Power Quality - Analysis of Harmonics in Electrical System

Identify the main non-linear load sources that generate current harmonics in industrial and commercial electrical systems, including drives, UPS, rectifiers, lighting, and EV chargers, and their impact on harmonic pollution.

Explain how non-linear loads inject harmonic currents through cables, transformers, and grid impedances to distort low voltage and medium voltage voltages, using Fourier analysis and practical measurement tools.

Explains total harmonic distortion (THD) as the RMS ratio of harmonics to the fundamental, and total demand distortion (TDD) as harmonics to the maximum demand at the PCC.

Learn how rectifier type and choke placement affect total harmonic distortion in low-voltage ac drives, comparing six-pulse, 12/18/24-pulse, and active front end topologies and their dominant harmonics.

Explain why THD of drive input current rises at partial loads as fundamental current falls while harmonic currents stay relatively constant.

Analyze how DC drives generate harmonics and commutation notches through a six-thyristor bridge rectifier, with 12-pulse options reducing fifth and seventh harmonics, and how multiple drives may partially cancel distortions.

Nonlinear loads such as CFLs, LEDs, and office equipment with solid-state converters generate harmonics that affect harmonic distortion, with the third harmonic dominant and cumulative effects in large facilities.

Analyze how harmonic distortion raises current rms and THD, increasing copper and iron losses in cables, transformers, and motors through skin effect, hysteresis, and eddy currents.

Examine how harmonic distortion from the grid causes distorted current in directly connected motors, increasing winding heating and torque pulsations, and highlighting negative-sequence harmonics as most damaging.

Explore how harmonics, especially triple harmonics like the third, drive neutral conductor overloading in unbalanced three-phase systems, causing overheating and voltage drop, and learn neutral sizing guidelines.

Explore how harmonics raise peak current via crest factor and total harmonic distortion, with third and fifth harmonics, and the implications for thermal and magnetic protection.

Explore how inductive and capacitive devices create electrical resonance and how harmonics near the resonant frequency amplify current or distort voltage, risking equipment damage through series and parallel resonance.

Analyze resonance caused by harmonics in a transformer feeding capacitor bank and how detuned capacitor banks with reactors prevent parallel resonance by shifting resonance below the third or fifth harmonic.

Explore global standards and regulations governing harmonic limits, including IEC 61000 series and IEEE 519, and learn voltage distortion limits across low, medium, and high voltage networks.

Identify practical actions to reduce harmonics from non-linear loads by adjusting connections and impedance, using special transformer configurations, and applying passive or active harmonic filters.

Connect non-linear loads upstream to minimize the impedance to the transformer, thereby reducing voltage distortion and protecting other loads. Group non-linear loads on separate busbars and consider a separate transformer.

Discover how transformer connections shape harmonics: delta-star, star-delta, and delta zigzag configurations cancel fifth and seventh harmonics, route third harmonics in delta, and reduce transfers to primary for 12-pulse drives.

Learn how passive harmonic filters use LC circuits tuned to targeted harmonics to shunt them to ground. Compare single tuned and double tuned designs, noting cost, efficiency, and resonance risks.

Explore active harmonic filters that sense distorted current and inject opposite-phase harmonics to cancel non-linear load harmonics in real time. Highlight their dynamic performance and compact size versus passive filters.