Phase sequence relay for Technotrans

A Phase Sequence Relay (also known as a phase rotation relay or phase sequence detector) is a protective electrical device used in three-phase electrical systems to monitor the order of the phases — typically labeled L1, L2, and L3.

It detects the correct rotation (sequence) of the three-phase power supply.

Ensures that L1 → L2 → L3 follows the standard phase sequence.

If the phase sequence is incorrect (e.g. L1 → L3 → L2), the relay can:

• Trigger an alarm,
• Prevent equipment startup, or
• Disconnect the load

In motors, an incorrect phase sequence will cause the motor to rotate in the wrong direction, which can:

• Damage equipment (e.g. pumps, fans, compressors),
• Cause unsafe conditions,
• Lead to system failures