Stevenson J. Power system analysis

CHAPTER

7

THE

ADMITTANCE

MODEL AND

NETWORK

CALCULATIONS

The typical power transmission network spans a large geographic area and

involves a large number and variety of network components. The electrical

characteristics of the individual components are developed in previous chapters

and now we are concerned with the composite representation of those compo

nents when they are interconnected to form the network. For large-scale system

analysis

the network model takes on the form of a network matr with elements

determined by the choice of parameter.

There are two choices. The current ow through a network component

can be related to

"

the voltage drop across it by either an admittance or an

impedance parameter. This chapter treats the admittance representation in the

fo

rm

of a primitive model which describes the electrical characteristics of the

network components. The primitive model neither requires nor provides any

information about how the components are interconnected to form the network.

The steady-state behavior of all the components acting together as a system is

given by the nodal admittance matr based on nodal analysis of the network

equations.

The nodal admittance matrix of the typical power system is large and

sparse, and can be constructed in a systematic building-block manner� The

building-block approach provides insight for developing algori thms to account

for network changes. Because the network matrices are very large, parsily

7. 1 BRANCH AND NODE ADMIANC

239

techniques are needed to enhance the computational eciency of computer

programs employed in solving many of the power system problems described in

later chapters.

The particular importance of the present chapter, and also Chap. 8, which

develops the nodal impedance matrix, becomes evident in the course of power