Electricity transmission with high voltage is usually done with overhead lines by using bare conductors. Population growth in settlements makes it necessary to transmit and distribute electric energy from underground. Insulation is the most important factor in ensuring that electrical energy transmission and distribution with underground cables safely. The insulation problems that may occur in the production of underground cables cause rapidly aging and failures due to partial discharges. In this study, the effect of defects that may occur in the insulation of XLPE insulated cables to electric field distributions in the cable is investigated. In the XLPE insulated cables with 20.3/35 kV, 240 mm(2) and 400 mm(2) conductor cross-sections; electrical field distributions have been investigated by considering problems such as air bubble, water droplets and fiber-like solid particles. Cases of these defects on the surface of the conductor, in the insulator and on the surface of the insulator were considered. The Finite Element Method Magnetics (FEMM) program was used in the analyses.