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Ground-fault protection (G)

The ID letter for ground-fault protection is "G" (ground fault).

The G protection detects residual currents between phases and grounded, electrically conductive parts. The ground-fault protection function responds if the ground fault current exceeds the set tripping current Ig for the set delay period tg.

Ground-fault protection can be implemented as a current-independent and a current-dependent function (I2t).

On 4-pole molded case circuit breakers and 3-pole molded case circuit breakers with external current transformer for N conductor, the G protection calculates the vector sum of the currents of the three phases and the neutral conductor. The G release trips the breaker or an alarm is issued via the communication system if the rms value of this vector sum exceeds the set trip value Ig for the duration of the set delay tg.