“Harmonics are not a problem unless they are a problem!”
Negative side effects of harmonics
Harmonics create heat in units proportional to the square of the harmonic order
50Hz or 60 Hz = 1 heating unit (amp)
5th order = 25 heating units (amp)
Excessive heat in a distribution system can have many adverse effects
Cable insulation breakdown
Transformer failure
Limits on generator & UPS capacity
Common symptoms of harmonics
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.
Harmonics
