CFRP is becoming in an important material for the future blades due to alternative renewable energy industry plans to increase the length of the blades. This work shows some analytical results about potential distribution on a CFRP coupon obtained after applying an impulse current with different rise time. Effects around electrodes are, symmetry behavior and some interesting comments about the influence of the rise time appear. A FDTD simulation is done and a comparison between FDTD and analytical results. The aim is to evaluate how useful can be this technique when current distribution is over an anisotropic material since tests are not always possible.