End-use equipment once consisted of incandescent lamps, resistive heaters and motors. These loads contained tungsten, iron, steel and copper as their primary internal components. Powered from the utility grid developed and installed over 100 years ago, end users rarely had a problem with these simple loads. Thunderstorms generated voltage surges and motor starts created sags, but operating these loads caused little to no problems for customers.
However, what happened in the mid-1950s changed the electrical nature of how electrical loads were powered forever. In 1956 John Bardeen, Walter Houser Brattain, and William Bradford Shockley were honored with the Nobel Prize in Physics "for their research on semiconductors and their discovery of the transistor effect. Twelve people are mentioned as directly involved in the invention of the transistor in the Bell Laboratory. Nearly every type of electrical and electronic equipment contains semiconductor electronic components as their central components. Soon after the advent of the transistor, analog electronics began taking shape. End users soon realized that analog-based equipment was very susceptible to poor PQ. The explosive growth in the use of this equipment captured the attention of utilities. Early into the deployment of this equipment, customers began to experience problems, and utilities began to receive complaints about equipment malfunctions and failures. Utilities responded with concern as to why these problems were occurring and what caused them.
Today, very few products use only analog components: resistors, discrete transistors, bulky diodes, etc. Most electronic products today use a mixture of analog and digital components. Unfortunately, the use of digital electronics in equipment designs increased the equipment's susceptibility to poor PQ. Researchers have even applied the use of power electronics to develop an electronic transformer to replace the classical steel-copper transformer. Vehicle manufacturers are now producing advanced electric vehicles with significantly improved performance. It is no longer uncommon to see electric vehicle charging stations at local restaurants, retail establishments and office buildings.
When end users need a hot plate, they can now shop for a single-eye induction cooking applicance—not a nichrome sand-filled metal stove eye mounted in a metal box with an analog thermostat. Televisions (TVs) are no longer available with large cathode ray tubes (CRTs) glass picture tubes—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. Advancements in microelectronics made it possible for computer manufacturers to take switching speeds to very high frequencies, increasing the requirement for DC power. Electronic ballasts and drivers for lighting use about six digital integrated circuits each. All power supplies are controlled by digital electronics. Moreover, digital-based equipment is more susceptible to PQ disturbances than analog-based equipment. As microelectronics continue to advance, the need for even better PQ protection in equipment designs just as the need for managed PQ in customer facilities will grow.
The reshaping of electronic 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 non-linear passive components (i.e., inductors and capacitors) changed the shape of the once-smooth and in-phase (with the voltage) 60-hertz AC current supplied by the utility. The use of electronics in equipment causes the addition of harmonic currents in the AC line current. Harmonics currents converging on specific points in the utility power distribution system caused serious grid operating problems for utilities. End users suffered from lower power factors with an increase in the flow of harmonic currents to flow in their facility electrical systems. Harmonic currents causes the utility voltage to become distorted which can affect the operation of electronic equipment.
Second, the use of transistors and diodes in equipment caused a significant increase in its susceptibility to PQ disturbances including voltage surges and transients. Analog equipment suffered damage in the 1970s and 1980s. Manufacturers didn’t know how to protect equipment from disturbances. With the onset and growth of this equipment, the increase in harmonic current levels in customer facility electrical systems and the increased failures of utility power distribution equipment stimulated the development new standards to begin imposing limits on harmonic currents drawn by non-linear electronic equipment.
When manufacturers were first faced with designing the control of harmonic currents into their electronic power supplies, their first attempt was to use passive filters tuned to specific harmonic frequencies. However, this approach resulted in the use of iron/copper-based filter inductors for the filters. The demand, weight and inefficiency associated with the use of lots of iron and copper were three of the primary reasons product designers wanted to use electronic switching power supplies in the first place, so bring these materials back into the design to provide harmonic filtering was a step in the wrong direction and didn't make much sense. So, power supply developers moved to design circuits which could provide the harmonic filtering but using electronics to do the job. From this, the active power factor correction (A-PFC) concept was developed.
One of the byproducts of using the A-PFC approach is the ability to provide a design that will operate from a universal AC input voltage like 120 to 277 volts, and 347 to 480 volts. A second byproduct is the ability of the A-PFC circuit to maintain a DC output voltage which can be held constant when the AC input voltage various within its design window. Power supply developers at semi-conductor manufacturers designed integrated circuits (ICs) that provide for these two function plus more, so product designers can quickly work up a design for an A-PFC circuit. These circuits can be set up to provide a lot of harmonic current control or just some control.
After "adding the harmonic currents back into" the distorted current waveform, the harmonic-related part of the power factor (i.e., the bumpiness in the AC current waveform making it distorted) is corrected as well. In addition the A-PFC circuit will correct the displacement power factor (DPF). This results in the true power factor (harmonics part of the power factor added to the displacement power factor) being corrected. The amount of total correction is also variable by the designer by changing the way these PFC controllers respond. Nowadays, A-PFC circuits are used at the front ends of every power supply powering electronic equipment.
The growth in the use of A-PFC in electronic equipment designs lowered the harmonic current levels and increased their power factor. While these PQ problems started to improve, electronic equipment began experiencing other more serious PQ problems which increased failure rates. A-PFC circuits used at least one power transistor to provide the switching function necessary to maintain charge (electrons) in an electrolytic capacitor to support the DC bus voltage. With the use of this transistor and the analog A-PFC controller chip, the A-PFC circuit became exposed to damage caused by power disturbances incident on the AC line. It didn't take long to determine that A-PFC circuits needed some targeted surge protection on the AC line.
The availability of higher performance surge and transient protection components improved, but the application of these components didn't keep pace with the advancement of surge protective devices. The use of A-PFC-based electronic equipment continued to skyrocket as the demand for personal desktop and laptop computers rose.
Significant growth in the usage of desktop and laptop computers plus the development of the Internet provided the platform for the exchange of massive amount of data for all types of applications. This stimulated the growth for the development of new electrotrotechnologies in areas including new communications devices to support the Internet, servers and data storage devices to fuel development of the Internet.
Significant growth in digital devices for communications systems, faster computers and advanced equipment in specialty industries like biotechnology, medicine and manufacturing fueled the need to send digital data across long distances. 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. Three key sectors critical to the US and world economies solidified and became stronger as a result of the Internet. These are:
The Digital Economy (DE)
Continuous Process Manufacturing (CPM)
Fabrication and Essential Services (F&ES)
Some very important and staggering characteristics1 regarding these key sectors include:
- They represent about two million business establishments in the US.
- As 17% of all US business establishments, they account for about 40% of the US gross domestic product.
- Disruptions caused by power quality have an abrupt effect on other business sectors depending on the services these three key sectors provide.
- Industrial and DE businesses combined lose $45.7 billion per year because of power outages.
- DE businesses lose $12.8 billion per year from lost productivity and idle labor.
- F&ES businesses lose $27.4 billion per year from their high vulnerability to equipment damage.
- CPM experience the highest losses per business entity from the loss of raw materials.
- A 1-second outage among industrial and DE businesses cost these businesses an average of $1,477.
- A 3-minute outage among industrial and DE businesses cost these businesses an average of $2,107.
- A 1-hour outage among industrial and DE businesses cost these businesses an average of $7,795.
- 49% of the outages experienced by industrial and DE businesses are shorter than 3 minutes.
- DE business experience smaller financial losses caused by PQ phenomena (voltage sags, voltage surges, voltage transients and harmonics).
- F&ES businesses who are more susceptible to PQ phenomena experience financial losses higher than $9,600 per year per entity.
- The US economy losses between
- $104 billion and $164 billion per year caused by PQ outages
- $15 billion and $24 billion per year caused by PQ phenomena
Some staggering financial statistics regarding PQ include:
- “Electrical disturbances cost US businesses $26 billion a year!” (Business Week: April 8, 1991)
- “1.5 to 3% of every sales dollar is spent on correcting power-quality problems” (IEEE Spectrum Magazine: June 1993)
- “Average cost for a 4-hour outage is $74,835 and $11,027 for a momentary outage.” (IEEE Trans. on Industry Applications: December 1997)
The cost of PQ problems often goes undocumented and continues to grow. The good news is that Electrotek Concepts, a professional consulting engineering firm with a 33-year history has the power systems and PQ engineering expertise to help utilities, A&E firms, manufacturers and end users understand, identify, solve and prevent PQ problems.
1 “2001 data from “The Cost of Power Disturbances to Industrial & Digital Economies” from Primen, 2001.”