There are many different types of stator protection. First, we examine the protection against
short circuits in the stator, and then consider other types of stator problems that might be
considered for special protective devices.
Stator faults result from insulation breakdown that causes an arc to develop, either from
phase to phase or from the phase conductor to the grounded magnetic steel laminations of
the stator. The cause of the insulation breakdown may be due to overvoltage, overheating, or
mechanical damage of the winding insulation due to faults. The overvoltage that may cause an
insulation failure might be due to lightning or switching surges, which are usually protected
against by surge protective devices. Overheating may be due to prolonged unbalanced loading
or to the loss of cooling, either of which may cause insulation deterioration over a period of
time.