The Table outlines the information you should document about the loads on all 480V buses in the plant.
Conduct power quality monitoring on your 480V buses and panels currently powering HID lighting. Knowing what types of disturbances are occurring on each 480V bus and lighting panel which will power LED lighting is a critical part of managing the power quality for your high-bay electronic LED lighting system. There is likely more than one 480V bus in your industrial plant powering lighting. These buses may be fed by different sections of switchgear on different electric utility feeds. Each bus likely supports different types of high-power non-linear with different degrees switching of these loads. Errors in the phase and neutral wiring will also cause disturbances generated by load operation to be worse when they reach the industrial LED lighting. You must also have a well-designed grounding system. Grounding must be of low impedance and able to support high-frequency disturbance currents. In older plants, these buses may be made from duct work or may use locking male-to-female connectors. There may be loose connections or worn terminals on connectors where fixture drop cords plug into bus networks. This will add to the voltage-related power quality problems that are already present.
Use portable advanced power quality monitoring instruments capable of measuring high-frequency transient voltages. Monitors that have Ethernet communication ports capable of being used with remote power quality monitoring systems will best serve these monitoring needs and eliminate plant personnel from having to manually retrieve data. All phases (including neutral and ground) should be measured during monitoring. Keep in mind that monitoring on 480V buses should be carried out long enough to capture disturbances characteristic of plant operating schedules and cycles as not all plant shifts use the same equipment. This should be done at least across two season changes — winter to spring and spring to summer are the two best seasons when thunderstorm activity is the highest.
Analyzing the power quality data
Hooking up a power quality monitor is not that difficult and can be carried out by qualified electricians. However, analyzing (or reading) monitoring data is a different story. Monitoring data files are best analyzed by power quality experts with years of experience. Even experts in the industry experience challenges when trying to analyze files. Custom software tools provide many data analysis functions to power quality experts. Proper analysis techniques yield the right trends, charts, disturbance waveforms, and statistics, which are critical to determining the types of disturbances, their severity, and likelihood of causing malfunction or damage to electronic LED lighting systems operating on 480V buses.
Determining the source (or cause) of the power quality disturbances captured during the monitoring period is also important prior to making a decision to purchase electronic LED luminaires. Determining the cause of a disturbance (or series of disturbances) can be very challenging and time-consuming. There’s room for significant error during the power quality data monitoring and analysis process if one has little to no experience in power quality. Additional information must always be gathered about the loads and plant operations as well as the customer’s business to determine the sources of disturbances measured by the monitor. Knowing the right questions to ask is critical. Disturbances may also be linked to operations occurring on the electric utility power distribution circuit or the utility transmission feeder, if the plant is fed at a higher voltage level.
Identifying power quality mitigation measures
Once the power quality data has been analyzed, the disturbances identified, and the causes determined, it is time to identify potential mitigation equipment to reduce or eliminate the disturbances. Here are some important points to keep in mind:
- No two power quality mitigation equipment or devices are the same.
- Mitigation at different points along the plant’s electrical system must be handled individually and has different performance, costs, and ROI.
- Different mitigation equipment or devices are typically required at different points along the plant’s electrical system to achieve effective mitigation across the plant’s power system. In other words, don’t expect one type of mitigation equipment or device to solve all of the power quality problems for the LED lighting installation.
- The high-bay LED luminaire may include a mitigation device as part of the lighting purchase. The type and level of mitigation device included in the luminaire must be included in an engineering analysis to determine what other mitigation equipment or devices are required in the plant to achieve proper mitigation on all of the lighting system branch circuits. In fact, many luminaire manufacturers miss-specify the mitigation device used in a luminaire to provide the required level of protection important to driver life in industrial plants.
- The type and level of mitigation included in the LED drivers is also important and must be included in the mitigation analysis. No type and level of mitigation internal to a driver is the same as what’s included in another model driver. Driver manufacturers don’t use the same type or level of mitigation in their driver designs.
In many cases, it may be necessary to identify and implement measures other than selecting and installing mitigation equipment and devices to eliminate a power quality problem. Changes to a plant’s wiring and grounding system and/or loads may be necessary. Power quality experts can model and simulate plant electrical systems and study potential changes to a system and/or load before money is spent actually implementing changes to a plant’s electrical system.
With the cost of high-bay LED luminaires still considered as an investment in plant infrastructure, verification that any power quality mitigation equipment or device installed in 480V switchgear and on 480V lighting branch circuits is still operational and can provide the required mitigation is critical before LED luminaires are installed. You should conduct another round of power quality monitoring on each lighting circuit undergoing mitigation before LED luminaires are installed. The second round of monitoring will determine the effectiveness of the mitigation equipment or device installed.
Conclusion
Understanding, identifying, solving, and preventing power quality problems in an industrial plant is critical to the success of any high-bay LED lighting project — retrofit or new industrial construction. Investing in the design and installation of new LED lighting for a plant is a major undertaking and should be handled carefully before signing off to start a project. Most LED luminaire and driver manufacturers, as well as lighting designers, are not fully prepared to help their customers overcome power quality issues. Reaching out to an expert power quality consultant prior to the installation of a LED high-bay lighting system in these settings can ensure a smooth installation and reliably operating system.
Keebler is a senior power quality engineer with Electrotek Concepts, Inc. in Knoxville, Tenn. He can be reached at [email protected].
SIDEBAR: Powering and Grounding Electronic Equipment
According to IEEE Standard 1100-1999 (R2005), Recommended Practice for Powering and Grounding Electronic Equipment, “power quality” is defined as the concept of powering and grounding electronic equipment in a manner that is suitable to that equipment. This definition applies to every piece of electronic equipment in a plant — not just the equipment powered and grounded at the 120V level.
In laymen terms, powering an electronic load means taking the power at the point where the branch circuit delivers it to the load — the power-to-equipment interface — and injecting 50 Hz or 60 Hz AC power to that load. Grounding an electronic load means bonding the equipment grounding conductor — usually the green wire — to the ground conductor in that branch circuit at the same interface. However, the quality of the power and the quality of the ground at the interface is what gets delivered to the electronic load, but that quality must start at the source of the power to the plant.
However, when it comes to power quality, the quality of power and the quality of ground at various power-to-equipment interfaces are different at different voltage levels. In U.S. commercial and industrial facilities, voltage levels of 480V, 277V, 208V and 120V are commonly used to power electrical and electronic equipment. In Canada, voltage levels of 600V, 347V, 240V, 208V and 120V are used, but 347V is a common industrial voltage for lighting in Canadian industrial plants. Because 480V circuits were typically conveniently located in the ceilings of industrial plants to power non-linear and high-power loads, it was easy for electricians to tap into these circuits to power magnetic high-intensity discharge (HID) lighting. When doing so, no additional 480V circuits had to be installed to support the magnetic HID lighting system.