Electrical Power Quality Analysis: Measuring Harmonics, Disturbances and Efficiency
Poor power quality generates motor overheating, malfunction of variable frequency drives (VFD), protection trips, damage to sensitive electronic equipment and energy supplier penalties. Identifying the cause requires a measurement with an analyzer at the low voltage or distribution point.
1. Main parameters to measure
- Harmonics: Distortion of the waveform, typically from nonlinear loads such as drives, rectifiers and computing equipment. THD (total harmonic distortion) of voltage and current and individual harmonics (5th, 7th, 11th, etc.) are evaluated.
- Voltage sags and swells: Momentary reductions or increases of voltage that can reset equipment or damage components.
- Phase unbalance: Difference in magnitude or angle between phases, which overheats three-phase motors.
- Flicker: Rapid voltage variations that produce lighting flicker and affect sensitive equipment.
- Frequency and transients: Frequency deviations and short-duration transient spikes.
- Power factor and demand: For efficiency and penalty control.
2. Types of analyzers
- Portable power quality analyzer: Records over time, with transient and waveform capture. Ideal for diagnostics, quality studies and troubleshooting. Allows correlating events (e.g., equipment failures) with grid disturbances.
- Energy meter with integrated power quality: Fixed installed for continuous monitoring and billing, with basic harmonic analysis.
- Event logger: Focused on capturing sags, swells and transients with timestamp.
MARPATECH represents the Dranetz power quality analyzers, world references for power quality diagnostics, with multi-channel logging, analysis software and reports.
3. Measurement procedure
- Connection: Connect the voltage and current clamps at the point to evaluate (main panel, supply of a drive or critical equipment), respecting the manufacturer diagrams.
- Define the standards: Configure thresholds according to standards such as IEC 61000, IEEE 519 (harmonics) or local supply regulation.
- Record for a representative period: Generally 7 days or a full production cycle, to capture load variability.
- Analyze the results: Review harmonic profiles, count and duration of sags/swells, unbalance and power factor. Correlate events with reported failures.
- Report: Generate a report with recommendations (harmonic mitigation, phase balancing, power factor correction, load relocation).
4. Interpretation and mitigation
If the voltage THD exceeds the recommendation, passive or active harmonic filters can be installed. High unbalance is corrected by balancing single-phase loads between phases or installing compensation. Low power factor is improved with capacitor banks, but the presence of harmonics requires a design that avoids resonances. Recurrent sags usually need supply correction or voltage support equipment.
Conclusion
Measuring power quality is the first step to protect equipment, reduce downtime and optimize costs. A suitable portable analyzer and a recording procedure of at least one week allow diagnosing and correcting problems in a grounded way.
MARPATECH SAC represents in Peru, Argentina and Colombia the Dranetz power quality analyzers and provides technical advisory for power quality studies, installation and result analysis in industrial and generation applications, including photovoltaic systems.
Frequently asked questions
The recommendation is at least 7 days or a full production cycle, to capture load variability and correlate events. For intermittent problems a longer period may be required.
Nonlinear loads, mainly variable frequency drives, rectifiers, switched-mode supplies and electronic equipment. They distort current and, circulating through grid impedances, also distort voltage.
A small unbalance (for example 2-3%) can significantly increase winding temperature and reduce motor life expectancy. Therefore it is recommended to keep unbalance as low as possible and correct it by balancing loads.