The quality of electric power that operates building systems has always been important, but as these systems have become more complex, the effects of power quality (PQ) issues have multiplied.
Most new equipment installations now include electronic controls, said Frank Healy, power quality manager at Fluke Corp, Everett, Wash.
“This increase in electronic loads creates two issues,” he said. “First, this type of equipment generates harmonic pollution, which winds up back in the power supply, and not all electrical distribution setups are equipped with the necessary filtering to manage that input. Second, electronic loads are more sensitive to harmonic and other types of power quality distortion and may go offline if power quality isn’t high enough. Combined, those two issues can be problematic. Today’s highly lean facilities are more sensitive to downtime and power disruptions. Power interruptions that were shrugged off 10 years ago now are viewed very seriously.”
In addition, there is a sustained interest in power-consumption efficiency.
“Building operators continue to see energy as a cost within their control,” Healy said. “Any decrease in energy consumption positively impacts their bottom line. The first step in assessing the opportunity for consumption reduction is to conduct an energy study with a power logger. Also, the introduction of energy-efficient electric motors requires more detailed measurements on motors to ensure loads are operating efficiently.”
PQ testers and loggers have evolved to support these changes. Tools have evolved in both the high-end and generalist markets.
“High-end tools perform a greater variety of tests with more memory, longer battery life and better software,” Healy said. “They also may have specific ways of discovering energy losses and motor efficiencies. Entry-level tools are completely new and enable a generalist electrician, who doesn’t do power studies every day, to easily and correctly set up an energy or power study. These new tools are small with highly intuitive user interfaces and improvements in memory, battery and software. They offer more memory and a wider range of communications and make instruments easier to use and are capable of a wider range of measurements.
“Today’s PQ testers can directly store many months of measurements. The data can [be] transferred either by a wired connection to the instrument via a USB or SD memory device or wirelessly using Wi-Fi to send collected data to the cloud and accessed from a desktop,” he said.
Andrew Sagl, product manager for Megger, Dallas, said the grid is changing rapidly, with increasing use of solar and wind energy creating higher frequency harmonics due to inverters and increased transients.
“These green-energy sources are not constant,” he said. “Solar panel outputs change with the amount of light and clouds. Wind energy changes with the wind speed. This causes RVC [rapid voltage change], which can cause flickering lights as well as equipment to trip offline. Smart grid is allowing utilities to send signals over the lines to turn equipment on and off. PQ issues can interfere with these signals. In addition, these signals can cause resonance in equipment.”
High-end instruments perform a wide variety of measurements, including voltage and current, active power, reactive power, apparent power, displacement power factor, true power factor, energy (up to 13 power configurations supported), sags/dips, swells, subcycle/waveform distortion, transients down to one microsecond, RVC, mains signaling, phase-angle shifts, total harmonic distortion, total demand distortion, harmonics, interharmonics, flicker, unbalance (IEC and ANSI), frequency and waveform captures triggered by events, and periodic captures.
Wireless capability allows for remote monitoring, so instruments can be placed in areas that may be difficult to access. Data can be analyzed from the office, saving time and money.
“Today’s instruments have memories in the gigabytes, and data is transferred to the PC via USB, ethernet, USB stick or SD card,” Sagl said. “PQ analyzers today are smart. They tell the users if they are connected properly, analyze the data immediately, and allow the creation of custom configurations based on the symptoms present at the location. Today’s instruments not only are more powerful and easier to use but are more rugged. The ability to be used indoor or outdoors, and powered off of phase A can be important depending on the application.”
Ed Cunnie, inside sales manager, AEMC, Orland Hills, Ill., said poor PQ issues have created problems for years. However, with the growth of more sensitive electronic equipment, the PQ problem threshold has been lowered significantly. Improvements in newer test instruments allow electricians to isolate, identify and quantify these power disturbances.
“First and foremost is the economic impact of downtime reflected in the loss of productivity and/or product quality,” Cunnie said. “Perhaps the biggest culprit is harmonics. Therefore, devices that can indicate and record basic total harmonic distortion and further identify individual harmonics should be a minimal requirement. Stress on delivery systems caused by initial inrush and secondary inrush are keys to identifying power quality issues.”
Improved electronics support more powerful PQ analyzers at more affordable prices, Cunnie said. Examples are the simultaneous monitoring and recording of a combination of some 41 variables in engineering units and math calculations. There is a subset of this group in the form of power quantity consumption from an economics standpoint.
“Increases of onboard solid-state memory in the gigabyte realm, plus the incorporation of high-volume SD cards, have drastically increased data storage,” Cunnie said. “Bluetooth, USB and ethernet communications vehicles provide multiple avenues for downloading and real-time data transfer.”
Bob D’Amico, senior sales and support engineer, Hioki USA, Cranbury, N.J., said voltage fluctuations and harmonics are the most common PQ issues. Harmonics cause equipment and motors to run hot, decreasing their efficiency.
“A basic power quality tester will include event capture capability and harmonics capture,” he said. “Today’s power quality testers are able to capture more types of events, and many can store up to three years of recordings and multiple events. Most data is stored on a removable memory device, and it can be used with software that accompanies the PQ meter. Some users today would like to see power functionality in a memory recorder which would combine a troubleshooting device that can make power calculations.”
Dave Kadonoff, field sales engineer, Ideal Industries, Sycamore, Ill., said any equipment that is under the control of logic circuits can be impacted by the loss of control signals if PQ to the control unit is compromised.
“PQ issues are most commonly thought of as disturbances to the purely sinusoidal waveform of 60 hertz and related amplitude for the appropriate rms voltage resulting in sags, swells, distortion, spikes, literally any deviation from the pristine waveform of sufficient magnitude (up or down) and duration that can impact reliable function of load or shorten equipment’s expected lifetime,” he said.
To find and categorize these distortions and the slightest of deviations from a pure sine wave, many overlook the integrity of the wiring and connections on electrical distribution systems.
“For example, hospital outlets are mandated to be tested once a year for retention force,” Kadonoff said. “That’s good, but only checks integrity to the length of the inserted prong. To look further into the branch circuit, and all the way back to the panel, an advanced receptacle/polarity checker combined with a circuit analyzer is needed.
“By plugging the SureTest into the outlet with the provided standard three-prong connector, the existing voltage is measured, a 15 amp load is applied for slightly less than one cycle to not disturb any sensitive electronics or trip any breakers, even if there are already loads on the circuit. Then the voltage is measured in the loaded state and voltage drop in percent is calculated. Less voltage drop is desirable—the [National Electrical Code] recommends 3 to 5 percent or less. This provides an immediate sense of the condition of the integrity of the branch-circuit wiring from the panel to that point and whether it can support loads to design limits without causing excessive voltage drop,” he said.
Jim Huekels, account manager for Extech, a Flir company, said PQ issues are generally perennial.
“Where we see changes are in today’s wider adoption of variable speed drives and motor controls, as well as DC motors in AC environments,” he said. “For energy efficiency, more and more sensitive electronics are being employed to play an important role in optimizing motors, pumps and other industrial electrical equipment. These pose a vulnerability to ‘dirty’ power quality.
“The emerging Internet of Things approach to industrial equipment management adds another dimension to vulnerabilities related to power quality. Are industrial IP-networked monitoring and control systems hardy enough to withstand surges from dirty power quality, or do they represent an additional weak link?
“PQ testing should be part of a well-defined predictive-maintenance program. Basic test equipment used for PQ-related testing includes insulation resistance testers, voltage and current data loggers, and power clamp meters. All of these complement the primary tools for PQ, the power and harmonics analyzers,” Huekels said.
Today’s PQ and harmonics analyzers can be used to provide a big picture of a site’s PQ conditions. With more than 30 metrics and functions, PQ analyzers offer a detailed view of PQ and harmonics.
“Current capacities have increased with options up to 3,000 amperes, and data-logging capacity has increased with the flexibility of removable SD memory cards,” he said. “Displays have improved with better contrast for improved viewing in both dim and bright lighting conditions.
“Some power quality analyzers can store up to 30,000 sets of records. Programmable sampling rates add flexibility to data logging, and a SD card ensures a convenient, portable format to transfer records,” Huekels said.