The simulation of electric field distribution on cable under the presence of moisture and air voids

Power cables as one of main components of power networks, play an important role in electric power transmission between different zones. Because of probable incidence of water tree phenomena, air cavity and also humidity in electric insulators, increase in electric field happens locally and can lead to breakdown in insulator. The goal of This paper is determining humidity and air cavity effects in cable insulation system on electric field intensity inside cable by using Finite Element Method. Therefore electric field distribution inside water drops and also air cavities existing in polyethylene insulation of one 20KV distribution cable has been simulated and calculated by Maxwell software. Since electric field intensity in cable depends on various factors such as cavity´s permittivity and its position respect to cable center, therefore by considering these parameters, FEM simulation has been done and the results were analyzed. Also relation between local field congestion in water drops corners and insulation failure possibility which can lead to insulator complete breakdown, is studied.