Simulation of partial discharge in closely coupled cavities embedded in solid dielectrics by finite element method

Nowadays, the existence of small gas-filled cavities in solid dielectric such as HV cables and transformers is difficult to avoid during manufacturing process, so detecting their effects on the equipments are very critical for the life of high voltage equipments. It is obvious that the simplest and most famous equivalent circuit of a solid dielectric with a cavity inside itself is the regular capacitance model. Simulation of PD for one cavity embedded in a solid dielectric indicates that calculation of voltage across the cavity using capacitance model must be modified because diameter of cavity and its distance to high or low voltage contacts have a big influence on cavity voltage in a solid dielectric [1]. In addition, in this paper, simulation of PD by finite element method (FEM) on two closely coupled cavities embedded in solid dielectrics shows that interactions between cavities are very important to illustrate the behavior of a cavity. Therefore, studies indicate that calculation of breakdown voltage in a cavity is completely dependent on locations of other cavities. Hence, using regular modeling for many cavities in a small area is not appropriate and it must be modified. This paper shows how Horizontal and vertical distance between two cavities has a big influence on breakdown voltage of a cavity.