Voltage
distortion is caused when harmonic currents flow through system impedance. Simply put,
when a piece of electronic equipment draws harmonic current, the harmonic currents flow though the power
source impedance (XL) and
voltage results at each harmonic frequency based on Ohm’s Law (amps times
ohms). The sources of harmonic voltage distortion are those electrical loads
the draw non-sinusoidal current.
On a 60 Hz
power system, 5th harmonic current is current flowing at 300 (5 x
60) Hz. Following ohms law, when
harmonic current flows though upstream impedance it will cause a voltage drop
at the same frequency. 5th
harmonic current will cause 5th harmonic voltage on the power system
that supplies this load. It is common to
all loads connected to the system.
Utilities
generate sinusoidal voltage, but power electronic loads in customer facilities
distort both current and voltage. To reduce power system harmonic voltage
distortion, one must typically identify the source of harmonic current and
minimize harmonic current distortion at this point.
