unit

1.0

1.05

0

0

0

0

Show 100 MVA, V 15 kV at buses 1, 3, and 345 kV at buses 2, 4, 5

R₁

per unit

0.0090

0.0045

0.00225

per

unit

0

oli

0.00150

0.00075

X

per

unit

0

5.2

X'

per unit

pla 0.02

0.01

0

V₂ = 1.05

Ps Pas-PL34.4

P=0, Q₂ = 0

Ps= 0, Q₁-0

0

per unit

0.100qni wot wo

0.050

0.025

and too

G

per

unit

Input Data

V₁ = 1.0, ₁ = 0

P₂PG2-PL2=-8

Q2QG2-Q₁2=-2.8

0

0

0

0

0

0

8.0

0.8

Bm

per

unit

0

2.8

0.4

0

0 b

per unit

1.72

0.88

0.44

Maximum

MVA

per unit

6.0

10.0

Unknowns

P₁, Q₁

V₂,

Q₂. d₂

V₁, da

V₂, ₂

QGmax

per

unit

-

4.0

QGmin

per

unit

Maximum

MVA

per unit

MAX 12.0

12.0

12.0

Maximum

TAP

Setting

per unit