Phase protection relay without neutral conductor - with asymmetry control and phase sequence control

The phase protection relay is designed to protect three-phase motors and other devices sensitive to voltage changes. It ensures safe operation even in an unstable network by monitoring phase asymmetry, phase failure control and, on selected models, correct phase sequence control.

The device operates without the need for a neutral conductor, allowing easy installation in industrial distribution systems.
Phase voltage monitoring range: 240-500 V AC.

Application and operating principle

1. Connect the relay according to the enclosed diagram.

2. Set:

   • Permissible asymmetry value (%)

   • fault delay (DT)

   • reset time (RT)

3. If the voltage is within the normal range and the asymmetry does not exceed the set limit, the relay will switch on and the RELÉ light will illuminate.

4. For versions with phase sequence control, the L1-L2-L3 sequence must also be correct.

5. If the voltage of any phase exceeds the asymmetry limit, the ASM. (asymmetry) indicator lights up and the relay drops out after the DT delay.

6. After the voltage returns to normal, the RT reset time is counted down. Then the fault goes out and the relay is reactivated.

Asymmetry calculation

The following formula is used to determine the asymmetry:

Asymmetry = ((Max. voltage - Min. voltage) / Max. voltage) × 100%

Example:
((245 V - 200 V) / 245 V) × 100 = 18.3%

This value should be adjusted according to the type of load connected.

Technical specifications