Digital station protection

A homogeneous and uniform protective system for all protected units in a substation, which uses the processing capabilites of modern microprocessors, is presented. The basic idea is to split protective tasks into processing and data communication. The processing units are located at each boundary of the protection zones, each of which always comprises phasor representation for currents and voltages, fault type, and fault direction are evaluated. The selective tripping command for each protection zone is produced by collective merging allows bridging of faulty components. The required communication can be adapted to both requested protective functions and availability, reliability, and maintainability. Cooperation with other protective devices, especially with stand-alone relays, further protection-related functions and other substation tasks are supported. Laboratory tests and field experience obtained so far have proved the feasibility of this digital station protection