IEEE 519-2022 shares responsibility: the user limits the harmonic current it injects, and the utility limits the voltage distortion it delivers, changing the network impedance if needed. The limits apply only at the PCC, in steady state, and are not meant to evaluate a piece of equipment or an internal point of the plant.
Short answer
IEEE 519-2022 treats harmonics as a shared responsibility between the user and the owner or operator of the network. The user limits the harmonic currents it injects; the utility is responsible for the harmonic voltage it delivers and, if needed, changes the network impedance. The limits apply only at the PCC, in steady state, and they are not meant to evaluate a piece of equipment or a point inside the facility.
What the standard covers
Clause 1.1 defines the scope. The standard sets design goals for electrical systems with linear and nonlinear loads. It describes the voltage and current waveforms that can exist in the system and sets distortion goals for the designer. The interface between sources and loads is described as the point of common coupling, and meeting the design goals reduces interference between electrical equipment.
The voltage and current limits apply at the user’s PCC, to the whole facility that contains harmonic-producing loads (nonlinear equipment).
Clause 1 lists the most common sources: power electronics converters, arc furnaces, static var compensators, distributed generation inverters, AC phase controllers, cycloconverters and rectifiers, such as those in switched-mode power supplies and pulse-width-modulated drives.
What it does not cover
- Transients. The standard addresses steady-state conditions. Transients that exceed these limits can occur (clause 1.1).
- Radio-frequency interference. It does not cover it; it offers guidance for wire-line telephone systems (clause 1.1, and Annex B on the telephone influence factor).
- Evaluation of equipment. The limits are based on assumptions that hold at the PCC, and not necessarily at any other point of the system. For that reason they should not be used to evaluate equipment (clause 1.1).
- Internal points of the facility. Clause 5 notes that inside the user’s facility the harmonic voltages and currents can be significantly higher than the PCC limits, because of lack of diversity, cancellation and other phenomena that reduce the combined effect of several sources below their algebraic sum.
- The limits are not absolute. Clause 1.2 clarifies that the values should not be taken as mandatory in every case, because there is some conservatism that may not always be necessary.
How responsibility is shared
The Introduction and clause 1.2 explain the mechanism in three parts:
- User. Limits its harmonic current emissions to reasonable values, shared out equitably
- Utility network. Harmonic currents flow through its impedance and produce harmonic voltages
- Voltage at the PCC. Combined effect of all users and of the network impedance
- Utility. If needed, changes the impedance characteristics to reduce voltage distortion
- Users limit their current emissions to reasonable values, defined equitably according to the share each one has in the supply system.
- The network owner or operator acts on voltage distortion, changing the impedance characteristics of the system when necessary.
- The user should not add equipment that worsens that impedance. So that the utility can control it, the user should not add equipment that changes its characteristic and increases distortion. The standard asks that these additions be controlled the way equipment that produces harmonic current is controlled.
The underlying reason is in the Introduction: users produce harmonic currents that flow through the utility’s network and create harmonic voltages in the voltage that other users receive. The amount of distortion reaching each user depends on the combined effect of everyone’s loads and on the impedance of the supply system.
A concrete case of the third rule: a user who installs a capacitor bank to improve the power factor changes the network impedance seen from the PCC. If that change creates a resonance with a harmonic of its loads, the distortion rises. The standard notes that power factor correction capacitors can produce resonant conditions when they coincide with a harmonic of the nonlinear loads (clause 1). See Capacitor Bank Resonance: Why Banks Fail.
How to read the requirements: shall, should, may, can
Clause 1.3 defines how requirements are worded, and it is worth keeping in mind when reading any clause:
| Word | Meaning in the standard |
|---|---|
| Shall | Mandatory requirement, no deviation permitted |
| Should | A recommended option among several, not necessarily mandatory |
| May | A permissible course of action within the limits of the standard |
| Can | Possibility or capability: material, physical or causal |
That difference matters. The clauses with current and voltage limits use shall, so the PCC limits are written as requirements (although clause 1.2 clarifies that they should not be considered binding in all cases). By contrast, the recommendation not to add equipment that worsens the impedance uses should, and the values in the informative annexes (interharmonics, TIF, notches) are guidance, not requirements.
What it means for your plant
- A piece of equipment does not “fail” IEEE 519. What is compared is the facility at the PCC.
- Measuring inside the plant is useful for diagnosis, not for declaring compliance. Internal values can be higher.
- A change in your facility can affect other users (new equipment, capacitors, filters).
- If the voltage at the PCC is distorted and your current complies, correction is up to the utility, according to clause 5.
For the details of the limits, see IEEE 519-2022 Voltage Harmonic Limits at the PCC and Harmonic Current Limits and TDD by Isc/IL. The point where they apply is defined in PCC in IEEE 519: Where Harmonic Limits Are Measured, and the case of a plant with generation in IEEE 519 with Inverters and Generation: When It Applies. The overview is in IEEE 519 Harmonic Limits: Key Concepts, PCC and TDD.
We help you place your responsibility
At Tiza Group we carry out power quality studies, in Colombia, or elsewhere on request: we assess how much of the distortion at the PCC comes from your facility, how much from the network, and which changes you must control before adding equipment. If you are going to expand your plant, the harmonic study is done before you buy.
Related guides
- PCC in IEEE 519: Where Harmonic Limits Are Measured
- IEEE 519-2022 Voltage Harmonic Limits at the PCC
- Harmonic Current Limits and TDD by Isc/IL
- IEEE 519 with Inverters and Generation: When It Applies
- IEEE 519 Harmonic Limits: Key Concepts, PCC and TDD
References
- IEEE Std 519-2022, IEEE Standard for Harmonic Control in Electric Power Systems: Introduction; clause 1 (harmonic sources); 1.1 (scope); 1.2 (purpose, shared responsibility); 1.3 (use of the words shall, should, may and can); clause 5 (limits at the PCC only).
Frequently asked questions
Does IEEE 519 apply to an individual variable frequency drive?
No. Clause 1.1 states that the limits are not intended to evaluate equipment, and clause 5 says they do not apply to individual pieces of equipment or to points inside the user's facility.
Who must correct the problem if the voltage at the PCC is distorted even though the user meets its current limit?
Clause 5 states that if limiting the currents is not enough to obtain acceptable voltages, the system owner or operator should modify the characteristics of the network to achieve it.
Does the standard cover transients or radio interference?
No. Clause 1.1 clarifies that it deals with steady-state conditions, that transients exceeding the limits may occur, and that it does not cover the effects of radio-frequency interference, although it gives guidance for wire-line telephone systems.