IEEE 519-2022 limits voltage distortion at the PCC according to voltage level: from 5.0 % per harmonic and 8.0 % THD at low voltage down to 1.0 % and 1.5 % above 161 kV. The utility must meet it with two statistical criteria: the daily 99th percentile of 3 s values and the weekly 95th percentile of 10 min values.
Short answer
IEEE 519-2022 sets in its Table 1 the voltage distortion limits at the point of common coupling (PCC): a maximum value for each individual harmonic and another for THD, depending on the voltage level of the PCC. They are evaluated with two criteria: the daily 99th percentile of the 3-second values must be less than 1.5 times the table, and the weekly 95th percentile of the 10-minute values must be less than the table. The utility must meet them.
Table 1
The limits are expressed as a percentage of the nominal fundamental frequency voltage at the PCC, for integer harmonics up to order 50 (clause 5.1):
| Voltage at the PCC | Individual harmonic (h ≤ 50) | THD |
|---|---|---|
| Up to 1.0 kV | 5.0 % | 8.0 % |
| Above 1 kV up to 69 kV | 3.0 % | 5.0 % |
| Above 69 kV up to 161 kV | 1.5 % | 2.5 % |
| Above 161 kV | 1.0 % | 1.5 % |
Table 1 has a note: high-voltage systems can have up to 2.0 % THD when the cause is a high-voltage direct-current (HVDC) terminal whose effects are attenuated at the points of the network where future users would be connected. That exception only covers the row above 161 kV.
Three clarifications for reading it correctly:
- Reference. The percentages are of the nominal fundamental frequency voltage at the PCC, not of the voltage measured at each instant.
- Line-to-neutral. The standard refers to line-to-neutral voltage harmonics.
- Maximum order. The table applies to harmonics whose frequencies are integer multiples of the fundamental frequency, up to and including the 50th. Components between harmonics (interharmonics) are treated separately, as explained in Interharmonics in IEEE 519-2022: Annex A Explained.
How they are evaluated: the two statistical criteria
Clause 5.1 establishes, at the PCC:
| Measured value | Period | Compared with |
|---|---|---|
| 99th percentile of 3 s values (very short time) | Each day | Less than 1.5 times the Table 1 value |
| 95th percentile of 10 min values (short time) | Each week | Less than the Table 1 value |
There is a difference with harmonic current: for voltage the standard does not use the weekly 99th percentile of 10-minute values. Clause 4.4 says so expressly: that value is not recommended for voltage harmonics.
With a numerical example, for a PCC at 13.2 kV (between 1 kV and 69 kV) and the 5th harmonic, the table value is 3.0 %. Then the weekly 95th percentile of 10 min must be less than 3.0 % and the daily 99th percentile of 3 s must be less than 4.5 % (1.5 × 3.0 %). For THD, 5.0 % and 7.5 %. The values are table arithmetic; they are not measurement results.
What those percentiles are and how they are built is explained in Measuring Harmonics for IEEE 519: the 12-Cycle Window and in 95th and 99th Percentiles in IEEE 519: How It Is Evaluated. Here it is enough to know that the criterion is not “no reading may exceed the limit”: the highest 1 % of the 3 s values in a day may exceed 1.5 times the table, and the highest 5 % of the 10 min values in a week may exceed the table, without any non-compliance.
Who must meet them
Unlike current, the voltage limit falls on the system owner or operator: clause 5.1 says that system owners or operators will limit voltage harmonics at the PCC. The Introduction and clause 5 explain the logic of shared responsibility:
- Users limit the harmonic currents they inject, to reasonable values distributed equitably.
- If limiting current is not enough to keep voltage at acceptable levels, the utility should act on the characteristics of the network, for example by modifying its impedance.
- The user should not add equipment that changes that impedance in a way that worsens distortion. The standard asks that such equipment be controlled as if it were a harmonic source.
In practice this means a user can meet its current limit and still see high voltage distortion: the voltage level depends on the set of users and on the system impedance. The guide Capacitor Bank Resonance shows a typical case in which equipment added by the user changes that impedance.
What the voltage limits are for
The voltage limits are given, according to the Introduction and clause 1.2, to reduce adverse effects on the equipment of the user and of the system. Clause 1 lists those effects: interference in communication circuits and other equipment, higher losses and heating in motors and transformers, and resonances with power factor correction capacitors that can raise voltage and current distortion.
That is why voltage is the indicator that all users of the same PCC “see”, and current is the cause that each user controls. For THD itself (definition, formula and the difference between THDv, THDi and TDD) see THD: What It Is, How It Is Calculated and IEEE 519 Limits.
The point where these limits apply is defined in PCC in IEEE 519: Where Harmonic Limits Apply. The current limits the user must meet are in Harmonic Current Limits and TDD by Isc/IL, and the split of responsibilities between user and utility in Scope of IEEE 519: Who Is Responsible for Harmonics. To compare a spot spectrum with Table 1 you can use our free harmonic distortion THD and TDD tool.
What to do if the PCC exceeds the limits
The standard does not detail specific measures, but the usual path is to identify whether the cause is in the current the users inject or in the network impedance. Mitigation measures are covered in Active vs Passive Harmonic Filters and in Harmonic Filters IEEE 1531. A study with the network model is the way to check any measure before installing it.
We help with the evaluation
At Tiza Group we carry out power quality studies and harmonic studies, in Colombia, or elsewhere on request: we evaluate your PCC against Table 1, identify the origin of the distortion and define the measures if correction is needed.
Related guides
- THD: What It Is, How It Is Calculated and IEEE 519 Limits
- Harmonic Current Limits and TDD by Isc/IL
- Measuring Harmonics for IEEE 519: the 12-Cycle Window
- 95th and 99th Percentiles in IEEE 519: How It Is Evaluated
- PCC in IEEE 519: Where Harmonic Limits Apply
References
- IEEE Std 519-2022, IEEE Standard for Harmonic Control in Electric Power Systems: clause 5 (introduction); clause 5.1 and Table 1 (voltage limits and statistical criterion); clause 4.4 (statistical evaluation; the weekly 99th percentile is not recommended for voltage); clause 1 and clause 1.2 and Introduction (effects, purpose and shared responsibility).
Frequently asked questions
Who is responsible for voltage harmonic limits, the user or the utility?
Clause 5.1 says that system owners or operators must limit line-to-neutral voltage harmonics at the PCC. The user is responsible for the current it injects; the resulting voltage also depends on the network impedance and on the other users.
Are the Table 1 limits compared with line-to-line or phase voltage?
With line-to-neutral voltage, as a percentage of the nominal fundamental frequency voltage at the PCC. They apply to integer harmonics up to and including order 50.
Why can some high-voltage networks have up to 2.0 % THD?
The Table 1 note allows up to 2.0 % THD on systems above 161 kV when the cause is an HVDC terminal whose effects are attenuated at the points of the network where future users would be connected. It is a specific exception, not the general limit.