Grounding practices ground fault currents

FIG. 29-8 Typical high-voltage ac motor starter illiistrating several protective schemes fuses, overload relays, ground-fault relays, and differential relays with the associated current transformer that act as fault-current sensors. In practice, the differential protection current transformers are located at the motor, hut the relays are part of the starter. 

The more recommended practice is to ground the neutral solidly or through an impedance, commensurate with the requirements of the protective scheme and the fault current limited to a desired level. The terminal equipment and the windings of all the machines may now be designed for a voltage corresponding to the relevant GFF. 

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