Why does the phase voltage of two healthy phases become equal to the line volt

Why does the phase voltage of two healthy phases become
equal to the line voltage in case of an ungrounded neutral
3 phase star connected sytem when a single line to ground
fault occurs ?

Question Posted / rakesh kumar

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Why does the phase voltage of two healthy phases become equal to the line voltage in case of an un..

Answer / shahzad

in my point of view that the when single line to ground
fault occurs that phase return and then we get phase
voltage of two healty phaase become equal

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Why does the phase voltage of two healthy phases become equal to the line voltage in case of an un..

Answer / nithi

The question what u have asked is technically termed
as "ARCING GROUND".
DUE TO VIRTUAL CAPACITANCE, THE VOLTAGE B/W THE LINE -
GROUND IS ALWAYS PHASE VOLTAGE.BUT IN THE CASE OF LINE-
GROUND FAULT IN UNGROUNDED SYSTEM,THE GROUND & THE
TRANSFORMER BODY ITSELF ACT AS A PHASE (AS THERE IS DIRECT
CONTACT WITH GROUND).
this is cumulative effect,due to capacitance again the
voltage b/w the line to ground keeps on increasing.this
will increase the pressure on the insulation,arcing
occurs,ultimately leads to breakdown of the system.

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