Carbon Fiber Reinforced Plastic (CFRP) components are commonly present in new generation of wind turbine blades and aircraft. CFRP components are preferred for its good mechanical strength and low weight. However, CFRP is more vulnerable to lightning currents and arcs. In addition, CFRP can present very anisotropic electric properties that can difficult its lightning protection. In this paper we present two types of tests intended for improving the understanding of electrical properties of CFRP useful for lightning protection. The experimental and simulation study of the potential distribution along a CFRP coupon suggest how the currents are distributed and some defects in the electrical connections. A new method in order to investigate connection effectiveness in full scale wind turbine blades is proposed. The method is minimal invasive. The second part of the paper discusses the possible current paths in different arrangements of connections by means of thermal imaging