The Electromagnetic Transients in Mixed Power Networks with Partial Undergrounding

Abstract

This paper deals with the electromagnetic transients in partially undergrounded mixed high voltage power networks. These networks can include several cable sections replacing parts of the overhead transmission lines. The analysis yields the transient voltage and current distributions along the normal and the partially undergrounded lines. Moreover, the results can indicate eventually existing localized voltage and current concentrations within the network. The study suggests an exact direct analytical distributed parameter approach for modeling the transmission lines and cable sections. Instead of representing the partially undergrounded line by the cascade connection of several two-port circuits, this paper proposes the use of a single equivalent nonuniform transmission line. The non-uniform circuit parameters are represented by means of several step functions in terms of the co-ordinates along the lines under investigation. The resulting expressions are substituted in the simultaneous voltage and current differential equations, for which direct and exact analytical solutions are available in terms of Mathematica parametric functions. The resulting Laplace s-domain voltage and current expressions will then be numerically inverted using the Hosono algorithm. The results of several case studies in which the transients are initiated by sources of step-function or double-exponential waveforms are presented and discussed. The impact of the partial undergrounding on the wave reflections and the matching conditions is also demonstrated.

Keywords: Power networks, mixed, nonuniform, overhead-cable lines, partial undergrounding, frequency characteristics, electromagnetic, transients, distributions, parametric functions

Cite this Article

Kaumil B. Shah, Hina Chandwani. Circuit Topologies, Operation, Control Schemes and Modulation Techniques of Modular Multilevel Inverter. Journal of Power Electronics and Power Systems. 2017; 7(2): 1–13p.