End-use equipment once consisted of incandescent lamps, resistive heaters and simple motors—loads that drew nice smooth linear AC current. These loads contained tungsten, iron, steel and copper as their internal components. Powered from the utility grid developed and installed some 75 years ago, end users rarely had a problem with equipment. Grid operations caused sags & interruptions, thunderstorms generated voltage surges and motor starts created sags. Yes, these disturbances impacted equipment but with no electronic controls onboard, restarting it wasn’t that much of a problem. Utilities, A&E firms, manufacturers & building owners didn’t receive near as many calls from their customers about electrical system & equipment failures as they do now. Those times are long gone now!
Nearly every type of electrical equipment contains electronic components that control all functions of the equipment. Very few products solely use analog components: resistors, single transistors, bulky diodes, etc. Most older products still in use in many plants use either all analog or a mixture of analog and digital components. Many plants are upgrading their equipment to digital systems including servo variable frequency drives (VFDs) to provide precision motion control for many processes.
Researchers have even been investigating replacing the classical transformer with a solid-state design. Vehicle manufacturers are now producing electric vehicles (EVs) of several flavors. It is no longer uncommon to see EV charging stations at local restaurants and office buildings. When end users need a hot plate, they shop for an induction model—not a nichrome sand-filled metal stove eye mounted in a metal box with an analog thermostat. Televisions are no longer available with large cathode ray tubes (CRTs)—flat screen TVs have become the standard. Every household has five flat screen TVs on average. Computers and servers contain rows and rows of printed circuit boards with all digital components. Electronic ballasts and drivers for LED lighting use about six digital integrated circuits each—all power is digitally controlled now. Moreover, digital devices are more susceptible to common everyday PQ disturbances than analog devices. The new times have long arrived—this trend will continue with significant growth & of continuing & new PQ problems.
The reshaping of equipment and the significant growth in its use resulted in a two-sided PQ impact. First, the increased use of switching devices (i.e., transistors and diodes) combined with inductors and capacitors changed the shape of the once-smooth 60-hertz AC current supplied by the utility. This change created harmonic currents which occur at frequencies other than 60 hertz. Many electronic loads that switch voltages & currents take a “slice” out of the voltage—they generate notches that cause significant system & equipment problems. Harmonics impacted utilities and end users causing power factors to collapse and harmonic currents to flow in utility and customer electrical systems. Harmonic current flow created the opportunity for harmonic voltages & currents to build up in customer electrical systems resulting in damage to the same equipment causing the harmonics.
Second, the use of transistors and diodes as well as microprocessors & digital signal processors (DSPs) in equipment caused a significant increase in their susceptibility to PQ disturbances—voltage surges and transients. Analog equipment suffered damage in the 1970s and 1980s. Manufacturers didn’t know much about how to protect their equipment from disturbances. The birth and growth in the use of digital devices began to reshape electronic equipment & cause an increase in the number of PQ problems for customers. More semiconductor devices appeared in the front-end sections of electronic components. Electronic power supplies were used in an increasing number of products. As more electronics products were connected to customer electrical systems, the severity and rates of disturbance also increased. Manufacturers started including additional circuitry that reduced harmonics. The bad news was this again changed the design of front-end circuitry, making it even more susceptible to PQ disturbances.
Aside from equipment becoming more sensitive to common everyday electrical disturbances, customer electrical systems can’t support electronic equipment very well. Their electrical systems were designed based on the National Electrical Code (NEC)—NFPA 70. Written by insurance companies, the NEC addresses fire & shock prevention, not PQ & equipment performance. Customers still believe the myth that “If my facility is designed, constructed & maintained per the NEC, I shouldn’t have any system or equipment problems that impact my operations.” Although the NEC is a very old standard that is updated every three years, its updates make electrical systems safer but don’t improve PQ inside customer facilities or improve electronic load performance. Its scope wasn’t based on the need to power & ground electronic equipment in a manner that improves equipment performance.
Moreover, customer electrical systems don’t receive the maintenance & upgrades required to manage the risks of malfunction, damage & failure of the electronic loads they must support. Research conducted by EPRI found that about 75 to 85% of all PQ-related equipment problems are caused by wiring & grounding (W&G) problems inside customer facilities.
Surge protection devices (SPDs), invented several decades ago, helped protect some electrical systems & electronic equipment. The application of SPDs in electronic equipment improved to some extent, but unfortunately not fast enough. SPD performance depends in part on the performance of the customers W&G system & how SPDs are installed. If customer W&G systems have problems, no protection or mitigation equipment will perform as expected.
The continued development of electronic equipment expanded its use. The development of the Internet provided the platform for designing and implementing a significant growth in digital devices for communications, computers and advanced electronic equipment in specialty industries like media, biotechnology, medicine and manufacturing. The need to store and transmit digital data across the Internet and the development of new applications using the Internet created the need for “data warehouses”, commonly referred to today as data centers, which are not 100% immune to common everyday electrical disturbances. Three key sectors critical to the US and world economy solidified and became stronger. These are
Some very important and staggering characteristics of these key sectors include:
Some staggering financial statistics regarding PQ include:
The cost of PQ problems is staggering and often goes undocumented. These are real problems which cost real money & can be prevented & mitigated if experience PQ experts are consulted. Interestingly, the cost of customers having to endure PQ-based equipment problems far outweighs the cost of improving the internal PQ of customer facilities & their equipment.
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