IEEE 519-2022 applies its current limits to installations with harmonic-producing loads. For installations with inverter-based resources it refers to IEEE 1547 or IEEE 2800, and for mixed installations it uses a decision criterion that compares the site's generation with 10 % of the average annual demand.
Short answer
IEEE 519-2022 uses its current limits at the PCC of installations where harmonic-producing loads predominate. If inverter-based resources (IBR) predominate, such as a solar plant, the standard refers to IEEE 1547 or IEEE 2800. If the installation mixes both, Figure 1 of the standard gives the decision criterion: it compares the combined rated generation of the site with 10 % of the average annual demand of the load.
What the scope says
Clause 1.1 establishes that the voltage and current limits apply at the user’s PCC to the entire installation that contains harmonic-producing loads. For installations of inverter-based resources, the standard directs users to other standards, such as IEEE 1547 or IEEE 2800, for the current distortion limits.
When no other standard applies, clause 1.1 indicates that users must continue to use note “c” of Tables 2 to 4 for IBRs connected to transmission systems. That note says generation facilities are limited to the values of the lowest Isc/IL ratio row (less than 20 in Tables 2 and 3, less than 25 in Table 4), regardless of their actual ratio, unless another standard with applicable scope covers them.
The standard defines an inverter-based resource as any electric energy source connected to the transmission system through a power electronics interface, made up of one or more units capable of exporting active power from a primary energy source or a storage system. An IBR unit is an individual inverter or a group of inverters connected at the same point of connection (clause 3.1).
Three cases
Clause 5.2 separates three situations:
| Installation | Which standard gives the current limits at the PCC |
|---|---|
| Mainly harmonic-producing loads | The IEEE 519 limits (Tables 2, 3 and 4) |
| Mainly inverter-based resources | Other standards with applicable scope, such as IEEE 1547 or IEEE 2800 |
| A mix of loads and IBR | The decision criterion of Figure 1 of the standard |
Figure 1 of the standard resolves it with two questions, in this order. First: does the site have distributed energy resources or inverter-based resources? If not, the IEEE 519 limits apply at the PCC. If it does, second question: is the combined rated generation of the site less than 10 % of the average annual load demand? If it is less, the IEEE 519 limits also apply. If it is not less, the limits come from a standard with applicable scope, such as IEEE 1547 or IEEE 2800. That 10 % is the threshold Figure 1 uses to decide which standard gives the limits.
An illustrative example to see the magnitude of the threshold, with made-up figures. A factory has an average annual demand of 2,000 kW. 10 % of that demand is 200 kW. If it installs 150 kW of panels with inverters, its generation stays below that threshold and the IEEE 519 limits continue to apply. If it installs 1 MW, it exceeds it by a wide margin and the limits come from IEEE 1547 or IEEE 2800. The calculation for a real installation is done with its data and Figure 1 of the standard.
What still holds at the PCC of a plant with generation
Even if the source of the current limits changes, some elements do not change:
- The PCC remains the evaluation point. The IEEE 519 limits do not apply to individual equipment or inside the installation; see PCC in IEEE 519: Where Harmonic Limits Apply.
- The current limits are those in Harmonic Current Limits and TDD by Isc/IL when Figure 1 leads to IEEE 519. Who answers for each limit is explained in Scope of IEEE 519: Who Is Responsible for Harmonics.
- Generation is limited to the lowest-ratio row when the reference standard is IEEE 519 and no other applies (note “c”).
- Voltage is limited by the utility. Table 1 does not change because of inverters.
- The harmonics that appear are those of the inverters and those of the loads, and they combine at the PCC. In a plant with generation and drives, the study must consider both.
What this guide does not cover
IEEE 1547 and IEEE 2800 are mentioned here only as the standards IEEE 519 refers to, and both are outside the text of this standard. Their distortion requirements are consulted in each one. For the context of inverter standards, see PV Inverter Standards: IEC 62109, IEC 62116 and IEEE 1547.
Also outside this guide is how each utility specifies power quality for plants. Those requirements come from the local code and the utility’s interconnection requirements, to which the study is adapted; they are not part of IEEE 519.
Harmonics from solar plants in practice
A solar plant with many inverters does not only contribute its own harmonics. The set of transformers, cables and capacitors of the plant network forms an impedance that can amplify them. That phenomenon is explained in Harmonics and Resonance in Solar Power Plants, and it is part of what a study evaluates before connection.
We help with your case
At Tiza Group we carry out power quality studies and connection studies for plants with inverters and for industry with its own generation, in Colombia, or elsewhere on request. We identify which criterion applies to your PCC, evaluate the harmonics of your inverters and of your loads and define the measures if they are needed.
Related guides
- Harmonic Current Limits and TDD by Isc/IL
- Scope of IEEE 519: Who Is Responsible for Harmonics
- PCC in IEEE 519: Where Harmonic Limits Apply
- Harmonics and Resonance in Solar Power Plants
References
- IEEE Std 519-2022, IEEE Standard for Harmonic Control in Electric Power Systems: clause 1.1 (scope, reference to IEEE 1547 and IEEE 2800, mix of loads and IBR); clause 3.1 (definitions of IBR and IBR unit); clause 5.2 and Figure 1 (decision criterion); note “c” of Tables 2, 3 and 4 (generation).
- IEEE Std 1547-2018 and IEEE Std 2800-2022: standards to which IEEE 519 refers for inverter-based installations.
Frequently asked questions
Must a solar plant meet the IEEE 519 current limits?
The standard directs installations based mainly on inverters to other interconnection standards, such as IEEE 1547 or IEEE 2800. When no other standard applies to inverter-based resources connected to transmission, the limits in note "c" of Tables 2 to 4 continue to be used.
What happens in a factory with a small rooftop solar system?
It is a mixed installation. Clause 5.2 refers to a decision criterion (Figure 1) that compares the combined rated generation of the site with 10 % of the average annual load demand to decide whether the IEEE 519 limits apply.
Do the IEEE 519 voltage limits also change with inverters?
The text of clause 5.2 deals with current limits. The Table 1 voltage limits apply at the PCC and must be met by the utility; the standard does not modify them because of inverter-based generation.