Analysis of Partial Discharge Behavior within a Spherical Cavity in a High Voltage Form-Wound Stator Coil

• Main Authors: Silva, F. R., Ferreira, R. S., Martins, F. G. R., Dias, D. H. N.
• Format: Conference Proceeding
• Language: English
• Subjects: Analytical models; Coils; Electric machines; Finite Element Analysis (FEA); form-wound coil; Insulation; Partial discharges; Partial Discharges (PD); Solid modeling; Stators; Voltage measurement
• ISSN: 2576-6791
• DOI: 10.1109/EIC55835.2023.10177361

Among several problems related to the insulation of electrical machines, internal cavities within the insulating material and subjected to high values of electric field can give rise the phenomenon known as Partial Discharge (PD), whose understanding is an important step to assess the electrical insulation's health condition and predict early degradation. Although the issue is widely researched, the partial discharge behavior, particularly in High Voltage (HV) coils, remains poorly understood, due to the constructive parameters of machine being kept under the manufacturer's confidentiality. This paper presents the results regarding to PD behaviour in a spherical cavity located within in main insulation of 13.8 kV form-wound stator coil under changing parameters such as size and position of the cavity, amplitude of applied voltage and thickness of the main insulation of the coil. The 3D model geometry of the HV coil is developed using Finite Element Analysis (FEA) software and MATLAB program to simulate the PD characteristics and analyze the change in electric field distribution during PD occurrence. The results show that PD activity has a strong dependence on the cavity size and main insulation thickness. In addition, the number of discharges per cycle is directly linked to electric field strength in the cavity, that is, as the thickness of the main insulation decreases or the amplitude of the applied voltage increases, the greater will be the number of discharges. The work aims to ensure a better understanding of PD in a model closer to reality, considering that it uses real constructive parameters of the stator coil, studying parameters related to manufacturing process and impregnation of the insulation (size and location of cavity, thickness of insulation) and others that can be controlled in electrical system operation (applied voltage and frequency).