# help in understanding harmonics as per IEEE 519 limits

#### ak52

Joined Oct 15, 2014
197
Hello everyone,

Consider this paragraph from the IEEE 519:
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Very short and short time harmonic values should be accumulated over periods of one day and one week,
respectively. For very short time harmonic measurements, the 99 th percentile value (i.e., the value that is
exceeded for 1% of the measurement period) should be calculated for each 24-hour period for comparison
with the recommend limits in Clause 5
. For short time harmonic measurements, the 95 th and 99 th percentile
values (i.e., those values that are exceeded for 5% and 1% of the measurement period) should be calculated
for each 7-day period for comparison with the recommended limits in Clause 5. These statistics should be
used for both voltage and current harmonics with the exception that the 99 th percentile short time value is
not recommended for use with voltage harmonics.
------x------

Clause 5:
------x------

------x------

What is the meaning of the 99th percentile value or the 95th percentile value??I am not able to understand the meaning of the bold line in the above paragraph.Can someone please elaborate on that?

Am i correct in assuming that if i have got 100 data samples ,i just need to consider 99 samples or 95 samples and ignore the rest?
Kindly help!!

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