The effects of power quality on LED lighting performance generally receive little attention prior to installation for most commercial building applications. Power quality issues such as dips, harmonics, interruptions, transients and surges can result in expensive, early replacement of damaged or failed LED lighting equipment.
While facility managers involved with smaller commercial projects may be able to ignore power quality without much consequence, larger industrial LED lighting projects, such as the replacement of existing HID high bay fixtures with new or retrofit LED high bay fixtures in a 480V system, require analysis of the power quality prior to the installation. Failure to take this step may result in poor performing LED systems and high costs to remedy the problems.
According to a recent report from EC&M, "High bay LED luminaires installed in industrial plants failed at rates of about 1% to as much as 50% two months to two years after installation." Even if manufacturer warranties replaced the LED equipment, facilities had to pay electrical contractors to remove the failed fixtures and drivers and replace them with the new equipment - sometimes at a significant cost.
Many, if not most, of the causes for early failures of LED installations in industrial settings are traced to power quality issues. Poor power quality can not only damage the LED equipment it can also cause power failures and increased utility costs.
Power quality disruptions may originate at the electric utility, but more likely they are generated within the facility's electrical system where they can be corrected or mitigated.
With existing magnetic HID lighting equipment installed in a 480V system, virtually all power quality disturbances can be absorbed by the lighting equipment and keep on operating. Poor power quality leads to few consequences for the performance of HID lighting.
The benefits of switching from HID to LED are significant - lower power costs, reduced maintenance (longer life) and high quality illumination. However, LED lighting equipment will not tolerate poor power quality. The ROI for new LED lighting can quickly evaporate if the LED fixture/driver system underperforms or fails completely.
Facility managers take note: A necessary first step in transitioning to LED lighting, particularly in an industrial setting, should be a power quality analysis of the network to determine if mitigation is required and specifically what type of mitigation is needed.
What Power Quality Issues to Look For
The purpose of this post is not to dive into the details of power quality issues that may be present in a facility. However, here are three common culprits that may be revealed in an analysis.
When AC power is converted to DC power through a semi-conductor, high frequency current is generated. Elevated harmonic distortion will generate stress in the electrical system. The result may be increased maintenance and ultimately equipment failure.
Some LED lighting systems may cause power factor problems in the facilty electrical system leading to a host problems including possible penalty charges from the utility.
High inrush current may be generated when LED lighting with built-in power factor compensation in energized. The result may be equipment failure.
For readers who want an in depth look at these and other power quality issues related to LED lighting installations, download this white paper, Impacts of LED Lighting on Power Quality, published by Schneider Electric.
The Cost of Analysis is Small Compared to the Cost of Equipment Replacement
If the facility does not have staff versed in power quality or able to conduct an analysis, it will be well worth the cost to hire a power quality consultant to perform the test and recommend the mitigation if required.
The objective of the power quality analysis is to identify the extent of current power quality issues and specify mitigation solutions. Specifically, voltage fluctuations and harmonic distortions should be monitored and addressed.
The cost of doing this type of power quality analysis and mitigation during the design phase, before an LED installation, will be more than returned by avoiding the even higher labor cost of replacing equipment after early failure of the LED lighting system. In addition, you will likely reduce the likelihood of utility power factor penalties and other increased energy costs.
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