Parameter determination for modeling system transients - Part II: Insulated cables

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.