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why is the vector group analysis done in transformer tests
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Answer Posted / fred jabagat
Vector Group can be used as basis in setting the phase
compensator factor for numerical transformer differential
relays, i.e. SEL387.
A 3-Ph Transformer is wired internally in different ways to
produce a desired phase position between primary and
secondary terminals.
IEC standards develop a transformer circuit configuration
and a corresponding vector group code which follows a clock
that represents a 30 degrees shift in every hour.
The CT's of a numerical transformer differential relays are
usually wired with its polarity mark facing away from the
protected winding. Because of the phase shift between the
primary and secondary terminals of the transformer it is
necessary to set a phase compensator factor to the
differential relay so that it will not trip on normal load.
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