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Propagation losses occur in medium voltage power cables as pulses propagate through them. Since cables have many components, these can make different contributions to the propagation losses. The relative contributions of the conductors, insulation and semi-conducting screens to the propagation characteristics of the cable are analyzed. The propagation characteristics of the cables are studied by a developed 'approximate' model providing analytical expressions that can quantify the contributions to the losses by the different parts of the conductor and dielectric system. The model is compared with an 'exact' model and is tested on four cables. Index Terms--Attenuation, dielectric, high frequency, insulation, phase velocity, propagation characteristics, semi-conducting screens, series impedance, shunt admittance.

Understanding the high frequency characteristics of the materials that make up medium voltage extruded cables is important in establishing diagnostics schemes based on electromagnetic pulse propagation methods. Two measurement techniques have been developed and used to characterize the high frequency material properties of semi-conducting screens and cross linked polyethylene (XLPE) insulation up to 100 MHz. The experimental details, parameter extraction and limitations of the two measurement techniques are presented. Index Terms--Complex permittivity, scattering parameters, insulation, semi-conducting, two-port, one-port, high frequency, measurements, characterization.

This paper proposes a method for comparing the effect of different maintenance strategies on system reliability and cost. This method relates reliability theory with the experience gained from statistics and practical knowledge of component failures and maintenance measures. ]'he approach has been applied to rural and urban distribution systems. In particular, a functional relationship between failure rate and maintenance measures has been developed for a cable component. The results show the value of using a systematic quantitative approach for investigating the effect of different maintenance strategies. Index Terms--Asset management, electric power distribution system, maintenance strategy, reliability evaluation, reliability-centered asset maintenance (RCAM).

Knowledge on the dependence of wave propagation characteristics on material properties and cable design is important in establishing diagnostic methods for cable insulation. In this study, a high frequency measurement technique to characterize the semi-conducting screens in medium voltage cross-linked polyethylene (XLPE) cables has been developed. The frequency ranges from 30 kHz to 500 MHz. The influence of the experimental set-up, sample preparation methods, pressure and temperature are investigated. A dielectric function is developed for the semiconducting screens and this is incorporated into a high frequency model for the cable. The propagation characteristics obtained from the high frequency cable model are compared with those obtained from measurements made on the same cables. Index Terms--Semi-conducting screen, semicon, geometric capacitance, admittance, complex permittivity, dielectric function, propagation constant, attenuation, high frequency cable model, scattering parameters, cross-linked polyethylene, XLPE, cables.

Dynamics of water penetration in mass impregnated cable insulation has been studied. For experimental purposes, artificial damage has been inflicted to a 40-cm-long cable sample and water ingress has been continuously monitored by frequency response measurements. A similar experiment has been conducted on 2.8-m-long cable sample, where both frequency response and time-domain reflectometry (TDR) measurements have been performed. After termination of both experiments, actual moisture content has been measured radially and axially. Based on dielectric measurements, a model of water ingress has been developed and diffusion coefficients have been estimated for mass impregnated cable paper. Index Terms--Dielectric response, Karl Fischer titration, mass impregnated cable, moisture content, oil paper insulation.