Harmonics

“Harmonics are not a problem unless they are a problem!”

Heating

• Cable insulation breakdown
• Random thermal breaker tripping
• Fuse blowing
• Transformer failure

Random logic faults

• CNC
• PLC
• Drives
• UPS
• Computers

Thyristor (SCR) converter shorting

• DC drives
• Battery chargers
• DC power supplies

Power factor capacitor incompatibility

• Harmonic heating effect
• Tripping on over-current
• Resonating power factor capacitors

AC motor winding and bearing destruction

• Path to ground for harmonics

Limits on generator & UPS capacity

• Harmonic heating effect

Generator faulting

• Not able to regulate to frequency

The power quality industry has developed certain index values that help us assess the quality of service as it relates to distortion caused by the presence of harmonics. These values, or harmonic indices, serve as a useful metric of system performance. The two most frequently used are Total Harmonic Distortion (THD) and Total Demand Distortion (TDD). They are measures of the effective value of a waveform and can be applied to both current and voltage. While K-factor shows how much more heat is produced from a non-linear load, it doesn’t portray anything about distortion of the sine wave.

 

 

See:

K-factor