High-speed current differential unit protection is provided by the MiCOM Alstom P541 and P542 series. Created for all overhead line and cable applications, the P541 and P542 can easily interface with the longitudinal (end-to-end) communications channel between line terminals.
Direct fiber optics or multiplexed digital links are managed by the interface options. This scheme measures the currents entering as well as those leaving the protected plant item, while at the same time, maintaining optimum selectivity. Stability is provided for any out-of-zone fault by the instantaneous tripping which will result in an internal fault. Such tripping uses a proven characteristic comparing differential current with through current. Phase differential elements of this type offer consistent detection of the solid and resistive faults.