The W-PR3 Phase Protection Relay is a digital electronic instrument designed for AC voltage monitoring and protection in 3 phase 4 wire and 3 phase 3 wire system. Used in application such as main failure, phase sequence, phase unbalance, under and over voltage. The W-PR3 is a designed to monitor the correct phase sequence of 3 phase system (L1, L2, L3). With correct phase sequence applied the output relay will energizes (N/O) and remains de-energized (N/C) if an incorrect sequence is applied, the display will show “Pr”.