Due to a lightning storm, during the last August 2007, the Catalonia Railway Electrical System (Spain) was victim of several disturbances and malfunctions. To give response to these problems a project has been established to reduce the risk by transient overvoltage. The project has different steps, and concern from the traction system DC, until the low voltage systems. To get these goals it was established a work plan covering (1) the study of the lightning occurrence in the area, (2) the transient analysis of the electrical system implemented in ATP (Alternative Transient Program), (3) the influence of pole earthing, (4) the influence of the distance between arrester, and (5) the influence of other services.