The boom of computer and other sensitive equipment markets, throughout manufacturing, office facilities, and even homes, has driven the need for electrical systems to address power quality issues.
According to a study performed by National Power, Necedah, Wis., of 112 sites of differing location, size and type, the average number of disruption events to electrical systems was 106 per month. As much as 80 percent of these power quality problems are related to inadequate wiring or grounding, according to the Electric Power Research Institute (EPRI), Palo Alto, Calif.
Frank Healy, power quality product marketing manager for Fluke Corp., Everett, Wash., said power quality is a measure of how close the operating voltage and frequency stay within limits that are acceptable for the correct operation of electrically operated equipment.
“If the voltage and frequency deviate outside of the acceptable limit, then the equipment may fail and cause disruption for groups and individuals or cause breaks in production,” Healy said.
A supply of clean, reliable power reduces waste and increases operational efficiencies and the optimal utilization of power, said Jim Davis, business unit manager at Eaton Corp., Cleveland.
“There are two types of power quality products,” he said. “Passive products are those that mitigate power quality issues, while active products reshape power to be of high quality.”
Rudy Wodrich, director, power quality group for Schneider Electric, Palatine, Ill., said power conditioning is the isolation of sensitive equipment from the effects of electrical noise and voltage fluctuations, otherwise referred to as “dirty power,” and falls into the reliability and availability of the utility supply aspect of active power quality.
“Power conditioning is often accomplished via the use of series-connected line conditioners and/or online uninterruptible power supply systems,” he said.
Ideally, the shape of the voltage waveform should be sinusoidal, but the actual shape is always distorted by harmonics. Waveform shape issues have been primarily addressed with passive filters that use capacitors and inductors. More recently, active filters are being used to perform electronic wave shaping.
“The obvious primary benefit is ensuring that sensitive process equipment is fed from a clean voltage source and that the distribution network is not thermally overloaded by high frequency pollution,” Wodrich said.
Transient protection is a separate and specialized field dealt with by using transient voltage surge suppression and lightning arrestor arrangements.
“Availability of the voltage from the utility can be addressed using UPS systems and backup generation and transfer schemes, which enable the facility to continue operating even when the utility power supply is lost,” he said.
Power quality can be measured at any point in a power network, from generation, transmission, distribution or utilization. The type of measuring instrument used can be as simple as a single-phase, plug-in voltage logger; a power quality logger that measures voltage, current, and power over time; or a power recorder that records all the power quality parameters possible.
“In progressive organizations, power quality is measured continuously so that problems can be spotted before they occur,” Healy said.
Risks of poor quality include damage to the electrical infrastructure; overheated or failed equipment and resulting downtime; increased energy consumption and maintenance costs; loss of sensitive data; and, most importantly, loss of life.
Promoting power quality
Electrical contractors who wish to promote power quality to their customers need to understand its basic underlying principles, according to Healy.
“Electrical contractors should first understand that the majority of power quality problems are caused by the equipment used within the facility, although some arise from external problems, such as blackouts caused by lightning strikes and equipment failure in the electrical supplier’s network,” he said.
Contractors can check the health of the customer’s electricity supply and explain the importance of planning for power quality and the correct installation of new equipment.
Davis said contractors need to be aware of the available power quality products and technologies to make value-added recommendations to customers.
“They must also listen closely to their customers’ power issues and understand the symptoms being described if they are to choose and promote the products that will best address customers’ problems,” he said.
Davis suggested working with manufacturers’ power quality experts to take advantage of their audit, consultation and application expertise. Equally important is the contractor’s ability to recognize the symptoms of poor power quality, such as overheating, nuisance breaker trips or premature electronic component failures.
“The key is to have the instrumentation that can examine and record waveforms and to log trends of the key power parameters and to help ensure power reliability for the customer,” Wodrich said.
BREMER, a freelance writer based in Solomons, Md., contributes frequently to ELECTRICAL CONTRACTOR. She can be reached at 410.394.6966 or firstname.lastname@example.org.