The Frequency Characteristics of Mixed Power Networks with Partial Undergrounding

Abstract

Abstract. This paper deals with the frequency characteristics of partially undergrounded mixed power networks, which include several cable sections replacing parts of the overhead lines. The analysis yields the voltage and current distributions along the normal and the partially undergrounded lines, as well as the frequency dependence of the networks' input impedance. Moreover, the results will show eventually existing localized voltage and current concentrations. The study suggests an exact direct analytical distributed parameter method for modeling the lines and cable sections. Instead of representing a partially undergrounded line by the cascade connection of two-port networks, this paper proposes the use of a single equivalent nonuniform line. The nonuniform circuit parameters are represented by means of step functions in terms of the co-ordinates along the lines. The resulting expressions are substituted in the simultaneous voltage and current differential equations, for which analytical solutions are available in terms of Mathematica Parametric Functions.