Difference between Internal and External Partial Discharge

Sr. No.

Internal
Partial Discharge

External
Partial Discharge

1.

This occurs
mainly due to presence of voids or occlusions.

This
occurs mainly due to atmospheric conditions, the outer surrounding air gets
ionized.

2.

This is
not visible to naked eye.

This is
easily visible in the form of violet glow, missing noise on the surface of
conductor.

3.

Since it
is not visible to naked eye it may cause breakdown after few days, months or
years i.e. it is unpredictable.

Since it
is visible some action to mitigate or restrict it can be initiated.