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1 Justifying and Planning an Energy Monitoring System In an Existing Plant 1995 IEEE. Reprinted with permission, from Proceedings of the Petroleum and Chemical Industry Conference, Denver, Colorado, September 11, 1995, Pages 13 to 19 Anne P. Stublen Craig M Wellman Steven A. Kell Member IEEE Senior Member IEEE Member IEEE E.!. du Pont de Nemours E.L du Pont de Nemours E.!. du Pont de Nemours and Company and Company and Company Louviers Building Louviers Building Louviers Building P.O. Box 6090 P.O. Box 6090 P.O. Box 6090 Newark, DE Newark, DE Newark, DE Abstract - Many electrical distribution specialists are using power monitoring systems to improve the effectiveness of their facilities. Information from power monitoring systems can be used to minimize permanent investment, reduce variable cost, and improve process availability. These benefits are discussed, and examples of suc:::cassful system implementation are given. Types of systems are described, and an approach to system planning is suggested. INTRCJCTION In order to stay healthy and competitive, businesses are using manufacturing metrics to help drive their goal of making profits in the most efficient way possible. When they are efficiently managed with power monitoring systems, electrical distribution systems can have a significant positive impact on many metric drivers. Monitoring systems, which many large companies are using successfully, can track energy usage within the plant, allocate costs, manage load, and collect information that can be used to identify equipment or operating problems. In addition, these systems can help reduce capital costs for power system expansion. This paper begins with an overview of power monitoring, describes system possibilities. and discusses system Table 1 Benefits of Power Monitoring Systems planning with a focus on how the latter is driven by business needs. System options are then developed for functionality, computers, and transmitters. The second half of the paper explains primary benefits such as avoided investment, improved cost allocation, demand control, and energy conservation. Other benefits in operation and maintenance are also discussed. AA OvERVIEW OF PO'M:R MoNITORING A modern power monitoring system begins with transmitters n electronic meters, trip units, or relays that are installed in switchgear to monitor system operations and energy use. These units are then linked to multiplexers, which can report to a central PC or minicomputer. They can provide information on voltage, current, power, breaker status, and waveforms. System capabilities include kilowatt-hour integration, alarm management, demand trending, and graphic displays. With the information provided by the power monitoring system, it is possible to take specific actions that can have a significant impact on process availability, permanent investment, variable cost, and fixed cost (see Table 1). Further discussion of how to use the information from power monitoring systems appears in the following sections. Manufacturing and Finance Drivers Benefits of Power Process Permanent Variable Monitoring Systems Availability Investment Cost --.;...--""""1 Avoiding investment Justifying minimum investment Improving cost allocation Implementing peak shaving Managing interruptible load Improving energy conservation Monitoring operation through displays Obtaining load switching information Monitoring equipment reliability Capturing disturbance waveforms Capturing harmonic waveforms 182 Proceedings from the Twentieth National Industrial Energy Technology Conference, Houston, T, April 22-23, 1998

2 SYSTEM POSSIBILITIES This section explores the varied possibilities for assembling a power monitoring system. These range from systems allowing complete remote monitoring to less capitalintensive systems offering more limited functionality while maintaining cost benefits. The oldest existing monitoring systems were assembled on shoestring budgets using separate, inexpensive components and watt transducers and were connected to existing Vax computers. While the older systems have proven the value of power monitoring, they are not necessarily the best approach today. System Planning Business-Focused Vision: Before beginning to implement a power monitoring system, it is important to develop a site vision or long-term plan. If this is not done, a vendor that has been selected or hardware that has been installed may not adequately address business needs. A system may have to be replaced later, or the site may incur undesirable lost opportunity costs. Table 1 illustrates benefits as they relate to business drivers. Note that not all benefits are needed on all sites. For example, harmonic monitoring is only needed on substations with tuned filters. Disturbance monitoring is only needed on purchased power substations and on large adjustable speed-drive applications where power dip ridethrough isa concern. The maintenance system option is only worthwhile to the extent that equipment is compatible. Benefits must be related to avoided business costs. For example, the cost of outages for each business relates to process availability. Under permanent investment, include the cost of potential new substations and medium voltage feeders; count potential energy savings from interruptible load and peak shaving under variable cost. Conceptual Design and Estimating. When a preliminary vision of worthwhile benefits is in hand, a costlbenefit test can be applied. The steps necessary to develop cost include preparing a conceptual design scope, preparing system specifications with hardware and software functions, soliciting quotations, and developing installation estimates. A range of functionality options, system options, and sensor options can be included in the specification to allow vendors flexibility and draw out the most cost-effective proposal. Varied approaches may be taken for different businesses on the same site and for future versus existing equipment. Cost/Benefit Testing: When expected benefits and estimated costs have been documented in the vision, the proposed system can be tested against business needs. Further development of needs versus wants and a schedule for implementation over a number of years may be necessary. Meeting the Challenge of an Older Plant: The installation of a monitoring system in an older plant brings additional considerations to the development of the site vision. Justifying the addition of a system to an existing site is much harder than providing one as part of a new electrical power system. Business-focused system planning should help here. Where older plants do not have independent instrument raceway systems, interconnection of devices becomes a major portion of the cost of installing a metering system. The layout of an existing facility spread over a broad area can then make the cost prohibitive. The use of phone lines, fiber optics, and remote data collectors such as PLCs can help minimize initial investment However, the reliability of the system must not be compromised by the misapplication of modems or other interconnection hardware. Using data collectors strategically located in the field may also be helpful if the cost of other utilities such as steam or gas must be allocated. Flow transmitters can be integrated into the system by using analog input cards. FynctionalitY Options Full Remote Monitoring: Table 2 shows field transmitters required for full remote monitoring. They eliminate the need for patrols to read wattmeters or to perform routine maintenance inspections while maintaining process availability. The table includes all electrical variables desired for recording, trending, alarming, and cost allocation, as well Table 2 Process Area Substation: Complete Field Monitoring Functionality Typical For Each Substation Continuous Inputs captured Waveforms Computed Data Alarms Quantity Motor Circuit Protection Breaker Heater Transformer Power Monitor Relay Trip Unit Monitor Monitor I (3), V (3), Breaker Status I (3), V (4), Breaker Status 1(1 ) T,P, Pressure Relay I (4), V (3), Breaker Status Disturbances, Harmonics kw, p.f. kw, kva, kw, kva, p.f. p.f. y y y y y 1 per medium voltage motor 1 per circuit At least 1 per substation 1 per transformer 1 per bus 183 Proceedings from the Twentieth National Industrial Energy Technology Conference, Houston, T, April 22-23, 1998

3 as status inputs for a software-based mimic panel. Transformer and switchgear heater monitoring are included to allow reliability monitoring. Disturbance capture and harmonic snapshots are listed, although they may be extra cost features and should be justified on their own merits. Figure 1 shows information displays, alarms, and report capabilities at various locations that meet the needs of several different system users. Using the functionality shown could certainly contribute to an increase in woridorce prod uctivity. Power-Only Monitoring: Several chemical plants have implemented a power-only system using watt transducers. The system easily allows power allocation but provides no data on power factor. Although power factor can be estimated, it can vary based on motor.loading. Transformer and cable loading is based on current, so power measurements alone are of limited value. While the full remote concept may be out of reach, power monitors that report kva on medium voltage feeders and transformers are highly recommended as a minimum system. The National Electrical Code's requirements on using kva demand figures to determine existing load are discussed in the subsection on avoided investment. Using Existing Meters: Two problems arise in implementing any remote system. Many plants currently use hard-wired local metering, and these businesses often have little capital available. When a company builds a new site or puts in new substations at an existing site, full remote microprocessingbased monitoring systems are easy to justify. They save the cost of hard-wired monitoring and help ensure process availability and capital productivity for operations and high productivity for maintenance. However, the cost of a retrofit installation can be quite high. Looking on the bright side. however, it is possible to accomplish some of the biggest benefits of power monitoring, for example, avoiding investment and justifying minimum investment, with existing metering and no capital investment [1]. Employees currently taking watthour meter readings can also take demand meter readings and reset the demand functions, and data can be manually added to a spreadsheet. This system might be called a hardwired, legbased monitoring system, and since records are kept on a spreadsheet, it can still be considered computerized. Labor is certainly short, but the efficient operation of existing facilities depends on obtaining benefits such as these, and even using such simple systems could result in substantial savings. Computer Qptions PC Option: Most vendors offer a standard PC-based system that uses their standard power monitoring software and allows easy configuration for the application. This system can ride on an existing site broadband or Ethernet network independent from the site process monitoring and control system. However, if multiple PCs are used the software cost can be quite high. Process Monitoring and Control (PM & C) System Option: A PM & C system operates on a broad band or Ethernet network. Such a system can display live values, monitor total loads, log 24-hour totals, and generate a monthly report of total kilowatt hours for each circuit according to business unit. It can easily provide all functionality of the full remote system shown in Figure 1 except disturbance and harmonic monitoring (waveform capture). The basic configuration provides functionality for monitoring, alarming, data archiving, and simple displays for viewing information. The effort required for configuration is similar to that of a vendor's Process Unit 1 Power Monitors Process Unit 2 Power Monitor Purchased Power Power MonItor Electrlcel Shop Engln..r's OffIce Telephone Lines Mimic Panel Harmonic MonlDring or PC_ DisllJrtl8nce MonilDring Power System AJanns System SlallJs Swill:hing Planning Demand Conll'lll Demand MonilDring MitTie Panel Po_ System AJanns System SlaIIJs Cost Allocation Load Analysis Harmonics Analysis OisllJrbance Analysis Figure 1. Complete Display Functionality li ocs - I cw.. =_ Fm- 184 Proceedings from the Twentieth National Industrial Energy Technology Conference, Houston, T, April 22-23, 1998

4 Process Unit 1 Power Monitors Process Unit 2 Power MonItor Purchased Power Power Monitor Electrical Shop Engineer's Office relephone Lines PC PM Interlace Board PM Software Con~gu'alion.-- ~oca Figure 2. PM &C and PC Combination Hardware and Software lioc.s~d"" I "---. "'==--1 proprietary power monitoring system; however, an additional data link connection to the computer is needed. In addition, power monitoring system interface software will be needed in the PM & C system. High interface development or support costs could affect decision-making for some system users whose site operation philosophy or investment base drives them to use the PM & C system. They may have to go to a vendor's power monitoring system different from that of the substation or to transmitters with more standard interlaces. Figure 3 shows the concept for a large chemical plant's maintenance system. It covers power monitoring, adjustable speed drives, burner management systems, and mechanical package system PLCs. Of the many PLCs in the system, only one is provided for common functions such as power monitoring. Others are provided as part of package systems. The principle cost of tying everything together is in interface software. Interlaces operate between the power monitoring hardware and the PLC and between the PLC and the DCS and the PC. PM & C and PC Option: A combination PM & C and PC system (see Figure 2) can provide all desired functionality with considerable flexibility. Using this option can lead to maximum benefits and is therefore the system of choice when using a PM & C system and if on-line harmonic or disturbance capture is required. Maintenance SYStem Option: The most modern approach to system options is to look at all eledrical maintenance data needs as a whole. Presently, most electrical equipment has microprocessor-based controls, with vendor's standard diagnostic software available. This software can run on PLC data links. but not on process control computers. A PLC-based maintenance system can be installed linking adjustable speed drives and power monitoring sensors to PCs in an ECR or electrical maintenance shop. The PCs can be permanently installed or portable. Drive configuration work can be done from the same PC that runs the power monitoring software. Links to the process control system can be established to carry only those alarms and status information need~d in a continuously manned location-the CCA. Control functions may run separately or on the same data link. I.. 11 Figure 3. Maintenance System Option I j OEMP\.C_ Proceedings from the Twentieth National Industrial Energy Technology Conference, Houston, T, April 22-23, 1998

5 This system was justified based on a study of life cycle costs. Using the maintenance system can mean significant reductions in troubleshooting time and repair cost, which are important considerations due to the site's maintenance philosophy. The planned power monitoring subsystem will include complete power monitoring in a PC and selected information in the DCS. DCS information is fairly complete and includes a high harmonic alarm. Transmitter Options Hardwired Transmitters: Hardwired transmitters with 4-20 ma output for watts, vars, current, and voltage are available from a number of vendors. So far, most older chemical plants just use watt transmitters. Using only watt transmitters and taking advantage of existing metering transformers has been an inexpensive way to add power monitoring. However, with the greatly expanded capability of microprocessor-based transmitters, simple transmitters are not likely to be widely used in the future. Microprocessor-Based Transmitters: These versatile transmitters are built into meters, circuit breakers, and relays. Monitors with basic functions such as watts, voltage, current, and kva are being widely installed in new substations. Power circuit breaker trip units with data link capability are also being installed. The cost is being justified in part by installing this equipment in place of hardwired metering. Use of these devices can lead to accomplishment of all the benefits of power monitoring. Many sites are adding microprocessor trip units to eisting 480V power circuit breakers. In particular. it is desirable to retrofit microprocessor trip units where either no trip units exist or electromechanical trip units are used, or where a motor is served from an electrically operated breaker. In many of these cases, microprocessor trip units with communications capabilities can be justified. On-line harmonic and disturbance snapshot capture are worthwhile on substations with large adjustable speed-drive loads. When a voltage dip causes loss of production. it is important to know if the dip exceeded the drive ride-through rating or if the equipment was not performing as expected. If a design depends on capacitors to limit harmonics or improve power factor. the right sensor can produce an alarm on failure before a substation is overloaded with vars or overheated due to harmonics. There are two types of microprocessor-based transmitters on the market-those sold as part of a system and that operate on a vendor's proprietary data highway, and those sold as single units with RS-232 or RS-485 interfaces. All the large electrical suppliers manufacture proprietary systems, and several suppliers sell single unit monitors. Data links are usually designed so that a failure in one device does not affect the communication capability of others. However. the affordability of interfaces is a major concern with these systems. While users want the ability to communicate between different vendors' systems. vendors have been slow to respond to that need. The authors believe that Field Bus, a communication standard that will provide that capability, will be applied on microprocessorbased transmitters before it replaces conventional instrument loops. Installation and Maintenance Considerations: When specifying monitoring transmitters, it is important to consider maintenance needs in order to avoid a shutdown when maintenance is required. Protective relays and wattmeters are installed in cases that have shorting blocks to allow pulling the relays without opening the current transformer circuits. Ammeters are normally installed with shorting blocks or switches. For power monitoring sensors, test blocks can be installed to enable maintenance without a substation shutdown. PRIMARY BeNEFrrs OF USNG POWER MoNrrORING SYSTEMS To develop a business-focused vision, the benefits for a particular site must be clearly understood. Primary benefits that are likely to provide the most justification are Jeseribed separately from other benefits that. while useful, provide more limited help. All benefits discussed are listed in Table 1. Users will think of additional benefits. Avoided Investment A power monitoring system can have a significant impact on permanent investment by enabling a site to avoid capital expenditures for additions to its electrical distribution system. For example. sometimes site engineers do not know if there is enough existing capacity or if expansion is necessary, and performing a surveyor recording information over several days often does not give an accurate picture of feeder and substation loads, especially in process units that make a variety of products or run at different rates. A power monitoring system can provide continuous. long-term data logging and trending that accurately reflects equipment loads. When available capacity is well understood, electrical system upgrades can often be delayed or limited in scope. As an illustration. prior to the installation of a power monitoring system, one chemical plant did not completely understand its feeder loads. Although certain conditions could lead to an overload on the site, available information did not provide an engineering basis sound enough for submitting corrective projects. This site was able to install a power monitoring system that saved $1 million in medium voltage feeder costs by providing a solid engineering basis for installing capacitor banks at the end of a feeder to release capacity. In the National Electrical Code. Article covers optional calculations for additional loads in existing instal/ations. The code allows the use of kva demand figures to determine the existing load on a service or feeder and requires that "the maximum demand data is available in kva for a minimum of a one-year period. If that criteria can be met, the load can be added to the extent that the existing demand at 125 percent plus the new load is equal to the feeder rating. The feeder must have adequate overcurrent protection. Providing monitoring and collecting the data helps take advantage of this code option when an expansion project arises. 186 Proceedings from the Twentieth National Industrial Energy Technology Conference, Houston, T, April 22-23, 1998

6 At one chemical plant, modernization and expansion projects required new substations, but single lines were out of date. A load study had to be prepared quickly. While the plant updated all single lines to establish connected load, operating load data logged by the power monitoring system was collected for analysis. When the load study was complefe, the need for just two new unit substations became clear, and low demand factors on some loads enabled the combination of some feeders to free up breakers. Improyed Cost Allocatipn Power monitoring systems allow a site to allocate energy cost by following each process unit's energy usage remotely, resulting in three main benefits. First, time is saved in reading meters in the field, which is helpful when plant workforces are reduced. For example. one site with rapidly changing businesses now has an employee working full time installing and operating recording watthour meters to allow load allocation. Second, cost allocation can be computed automatically. which also saves time. For example, a power monitoring system with a cost accounting spreadsheet can take information from remote devices and then separate it according to business unit. Third, each business component can get a statement detailing its share of both energy usage and demand [2]. Existing hardwired systems have facilitated the charging of energy costs, but now costs of demand peaks can also be allocated. Fourth. for PLC-based systems. several different utility costs can also be allocated using one PLC system and data links. Utilities of concern in large plants include steam, cooling water, compressed air, and natural gas. Thus, each business group can become more accountable for using energy efficiently, which could cut costs significantly as energy conservation programs encourage businesses to address energy more aggressively. Demand Control Implementing Peak Shaving: A large part of any site's energy bill is the demand charge. The demand charge is based on the highest electrical demand during a given month multiplied by a dollar value. It is typically measured over any 15- to 30-minute period during the month. The demand charge compensates the power company for the cost of installing equipment large enough to supply its customers' highest demand. A large peak can mean a huge increase in a power bill [3]. In the past, demand control could be achieved only by load shifting. Le., temporarily shutting down a large load. such as a furnace. auxiliary line. or generator, in order to decrease demand during a specific period in the day when loads were known to peak. In contrast, a power monitoring system can reduce variable costs by measuring every 15- to 30-minute period and predicting when a new peak is about to be set. Manual or automatic shutdown of equipment or deferment of a large motor or generator startup can then prevent a potential increase in the power bill [2]. One chemical plant is saving $ per year this way. Managing Interruptible Load: Utilities are looking for businesses that will voluntarily reduce or interrupt part of their load during peak hours. Sites with interruptible loads that are willing to work with the utilities can achieve substantial savings. When requests from the utility come in, usually a few times each summer, the site can reduce load by a pre-agreed-upon amount or maintain the load and pay a penalty. 8efore the advent of power monitoring systems, it was difficult to know if adequate load or more load than necessary was dropped. Now, however. a power monitoring system can track purchased power and individual feeder loading to ensure that commitments are met by each process unit. The purchase of generators cannot be justified solely to take advantage of load management programs; however, if standby generators are already in place or are being provided for other purposes, additional controls needed for generator synchronization can be justified. On-line power monitoring is considered essential to manage a loadshedding program and can be justified to support the program. Many sites are also taking advantage ot interruptible contracts by dropping nonessential load and starting available generators. Improyed Energy Conservation A power monitoring system can be an asset to any business's energy management program. A plant can realize significant energy savings if employees read even the most basic meters and use that information to direct their conservation efforts. Each department within a plant can maintain weekly or monthly consumption records that can immediately identify areas of potential savings. For example, a motor using a lot of energy may be running continuously because a valve is stuck in the open position, or an inefficient unit may be chosen to be shut down if its use is not essential to plant operations. Reporting the resulting savings to employees at the end of every month can encourage them to continue to set and improve their energy conservation goals [1]. OTHER 8 ENEFrrS IN OPERATION AND MAM'ENANCE Monitoring Qperations and Load Row through Graphic Pisplays Most power monitoring systems provide software-based mimic panels through which load flow and electrically operated circuit breakers can be monitored and sometimes controlled from one or more locations. At one chemical plant, such a system helped discover that the utility was occasionally wheeling through the site's 230kV transformers. Although this did not cost the site anything, the transformers were being loaded to a higher than normal level Without monitoring, the problem would have gone undiscovered. 187 Proceedings from the Twentieth National Industrial Energy Technology Conference, Houston, T, April 22-23, 1998

7 Obtaining Laad Swnchjng Information When a facility needs to switch between feeders for maintenance purposes, prediding feeder load is essential to prevent overloading. A power monitoring system can provide accurate, up-to-date information to avoid an overload and possible failure. It can also allow higher loading than system operators previously would have permitted. Finally, a power monitoring system can report trends in consumption and monitor voltage when problems are reported. Monnoring EQuipment ReliabilitY Maintaining high process availability is becoming more difficult as the plant forces that previously made routine patrols are reduced. A power monitoring system can track voltages, transformer temperature and pressure, switchgear space heater amps, and feeder load. For example, transformer monitors can transmit temperature and pressure on a power monitoring data link, and heater current can be tracked as a single circuit if existing heater circuits in a substation are combined. Feeder loads on 480V SUbstations can be monitored through circuit breaker trip units with data link capability. Finally, actual demands can be trended, which is especially worthwhile if connected load is close to or exceeds feeder rating. Mannaring Disturbances Many manufacturing processes depend on adjustable speed drives riding through power dips. A voltage dip caused by off-site lightning strikes or switching can cause drives to slow down or trip, resulting in lost production and process availability. Monitoring such a dip at the drive's substation bus can help determine if the dip was larger than the dip rating on the drive, or whether the ride-through system failed to perform. In addition, a power monitoring system's computer can capture and store information on disturbances in order to allow analysis of disturbances both at a purchased power substation and within the main plant. Many power monitoring systems have waveform capture as an optional feature. Harmonic levels and THO (total harmonic distortion) are computed automatically so that engineers can improve process availability by identifying and correcting harmonic problems. However, the waveform capture feature is recognjze~ as. ~n extra cost option (for some vendors) that may not be Justified because a portable meter can provide the same data CONCLUSION Power monitoring systems stand out among all plant equipment investments as well justified. Example installations demonstrate such benefits as avoided substation investment, improved cost allocation, demand control. and energy conservation. To capture the benefits cost effectively, business "owners" must plan power monitoring systems based on their business needs, and they must evaluate the many options available for the best fit. Options developed at various sites range from watt transducers in 4-20 ma loops. to standalone systems. to maintenance data highways. REFERENCES [1J W. L. Stebbins, Utility Monitoring and Reporting Systems: Key to Successful Energy Management, in Proceedings of the 6th World Energy Engineering Congress, 1983, pp [2] J. R. Bartoletti et ai., "Evolution of Power Management Systems for the 1990's, in Record of the 1991 IEEE Industry Applications Society Annual Meeting, 1991, vol. 2, pp [3J R. A Kennedy and O. N. Rickey, "Monitoring and Control of Industrial Power Systems, IEEE Computer Applications in Power, vol. 2, pp , October Proceedings from the Twentieth National Industrial Energy Technology Conference, Houston, T, April 22-23, 1998