Color of indicator lights for relay protection devices

Relay protectors typically use red, yellow, and green indicator lights to signal faults, phase issues, or normal operation.

Color Meanings

Red Light: Indicates a fault condition such as phase loss, voltage imbalance, or out-of-phase connections. When the red LED is illuminated, the relay may be released or tripped to protect the equipment. In some models, the red light flashes during a time delay before the relay activates.

Yellow Light: Signals a wrong phase sequence or phase connection issue. It serves as a warning that the phase order of L1, L2, and L3 is incorrect, and corrective action is needed before normal operation can resume. Green Light: Indicates normal operation.

When the three-phase wiring is correct and voltage levels are within limits, the green light is on, and the relay remains closed, allowing the equipment to operate safely.

Operational Notes

During normal operation, the green light is on. If a phase sequence is incorrect, the yellow light illuminates, and the relay may not engage until the phases are corrected. For phase loss or voltage imbalance, the red light turns on, and the relay trips to prevent damage.

Some relay protectors include a time delay, during which the red LED may flash before the relay fully trips. These color-coded indicators provide a quick visual reference for operators to identify the status of the relay protector and take appropriate action to maintain safe operation of three-phase equipment.