Harmonics & power quality

Power quality issues can be costly

Problems such as voltage sags and surges, transients and harmonics are estimated to cost Canadian businesses about $1.2 billion annually in lost production, and about $140 million a year in B.C. according to studies by the Canadian Electrical Association.

The financial impact of these power disturbances varies by industry. For example, the U.S.-based Electric Power Research Institute found that a mere two seconds of power disruption in the paper industry results in production losses amounting to about $30,000 per event. Momentary power disturbances in the chemical industry can cost large companies up to $75 million annually.

Learn about the symptoms and causes of harmonics and what you can do to effectively eliminate harmonics in your facility's electrical system to keep your business running efficiently.

• What are harmonics
• Causes of harmonics
• Symptoms of harmonics
• Eliminating harmonics
• Working together to find solutions on harmonics

What are harmonics?

The term harmonics commonly refers to a distortion of the normally smooth utility power. Harmonics are actually higher frequency voltages and currents and when added to the utility power, produce a distortion of the normal voltage or current waveform. Usually, harmonic distortion must be present continuously to have an adverse effect on the power system.

Causes of harmonics

Harmonics are produced by "non-linear" loads in power systems. A non-linear load does not draw current in proportion with the applied 60 Hertz sinusoidal voltage waveform. In other words, this equipment "gulps" electric current from the supply rather than taking current in a smooth fashion.

Harmonic-producing non-linear loads comes from devices with power electronics such as:

• Computer equipment
• Adjustable speed motor drives (ASDs)
• Consumer electronics
• Electronic lighting ballasts
• Welders and battery charges

Symptoms of harmonics

In small quantities, harmonics are of little concern. However, too many non-linear loads in your facility can lead to significant power quality problems.

How do you know if you have harmonics in your facility's electrical system? Here are a few symptoms to be aware of:

• Over-loaded neutral conductors
• Over heated motors and transformers
• Blown fuses or breakers tripping repeatedly
• Failure of power factor correction capacitors
• Timing errors in sensitive electronic equipment

Eliminating harmonics

While there are several products available on the market designed to deal with harmonics, each requires careful analysis to ensure proper application. Both passive and active harmonic filters can be applied in specific situations.

Passive harmonic filters are the most common and are always custom-designed for the application or site. Active harmonic filters are a relatively new technology that will gain market share quickly as their initial cost becomes competitive with the passive variety.

Working together to find power quality solutions

If you're experiencing power quality problems in your facility, BC Hydro's power quality specialists can work with you to help you identify the source of your electrical disturbances and recommend the best solution for your facility.

Here are a few examples of companies from various industries that have encountered power quality problems in their facilities and the power quality solutions we offered to eliminate harmonics in their electrical system.

Telecommunications: A large telecommunications company had an ongoing problem with failing capacitors. We conducted a power quality study of the facility and determined that the installation of a fixed harmonic filter bank, which provides the necessary power factor correction while eliminating capacitor failures, was the most cost-effective solution.

Manufacturing: A manufacturer of plastics was experiencing difficulties correcting the facility's electrical power factor to greater than 90%. Having added more capacitors only served to accelerate their failure rate. In some cases, the capacitors lasted only a few months.

We surveyed the plant and recommended a fixed filter bank on each of the facility's two main electrical services. The fully engineered harmonic filter installation provided the company with the required power factor correction to eliminate surcharges, while absorbing a measured amount of harmonic current from the electrical system.

The filter configuration is immune to power quality disturbances ensuring a long life expectancy for the equipment.

Transportation: A company in the transportation industry experienced premature failure of capacitors in its existing harmonic filter bank. After conducting a power quality study of the facility we found that in its present configuration, the filter was actually amplifying harmonic distortion.

Using computer models of the electrical system, we identified acceptable operating modes and necessary upgrades for the filter bank to achieve reliable operation. The company received our power quality solutions report outlining the filter operating modes, which would produce excessive harmonic distortion in the electrical system, potentially causing violent failure of the filter bank and/or over-heating of motors and other electrical equipment.

We recommended the company operate the filter with a new optimal configuration and be refurbished with capacitors designed to withstand the stress of the harmonic filter application.

Like these companies, we can help you to maximize the performance of your electrical system.