Reducing harmonics with IEEE 519 practices, procedures
Technology Update: Industrial facilities should include a system evaluation, including a harmonic distortion analysis, while planning facility construction or expansion. Vendors of nonlinear loads, such as variable frequency drives, can provide services and recommend equipment that will reduce harmonics to comply with IEEE 519.
With increased use of nonlinear loads, power supply harmonics are more noticeable than ever. Controlling and monitoring industrial system designs and their effects on utility distribution systems are potential problems for the industrial consumer, who is responsible for complying with the IEEE 519 recommended practices and procedures. Industrial facilities should include a system evaluation, including a harmonic distortion analysis, while planning facility construction or expansion. Vendors of nonlinear loads, such as variable frequency drives, can provide services and recommend equipment that will reduce harmonics to comply with IEEE 519 guidelines.
Generally, at any point of common coupling (PCC), the measured value of total harmonic voltage distortion should not exceed 5% and that of any individual harmonic voltage distortion should not exceed 3% of the fundamental value of the line voltage. Normally, in typical applications, the harmonics are measured up to 25th order, but in critical applications, those are measured up to 50th or 100th order.
There are many harmonic mitigation methods available for individual applications (for example, per drive) and for "global mitigation" (such as a common harmonic mitigation solution for a group of nonlinear equipment). A particular type of harmonic mitigation solution can be used depending upon the application and desired level of attenuation to meet the limits given in IEEE 519.
Control of harmonics, IEEE 519-1992 Guidelines
IEEE 519 was initially introduced in 1981 as an "IEEE Guide for Harmonic Control and Reactive Compensation of Static Power Converters." It originally established levels of voltage distortion acceptable to the distribution system for individual nonlinear loads. With the rising usage of industrial nonlinear loads, such as variable frequency drives, it became necessary to revise the standard.
The IEEE working groups of the Power Engineering Society and the Industrial Applications Society prepared recommended guidelines for power quality that the utility must supply and the industrial user can inject back onto the power distribution system. The revised standard was issued on April 12, 1993, updating the 1992 version of IEEE 519 that established recommended guidelines for harmonic voltages on the utility distribution system as well as harmonic currents within the industrial distribution system. According to the standard, the industrial system is responsible for controlling the harmonic currents created in the industrial workplace. Since harmonic currents reflected through distribution system impedances generate harmonic voltages on the utility distribution systems, the standard proposes guidelines based on industrial distribution system design.
In 2004, an IEEE working group named "519 Revision Task Force (PES/T&D Harmonics WG)" was created to revise the 1992 version of IEEE 519 (Recommended Practices and Requirements for Harmonic Control in Electric Power Systems) and develop an application guide IEEE 519.1 (Guide for Applying Harmonic Limits on Power Systems). A revision to IEEE 519 includes the changes based on the significant experience gained in the last 20 years with regard to power system harmonics, their effects on power equipment, and how they should be limited. In addition, this document contains certain material dedicated to the harmonization of IEEE and other international standards where possible.
The application guide IEEE 519.1 contains significant rationale for and numerous example scenarios of the limits recommended in IEEE 519 and provides procedures for controlling harmonics on the power system along with recommended limits for customer harmonic injection and overall power system harmonic levels.
Both documents, revised IEEE 519 and the application guide IEEE 519.1, are considered complementary.
Evaluation of system harmonics
To prevent or correct harmonic problems that could occur within an industrial facility, an evaluation of system harmonics should be performed if:
- A plant is expanded and significant nonlinear loads are added
- Power factor correction capacitor banks or line harmonic filters are added at the service entrance or in the vicinity
- A generator is added in the plant as an alternate stand-by power source
- The utility company imposes more restrictive harmonic injection limits to the plant.
Often, the vendor or supplier of nonlinear load equipment, such as variable frequency drives, evaluates the effects that the equipment may have on the distribution system. This usually involves details related to the distribution system design and impedances, similar to performing a short circuit study evaluation.
[This article online, below, explains various harmonic mitigation methods and provides 7 more online figures for connections of passive harmonic filter, 12 pulse converter front end, 18 pulse converter front end, active filter, and active front end, along with a values table of harmonics corrections for different types of front ends.]