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Anonymous Poster #1

Harmonic Measuremnt

10/22/2012 8:51 AM

I have some harmonic values from a HV system. They were measured based on the IEC standard. My concern is this: I have values such as mininum, average, and maximum( i.e. Vrms.) within the time interval of 10 minutes, which level I should use to evaluate the maximum permisible level as specified in the IEC (IEC call them compatibility values).

For instance: within 10 minutes window I got the following values for the 5th harmonic

Minimum 1%

average 5%

maximum 8%

then the IEC limit is 6%. So should I say that the 5th harmonic is out of range based on the maximum value or is within ragen based o the average value?
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Joshi
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Join Date: Oct 2007
Location: India
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Good Answers: 34
#1

Re: Harmonic Measurement

10/22/2012 9:13 AM

One should go by the max. value.
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JSchonek
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Join Date: Jul 2012
Posts: 2
#2

Re: Harmonic Measuremnt

10/26/2012 9:43 AM

The compatibility levels described in IEC standards should be considered as long term limits. the exact statement is:"by convention, the compatibility level is chosen so that there is only a small probability that it will be exceeded by the actual disturbance level".

So, if the maximum value of 5th harmonic voltage (8%) is observed during short times, everything is OK.

Generally, the Power Quality is assessed by using statistical analysis. For example: 95% of the 10 minutes measurements during a given period must be below the maximum limit.

Check EN50160 (Voltage characteristics of electricity supplied by public electricity networks) for more information.
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