--- title: "Standards compliance: a number is not a limit on its own" url: "https://3dfs.com/technology/standards-compliance" description: "Each limit names its window, percentile and place. Our controller helps a site meet IEEE 519-2022 at the point of common coupling." updated: "2026-10-15" --- # Standards compliance: a number is not a limit on its own > Each limit names its window, percentile and place. Our controller helps a site meet IEEE 519-2022 at the point of common coupling. A compliance claim that leaves out the window, the percentile or the place cannot be tested. This page names the three for each limit. A measurement campaign at the site shows whether it meets them. Power quality standards do three things. They define the quantities, prescribe how to measure them and set limits at a named point. A facility is compliant when an instrument at the named point reports a percentile of windowed values under the limit. This page names the standard behind each limit, what it measures and where. It also shows what a corrector beside the panel contributes under each limit. The corrector supplies the loads’ distorted current itself. ## What a limit is The controller works on the current side of each limit. We designed it to help a site meet IEEE 519-2022 at the point of common coupling. The controller does not provide ride-through [6](https://3dfs.com/technology/standards-compliance#src-6). - Utility connection. Harmonics at the point of common coupling. IEEE 519 reads daily 99th percentile values over 3 seconds and weekly 95th percentile values over 10 minutes [1](https://3dfs.com/technology/standards-compliance#src-1). - Motors. Unbalance at the motor terminals. NEMA MG 1 rates a motor for 1% unbalance and derates it to 75% of rating at 5% [3](https://3dfs.com/technology/standards-compliance#src-3),[9](https://3dfs.com/technology/standards-compliance#src-9). - Data centers. Large computational loads. ERCOT now requires a large computational load to ride through voltage at 50% of nominal for half a second [17](https://3dfs.com/technology/standards-compliance#src-17). - At the panel. What the controller changes. The current distortion and current unbalance measured upstream of the panel fall. Harmonic orders above the 23rd remain [6](https://3dfs.com/technology/standards-compliance#src-6). Each standard reads its limit at its own place. IEEE 519 evaluates harmonics at the point of common coupling (PCC), where the plant meets the utility [1](https://3dfs.com/technology/standards-compliance#src-1). EN 50160 evaluates supply voltage, harmonics and unbalance at the customer’s terminals, as 95% of the 10-minute values in a week [2](https://3dfs.com/technology/standards-compliance#src-2). NEMA MG 1 evaluates unbalance at the motor terminals with no window at all, because it rates the motor and not the supply [3](https://3dfs.com/technology/standards-compliance#src-3). NEMA MG 1 names no window at all, because it rates the motor and not the supply. A device that acts inside a cycle shows in each Class A number. A device that acts in seconds shows only in the 3-second and 10-minute values. ## The limits IEEE 519-2022 is North America’s harmonic standard. Below 1 kV it limits voltage to 5% per harmonic and 8% total, and current by total demand distortion from 5% to 20% with the short-circuit ratio [1](https://3dfs.com/technology/standards-compliance#src-1). The 2022 edition is titled a standard rather than a recommended practice, and its values are stated as limits [7](https://3dfs.com/technology/standards-compliance#src-7). An illustrative trace, not a capture. It draws three harmonics at 20%, 14% and 9% of the fundamental. The readout is the square root of their sum of squares. Correction runs through the 23rd order, so higher orders remain [6](https://3dfs.com/technology/standards-compliance#src-6). IEEE 519-2022 limits voltage distortion below 1 kV to 8% total and current by total demand distortion through the 50th order [1](https://3dfs.com/technology/standards-compliance#src-1). ANSI C84.1 sets service voltage at plus or minus 5% in Range A and asks utilities to hold unbalance to 3% at the meter [8](https://3dfs.com/technology/standards-compliance#src-8). NEMA MG 1 rates motors for 1% unbalance and derates above it [3](https://3dfs.com/technology/standards-compliance#src-3),[9](https://3dfs.com/technology/standards-compliance#src-9). EN 50160 holds supply voltage within plus or minus 10%, total harmonic distortion (THD) under 8% and unbalance under 2% for 95% of a week [2](https://3dfs.com/technology/standards-compliance#src-2). IEC 61000-2-2 sets compatibility levels in the 2 to 150 kHz band that switching equipment fills [10](https://3dfs.com/technology/standards-compliance#src-10). MIL-STD-1399 holds shipboard 60 Hz power to 5% THD and 3% unbalance [11](https://3dfs.com/technology/standards-compliance#src-11). The current and voltage panels are IEEE 519-2022 Tables 2 and 1 [1](https://3dfs.com/technology/standards-compliance#src-1). The third panel is the NEMA MG 1 derating curve as a 2005 motor-protection bulletin reproduces it, with the NEMA 1% line [9](https://3dfs.com/technology/standards-compliance#src-9),[3](https://3dfs.com/technology/standards-compliance#src-3). ## What the equipment must tolerate Compliance has a second side: what the equipment must survive. The ITI curve gives 120 V equipment 20 ms of dropout tolerance, half a second at 70% voltage and 10 s at 80% [13](https://3dfs.com/technology/standards-compliance#src-13). SEMI F47 sets 50% for 200 ms, 70% for half a second and 80% for one second [14](https://3dfs.com/technology/standards-compliance#src-14). IEC 61000-4-11 Class 3 tests dips to 0% for a cycle and 70% for 30 cycles [15](https://3dfs.com/technology/standards-compliance#src-15). IEEE 1668 adds three-phase points [16](https://3dfs.com/technology/standards-compliance#src-16). ERCOT’s ride-through rule is NOGRR282 [17](https://3dfs.com/technology/standards-compliance#src-17). A FERC order of 2026-07-16 (Docket RD26-7-000) directs NERC to file reliability standards for computational load integration by the end of 2026 [18](https://3dfs.com/technology/standards-compliance#src-18). ## How the industry has dealt with it Compliance is a measurement campaign. The commissioning engineer installs a Class A analyzer at the PCC for at least a week. The engineer computes the 3-second and 10-minute percentiles, then compares them with the IEEE 519 tables for the site’s short-circuit ratio [1](https://3dfs.com/technology/standards-compliance#src-1),[5](https://3dfs.com/technology/standards-compliance#src-5). We found no published figure for what a missed limit costs a facility. Mitigation follows the report: a capacitor bank for displacement power factor, a tuned or active filter for orders over the limit and a K-rated transformer for the heat. Several standards the industry still cites by name have left active status, including the IEEE color books and the C62.41 surge standards [19](https://3dfs.com/technology/standards-compliance#src-19). A campaign report has to name the edition it was measured against. ## How Software-Defined Electricity handles it We designed the controller to meet IEEE 519-2022 at the PCC. It carries a CE conformity assessment under IEC 62477-1 and is installed with a UL field evaluation [6](https://3dfs.com/technology/standards-compliance#src-6). Those facts cover the product. We recommend that a third party run the campaign, so the number that says the site complies is theirs. The controller contributes the current side of the ledger. It corrects the current, not the voltage. It supplies harmonic current through the 23rd order, reactive current and unbalanced current locally, in under 5 microseconds. The total demand distortion and the current unbalance measured upstream of the panel fall. The displacement power factor rises toward 1.0 [6](https://3dfs.com/technology/standards-compliance#src-6). Where the PCC aggregates many panels, voltage-side limits move by one panel’s share: the corrected current times the plant’s upstream impedance. The share the utility delivers stays [4](https://3dfs.com/technology/standards-compliance#src-4). The SEMI F47 and IEC 61000-4-11 test points all lie below 85% of nominal. That is outside the controller’s stated band of plus or minus 15% [6](https://3dfs.com/technology/standards-compliance#src-6). ## Where it matters A [data center](https://3dfs.com/solutions/data-centers-compute) now answers to ERCOT and FERC as well as IEEE 519. A [defense facility](https://3dfs.com/solutions/defense-critical-infrastructure) and a [ship](https://3dfs.com/solutions/maritime) answer to MIL-STD-1399 at the switchboard. An [industrial plant](https://3dfs.com/solutions/industrial-manufacturing) answers to IEEE 519 at the PCC and to NEMA MG 1 at every motor. The places map to the Opportunity Pillars. The PCC and the motor terminals are the [Consumption](https://3dfs.com/technology/consumption) side. The meter and the customer’s terminals are the [Delivery](https://3dfs.com/technology/delivery) side. Ride-through for computational loads is where Delivery meets [Generation](https://3dfs.com/technology/generation). ## What to measure Name the point, the window, the percentile and the edition on the report. Keep the corrector within its rating through the peak hour. A device that stays within rating through the peak improves the weekly 95th percentile. A device that runs out of rating during the peak improves the off-peak values. It leaves the percentile where the peak left it [4](https://3dfs.com/technology/standards-compliance#src-4). Start by logging one week at the PCC before claiming a number. Sources - IEEE 519-2022, clauses 3 and 5, Tables 1 and 2. - EN 50160:2022+A1:2025. - NEMA MG 1-2024, clauses 12.45, 14.36.2 and 30.1.2. - Rule review for this series: the averaging-window rule, the two-share rule, window and rating. First-party derivation. - IEC 61000-4-30:2025, clauses 4.4, 4.5 and 5.4.2. - 3DFS, VectorQ Technical Overview (current revision), Technical Specifications table and p. 14. First-party. - Trade summaries of the IEEE 519-2022 changes. - ANSI C84.1-2020 (R2025), Table 1 and Annex C. - A leading maker’s fuse and motor protection guide, Motor Protection, Voltage Unbalance and Single-Phasing (2005), derating table. - IEC 61000-2-2:2002+AMD1:2017+AMD2:2018. - MIL-STD-1399 Section 300 Part 1 (2018), Table II. - 3DFS, electrical network analysis of server racks at a data center, p. 25. First-party. - Information Technology Industry Council, ITI (CBEMA) Curve Application Note (2000). - SEMI F47-0706 (Reapproved 0812), Table 1. - IEC 61000-4-11:2020, Table 1, Class 3. - IEEE 1668-2017, three-phase points as reproduced in the EPRI seminar of 2018. - ERCOT, NOGRR282, Large Computational Load Ride-Through Requirements, effective 2026-08-01. - POWER magazine, FERC orders mandatory NERC reliability standards for data center and other computational loads (2026-07-16). - IEEE standards status pages: IEEE 141, 241, 446 and 1100 Inactive-Reserved since 2021-03-25. IEEE C62.41.1 and C62.41.2 Inactive-Reserved. Version 5.1