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, monitoring phase asymmetry, controlling phase asymmetry, phase failure control, and in some models - correct phase sequence control.

The device operates without a neutral conductor, which allows it to be easily installed in industrial distribution systems.
Phase voltage control range: 240-500 V AC.

Application and operating principle

1. Connect the relay according to the attached 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 switches on and the RELAY indicator lights up.

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 ASYM. (asymmetry) indicator lights up, and after the DT delay, the relay trips.

6. When the voltage returns to normal, the RT reset time counts down. The fault is then cleared and the relay reactivated.

Asymmetry calculation

The following formula is used to detect asymmetry:

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

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

This value should be adjusted depending on the type of connected load.

Technical specifications