IEEE 519-2014

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The uses of nonlinear loads connected to electric power systems include static power converters, arcdischarge devices, saturated magnetic devices, and, to a lesser degree, rotating machines. Static powerconverters of electric power are the largest nonlinear loads and are used in industry for a variety ofpurposes, such as electrochemical power supplies, adjustable speed drives, and uninterruptible powersupplies. These devices are useful because they can convert ac to dc, dc to dc, dc to ac, and ac to ac.Nonlinear loads change the sinusoidal nature of the ac power current (and consequently the ac voltagedrop), thereby resulting in the flow of harmonic currents in the ac power system that can cause interferencewith communication circuits and other types of equipment. These harmonic currents also lead to increasedlosses and heating in numerous electromagnetic devices (motors, transformers, etc.). When reactive powercompensation, in the form of power factor improvement capacitors, is used, resonant conditions can occurthat may result in high levels of harmonic voltage and current distortion when the resonant condition occursat a harmonic associated with nonlinear loads.Common sources of harmonic currents in power systems include power electronic converters, arc furnaces,static VAR systems, inverters for distributed generation, ac phase controllers, cycloconverters, and ac-dcconverters (rectifiers) commonly used in switched mode power supplies and pulse width modulated (PWM)motor drives. Each of these harmonic-producing devices can have fairly consistent harmonic currentemission characteristics over time or each may present a widely-varying characteristic depending on thecontrol of the device, the characteristics of the system, and other variables. This recommended practice is tobe used for guidance in the design of power systems with nonlinear loads. The limits set are for steady-stateoperation and are recommended for “worst case” conditions. Transient conditions exceeding these limitsmay be encountered. In any case, the limit values given in this document are recommendations and shouldnot be considered binding in all cases. Because of the nature of the recommendations, some conservatism ispresent that may not be necessary in all cases.This recommended practice should be applied at interface points between system owners or operators andusers in the power system. The limits in this recommended practice are intended for application at a pointof common coupling (PCC) between the system owner or operator and a user, where the PCC is usuallytaken as the point in the power system closest to the user where the system owner or operator could offerservice to another user. Frequently for service to industrial users (i.e., manufacturing plants) via a dedicatedservice transformer, the PCC is at the HV side of the transformer. For commercial users (office parks,shopping malls, etc.) supplied through a common service transformer, the PCC is commonly at the LV sideof the service transformer.The limits in this recommended practice represent a shared responsibility for harmonic control betweensystem owners or operators and users. Users produce harmonic currents that flow through the systemowner’s or operator’s system, which lead to voltage harmonics in the voltages supplied to other users. Theamount of harmonic voltage distortion supplied to other users is a function of the aggregate effects of theharmonic current producing loads of all users and the impedance characteristics of the supply system.Harmonic voltage distortion limits are provided to reduce the potential negative effects on user and systemequipment. Maintaining harmonic voltages below these levels necessitates that⎯ All users limit their harmonic current emissions to reasonable values determined in an equitablemanner based on the inherent ownership stake each user has in the supply system and⎯ Each system owner or operator takes action to decrease voltage distortion levels by modifying thesupply system impedance characteristics as necessary.