Generally, protection against phase imbalance/loss is one of the standard protection functions of motor circuit breakers.

Therefore, all thermal-magnetic GV circuit breakers (GV2ME/P, GV3P, GV4P/PE/PEM, GV7...) have protection against phase imbalance/loss, except of GV2RT that is dedicated for protection of transformers (imbalanced load is supposed there).

The magnetic GV circuit breakers (GV2L/LE, GV3L, GV4L/LE, ...) do not have protection against phase imbalance/loss, but use of overload relay with protection against phase imbalance/loss is supposed for motor application.

Concerning the difference between phase currents for tripping, it is not quite simple as it is time-dependent.
Details for phase imbalance/loss are described in IEC 60947-4-1, chapter 8.2.1.5.2-Limits of operation of three-pole time-delay overload relays energized on two poles. For GV2ME (thermal, compensated for ambient air temperature variations, phase loss sensitive) it is following:

1. With the relay energized on three poles, current at 2 poles 1xIr + 1 pole 0.9xIr, tripping shall not occur in less than 2 h, starting from the cold state, at ambient air temperature 20 deg. C.

2. Moreover, when the value of the current flowing in two poles is increased to 1.15xIr and the third pole de-energized (=0), tripping shall occur in less than 2 h.

For the situation when 1 pole of GV2ME is de-energized (current=0) we can also provide tripping curve - see curve 2 in Attachment.

Udgivet til: Schneider Electric Danmark