EFFECTS OF HARMONICS TO ELECTRONIC EQUIPMENT

Saturday, December 31, 2011

The Effects of Harmonics to Electronic Equipment are experienced in various ways depending on the type of device - from slight to serious consequences. Ironically, it is a known fact that most electronic equipment is prone to misoperation due to harmonic distortion, even though it is a harmonic generator itself. In this post, these common effects will be briefly discussed.

Power Electronic Equipment

This equipment is reliant upon accurate determination of voltage zero crossings or other facets of the voltage wave shape. Unfortunately, harmonics can shift the voltage zero crossing, or the point at which one phase-to-phase voltage becomes greater than another phase-to-phase voltage. These are both significant points for many types of electronic circuit controls, and the unwanted shifts can lead to equipment misoperation.
Voltage Zero Crossing
Voltage Zero Crossing Point
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.

Reference:
IEEE 519-1992. Recommended Practice and Requirements for Harmonic Control in Electrical Power Systems

2 comments:

Stanly said...

very great insights on harmonics to equipment. keep it up.
transmission lines

Electrician Perth said...

Once you've recognized that harmonics are in a circuit or in an electrical system, the next step is to carry out tests to determine the magnitude and type of harmonics.

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I am an Electrical Engineer with a Masters Degree in Business Administration. My interest is in Power Quality, Diagnostic Testing and Protective Relaying. I have been working in an electric distribution utility for more than a decade. I handle PQ studies, power system analysis, diagnostic testing, protective relaying and capital budgeting for company projects.