Nowadays, generation of electricity from multiple local sources is preferred rather than generation from a single central source. Thus, active distribution network concept rises to prominence in distribution networks that distributed generation is widely applied. Protection of such networks using bidirectional power flow is more difficult, that's why, different approaches were developed for protection. Unit protection method, whereby lines of the distribution system are protected individually and faults are detected by comparing current data obtained from both end of the line is one of these methods. In this study, ratio unit protection for active distribution networks is analysed by comparing other methods based on over current protection method. To determine the performance of developed ratio unit protection system, the system is applied on a ring distribution system with sources on the both ends and observed if operates properly during various possible faults. Ratio unit protection system protects the active distribution system successfully in all cases.