Power Quality (PQ) is key to the continuous, cost-effective, and reliable flow of electricity powering water and wastewater treatment plants. Depending on the size of the plant, dozens of PQ devices may need to be cascaded throughout the electrical distribution system.
Here’s why: Eighty percent of electrical disturbances that cause poor PQ originate inside the treatment facility. Powering “on” and “off” very large equipment, wiring errors, poorly specified or improperly serviced power conversion equipment, grounding loops, and even normal daily operations can foster PQ issues that lead to production disturbances and shutdowns, equipment damage, and lost data.
The most common PQ problems in treatment plants are harmonics, voltage sags and swells, noise and lightning strikes. Below we discuss each:
Harmonics are created whenever a non-linear load draws current in pulses. Harmonics represent trouble in treatment plants because they can overheat neutral conductors and transformers, trip breakers, create a high neutral current, reduce system capacities, and loosen electrical connectors.
Transformers are your first line of defense against harmonics, especially those models designed for variable speed motor drive applications. A power conditioner is an added means of harmonics mitigation. SolaHD™ Drive Isolation Transformers by Emerson are specifically designed to handle the mechanical stresses, voltage demands, and harmonics associated with water and wastewater treatment applications. SolaHD Transformers meet applicable industry standards, are listed per UL 5058 and UL 1561 specifications. They are available in 7.5 through 440 kVA, 3 Phase, 60 Hz models. Emerson offers a range of SolaHD Power Conditioners for various applications. The CVS and MCR Hardwired Series supply output voltage regulation of ±1% and ±3%, respectively, and are solid state devices so they provide extreme reliability and a long-lasting life.
Water and wastewater treatment plants are highly vulnerable to voltage sags (undervoltage) brought about by large loads coming online. A sag typically lasts at least one-half cycle but can endure for up to several cycles. In severe cases, PLCs and PCs can crash and other equipment can abruptly shut down.
Uninterruptible Power Supplies (UPS) and power conditioners are deployed to protect critical process systems against voltage sags. Only industrial-grade UPS with rugged components should be specified for treatment plants subject to severe environmental challenges. SolaHD S4K Industrial On-Line UPS provide flexible output voltage. Online design means zero transfer time from external to internal power, so when utility power fails, a critical load remains fully supported by a seamless flow of power. SolaHD voltage regulators and power supplies with sag immunity also provide protection against sags. Additionally, engineers can rely on the SolaHD SOLATRON™ Plus Three Phase Power Conditioner to protect equipment from chronic over- and undervoltage, switching transients, lightning and induced surges.
Power quality problems can occur because of a voltage swell (transients, spikes, impulses). The opposite of a voltage sag, swells are caused by large loads going offline or by a lightning strike which generate a sudden massive increase in voltage. In cases of a more than 10 percent swell, sensitive electronic components may be damaged. System lock-up or failure can corrupt valuable operational data.
SolaHD STC-SS Series Surge Protection Devices address overvoltage transients with gas tube and silicon avalanche technology. Sneak and electrical fault currents are mitigated with positive temperature coefficient (PTC) devices that consist of solid-state resettable fuses. The units are encapsulated in stainless steel pipe nipples making them suitable for use in severe environments. The SolaHD STC-SLAC Series Surge Protection Devices are surge suppressors specifically designed for WTP/WWTPs to protect sensitive electronics that contain both low-voltage control circuit signal lines and 120-volt AC power. Their rugged waterproof NEMA (National Electrical Manufacturers Association) 4X polycarbonate enclosures are suited for installation in the most severe environments.
Noise can be generated from any piece of equipment when it is turned on or off, inducing an influx or efflux of voltage and current, and producing undesirable effects in electronic circuits such as very rapid or very large amplitude changes. In general, noise is a more severe problem in signal and data circuits. These types of circuits operate at faster speeds and with low voltage levels. The lower the signal voltage, the less amplitude of the noise voltage that can be tolerated.
SolaHD Active™ Tracking Filters (STFE and STFV Series) guard against lower energy transients. Offering excellent noise reduction, the filters continuously track the input AC power line and respond instantly upon detecting extraneous high frequency noise. The filter eliminates low voltage/high frequency noise via a low-pass or L-C filter. Filters are used for low energy, high frequency noise reduction and consist of a series of inductors, capacitors, and resistors.
5. Mitigating Lightning Strikes
Lightning strikes are an extreme example of a power surge. Predictably, they are also the most damaging. Treatment plants are built on large, exposed surface areas in isolated locations and are equipped with pumps, ponds and electronic equipment. When combined, these factors make them attractive targets for lightning strikes. Overvoltage from lightning directly impacts instrumentation, communications and sensitive electronic equipment such as gauges, meters and PLCs. It is important to note that for direct lightning strikes, surge protection devices alone are not a replacement for a comprehensive lightning protection system (refer to UL96A Master Lightning Certification). For additional information, Emerson recommends carefully reviewing NFPA (National Fire Protection Association) 780, “Standard for the Installation of Lightning Protection Systems” (United States) and BS EN (European Norm)/IEC (International Electrotechnical Commission) 62305 “Protection Against Lightning” that informs the standards for lighting protection globally.
Industry loses billions of dollars every year due to power quality issues. In fact, the annual cost is estimated by the U.S. Department of Energy to be $110-150 billion. Emerson can solve virtually any power quality problem within an industrial or commercial facility worldwide. From the service entrance to point-of-use, SolaHD power quality solutions by Emerson protect and insulate industrial operations from the threat of disturbances and secure the highest level of power quality throughout the plant. Safeguarding incoming power drives system reliability, return on investment (ROI) and customer satisfaction, making SolaHD total power quality solutions by Emerson indispensable to today’s industries. Selecting the proper power quality solution for your application can be tricky. Experienced and dedicated sales representatives, along with award-winning online tools, help you make the right choice, every time.
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