Power System Harmonics Power systems are designed to

Power System Harmonics Power systems are designed to operate at frequencies of 50 or 60 Hz. Pure Sine Wave However, certain types of loads produce currents and voltages with frequencies that are integer multiples of the 50 or 60 Hz fundamental frequency.

These higher frequencies are a form of electrical pollution known as power system harmonics. Harmonic Sources Systems HVDC SVC Transformer etc. Loads Nonlinear Loads

Examples • Adjustable speed drives • TVs • Computers • Gas discharge lamps • Switching mode power supplies (SMPS) • Arc furnaces • etc.

Three Phase 3 rd harmonic the 3 rd harmonic and its multiples have their own special name: triplen harmonics

Y-Y 4 wires system Harmonic currents add in neutral conductor

Y-Y 3 wires system

Delta-Y system

Delta-Delta system

Harmonic phase sequence

THD = 30%

Single Phase

Typical waveforms voltage current

Transformer magnetizing current THD = 76%

Refrigerator current THD = 6%

Air conditioner current THD = 10%

Fluorescent lamp current THD = 18%

Light Dimmer Circuit 220

Nonlinear components are those that draw a nonsinusoidal current waveform when energized by a sinusoidal voltage. Since any distortion of an originally pure sine-wave constitutes harmonic frequencies, we can say that nonlinear components generate harmonic currents.

Fourier series Periodic functions and signals may be expanded into a series of sine and cosine functions • Analysis • Synthesis