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what use can we make of 3rd harmonic component
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Answer Posted / ketul
Yy connection without neutral wires with both primary and
secondary connected in
star no closed path exists. As the triplen harmonics are
always in phase, by virtue
of the Y connection they get canceled in the line voltages.
Non-triplen harmonics
like fundamental, become rt3 times phase value and appear
in the line voltages. Line
currents remain sinusoidal except for non-triplen harmonic
currents. Flux wave in each
transformer will be flat topped and the phase voltages
remain peaked. The potential
of the neutral is no longer steady. The star point
oscillates due to the third harmonic
voltages. This is termed as ”oscillating neutral”.
Yy connection with neutral wires When a neutral wire is
provided the triplen har-
monic current can flow and the condition is similar to the
single phase case (with a star connected 4 wire source or
with the system earth).The neutral wire carries three
times the triplen harmonic current of one transformer as
these currents are co-phasal.
Unloaded secondary neutral will not be operative. In a Yy
connection, to obtain third harmonic suppression one may
provide a third
winding which is connected in mesh, which can be an
unloaded winding. It is called a
tertiary. This winding improves the single phase to earth
fault detection also. Further,
this winding can be used to feed some permanent station
loads also. Such transform-
ers are designated as Yyd transformers. If the neutral
wires are provided and also
mesh connected winding is present, then triplen harmonics
are ’shared’ between them
depending upon their impedances.
| Is This Answer Correct ? | 7 Yes | 6 No |
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