Electrical Tree Growth and Its Partial Discharge Pattern in Silicone Rubber under AC Voltages

Electrical tree aging is one of the main causes of failure for insulated electrical equipment. In this paper, electrical tree growth morphology and partial discharge (PD) characteristic were synchronously captured in silicone rubber (SIR). The experimental observations demonstrate that there are three typical tree morphology in SIR which are affected and transferred by the magnitude of AC voltage. Meanwhile, there are two typical tree growth pattern in SIR, including “growth-stagnation” pattern and “growth-fast growth-breakdown” pattern. It is found that the PD magnitude and PD pulse sequences are closely related to the electrical tree growth. The large discharge pulse number in half cycle is corresponding to the number of main tree channels. It is believed that PD is one of the contributing driving forces for electrical tree growth after it initiates. Small molecule cyclic polysiloxane generates and fills the channels in SIR with the PD happens. This mechanism is able to explain most of the phenomena observed in electrical treeing experiments of SIR, providing a theoretical basis to proper application of SIR in high-voltage electrical equipment.