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Overhead line parameters are calculated, taking into account the length of the line and the frequency range of the transient to be simulated. Depending on the frequency range and the origin of the transient, several parts of the line (phase conductors, shield wires, towers or poles, footing impedances, insulators) have to be included in the model. In all cases, the most important part is phase conductors. This paper describes an input requirement for obtaining electric overhead line parameters and investigates the sensitivity of these parameters with respect to some input data. The aim is to conclude on the accuracy with which input values must be specified. An illustrative example is included to support the main conclusions. Index Terms--Modeling, overhead lines, power system transients, simulation.

EMTP-type programs include dedicated support routines (cable constants) for calculating an electric representation of cable systems in terms of a series impedance matrix Z and a shunt admittance matrix Y, based on cable data defined by geometry and material properties. Z and Y are the basic input of the various cable models that are used in time-domain transient simulations. This paper discusses the modeling of high-voltage cables: single-core, three-phase, and pipe-type cables. Material properties are given for commonly used conductive and insulating materials, and how to represent semiconductive screens, lossy insulation materials, and magnetic armors is shown. The significance of the grounding condition of sheaths and armors is discussed. In transient calculations, it is always important to accurately represent the core conductor, insulation, semiconductive layers, and the metallic sheath. Frequency-dependent losses of paper-oil insulation need to be taken into account for very-high-frequency transients. The significance of conductors external to the cable depends on the shielding effect of the cable sheath, which depends on the sheath design and the frequency content of the transient. The conclusions are supported by numerical simulation results. Index Terms--Insulated cables, modeling, power system transients, simulation.

This paper is concerned with methods of limiting the build-up of transient voltages between sheath and armour in long armoured power cables. Calculations by a frequency dependent cable model demonstrate that this voltage can be efficiently limited to an acceptable level by introducing sheath-armour bondings at regular intervals, or by using a semiconductive sheath-armour interlayer. The paper investigates the required minimum length between bondings, as well as the required conductivity of the sheath-armour interlayer if the use of bondings is to be avoided.

This paper presents a travelling wave model for transmission cables and lines in which the frequency dependence of the modal transformation matrix is accurately taken into account. This is achieved by carrying out the convolutions in the actual phase domain. The computational efficiency is increased by fitting the tail portion of the step responses with linear segments. The paper also discusses two versions of the inverse Fourier Transform which are highly efficient when calculating the step responses needed for long observation times.

The series impedance needed in simulation of cable transients is commonly calculated using formulae that neglect the presence of proximity effects. Further, when applying these formulae, sheaths constructed as wire screens must be treated as tubular conductors. This paper investigates how these simplifications affect the occurrence of transient sheath voltages. The analysis involves calculations by the Finite Element Method and comparison of calculated results with field measurements. It is shown that the sheath voltages are dependent on the proximity effect and the helical winding of the sheath wires.