Optical and electrical detection of single pulse of partial discharge on electrical treeing

The purpose of this study is to analyze the treeing degradation process by measuring partial discharge pulse and discharge luminous image of single pulse. In the measurement system, PMMA blocks were used with electrodes consisting of a needle and a plate. One cycle of an applied ac voltage was divided into twenty equal phase angle sections, labeled φ₁,φ₂,…,φ₂₀ in order, from one negative peak to the next negative peak of the applied voltage. A high voltage was applied to the needle electrode, positive discharge pulses and discharge luminescences were measured at the same time between φ₃ and φ₉. As a result, the discharge luminescence at φ₃ and φ₄ occurred mainly in the void area independently of the discharge magnitude. At φ₇,φ₈ and φ₉, the discharge luminescence was observed in the void area when the discharge magnitude was small, in the tree area when it was comparatively large. The discharge luminescence reached near the tip of tree channel