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Harmonics is __________________ type of PQ problem.
transients
wavefrom distortions
voltage flicker
frequency variations
wavefrom distortions
Harmonics are defined as sinusoidal components of a periodic wave having frequencies that are integer multiples of the fundamental frequency (50/60 Hz). They are classified as waveform distortions because they deviate the ideal sinusoidal supply voltage or current into a non-sinusoidal periodic shape.
Harmonics are defined as sinusoidal components of a periodic wave having frequencies that are integer multiples of the fundamental frequency (50/60 Hz). They are classified as waveform distortions because they deviate the ideal sinusoidal supply voltage or current into a non-sinusoidal periodic shape.
fnтАЛ=n├Чf1тАЛ тАФ Definition of nth harmonic frequency
THD=X1тАЛтИСn=2тИЮтАЛXn2тАЛтАЛтАЛ тАФ Total Harmonic Distortion calculation
Harmonics are generated primarily by non-linear loads such as power electronic converters (rectifiers, inverters), variable frequency drives (VFDs), and saturated magnetic cores (transformers). These devices draw current in pulses rather than a smooth wave, causing the resultant voltage drop across the system impedance to be distorted, which propagates through the network.
The fundamental frequency in India is 50 Hz.
Harmonics increase I2R losses and heating in transformers and motors.
Non-linear loads are the primary source of harmonic current injections.
Passive filters (LC circuits) or Active Power Filters (APFs) are used to mitigate harmonics.
Identification of harmonics allows for targeted use of detuned filters.
Active filtering can mitigate multiple harmonic orders simultaneously.
High harmonic content leads to premature aging of insulation due to overheating.
Interference with sensitive communication and control circuits (EMI).
Variable Frequency Drives (VFDs) in industrial motors.
HVDC converter stations for power transmission.
Grid-connected solar photovoltaic inverters.
IEEE 519 is the standard that limits harmonic levels in power systems.
Option A (Transients) are short-duration impulsive or oscillatory surges.
Option C (Voltage flicker) is caused by rapidly varying loads like arc furnaces.
Option D (Frequency variations) relates to the balance between generation and demand.
B is correct тАФ Harmonics cause the periodic waveform to deviate from its pure sinusoidal shape, thus classifying them as waveform distortions.
In exams, always distinguish between 'steady-state' distortions (Harmonics) and 'event-based' phenomena (Transients/Sags/Swells).