Continuous monitoring of dielectric properties of LDPE samples during electrical treeing

A technique capable of utilizing voltage waveforms containing harmonics for measurements of dielectric response over a range of frequencies is presented. It has proved useful in several applications and offers high accuracy and flexibility. This paper presents measurement of the changes imposed by electrical treeing in the dielectric properties of LDPE samples and shows that the capacitance increase monitored during the tree growth corresponds well with the optically measured tree length. There is also a change of dielectric loss associated with partial discharge activity during the tree growth, which could be correlated to different treeing modes. The method provides an attractive alternative to the traditional measurements of tree growth by means of optical observations, as it allows for investigations of nontransparent materials.