The P152 Self or dual-powered over current relay is a state of the art equipment. It provides protection for applications where no external auxiliary power is available or the auxiliary supply does not guarantee the dependability required for protection applications. It is designed for medium voltage and low voltage industrial installations, distribution network substations and more specifically in ring main unit (RMU) networks for protection and monitoring purposes . Other applications for this is main protection functions in the relay are timed and instantaneous phase and earth fault protection, with up to 3 independent stages available. A definite must have.