Using HarmonicGuard® Passive Filters
Written By: John F. Hibbard Michael Z. Lowenstein
loads, it became apparent that a rewrite of IEEE 519, treating the relationship of harmonic voltages to the harmonic currents flowing within industrial plants, was necessary to support control of harmonic voltages. The new IEEE 519, published in 1992, sets forth limitsfor both harmonic voltages on the utility transmission and distribution system and harmonic currents within the industrial distribution systems. Since harmonic voltages are generated by the passage of harmonic currents through distribution system impedances, by controlling the currents or system impedances within the industrial facility, one can control harmonic voltages on the utilitydistribution. Unfortunately, there is some user confusion regarding the application and intent of the information included in IEEE 519, 1992. Section 10, “Recommended Practices for Individual Consumers” describes the current distortion limits that apply within the industrial plant. Consulting engineers and applications engineers may not be clear as to the proper use of Table 10.3, which outlines the limitsof harmonic distortion as a function of the nature of the electrical distribution system. This paper will explain, with examples, the proper use and interpretation of this table. Using a computer model, we have outlined the level of distortion one might expect to encounter for various types of loads and distribution systems and the level of correction obtainable through the use of line reactors andpassive harmonic trap filters has been detailed. It is hoped that the readers of this paper will come away with a better understanding of the meaning and application of IEEE 519, 1992.
With the advent of IEEE 519-92, the increasing demand by utilities for power factor improvement, and the proliferation of non-linear loads in industrial power distribution systems, specification ofharmonic mitigation has become common. Questions arise regarding the performance of passive harmonic trap filters in removing harmonic distortion. Data from a number of TCI HarmonicGuard trap filter installations have been collected which illustrate how closely IEEE 519-92 limits can be met. ® HarmonicGuard filters have been installed, both for power factor improvement and to meet harmonic distortionlimits based on IEEE 519-92. A computer model has been developed to help predict the harmonic reduction that can be expected for specific load-filter combinations and the model has been verified with field data. This paper outlines and explains the computer model and details the application of harmonic trap filters. Computergenerated design curves are provided which can be used by a systemdesigner to predict success in meeting harmonic specifications using ® HarmonicGuard trap filters.
IEEE 519, 1981
IEEE 519, “Recommended Practices and Requirements for Harmonic Control in Electric Power Systems,” was published in 1981. The document established levels of voltage distortion acceptable to the distribution system. This document has been widely applied in establishing needed harmoniccorrection throughout the electrical power industry. However with the increase in industrial usage of adjustable speed drives, rectifiers, and other non-linear
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Generation of Harmonic Currents
Power electronic equipment iscalled non-linear because it draws non-sinusoidal current. Fig. 1a shows the linear relationship between voltage and current for one phase of a 3-phase induction motor connected to the line, while Fig. 1b shows the nonlinear current drawn by the same motor powered by an adjustable drive. IEEE 519, 1992 defines a harmonic as, “A sinusoidal component of a periodic wave or quantity having a frequency...