Research on the Growth Characteristics of the Electrical Tree at Polyethylene/Silicone Rubber Composite Interface Under Power Frequency Voltage

Abstract

During operation, the composite interface of the cable joint will experience a tangential electric field. When the composite interface has insulation defects, it is easy to experience interface discharge. Electrical tree is a phenomenon of electrical degradation and it’s a precursor of polymer breakdown. It is observed in the laboratory that under the power frequency voltage, the electrical tree will initiate at the composite interface, and the tree growth will finally lead to the interface breakdown. This paper investigates the development of an electrical tree at the composite interface of polyethylene/silicone rubber under power frequency voltage through microscopic observation. The results show that the air gap of the interface is the weak position of insulation, and the electrical tree will be initiated from the triple junction of the air gap and the impacted area of the two materials. The increase in voltage amplitude will speed up the initiation. High amplitudes also promote the electrical tree. The electrical tree shape will be changed from a branch structure at low voltage to a single branch structure at high voltage. The study on the electrical tree at the interface provides a visual display of the degradation process of the material before the breakdown at the composite interface.