Time and Frequency Domain Measurement Methods for High Frequency Characterisation of Power Cables

R. Papazyan

ime Domain Reflectometry (TDR) has been used for localisation of transmission line discontinuities in various applications. One of the challenges when applying TDR on power cables is to obtain knowledge of the high frequency characteristics of both the degraded and the undegraded sections of the cable.

Two methods for extraction of the wave propagation properties of power cables are developed in this thesis. The first one uses TDR measurements and analyses the short pulse propagation along the cable. It delivers the complex propagation constant in the frequency range 1 MHz - 300 MHz. The second method is based on the S-parameter measurements with a Network Analyser (NA). The method extracts the complex propagation constant and the characteristic impedance, as well as the LCRG Telegrapher's Equation parameters for the frequencies between 300 kHz and 300 MHz.

The developed system and methods are then applied for diagnostics of water degraded cable insulation. The first experiment uses TDR for localisation and parameter estimation of water ingress in mass-impregnated paper insulation. The second experiment utilises the S-parameters technique for high frequency characterisation of water-treed XLPE cable sample. A sensitivity check of the TDR system for measurements in the field is also performed.

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