Power electronic equipment is susceptible to mis-operation if there are significant levels of harmonic distortion. Some of the control systems for power electronic devices use zero crossing detection to control switching.
Harmonic distortion can result in shifting of the voltage zero crossing points, and these changes can be critical for many types of electronic control circuits. Also, if incorrect switching occurs, more harmonics can be produced, compounding the problem.
Medical Instruments
Malfunctioning medical instruments present the most serious negative effect of harmonics to electronic devices. This is because it may place a person’s life in jeopardy. For this reason, many medical instruments are provided with line-conditioned power and protected by proper power quality devices.
In addition, less dramatic interference effects of harmonics can sometimes be observed in radio and television equipment, as well as in video recorders and audio reproduction systems.
Computers and Other Electronic Devices
Computers and allied equipment like programmable controllers typically require AC sources that have no more than a 5% harmonic voltage distortion factor, with the largest single harmonic being no more than 3% of the fundamental voltage.
Harmonic distortion levels that exceed standard limits may result to malfunctioning equipment, which in some cases, have serious consequences. It must be noted that electronic devices can be disturbed by the transmission of AC supply harmonics via the equipment power supply or through magnetic coupling of harmonics into equipment components.
Moreover, other electronic instruments can be affected by harmonics by giving incorrect data or unpredictable performance (i.e. digital energy meters).
Voltage Notching
Most electronic devices are installed at the low voltage level of its associated power distribution system. As a result, they also become exposed to the effects of voltage notching. Voltage notches often introduce frequencies, both harmonic and non-harmonic, which are much higher than those exhibited in 5 kV and higher voltage distribution systems.
Subsequently, these frequencies are in the radio frequency (RF) range, which can lead into detrimental effects associated with spurious RF, such as signal interference introduced into communication or logic circuits. Sometimes, the voltage notching effect is of adequate power to overload electromagnetic interference (EMI) filters and similar high-frequency sensitive capacitive circuits.
Source:
IEEE 519-1992 Recommendation & Practice
