To compare with the IEEE 519-2022 limits, the instrument must comply with IEC 61000-4-7 and IEC 61000-4-30 Class A and measure at least up to the 50th harmonic. It measures with 12-cycle windows (about 200 ms at 60 Hz), which are grouped into 3-second values and then into 10-minute values.
Short answer
IEEE 519-2022 requires the instrument to comply with IEC 61000-4-7 and IEC 61000-4-30 Class A and to measure at least up to the 50th harmonic. Each measurement uses a 12-cycle window (about 200 ms at 60 Hz). Fifteen windows are grouped into a 3-second value and 200 3-second values are grouped into a 10-minute value. With those two values the percentiles that are compared with the limits are calculated.
The instrument
Clause 4 establishes that any instrument used to compare with the limits must meet the specifications of IEC 61000-4-7 (general guide on harmonics and interharmonics measurement) and of IEC 61000-4-30 Class A (power quality measurement methods).
IEC 61000-4-30 defines two classes. With Class A it is required to measure at least up to order 50, while with Class S only up to order 40 is required. Since IEEE 519 requires measuring at least up to the 50th, not any instrument will do: an analyzer that only reaches the 40th does not allow evaluating the harmonics of orders 41 to 50 that the tables cover. The instruments of both classes are compared in Power Quality Analyzer.
The standard summarizes in clauses 4.1 to 4.4 the most relevant parts of those specifications, which follow.
The 12-cycle window and the 5 Hz bins
Digital instruments calculate harmonics with the discrete Fourier transform (DFT) over a stretch of signal. Clause 4.1 sets the width of that stretch, or window, at 12 cycles for 60 Hz systems, approximately 200 ms, and at 10 cycles for 50 Hz systems.
With that window, the spectrum has one component every 5 Hz: 0, 5, 10, … 55, 60, 65, 70 Hz and so on. The standard defines the magnitude of a harmonic this way: take the component at the center frequency (60, 120, 180 Hz, etc., or 50, 100, 150 Hz at 50 Hz) and combine it with the two adjacent 5 Hz bins. The three values are combined into a single RMS value that represents that harmonic.
An example for 60 Hz: the 5th harmonic (300 Hz) is obtained by combining the bins at 295, 300 and 305 Hz. In this way the harmonic value also captures the small frequency variations around its center.
From the window to the 3-second value and the 10-minute value
200 ms windows are too many to compare one by one. The standard groups them in two steps:
- 12-cycle window (60 Hz). About 200 ms; one measurement per harmonic order
- 15 consecutive windows. Combined with an RMS calculation
- Very short time value. 3 s; clause 4.2
- 200 consecutive 3 s values. Combined with an RMS calculation
- Short time value. 10 min; clause 4.3
- Very short time (3 s). Clause 4.2 aggregates 15 consecutive 12-cycle windows (10 at 50 Hz) into one value, with an RMS calculation for each frequency component (equation 1). Fifteen 200 ms windows add up to 3 seconds.
- Short time (10 min). Clause 4.3 aggregates 200 consecutive 3-second values, again with RMS per component (equation 2). Two hundred 3-second values add up to 600 seconds, that is, 10 minutes.
In both cases the calculation is the RMS of the grouped values: they are squared, averaged and the square root is taken.
What is done with those values
The 3-second and 10-minute values are accumulated over a day and a week respectively, and from them the percentiles that are compared with the clause 5 limits are calculated. Clause 4.4 defines those periods and percentiles, and the guides on voltage limits and on current limits give the values they are compared against.
A full day has 28,800 3-second values. A full week has 1,008 10-minute values. 95th and 99th Percentiles in IEEE 519: How It Is Evaluated explains how the percentiles of those series are obtained.
What it means for the measurement plan
These rules define what the instrument must be able to do, and therefore how much must be planned before connecting it:
- Continuous recording over full days and weeks, because the percentiles are calculated for each 24-hour period and for each 7-day period.
- Store the 3-second and 10-minute values for each harmonic order, up to the 50th, and not only the total THD.
- Measure at the PCC. The limits belong to that point (see PCC in IEEE 519: Where Harmonic Limits Apply).
- Record the demand current so harmonics can be related to IL.
The standard also states that measurement methods are being investigated for ranges beyond what the document covers.
What this guide does not cover
This guide describes what the standard requires of the instrument and of the aggregation. It does not cover analyzer models, settings or connection: those depend on the equipment and the site, and are defined in the project’s measurement plan.
We help with the measurement
At Tiza Group we carry out power quality studies and measurements with Class A analyzers. If your project needs to verify compliance with IEEE 519-2022 at the PCC, we include the measurement as a recommended test within the quote for testing and commissioning. Field measurements are carried out in Colombia, or elsewhere on request.
Related guides
- 95th and 99th Percentiles in IEEE 519: How It Is Evaluated
- IEEE 519-2022 Voltage Harmonic Limits at the PCC
- Harmonic Current Limits and TDD by Isc/IL
- PCC in IEEE 519: Where Harmonic Limits Apply
- Power Quality Analyzer
References
- IEEE Std 519-2022, IEEE Standard for Harmonic Control in Electric Power Systems: clause 4 (Class A instrument, measurement at least up to order 50); clause 4.1 (12-cycle window and 5 Hz bins); 4.2 (very short time, 3 s, equation 1); 4.3 (short time, 10 min, equation 2); 4.4 (statistical evaluation).
- IEC 61000-4-7, general guide on harmonics and interharmonics measurement.
- IEC 61000-4-30, power quality measurement methods (Class A and Class S).
Frequently asked questions
Can I use a Class S analyzer to evaluate IEEE 519?
Not if it only reaches order 40. Clause 4 points out that Class S instruments require measuring up to order 40, while to evaluate IEEE 519 you must measure at least up to order 50, as Class A instruments do.
Why is the window 12 cycles and not 10?
The standard sets 12 cycles (about 200 ms) for 60 Hz systems and 10 cycles for 50 Hz systems. In both cases the window lasts about 200 ms and the resolution is 5 Hz.
What are the 3-second and the 10-minute values?
The 3-second value groups 15 consecutive 12-cycle windows with an RMS calculation. The 10-minute value groups 200 consecutive 3-second values with the same calculation. These two values are used for the statistical comparisons with the limits.