Stator Earth Fault Protection of Alternator

Stator Earth Fault Protection Definition

Stator earth fault protection limits ground fault current to minimize damage to the stator core and winding.

Ground Impedance Role

Grounding the stator with high impedance can reduce fault current but may lower relay sensitivity, requiring additional sensitive relays.

Resistance Neutral Earthing

In this method, the stator’s neutral point is grounded through a resistor, which is connected with a current transformer and protective relay.

Relay Types

Depending on the connection method, either an inverse time relay (for direct substation connection) or an instantaneous armature attracted relay (for star-delta transformer connection) is used.

Alternative Grounding Method

A distribution transformer and resistor setup can also ground the stator, with an overvoltage relay ensuring protection.