Stevenson J. Power system analysis

APPENDIX

B.l

SPSI AND NE-OI OENG

Section 7.6 shows that the equivalent network corresponding to the coecient

matrix at each step of the gaussian-elimination procedure has one node less

than that for the previous step. However, the number of branches in the

equivalent network at each step depends on the order in which the nodal

equations are processed. To see the eect of ordering, consider the graph of the

ur-bus system shown in Fig. B.1(a). In this example the o-diagonal elements

are nonzero in row 1 and column 1 of

�because of the branches connected

from bus  to buses



, and 4. All the remaining o-diagonal

elements of Y bus

are zero since buses 2  and

are not directly

con nected to one another. If bus



is processed rst in gaussian elimination of

the nodal equations, the eect on

is similar to the usual Y - transforma

tion symbolically indicated by







X X

Initial

Y bu

