Siemens Phase Monitoring Relay, SPDT

The Siemens phase monitors monitor the voltages in three-phase system and signal the power failure of one or more phases over a floating contact. Phase sequence monitors monitor the phase sequence in three-phase systems and signal any changes in the phase sequence - change of rotating field - over a floating changeover contact.

The 3-phase LED display in the phase monitor and the LED display in the phase sequence monitors provide constant information on the switching state of the plant
The compact design in 1 MW saves space.