电源管理Helps Your Plant ‘Live Long and Prosper’

栏: Superconductivity gets into the act Power management in action

Management of industrial power means many things to many people. Available technology ranges from increasingly sophisticated devices that meter power consumption, monitor quality, or provide emergency backup, to full systems able to do all that plus overview usage of power for efficient production and diagnose and possibly prevent outage problems. The latter technology is the focus here. These power management systems also represent the leading edge of a trend to integrate with manufacturing controls to form one plant system.

Intelligent, productive power management translates to the need to know a lot more about the plant’s power requirements—details of load profiles, where and when power is consumed, etc. This is where power management systems (PMs) can become a significant tool.

Related issues of power quality and reliability are receiving new scrutiny because of utility deregulation. Users will have to pay greater attention to specifying, purchasing, and operating plant equipment in this new era. The potential of electrical cost savings also will be there, but dependent on the knowledge of users.

Last great frontier

Pittsbur Cutler-Hammer,伊顿公司(碳氢键gh, Pa.) regards managing the electricity that powers production the “last great frontier” for cutting costs from manufacturing.

“Today, power management systems can be directly linked to plant control systems,” says, Frank Pulaski, applications and systems manager at C-H. This contrasts starkly with the scene just 10 years ago, when information for production, quality, and inventory were often gathered in separate data systems—even within the same facility. “Too often, maintenance and production engineers came together only in staff meetings,” he states.

Existing technology hampered efficient maintenance and production control functions. Without a convenient way to measure power usage, maintenance engineers found it difficult to control energy costs as they tried to balance loads and reduce breaker trips. Production control specialists also were frustrated by the cost and complexity of computer integrated manufacturing. “Proprietary control systems and lack of standard communication networks made connectivity difficult to implement and costly to maintain,” comments, Brian Brickhouse, automation marketing manager at C-H (Westerville, O.).

Times have changed. Linking of power management and plant control systems—with unified information flow—offers numerous advantages, among them cost savings and a “new level of predictive maintenance.” C-H cites proactive replacement of equipment as one benefit of such total control. For example, monitoring energy usage of a motor over time can predict wear out in a cutting tool or when the motor is likely to fail. It avoids downtime and making bad product.

Other productivity drivers of today’s PM systems include tying power variations (voltage sags, swells, etc.) to product quality deviations by analyzing process flow, and tracking energy cost of a product throughout the manufacturing process, says Cutler-Hammer. True cost of making a given part should account for energy cost, as well as labor and materials.

Smart devices have played a major role in PM systems, much like linking factory floors with plant business systems. And, Ethernet and standard “connectivity tools” like Microsoft ActiveX and DDE are the integration tools to make it happen. “That integration has been in simple straightforward software, putting information in front of decision-makers in real time,” adds Mr. Pulaski.

Cutler-Hammer’s PM system offering, called IMPACC (Integrated Monitoring Protection and Control Communications), includes metering devices, protective relays, circuit breaker trip units, and motor starters. The elements communicate over a noise-immune network to a central location for remote monitoring, alarming, trending, and control. About 2,000 IMPACC systems are installed. IMPACC’s software component analyzes energy usage and power quality. It coordinates loads, turning loads and equipment on/off as needed and predicts maintenance needs.

Controls’ changing scene

Bill Whitehead, senior application engineer for Siemens Energy & Automation (Alpharetta, Ga.) likewise notes progress of power management from its limited, costly days, when data had to be gathered manually and interconnect devices to collect and analyze data were not readily available.

But, functional capability and availability of PM systems have advanced rapidly with microprocessor-based monitoring/control devices and computer networking. “The result is a significant new potential for increasing power system reliability while lowering system operating costs,” says Mr. Whitehead. “This, along with utility deregulation, is causing a growing number of industries to develop comprehensive new energy management strategies to help maximize valuable energy resources.”

Mr. Whitehead sees growth in customer requests for unified power management and control systems. “People want to look at one set of operator interface screens,” he remarks. “There is also the need for engineers in one department to communicate freely with those in another.”

He views power management as a complicated arena, due to the complexity of most power systems. An effective PM system requires sophisticated field hardware and software to gather, analyze, and display data—in, or close to, real time—if plant personnel are to make proactive decisions.

监控设备可以连接到plc或DCS via a data transfer unit interface, for example, using Modbus RTU or Profibus DP. In a PC-based approach, software such as Siemens WinPM runs in the background and links to an MS-Windows master control system’s HMI front-end, using DDE, OLE, and ActiveX tools.

Complex task

Ralph Rio, Cimplicity manager, GE Fanuc Automation (Charlottesville, Va.), agrees that power management is complex. He regards finding the causes of power spikes and avoiding their future occurrence as a much more complex (and useful) task than just tracking power usage. Still, the latter provides valuable information. “Power companies charge per kilowatt based on a forecast. If usage peaks above forecast, a premium is applied to all power used that month,” he says.

Manufacturing plants can save thousands of dollars per year if power usage can be made more efficient and its significant trends identified. “Software tools for power management allow facilities to avoid peaks in power consumption and thereby decrease costs,” continues Mr. Rio.

One solution developed by GE Fanuc, together with GE Electrical Distribution & Control, is Cimplicity PMCS (Power Management Control System). This HMI software package features a wide range of power management tools: facility planning, cost allocation, load manager, diagnostic waveform capture (photo, next page), wizards for easy configuration, and an event logger.

Among PMCS tools, diagnostic waveform capture identifies the negative effects of nonlinear, harmonic-generating loads so that corrective action can be taken to reduce downtime. The load manager tool helps avoid peak-demand surcharges. “The load manager allows users to create routines for automatic shutdown of loads when a peak-demand threshold is approached,” adds Mr. Rio. Users can further schedule automatic shutdown of selected loads or zones within a facility. This can be done daily, weekly, monthly, or by a “custom pattern.” For example, if some rooms are unlikely to be used evenings or weekends, the load manager switches off lighting and equipment to avoid wasted power.

Cimplicity PMCS links to plant equipment such as switches, breakers, meters, and PLCs. It communicates with higher level, plant-wide systems. Connectivity to devices is accomplished through Modbus RTU or Ethernet. “Connecting power management systems with manufacturing process control systems offers a powerful solution,” remarks, Mark Hall, application solutions manager, Square D Co. (La Vergne, Tenn.). Square D’s perspective stems from potential electric service interruptions that translate to the tremendous cost of lost production, particularly for continuous process plants. “By linking the two systems, process and plant engineers can learn more about their power usage to avoid costly shutdowns and operate with peak efficiency.”

But, this trend is not well established. Many manufacturers resort to automatic load shedding (of noncritical loads) and on-site power generation to assure reliability. According to Square D, some users with critical power needs—for example, refineries, data centers, and semiconductor fabricators—run their generators constantly, while using PM systems to manage other power control methods. Such users have the most to gain from PM systems, not just to avoid outages but operate as efficiently as possible.

“Power management system suppliers are responding with products that can communicate over a variety of networks and work seamlessly with process control systems,” adds Mr. Hall. He uses load shedding to illustrate how PM systems are useful to make informed decisions. Indiscriminate shedding can be avoided if engineers have exact data to decide “how much to shed, which loads, or whether to shed loads at all.”

Within the growing community of PM technology providers is Power Measurement Ltd. (Saanichton, B.C., Canada). Its hardware and software products provide complete power management for smaller facilities, and data gathering/monitoring functions for any size plant, according to applications engineer, Rudolf Carolsfeld. The company’s Pegasys 2.0, MS-Windows NT software is a suite of applications that offer a view into various PM functions, such as power consumption, quality, load trending, etc. Pegasys has web browser access, interfaces with Ethernet and existing plant networks, and can be used alone or in a distributed system.

Deregulation cometh

Utility deregulation now unfolding in the U.S. offers both challenges and opportunities for industry. Ability to integrate PM systems with plant controls has high potential for energy cost savings.

One possibility—using the added information—is to negotiate better energy rates and reduce energy consumption, according to Cutler-Hammer (and other suppliers). PM software can provide energy bills for individual departments or machine processes. C-H also sees more manufacturers starting to analyze how, when, and where they’re using electricity. “As they begin to understand how power quality and reliability issues impact their businesses, they will be able to take fuller advantage of these new opportunities,” explains Mr. Brickhouse. (And users need to learn more, as a survey of power management/quality issues indicates. See following article.)

Siemens’ Mr. Whitehead also mentions the potential for automated billing and sub-billing for accurate cost allocations by department, process, etc., coming from a PM system. As for deregulation, he points to a greater need for users to know the quality of electricity purchased from their utility. “Reliability will be the weak link in the chain,” he adds. “Power monitoring and management tools will become more valuable as deregulation becomes a reality.”

Square D likewise notes its customers’ concerns about reliability of power as utility deregulation occurs. Many manufacturers link the incoming power feed with their power generation controls to manage loads, preserving critical loads during an outage. “Load shedding and back-up generation also are critical to avoid a peak demand, thus saving thousands of dollars in extra utility costs and penalties,” says Mr. Hall.

Lastly, Square D’s Mr. Hall says humans still factor into the equation—departments also have to work together to operate plants efficiently. “Unfortunately, plant and process engineers often don’t communicate or work proactively together until there’s a problem—and then it can be too late. Power is such a critical part of manufacturing they can’t afford not to work together,” he concludes.

This is where power management systems have a growing future.

Superconductivity gets into the act

Methods and devices abound for minimizing power sags and outages—for example, transient voltage surge suppressors, UPSs, and backup generators, to name a few.

一个不同的、高科技的方法,倡导的American Superconductor (ASC, Westborough, Mass.), involves a superconducting magnetic energy storage system, known as a micro-SMES. In a SMES, current flows in a superconducting coil, generating a magnetic field that stores electric energy (diagram). Supercooled by helium at 4.2 K, the magnet coil of niobium-titanium wire offers minimal electric resistance and, when charged, holds “large amounts of current over substantial time periods with very little power loss,” states ASC. The whole SMES—including the cryostat that contains the magnet and its liquid helium bath, refrigeration, and control devices—fits into one trailer for portable application.

“SMES targets power sags of very high power (1-10 MW) and short duration (1-2 sec range), withicro-SMES can be configured to control different service voltages, supplying 400-950 V dc input to an inverter.

Micro-SMES is an existing product, with seven units installed in the U.S. and one in South Africa. Current production program is 10 systems per year. Typical cost range is $400-600 per kVA. “Main applications are in pulp, paper, and plastics industries, involving heavy motor loads and inertia changes,” adds Mr. Abel.

Power management in action

AK Steel Corp. (Rockport, Ind.), a newly built steel manufacturing facility, has taken the first step to fully integrate a power monitoring system into its process control system. This union was considered right from the initial design as AK Steel challenged all three construction contractors (Eichleay, Siemens Systems, and Cegelec) to fully integrate all systems across an Ethernet backbone into one HMI package (Intellution’s Fix Dynamics).

Eichleay和西门子选择集成工厂的s intelligent devices into the HMI package via a data transfer unit interface. Cegelec used Siemens’ WinPM 4.0 power management software with DDE functions to collect data from the monitoring, control, and protection devices. Now, one system handles alarms from anywhere in the plant, with access at any of 50-plus nodes.

AMP Inc., a leading global supplier of electrical connectors and interconnect systems, uses electricity as a competitive advantage. At its Greensboro, N.C.-plant, AMP runs three shifts, coping with frequent, overnight product changes and the need to reconfigure equipment or production lines. At AMP,

Square D Co.’s PowerLogic Power Monitoring and Control System is used to manage the available electrical system capacity (see lead photo). This is one of 10 plants (with a total of 30 monitors for 300 circuit breakers) tied into a network feeding information to PCs in each plant. Operators can dial up a system overview or display status of any branch circuit from a central location in Winston-Salem, N.C., the corporate center (Harrisburg, Pa.), or each facility.

One application of GE Fanuc’s Cimplicity PMCS is power management at General Motors’ Spring Hill, Tenn. Saturn automotive plant. The goal was to reduce energy consumption by 10% during the first year of operation. This would pay for all the computer systems installed at Saturn (not just the Cimplicity system), according to GE Fanuc Automation.

A large power consumer at the Spring Hill plant was the air conditioning system, with several compressors powered by 5,000 hp motors. Automatic peak load shedding of air conditioning was considered (while production processes keep running), but the decision was for PMCS to only generate an alarm when demand was rising too high. Starting and stopping such large motors remains an operator decision.

PMCS monitors the various manufacturing processes, advising each area manager in the plant of how much energy is being used. This helped target efficient operations and achieve the above energy savings goal. Return on investment was said to be “less than three months.”

In early 1997, Cutler-Hammer installed a PM system in its Asheville, N.C. switchgear manufacturing plant, where energy bills ran nearly $45,000 a month. IMPACC system (see main text) helped plant engineers identify wasteful practices, shift loads to level demand, and do preventive maintenance. A process using large electric ovens was moved to later shifts with lower total energy demand. Maintenance technicians rely on IMPACC screens to spot abnormal conditions and service equipment before a breakdown. In the first six months of operation, IMPACC reduced the Asheville plant’s energy costs by $40,000. Return on investment, set at less than two years, was achieved in 14 months.

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