Partial Discharge Characteristics in Electrical Tee Near Multi-layer Interface

To understand the relationship between the tree propagation near the interface in a multi-layer insulation system, which is likely to serve as electrical weak points, and partial discharge (PD) characteristics, PD patterns were measured for propagation of electrical trees in the Epoxy/Glass (EP/Glass) sample. When the maximum tree length is short, the number of detected partial discharges (PDs) in the composite-layer sample becomes smaller than that in the monolayer sample. Charges can easily move across the interface, which tends to act as an electrical weak point, resulting in a relatively small potential difference between the needle tip and the tree tip required for PD occurrence. Regardless of the presence or absence of an interface, the maximum PD charge also tended to increase as the maximum tree length became longer. This can be attributed to a larger potential difference between the needle electrode tip and the tree tip in longer trees, an increase in the number of tree branches leading to simultaneous PD events, or a combination of both factors.