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Introduction to Power Quality

Electric Power Quality: A Rising Concern

Electric power quality has emerged as a significant area within electric power engineering, driven primarily by the increasing sensitivity of end-use equipment. This chapter addresses various aspects of power quality as it affects utility companies and their customers, covering grounding, voltage sags, harmonics, voltage flicker, and long-term monitoring. These topics provide a broad overview that enhances the understanding of power quality issues.

Grounding: Ensuring Safety and Performance

Proper grounding is crucial for the safe and efficient operation of sensitive electronic equipment. Historically, there was a belief that grounding practices as specified by the National Electric Code (NEC) conflicted with those required for power quality. However, extensive evidence now supports that NEC-compliant grounding is essential for proper equipment operation and personnel safety.

Voltage Sags: A Pervasive Issue

Voltage sags, primarily caused by system faults, are among the most significant power quality problems. These sags can occur far from the fault point, affecting numerous utility customers. Given the inevitability of power system faults, end-use equipment must be designed to withstand brief periods of reduced voltage.

Voltage Flicker: Human Perception Matters

Voltage flicker, unlike voltage sags, is related to human perception of light variation caused by periodic voltage fluctuations. These fluctuations, typically under 30-35 Hz, can cause annoyance rather than equipment malfunction.

Harmonics: Distorted Waveforms

Harmonics involve periodic waveform variations where non-fundamental frequency currents create voltages at those same frequencies in the power delivery system, leading to potential equipment malfunctions. Effective power quality management requires substantial measurement and analysis of these distortions.
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