Low-frequency loss spectra and ageing in paper-insulated cables

This paper is concerned with a method for the assessment of degradation in underground paper-insulated power cables. One advantage of the proposed method is that less energy, and so lighter equipment, is needed to produce a transient than to sustain an alternating current in a long buried cable. Another is that the intrinsic loss at working voltage is derived independently of partial discharge activity (this is recorded and analysed more effectively by separate pulse counting methods). And finally, the measurement yields a spectrum of loss values over a broad frequency range, which affords more physical insight than a single-frequency measurement. The purpose of the present work is to develop the method for use with 11 kV and 33 kV cables, and to demonstrate the enhanced value of the low frequency spectrum in assessing ageing