Power quality, as a crucial indicator for measuring the operational status of a power system, has seen its connotation continuously enriched with the evolution of power grid configurations and application scenarios. Scientific classification helps in accurately identifying problem characteristics, formulating targeted governance strategies, and providing a basis for standard setting and technology selection. Currently, the industry generally classifies power quality problems based on dimensions such as disturbance nature, spectral characteristics, duration, and affected objects.
Based on the nature of the disturbance, power quality problems can be divided into two main categories: steady-state deviations and transient disturbances. Steady-state deviations refer to phenomena where voltage or frequency deviates from its rated value over a relatively long period, including voltage deviation, frequency deviation, three-phase imbalance, and harmonic distortion, often stemming from load characteristics or system structure asymmetry and nonlinearity. Transient disturbances manifest as abnormal states with short duration and high rate of change, such as voltage dips, swells, short-term interruptions, and pulse transients, often caused by short-circuit faults, large equipment start-up/shutdown, or lightning strikes, posing a significant threat to sensitive loads.
Based on spectral characteristics, power quality problems can be categorized into fundamental component anomalies and harmonic problems. Abnormalities in the fundamental frequency component mainly refer to voltage or frequency amplitudes deviating from the rated value at the power frequency, affecting the rated operating state of equipment. Harmonic problems consist of distorted components with frequencies that are integer or fractional multiples of the fundamental frequency, originating from nonlinear loads such as power electronic equipment and arc devices, and can lead to additional losses, resonance, and protection malfunctions.
Based on duration, disturbances can be categorized into four types: instantaneous (milliseconds to tens of milliseconds), short-lived (hundreds of milliseconds to several seconds), temporary (several seconds to one minute), and persistent (more than one minute). Instantaneous and short-lived disturbances have a significant impact on fields with high continuity requirements, such as precision manufacturing and information technology; persistent deviations involve more adjustments at the system planning and economic operation levels.
Based on the affected object, problems can be categorized into voltage quality problems, current quality problems, and comprehensive quality problems. Voltage quality problems focus on the stability of waveforms and amplitudes at the power supply end; current quality problems emphasize the feedback effect of nonlinearity and impulse characteristics on the load side; comprehensive quality problems emphasize the bidirectional coupling effect caused by source-load interaction, which is particularly significant in scenarios with a high proportion of distributed power sources.
With the development of new power systems, the power quality classification system is trending towards multi-dimensional integration, retaining traditional technical attribute classifications while incorporating scenario adaptability and impact assessments, providing a clear framework for differentiated governance and cross-domain collaboration, and helping to improve grid resilience and energy quality.
