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7/28/2019 5th March Sud Khatri
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INTRODUCTION
A harmonic of a wave is a
component frequency of the
signal that isan integer multiple of
the fundamental frequency,
i.e. if the fundamentalfrequency is f, the harmonics
have frequencies 2f, 3f, 4f, . . .
etc
http://en.wikipedia.org/wiki/Wavehttp://en.wikipedia.org/wiki/Frequencyhttp://en.wikipedia.org/wiki/Integerhttp://en.wikipedia.org/wiki/Fundamental_frequencyhttp://en.wikipedia.org/wiki/Fundamental_frequencyhttp://en.wikipedia.org/wiki/Integerhttp://en.wikipedia.org/wiki/Frequencyhttp://en.wikipedia.org/wiki/Wave7/28/2019 5th March Sud Khatri
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PROBLEM
1) East Bus harmonic filter experienced failureof fifth harmonic reactor, fuses, and capacitor
cans. 2) West Bus harmonic filter experienced
failure of fuses and capacitor cans.
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SOLUTION
The East Bus fifth harmonic filter may not be
filtering properly for several possible reasons.
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REASONS GIVEN
First, measurements have shown an unbalance inthe phase currents to the entire filter shown anunbalance in the phase currents bank of 12.7%13.1%. Phase-B current is 282 A, while Phase-A
and Phase-C are 347 and 343 A, respectively, onaverage. So some capacitors were underratedand some were overrated.
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REASONS GIVEN
Second, the inductance of the East Bus fifth
harmonic was estimated to be 25 mH, which
gives a tuned frequency of 3.9th harmonic.
No design data were available from the
manufacturer, and the rewind shop did not
conduct an inductance test on either the
rewound or undamaged reactors
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REASONS
Voltage rating of the capacitors was
underrated for applications at 13.8 kV, putting
undue stress on the for applications at 13.8
kV, putting undue stress on the capacitors in
the steady state and providing no margin for
transient conditions. Since the rating of
voltages had increased since installation.
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SOLUTION GIVEN
The capacitors which were underrated ,were
replaced by new capacitors.
The inductance which was making filter to
remove 5th harmonic,was dimensionally
corrected to make it tuned to 5th harmonic.
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Problems Caused by
Harmonics
Transformer over-heating
Circuit breaker trips
Fuse blowing
Equipment malfunction
Increased KVA demand
rms and peak
Total Power Factor reduction
Wasted energy
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OTHER POSSIBLE SOLUTIONS
We can use harmonic filter at transformer
end, so that transmission line is free from
carrying harmonic current.
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OTHER POSSIBLE SOLUTIONS
We can also use harmonic filter at the load
end ,so that the harmonics which were
introduced at transmission line can also be
removed.
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OTHER POSSIBLE SOLUTIONS
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OTHER POSSIBLE SOLUTIONS
We can use power quality meters at regular
distances in system to measure wave
distortion quantitatively.
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OTHER POSSIBLE SOLUTIONS
The rating of inductance and capacitance
used should be such that they can withstand
the temporary surges, so that they do not
damage during surges.
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