Burton Thornley MacKenzie

Development of optimized insulation for HVDC extruded cable

The radial stress distribution and the maximum stress in a loaded dc cable are governed by the volume resistivity of the insulation. Since the resistivity is dependent on temperature, the maximum stress in the loaded cable is transferred from the hot conductor area to the cooler external portions of the insulation (stress inversion), and, according to load conditions, may be multiplied several times (Figure 1). This results in limitation in either stress or load rating of a dc cable.

Influence of Inorganic Fillers on the Voltage Endurance of Solid Dielectric Power Cables

Results of work undertaken to evaluate solid dielectric materials containing inorganic fillers with respect to voltage endurance are reported. The results obtained are associated with degradation caused by the growth of dendrites within the solid dielectric when under voltage stress.

Filler effects and treeing phenomena in laboratory models and cable sections

The nucleation and growth under high voltage stress of tree-like shapes in solid dielectrics is a phenomena reported by many observers. The major investigative effort has been on dielectrics which are unfilled.1–3 Some investigations have been done on the effects of filler on high voltage treeing.4,5 This paper presents some observations of high voltage treeing made on point-to-plane models and cable sections containing steel needles. Tree growth inhibition caused by mineral fillers is demonstrated.