... asymmetry ,incorrect phase sequence faults etc. Can be used for fault monitoring under the conditions any phase loss. General: ... AC 50/60Hz 220V, 230V, 240V, 380V, 400V, 415V for overvoltage, undervoltage, phase failure, phase sequence, three phase asymmetry ... two phase circuit. They are widely used for industrial control systems, capacitor of power compensation, switch boards, air condition systems, ...