the possible effect of low frequency electric field exposure in occupational and residential environments raises the question of how electric fields are created, and what effects they may have. Utilities in particular are interested in the sources and levels of electric fields associated with their transmission lines, feeders, substations and related equipments. Moreover the value of electric field distribution produced by or around the electrical equipments is one of the essential factors in the design and development of high voltage electrical equipments (transmission lines, bus bars & insulators�.etc). Therefore monitoring these equipments for electric fields is achieved in this paper. In this paper not only the simulation of electric field using charge simulation method (CSM) in three dimensional (3-D) is achieved by using electric field modeling program developed by the authors but also the electric field is measured into actual conventional 500/220 kV Cairo 500 substation under 500 kV busbar and the simulated results is compared with the actual measured values. The simulation results are matched with the measured values with a very small tolerance about 4.4%.