Section II:   Short Line Approximation

The shunt capacitance for a short line is almost negligible. The series impedance is assumed to be lumped as shown in Fig. 2.2. If the impedance per km for an l km long line is z₀ = r + jx , then the total impedance of the line is Z = R + jX = lr + jlx . The sending end voltage and current for this approximation are given by

(2.7)

(2.8)

Therefore the ABCD parameters are given by

(2.9)

Fig. 2.2 Short transmission line representation.