This work presents an analysis of the behavior of the electromagnetic field inside a shielded structure (shielded enclosure), when it is submitted to a transitory of electric current. The shielded structure is used in systems of electrical protection by annulling the electromagnetic field in its interior. A closed structure, made up of a considerable number of interconnected cables, it can become a good approach for a Faraday cage. Based on this approach, simulations of the transitory of electric current in the structure were made. Connected to this was a current source at one of its borders, and grounding the plane of its base. Through the transitory of obtained current, the electromagnetic field, in time domain, applying an expression adequately developed for this end was simulated. Analysis of results for different configurations were made.1 239242Thomas, D., Christopoulos, C., Pereira, E., Calculation of radiated electromagnetic fields from cables using time-domain simulation (1994) IEEE Transaction on Electromagnetic Compatibility, 36. , AugustRubinstein, M., Uman, M.A., Methods for calculating the electromagnetic fields from a know source distribution: Application to lightning (1989) IEEE Transaction on Electromagnetic Compatibility, 31. , MayPaul, C.R., Bush, D.R., Radiated fields of interconnected cables (1984) IEEE International Conference on Electromagnetic Compatibility, pp. 259-264. , SeptemberCaixeta, G.P., Pissolato Filho, J., Electromagnetic fields generated by lighting on protection structures of telecommunication centers (1997) IEEE International Symposium on Electromagnetic Compatibility, , AugustRamo, J.R.W.S., Duzer, T.V., (1984) Fields and Waves in Communication Electronics, , John Wiley & SonsCaixeta, G.P., Pissolato Filho, J., Calculation of electromagnetic fields from arbitrary conductors configurations in time-domain simulations (1998) International Symposium on Electromagnetic Compatibility, EMC'RomaS8, , SeptemberChristopoulos, C., Propagation of surges above the corona threshold on a line with a lossy earth return (1985) COMPEL, 4 (2), pp. 91-102