The quality of electrical power is an issue that most of us tend to leave unmeasured and unexamined. The general feeling seems to be: "Lights are on, no problem." Yet U.S. companies waste an estimated $26 billion a year in lost time and revenue stemming from electrical power-related problems.
This extraordinarily high figure reflects increased use over the last few years of sophisticated electronic equipment in business and industry-from front office to assembly lines-that is sensitive to the vagaries in power.
But interest in power quality has been building for the past decade. In the early '90s, the utility-funded research organization Electrical Power Research Institute (EPRI) placed several hundred monitors around the country for a few months to test power quality. The results were surprising. Power quality was far worse than had been anticipated, with disturbances and interruptions, and sags and swells. That somewhat alarming survey essentially kick started broad-based discussion on power quality that continues in this new millennium.
In the years since the survey, there has been a huge increase in the use of switchable power supplies for personal computers, Internet servers, and other computer technology has seen a dramatic increase. Variable speed drives in manufacturing facilities, varistors, and rectification circuits to supply electronic loads, step motors, and similar devices, all of which can create a fair amount of "dirt" in a power system, have seen similar increases. Along with equipment such as arc furnaces for steel plants, these devices affect the quality of power received by others.
A facility that requires clean power to avoid disruptions to its processes (such as a plant making semi-conductors) might experience a fleeting, possibly harmful dimming of power when a neighbor (such as a steel mill or furnace) turns on a particular load. A major auto plant that manufactures axles recently determined that a 1/10 of a second (six-cycle) disturbance would cost the company about half a million dollars because major loads have to be reset and restarted, causing a loss of about an hour in production. The price of the power quality equipment to test for and protect against sags and swells, harmonic distortion, line noise, and high-energy transients spurred by lightning-induced surges and power company switching that can destroy electronic components instantly, can, for some industries, start to seem modest by comparison.
And fleeting surges and spikes-caused by on/off cycles in motors, as well as by lightning and utility switching-frequently cause physical damage to many kinds of motorized equipment, from air conditioners to elevators. Monitoring, analyzing, and protecting power quality, as well as correcting imperfections in power quality, can protect against loss of revenue when computerized and other equipment is down because it does not have pure power. It can reduce excessive operating costs resulting from poor quality power, and it can eliminate utility surcharges resulting from a low power factor.
When monitoring an entire system, experts suggest running the tests throughout one business cycle, whether one work shift or an entire week. To test power quality, use either portable equipment or equipment permanently connected to various circuits throughout a facility for continual monitoring and tracking of changes.
If there is a problem with full-time metering equipment, the printout from the meter--which has kept a constant record--is available to indicate the source of the problem, much like the data stored in a "black box" flight recorder on an airplane. With portable equipment, you will have to go back and sleuth to find the source of the intermittent problem unless the event happens while the equipment is connected. Contractors can also use more expensive portable equipment that often has more sophisticated troubleshooting features.
Monitoring is necessary not only to keep tabs on power quality but also to measure cost allocation and consumption. On the local level, plant managers want to know that power quality is good; on a corporate level, managers want to be able to determine the exact cost of power as part of the cost of production.
Once results of monitoring are in, attention can shift to protection products like transient voltage-surge suppressors (TVSS), uninterrupted power supplies (UPSs), and other equipment appropriate to mitigate the conditions found. (You may also need to derate the transformers, or add additional transformers, change breaker settings, or size.) After you install equipment such as TVSS, breakers, UPSs, harmonics filters, or capacitor banks, your clients could still benefit from continuous monitoring of the power system to ensure new equipment is responding up to its specifications and doesn't harm the overall system.
The Fluke 43 Power Quality Analyzer is a portable troubleshooting tool that can be quickly connected to display voltage and current waveforms or harmonics spectrums. These functions enable the troubleshooter to track sources of voltage distortion. It can track single-cycle sags and swells, and it can capture and timestamp 40 transients less than one microsecond long. The Fluke 43 performs all the standard measurements that a scope or meter can perform, including resistance, capacity, and peak voltage. It lets a contractor provide basic power quality service without tying up a three-phase analyzer.
The Amprobe Data Logger/Recorder DM-II is a self-contained, portable single- or three-phase power/energy data logger that measures and records single (two-wire or three-wire) or three-phase (three-wire DELTA or four-wire WYE). Power measurements include watts, var hours, volt ampere and power factors (PF); energy measurement includes kilowatt-hours and demand in kilowatts. All set-up information and recorded data can be viewed on the large LCD screen, which has a backlight. The unit comes with current transducers, voltage-test leads, and software for downloading recorded data to a personal computer.
Dranetz-BMI's Power Platform 4300 is a hand-held three-phase meter and analyzer used for power quality troubleshooting and monitoring of harmonic susceptibility and energy management. The company's best-selling instrument, it can be set up to perform preconfigured tasks by inserting PCMCIA modules to perform various tasks, including measuring, recording, and analyzing up to 16 power and power quality parameters.
The company also offers Powervisa, a single-phase, plug-in power quality analyzer with built-in printer, well-suited to field service diagnosis of intermittent power problems on data networks, and a variety of other systems. These systems include electronic cash registers, equipment in hospitals and medical labs, and other field locations where single-phase power could be critical. The unit automatically sets its own thresholds and prints reports daily, weekly, or as events happen. After each event, it can offer automated advice on causes and solutions.
Dranetz-BMI also offers the Windows-based DRAN-VIEW 4.0 to access data gathered by the 4300 and PP1, as well as that provided by other power quality instruments. Energy faults can be utility-generated or be the result of onsite errors.
Power Measurement Ltd. produces a line of multifunction digital power meters with capabilities ranging from basic monitoring and revenue-class metering functions to comprehensive tools for control, data logging, and power quality analysis.
Power Measurement's new revenue-accurate 8500 ION socket-mount meter optimizes energy use and monitors power quality through detailed harmonic distortion measurements, sag/swell detection and analysis, sub-cycle transient detection, digital capture of multifunction waveforms, and hundreds of additional power, energy, and demand measurements.
Collection and analysis of this data, the company points out, can help to reduce energy costs through distributed load shedding, automated peak shaving, and reduced downtime. It can also provide a useful resource when selecting or assessing the services of an energy provider.
The 8500 ION can also be used to sub-bill tenants or allocate electricity costs to individual buildings or departments. In addition, the equipment can be used to verify monthly utility bills and ensure compliance with power quality standards--management can perform "what if?" scenarios based on alternative rate structures.
For extensive monitoring of three-phase industrial, commercial, and utility power systems, including waveform recording for disturbance analysis, GE offers the Power Quality Meter (PQM), a digital three-phase power meter with remote capabilities. PQM can operate alone or communicate with the GE Power Management Control System software. The unit provides continuous metering of current, voltage, real and reactive power, energy use, cost of power, power factor, and frequency for feeders, transformers, capacitor banks, motors, and generators. Other features include harmonic analysis, event recorder, waveform capture, data logger, triggered trace memory, dual RS485 ports and single RS232 port.
ACR Systems Inc.'s PowerWatch is a stand-alone voltage disturbance recorder that will detect and record surges, sags, impulses, outages, and frequency variations. Plugged into any 120-volt outlet, it features an optical alarm indicating that events have occurred, and a 4,000-event memory. The software displays information graphically or in list format. Data can be downloaded to your PC using the supplied LIC-1-1 interface cable. The device has default threshold settings in three categories: hot to neutral, neutral to ground, and frequency. Users can modify these settings.
An increasing number of systems rely on dedicated computer software that records and analyzes power quality data communicated in conjunction with specific measuring equipment. Software, typically Windows-based, is particularly useful for extensive or repetitive monitoring, when management wants to look for trends, reasons, or problems, or wants continuous monitoring at a remote location. Monitoring equipment can be hooked up through an Ethernet connection for remote monitoring through a PC.
Siemens Energy & Automation, Inc.'s WinPM 5.0 Power Management and Control Software for managing power within electrical distribution systems, part of the company's ACCESS power monitoring and control system, is used in conjunction with various third party intelligent electronic devices such as power meters, relays, and trip units. The software identifies problems, including harmful harmonics, surges, sags, and tripping of protective devices. WinPM warns technicians of problems via pop-up messages or alarms, or by pager before an equipment shutdown. It will also identify the major consumers of power in a facility.
For in-depth analysis, an on-screen summary of electrical data in real time of an entire electrical system can be superimposed on a one-line drawing of the entire system. It is possible to view detailed and minimum/maximum electrical data from any communicating electrical device in the system with one click of a mouse.
Users can also view data snapshots that record a trend of device data over time. The software also captures and records voltage or current waveforms that can be analyzed to diagnose disturbances and to look for potentially harmful harmonics.
GE's Power Management Control System, based on open network architecture and nonproprietary communication protocols, integrates with many manufacturers' standard devices for monitoring temperature, pressure, gas etc., in addition to electrical parameters. The system (part of GE's comprehensive Energy Management solution, which includes intelligent electronic devices (IEDs), and services that provide analysis of customer data) can continuously monitor for sags, surges and harmonics. In case of harmful waveforms, as defined by the user, the system can automatically capture several cycles of the waveform and report it to the central system with a millisecond timestamp. The waveform and harmonics can be stored and retrieved for further analysis.
and remotely control (automatically or manually) any IED using the standard communication network or through the Internet. The system can generate user-defined alarms and events. It can also be used to reduce energy costs through GE's Cost Allocation Module, which allows creation of "what-if" scenarios.
Square D's PowerLogic System Manager Software v.3.1 provides real-time electrical distribution information and historical data gathered by PowerLogic Circuit Monitors, power meters, digital protective relays, and electronic circuit breakers, as well as from many third-party devices. The system allows electrical and non-electrical pulses to be scaled and used in tables, diagrams, alarming, logging and trending. The software reads electrical and non-electrical utilities, such as pulses from gas, water, or steam detected by monitoring devices, to determine true energy and utility costs.
An interactive graphics add-on module animates real-time status for electrical equipment (e.g. breakers open or closed) and enables technicians to execute control commands facilitating quick response to maintain equipment operation. Alarm capabilities include notification of various system anomalies (such as over-voltage, phase reversals, or user-defined conditions) through workstation alarms, pagers, or e-mail. Events are sorted by date and time to assist in subsequent analysis.
Extensive waveform control capabilities enable users to overlay voltage and current for each phase, all phases of current, or all phases of voltage. This allows owners to identify power quality issues that might have been undetected, thus reducing utility power usage and, points out Square D, possibly avoiding newly implemented power quality penalty charges from the utility.
Power Measurement Ltd. also offers its own software, called PEGASYS, that delivers broad-ranging capabilities similar to the packages from Siemens, Square D, and GE.
ASCO recently introduced Site Web 3000, a Windows-based power monitoring and management system that allows multiple engine generator paralleling systems to be controlled remotely or from a single desktop located on-site.
The system can perform network monitoring, data logging, system control, external monitoring, and power analysis. A systems summary screen gives a snapshot of both digital and analog data being monitored on the emergency power system. Normal, pre-alarm, and shutdown conditions are color-coded, with a flashing icon indicating a pre-alarm or emergency situation.
Protection and Mitigation Equipment
To avoid problems resulting from the time delay in transferring power to many of today's sophisticated controls and equipment, companies can use equipment that provides subcycle switching between two independent sources before critical loads are affected. S&C Electric Co.'s medium-voltage PureWave Source Transfer System, for example, utilizes two or more power-electronic switches to transfer from a lost or depressed power source (as occurs when a voltage sags or swells outside a preset level) to a good power source. If a facility has mechanical source-transfer switchgear, they can be upgraded to include these high-speed power-electronic switches. S&C Electric also manufactures UPS systems appropriate for an entire facility. In instances when a facility has sensitive loads interspersed throughout and space is at a premium, it might be more cost-effective to install such a full-facility UPS system. S&C Electric's PureWave UPS Systems, available in ratings from 380 volts to 34.5 kilovolts, provides back-up power for a minimum of 15 seconds, and may be applied with a back-up generator, providing there is 100 percent protection from extended power outages, the company says.
Controlled Power Company's UltraUPS is a true on-line double conversion UPS that provides accurate, high-frequency isolated gate bipolar transistor (IGBT) digitized power. This new UPS, which the company says exceeds all existing harmonic standards, offers an advanced battery management system that automatically determines the precise charge and discharge rate, maximizing run times and battery life. Available in modular or rack-mounting configurations in 3kVa and 5kVa sizes, the UltraUPS protects critical operations in industrial automation, mid-range computing, telecommunications, emergency lighting, and medical equipment applications.
American Power Conversion's Silcon DP300E three-phase online power protection unit, newly available in 240 and 320 kW units, is designed to support high-power factor computer loads and provide 20 to 30 percent more power protection capacity than double-conversion UPSs. The product is scalable, accepting up to nine units in a parallel configuration. The Silcon DP300E 240- and 320- kW units have a separate set of input terminals for the built-in static bypass switch, which, in the unlikely event of UPS problems, enables the UPS to transfer the load to an alternative source of power without interruption. The 240 -kW and 320-kW units also include APC's Web/SNMP Management Card, which allows users to identify potential problems and manage all APC devices via Web browsers and industry-leading management platforms.
Best Power recently introduced Axxium TriStar, a double-conversion, three-phase UPS. Designed to protect mid-range computers, telecommunications equipment, factory automation systems, and building management and security systems, it is currently available in 10- and 15-kVa models, and will be available in 20-, 30-, and 40-kVa models beginning in April. According to the company, the unit reaches an operating efficiency as high as 94 percent, with an input power factor correction that can exceed 0.98, resulting in lower operating costs from reduced kW charges and lower varhs charges from the utility supplier. Axxium TriStar's modified input circuit also reduces total input current harmonic distortion to less than 15 percent, Best Power says, saving the additional costs of harmonic filters and floor space.
Chloride Power Protection offers a variety of UPSs for the three-phase and single-phase markets. The EDP70 and EDP70L series cover 10kVa to 250kVa three-phase. Designed to protect advanced data processing equipment, telephone system, industrial computer and lighting system, the EDP70 series features microprocessor-based controls and diagnostics. The company's EDP90 series covers up to 3,000kVa with parallel and redundant systems. Chloride provides protection for the single phase market from 4kVa to 18kVa, with units that offer a proprietary "intelligent switch" that, notes the company, enables the product to operate in either the "energy efficient" mode or the "double conversion" mode.
Innovative Technology, Inc. manufactures surge suppressors for commercial and industrial applications for alternating current (AC) power, data, and telecommunications meeting the standards as defined by American National Standards Institute/Institute of Electrical and Electronic Engineers (ANSI/IEEE) C62.41. Their surge suppressor devices, under warranty for 20 years, are rated for use in categories A,B,C, and under high exposure, medium exposure, and low exposure under either general purpose loads or mission critical/sensitive. The I.T. Protector Surge Protective Device, for example, features a multi-stage hybrid active tracking network circuit that utilizes a base threshold response network circuit and adds a multi-stage hybrid active tracking network for, says the company, "superior suppression" of both switching generated ringing and high energy impulse generated transients. The company also offers an optional diagnostics package for AC power panel suppressors, complete with surge counter.
Powerware Corporation's 9315-750 is a 750 kVa UPS for data centers, server farms, and other enterprise computing and industrial applications. It can be paralleled for N+1 redundancy and applications that exceed 750 kVa can be paralleled to increase the capacity of the overall system. This paralleling can be achieved using Powerware Hot Sync technology, which significantly increases the availability of protected systems and allows additional modules to be added as capacity grows, according to the company. Options with the Powerware 9315-750 include: Outcall Paging/Remote Notify system, which automatically calls for help if power or equipment problems occur; advanced software management for remote monitoring; and performance and trend analysis, with Powerware's FORESEER software, which enables administrators to identify and prevent power problems before they happen.
Leviton Manufacturing's line of power quality products for residential, commercial, and industrial applications includes panel-mounting devices for installation at the service entrance. These provide protection against external surges that enter the AC power lines, and branch-panels and point-of-use devices to protect equipment throughout a facility from both internal and external surges. The point-of-use devices are available as hard-wired receptacles, plug-ins, plug-strips, power control centers (for computers and peripherals), and low-voltage and data-line surge protective modules for data communications, CATV, and phone lines. The company also offers power line conditioners for a wide variety of commercial microprocessor-based equipment by maintaining the "zero" reference ground critical to logic circuitry.
Cutler-Hammer has a facility-wide approach to power quality disturbances. Its Clipper Power System surge protection devices can be placed at the electrical distribution system to eliminate voltage-transient and electrical noise disturbances and protect sensitive electronic equipment from high and low energy transients. Incorporated into panelboards, switchboards, switchgear, and motor control centers, the system consists of transient voltage surge suppression (TVSS) and active hybrid filtering (55 decibels @ 100kHz). The device features a zero-lead length direct bus bar connection which, states the manufacturer, eliminates many of the problems that can arise in traditional installation methods. By integrating surge protection into the distribution equipment, the Cutler-Hammer system reduces the amount of wall space.
Ferraz Shawmut's TVSS uses metal oxide veristors (MOVs) to limit overvoltages caused by lightning or switching to levels below those which cause damage to equipment. As MOVs are susceptible to failures caused by excessively large surges or sustained overvoltage conditions, the use of Ferraz Shawmut's VSP fuses with thermally protected MOVSs (TPMOVs), the company says, protects equipment and systems from sustained overvoltages as well as from potential short-circuit conditions caused by MOV failures.
Whatever the mix of products you select, providing power quality solutions to your clients can be a good generator of revenues that could compensate for any brownouts in your own workload.
The FELDMANS write on trends and products, including computers and electronic commerce technologies, for the electrical and general contracting fields. Authors of Construction & Computers (McGraw-Hill), they can be reached at firstname.lastname@example.org or at (914) 238-6272.
Companies mentioned in this article:
American Power Conversion (APC): www.apcc.com, 800-800-4APC
AMPROBE Instrument: www.amprobe.com, 800-477-VOLT
ACR Systems Inc.: www.acrsystems.com, 800-663-7845
Automatic Switch Co.: www.asco.com, 800-937-ASCO
Best Power: www.bestpower.com, 800-356-5794
Chloride Power Protection: www.chlorideups.com, 800-239-2257
Controlled Power Company: www.controlledpwr.com, 800-521-4792
Cutler-Hammer: www.cutlerhammer.eaton.com, 800-957-7050
Dranetz-BMI: www.dranetz-bmi.com, 800-372-6832
Ferraz Shawmut: www.ferrazschawmut.com, 978-465-4259
Fluke Corporation: www.fluke.com, 800-44-FLUKE
GE: http://ge.com/industrialsystems/pmsys/index.htm, 860-747-7295
Innovative Technology, Inc.: www.itvss.com, 800-647-TVSS
Leviton Manufacturing Co., Inc.: www.leviton.com, 800-824-3005
Power Measurement Ltd.: www.pml.com, 877-638-3748
Powerware Corporation: www.powerware.com, 877-797-9273
S&C Electric Company: www.sandc.com, 773-338-1000
Siemens Energy & Automation, Inc.: www.sea.siemens.com, 800-964-4114
Square D company: www.squared.com, 847-397-2600