The high penetration of distributed generation in distribution grids and the development of microgrids may cause the malfunctioning of the conventional distribution level protection systems. Despite multiple works dedicated to addressing this problem, the development of reliable, high-speed, and cost-efficient protection systems for active grids remains a topical issue. This study proposes a protection system for medium voltage lines that relies entirely on the analytical description of travelling wave transients. This protection uses only local high-frequency current measurements and power-frequency voltage measurements, which potentially makes it a low-cost yet reliable solution. The protection system operates securely by not tripping healthy lines in case of disturbances that do not lead to any faults. The proposed protection is tested on the IEEE 34-bus distribution system with distributed generation.