Nucleation and growth of electrical trees in polyethylene: Studies by electron spin resonance(ESR)and other techniques

We have used ESR, a powerful technique for detecting very small concentrations of paramagnetic species, to study both the “nucleation” as well as the “growth” phases of electrical trees in LDPE. We have shown that important space charge densities can accumulate in the polymer near the electrodes, in agreement with the Ashcraft model. Finally, we provide evidence that the transition from “nucleation” to “growth” is dominated by partial discharges of steadily increasing magnitude.