What is Harmonic Distortion?

For most people electricity is a pretty abstract concept. You walk in a room…hit the switch and the light comes on. What else is there to know…right? Well we can all agree that in today’s world, we would be lost without it.

Electricity is a lot like the wind. We can’t see it, but we know it’s there. We can feel the wind and when there is smoke in the air, we can see the wind’s effect on the smoke. With electricity we can actually see it in its waveform when we use an oscilloscope. That’s a meter that measures the wave shape of an electrical signal.

Here is a picture of one cycle of the voltage waveform. In North America our electricity is delivered at 60 hertz. That means the electricity is pulsing in your electrical system at 60 times per second. This picture below is a snapshot of the waveform that lasts for 1/60th of a second.

The History of Harmonic Distortion

For most of the twentieth century, the predominant use of electricity for business and industry was to power motors, lights and heating devices. These uses have little effect on the electricity delivered to them from their utility. This means that using electricity to power these types of devices does not disturb or distort the electric supply waveform. They are called linear loads.

A few industries like steel mills and aluminum smelters used electricity to power arc furnaces, which distorted the waveform, because the current flow was not directly proportional to the voltage. These loads are called non-linear loads. Non-linear loads distort the waveform at the load and from the supply.

The picture to the right shows the waveform with relatively high levels of harmonic distortion. Harmonics can cause critical problems throughout the electrical system as well as create an environment where energy is not being used effectively and efficiently. These created problems can cause waste, downtime, equipment failure and loss of revenue.

In the last 20 years, there has been an explosion of microprocessor based equipment which are also non-linear loads. Examples include computer systems, variable frequency drives, adjustable speed drives, AC/DC converters, electronic lighting ballasts, X-ray machines, MRI equipment, uninterruptible power supplies and the list could go on and on. What was once a problem for a very limited number of heavy industries, is now a concern for almost everyone.

All business types, commercial, industrial, government and energy/utility have a concern with power quality. The reliable and continuous delivery of “expected quality” electricity is critical for proper daily operations. From a manufacturing facility to a brokerage firm, the need for utility grade or better power exists. Further, with more digital technologies installed on the load, it is even more important to have power quality maintained at the highest levels. Environments rich in harmonic content can place serious burdens on power distribution systems and the equipment that is connected to it.

What Are the Problems Associated With Harmonics

Harmonic Distortion may cause interference and inefficiencies in power systems and equipment. Some of the potential problems include:

• Malfunctioning of microprocessor-based equipment.

• Overheating in neutral conductors, transformers, or induction motors.

• Deterioration or failure of power factor correction capacitors.

• Erratic operation of breakers and relays.

• Pronounced magnetic fields near transformers and switchgear.

To make matters worse, harmonics can sometimes be transmitted from one facility back through the utility's equipment to neighboring businesses, especially if they share a common transformer. This means harmonics generated in your facility can stress utility equipment or cause problems in your neighbor's facility and vice versa. Electric utilities have recognized this problem and are adopting standards. The Institute of Electrical and Electronics Engineers have adopted (IEEE) Standard 519 which defines allowable harmonic distortion at customer service entrances. This standard is designed to protect both businesses and utilities.

The IEEE Standard 519 states that all general loads should
produce harmonic distortions in the range of 5% or less.

Global Energy Solutions Can Help

Harmonics are not a problem for everyone. Most facilities probably have some level of harmonic distortion, so the mere presence of harmonics does not warrant concern. However, you should be concerned when you see the problems described above. Another time to give harmonics some thought is when purchasing new equipment that is known to produce harmonics. Global Energy Solutions has answers on harmonics problems and solutions. We can help you diagnose harmonics problems using our array of metering devices and troubleshooting skills.

Contact Us today to discuss your needs.