Stevenson J. Power system analysis

286

CHAPTER 8 THE IMPEDANCE MODEL AND NETWORK CALCULATIONS

of the adm;ttance directly connected between buses



and

, as we would

expect since mutually coupled branches are absent.

We have made this detailed examination of the bus admittances in order

to dierentiate them clearly from the impedances of the bus impedance matrix.

Conceptually, we solve Eq. (8.3) by premultiplying both sides of the

quatio

YI� =

hus

to yield

(B.B)

and

we must remember when dealing with

hus

that V and I are column vectors

of the bus voltages and the currents entering the buses from current sources,

respectively. Expanding Eq. (8.8) for a network of three in

ependent nodes

yields

(

8.9)

(8.10)

(8.11)

From Eq. (8.10) we see that the driving-point impedance 22

is deter

mined by open-circuiting the current sources at buses



and  and by

injecting the source current

at bus

. Then,

222

(8.12)

Figure 8.2 shows the circuit described. Since 2

2 IS dened by openmg the