Dielectric response measurements during electrical treeing in sub-picofarad samples

A technique called Arbitrary Waveform Impedance Spectroscopy (AWIS) developed for measuring dielectric properties in insulating materials has been used to study capacitance and dielectric loss changes during electrical tree growth in LDPE samples. The sample capacitance is small, in the range of 0.1–0.15 pF, placing high demands on the measurement system. Simulations in FEM-software show that the measured capacitance is in agreement with simulated values and can be used to estimate tree growth rate. It also seems to be possible to differentiate between different regions of tree growth by analyzing changes in capacitance and loss of the studied samples.