Carol Brzozowski 2015-11-11 14:06:26
Facilities depend on an uninterruptible power supply or power source (UPS) to provide nearly instant power to a load when the main power fails, or an automatic transfer switch (ATS) to switch the load between the utility power and a backup generator when it senses a power outage. A load bank mimics a real load that a power source supplies to in real operation. The load bank serves the power source through its energy to test, support, or protect it. About Load Banks Whether load banks, ATS, or UPS systems are best rented or owned depends on the situation, says Bhavesh Patel, vice president, ASCO (Automatic Switch Company) Power Technologies, a business unit of Emerson Electric Company, which manufactures and sells transfer switches, power control systems, and industrial control products for business-critical continuity. Load banks also are part of the company’s portfolio. Load banks are needed to certify facility readiness before bringing in expensive equipment, notes Patel. For instance, a new hospital is constructed and before the expensive medical equipment is installed, there must be assurances that the systems will operate properly from an electrical standpoint. “You use the load bank as if it is the MRI equipment that is consuming electricity,” he says. “That is how you test the electrical infrastructure—the distribution within the normal facility—to make sure that everything is OK before you put in the MRI equipment.” Because testing is predominantly done at the beginning of the site installation and commissioning, a good chunk of load bank opportunities are rental in nature, says Patel. But there are situations that call for a permanent load bank installation, such as the hospital example cited above, and in critical data centers; they are required by code to test on a regular basis, or some have to test because of business conditions. In choosing the appropriate load bank, the first consideration is size as well as future plans, Patel says. “You may start a data center that has a certain computer capacity, but that is not the computer capacity functioning on day one. On day one, you might have 0.25 X computer capacity and five years down the road, you reach that full X computer capacity. You need the load bank to be sized to that entire range so that you can gradually add load as your computer capacity increases, rather than having to constantly change that equipment.” Getting and retaining results is another factor. “It’s more than just a pass/fail result. You need to be able to capture the details of the results,” says Patel. “You need to be able to get that electronically so it can be recorded and saved for future reference, such as if your facility is mandated to prove it has done the tests and you need to show the results to an inspector.” It’s important to do analytics and trending, which is accomplished through a load bank’s metering capabilities, he adds. With load banks, the path of the air flow needs to be kept clean, as there has to be enough ambient air flow as part of the design; the air flow takes away the heat, says Patel. “If it is not clean and gets clogged up, then the load bank will not be able to dissipate the heat that it generates each time it is used, and that degrades its capacity and creates other potential problems.” Real-World Examples An Arizona copper mine needed to test a new, 40-MW, low-emission, natural gas turbine generator deployed to augment local utility power in support of expanded mining and smelting operations, and turned to ComRent for help. ComRent assists mission-critical facilities that need to test their models under construction prior to energization. Load banks are one of the solutions ComRent offers. The most expeditious route the copper mine could take for its power needs was purchasing and installing a turbine, notes Terrence Whalen, director of sales. “As they were in the construction phase, they kept trying to wrestle with the fact that the typical way to commission a turbine is off the load of the facility,” says Whalen. “That represents a few problems. One: this was a high-efficiency 50-megawatt turbine, and they needed real small steps—small as 500 kilowatts—to prove out the commissioning process. We could not jeopardize this facility, because any outages that they would have could be detrimental—they’ve got an industrial process going on, and a lot of material could harden and additional costs and loss of revenue would result.” “The turbine that was being tested ran the process of air exchange while the staff worked in the mine,” continues Whalen. “During the mining process, microscopic particles float in the air. These particles can become ignited and with the presence of oxygen cause an explosion. The turbine works to exchange out the microscopic particles and replace with clean air to breathe. The importance of keeping the turbine up and running was critical to the life of the facility as well as to life itself.” In addition to the challenge of the operation not being in a position to lose power to the currently running plant, the cost to shut down parts of the plant to provide incremental load was too high, as the plant’s revenue averaged about $200 million per year. Elevation and high temperatures added more hurdles. ComRent’s team of five technicians provided seven CR922 medium-voltage load banks, two K975 resistive load banks, two 3,500-kVA transformers, switchgear, and 3,000-amp MVCB + fused disconnects. ComRent was able to deliver 40.862 MW at a unity power factor, which is strictly a resistive load at 13,800 V, to test the turbine generator, says Serafin Gutierrez, load bank technician. “We were able to achieve almost a full megawatt above what they were expecting from us. That was due to the amount of the load we had arrived with at the site. At that point, we continued eight to 10 hours of 40 megawatts constantly running on the turbine to a point where after that 10-hour run, the turbine manufacturer, the copper mine commissioning agency plus ourselves were all OK with everything being a success, and we shut down with everything in the loading sequence.” The process spanned two weeks. “The copper mine’s project managers were able to rapidly commission the gas turbine’s additional electrical generating capacity, eliminating the long lead times and high costs associated with extending additional local utility power to the mine, while also verifying the natural gas turbines’ operational capacity, emissions, and safety functions without impacting the mine’s ongoing mining and smelting operations,” says Whalen. In another case, a refinery needed to have its own power grid. “The problem is there was always a generator that was constantly not sharing the load or being friendly with the counterpart generators,” says Gutierrez. “They didn’t know how and why this was happening, so they requested us to bring in equipment so they could individually test each genset.” Three generators were tested in pairs: generator one to two, one to three, and then two to three. “They found out that the unit that was not being friendly was number two, which in turn was the one that they had the most reliance on and that’s why they were having issues,” says Gutierrez. “It would cause failure across not just that generator, but all of them would shut down. They needed to find a way to have constant and guaranteed load without having interruption to their service, their field, the pumps, and refinery. “Bringing in our equipment and our solution, they were able to find that single generator that was giving them problems and repair it. They are adding a fourth cogen into that system and looking at bringing us in to do that test to make sure the load sharing they were having a problem with originally isn’t having a problem again prior to putting that fourth one on.” Gutierrez says that a relay manufacturing company, that conducts modeling for utilities to show how their new line will react to customer loads, told him “they still see more than 20% failure when they energize due to construction errors.” He adds that, in many cases, a site is “about to put live power to a utility substation or turn on a generator when it’s in a mission critical situation, and coming toward the load test, they find a lot of the problems. It doesn’t show up until the moment they’re needing that power and now they don’t have it due to the fact that they were not able to load test. Eighty percent of the problems they find are prior to putting the load into play.” Digital Controls The movement from manual operator controls to digital controls is one of the big movers for Load Banks Direct, points out its president, Martin Glover. Digital simplifies data collection and enables master/slave operations, whereby a facility operator can use multiple load banks in parallel and control all off one controller. Another new development for Load Banks Direct is its 1,000-kW load bank. Mobile load banks are used in settings such as campuses and other large facilities where the need to move them from generator to generator, or another power source, is paramount. “They also can be rented for service companies,” adds Glover. Load banks are not only used for regular testing and maintenance of emergency power sources, but also as a supplemental load. “If you’re testing a load bank, you put that into the system for a period of time to conduct the test,” he explains. “But you can also put a load bank into the system as a supplemental load if you have a lightly loaded generator and you’re having issues relative to wet stacking. Lightly loaded generators can be challenged with unburned fuel and some of the effects on the generator relative to that.” Load Banks Direct has auto load level controls that will pull in a certain amount of load bank load as required to ensure a minimum on the generator at all times to help avoid wet stacking, Glover adds. In selecting the best load bank for the application, intended use is the prime consideration. “Rental and service companies need to look for robust load banks just by the nature of how they’re used and transported from site to site,” says Glover. “There are certain requirements in terms of a construction of a load bank that would be important.” Load Banks Direct’s portable units are designed for rugged use demanded in rental industry, including the frames, castors, and protected controls. The company also offers shipping, bolt-on, and rollout frames to the rental industry. Testing HPS Loadbanks is an authorized dealer for Crestchic load banks from 500 kVA, to 6,125 kVA. The company packages the units in all-weather ISO shipping containers for use in a variety of conditions. Because the units are resistive-reactive, they can simulate a power factor as low as 0.4, notes Paul Karpf, general manager for HPS Loadbanks. “After a huge investment in onsite power, load banks can give a facility operator a sense of confidence in that equipment,” he says. “When engines are installed in, for instance, a pharmaceutical plant, they may run a 12- to 24-hour load test on those engines before the end users sign off on the job.” There’s a significant difference between resistive testing and resistive/reactive, states Karpf. “Resistive testing is just heating up elements and blowing out hot air. Today, most engineers want reactive testing so they can simulate 0.8 power factor. Essentially, reactive testing tests a lot more than just the engine and generator’s ability to generate power. It also will test the voltage regulator and other components inside the generator.” HPS Loadbanks recently worked on a hospital project involving 2-MW Caterpillar generators. Switchgear was utilized to parallel the two units and route the power through six automatic transfer switches. “We tested the engines and now, the hospital has issued a purchase order to have its quality control person test the automatic transfer switches at full capacity,” says Karpf. “Once we’re done with our parallel switchgear engine testing, the hospital will then take over and its quality control manager will put full load through each one of the ATS switches to make sure they can carry that load.” Karpf says many hospitals are now doing full load tests once, or even twice, a year by simulating full loads on their engines, generators, and switchgear. If that works out, then they might conduct a test through their automatic transfer switches. “But being a hospital, many of them prefer to do the testing with load banks and not run through the automatic transfer switches because of patient care and related issues,” he adds. Karpf says their load banks require very little maintenance. “If a load bank’s capacity is five megawatts, you could use a 400-kilowatt generator, or an equivalent source of power, to cycle through the load steps,” he says. “You can apply 400 kilowatts at a time to each load step on the load bank, and essentially you’re testing the load bank at full capacity. If you want to test a five-megawatt load bank to full capacity all at once, you’re talking about three huge generators, and potentially 350 to 400 gallons an hour of fuel.” That’s why HPS Loadbanks uses a “test the load steps” approach, says Karpf. “We use much less power, cycle through the different load steps, and at the end of the test, we know that they will carry the full load when the load bank goes into action.” After running through the load steps one at a time, the company conducts a full visual inspection on the unit. “If we find that a load step is not pulling the power it’s supposed to—let’s say it’s pulling 150 kilowatts instead of 200 kilowatts—that usually indicates a bad fuse, a bad resistor, or maybe even a bad electrical contractor,” says Karpf. “When cycling through the load steps, we’ll occasionally find an issue and we’ll try to handle it on the spot, go back to the load step, and then when we see the power capacity go up to where it should be, we know it’s fixed. Other than that, there’s very little maintenance of our units aside from the occasional cleaning of the interior for dust that builds up inside the units.” Choosing a Load Bank In choosing the appropriate load bank for the application, the first consideration would be whether the testing will be straight resistive, or if it will be a resistive/reactive load test to simulate power factor. A second would be if the load bank going to be portable and be moved around or is it going to be stationary, Karpf points out. “A lot of end users will install a stationary load bank on the roof or next to their backup generator, and then it’s all hooked up for testing. They’ll do testing two to four times a year. A stationary load bank is going to cost a lot less than a portable, because it’s not meant to be jarred and moved around.” Stationary load banks are also installed to keep the exhaust and emission systems free of the carbon buildup that occurs when generators are operated at a reduced capacity. Weather conditions are another consideration. “If you’re buying a stationary load bank but you’re in a heavy rainfall, high-moisture location, that might impact your decision on what type of load bank to buy for that application,” says Karpf. HPS Loadbanks offers units with heaters inside to prevent moisture build-up for those who want to make such an investment. Most of the load bank units are rented for temporary onsite jobs and designed for portability, but occasionally a facility owner will invest in a highly reliable portable unit to be placed next to a standby generator. Those who spend the extra money on a portable unit will also benefit from a potentially higher resale value, Karpf says. “There are certainly higher quality, more robust designs being sold to customers, but many lower cost stationary units have a life cycle of eight to 10 years and are either replaced or junked—the lower cost is a tradeoff. It’s a fourth or third of the cost of a portable unit, so the components may not be nearly as robust.” ATS The fundamental use of an ATS lies in its intelligence and monitoring capability of the availability of normal supply. “If it sees any disruption, it sends a signal to the generator to turn on,” notes ASCO’s Patel. “Once the generator is up-and-running, it senses voltage. If the voltage is within the parameter, then it switches over.” Having metering and analytics capabilities on transfer switches leads to identifying potential problems before they become disasters, Patel says. “On transfer switches, you buy an additional metering feature that becomes part of your switch, allowing you to capture this trending and analytics capability.” He adds that testing a generator helps extends its life. “Having this capability in both motivates you to go to the testing more than the switching capability because the switches do more than just consume electricity. They can interact with the generator and with the facility, turning loads on and off. Having the trending and analytics capability in a switch motivates people to go through their prescribed testing on a regular basis.” A transfer switch is akin to an insurance policy for facilities, says Patel. “It only needs to function when there’s a problem, so 90% of the time it’s just sitting idle collecting dust.” Dust, however, conducts electricity. “So at the bare minimum, cleaning up the switching device or the environment around it is a huge requirement,” says Patel. “Keeping the environment clean will prevent the electrical arcing when you switch from one to the other. Each electrical arc eats into the copper and degrades the contacts used in the switching solution.” Additionally, because the ATS is an electromechanical component, lubrication may be required over time to help extend the life of the switch. One of the critical factors in choosing an ATS switch is that it be UL-1008 compliant, says Patel. Product support is also important. “All of these products have a very long life. Transfer switches typically are good for at least 20 years—load banks, maybe 10 years,” he says. “You need to make sure you’re buying a product that has parts availability or just basic phone support over a long period of time.” Many people don’t pay attention to the issue of codes and standards, says Patel, adding that in a company survey two years ago, 92% of the respondents were unaware of their switch’s UL certification, and in more than 65% of the facilities—such as hospitals, data centers, and utilities—a UL 1008 labeled switch is required. “Should that particular facility run into any issue, then it results in an insurance claim,” he adds. “The insurance company will dig into the details and if there is anything outside of code, they could technically reject that claim. Or when they are ready to open the facility, somebody notices this and could red tag your facility. Rather than to be subject to a last minute surprise that becomes expensive, it’s important to pay attention to this upfront.” Mission Critical Russelectric’s market is mission-critical facilities. “If you’re trying to control emergency backup power in a data center or a hospital, you’re truly mission-critical,” says John Stark, company spokesperson. “In a data center, the loss of power could result in a significant loss of data. In a hospital, it could result in a loss of patient lives as well as the loss of patient data. With electronic patient records now, a doctor can’t even prescribe an aspirin without checking a patient’s records, and without power he doesn’t have access to those records.” Stark says Russelectric switches feature a spring-loaded “over center” mechanism. “They are ‘break before make’ switches, where the contact with the utility source breaks and connects to the emergency source. They also have closed transition switches, which will avoid that break. They offer a full range of switches in ratings from 100 amps, to 4,000 amps.” Russelectric also offers a time-delay function for high-inductive loads. “If power is lost, any motors that are powered can actually feed power back into the system so that in order to prevent that power from causing a trip, you can specify a time delay between the time the utility power goes out and the emergency power kicks in,” says Stark. “That could be as much as three to five seconds, depending on your application. That gives the motors a chance to wind down and prevent the trip on reconnect.” Russelectric Open-Transition Automatic Transfer Switches are available in a dual-operator design with an adjustable time delay between the disconnect from one live power source and the connection to a second live source. “This delay is ideal when switching large inductive loads consisting of large motors or transformers,” says Stark. “It allows residual voltage produced by motor generator action to decay sufficiently in amplitude and frequency so that the two sources are in synchronism at the time of the transfer, thereby preventing the tripping of circuit breakers.” Russelectric Bypass/Isolation Switches are available in load break as well as no-load-break designs. “No-load-break bypass switches allow bypass of the ATS from either the normal source or emergency source to load, without load interruption only if the ATS is connected to the source to which the operator wishes to bypass,” says Stark. “Otherwise, the operator must first manually transfer the ATS to this source and experience a load interruption.” Designed for rapid response in emergencies, the Russelectric Load Break Bypass/Isolation Switch is designed to offer fast, easy, and mechanical bypassing of the ATS—regardless of position or condition—to allow the operator to quickly restore power to vital circuits in an emergency. Russelectric also offers UL-tested, listed, and labeled 30-cycle close-and-withstand rated automatic transfer switches and bypass/isolation switches. “With the ability to withstand fault current for 30 cycles—10 times the duration of three-cycle transfer switches—Russelectric 30-cycle rated switches allow coordinated overcurrent protection to interrupt the fault and protect downstream equipment such as expensive medical devices,” adds Stark. He says the 30 cycle switches offer the ability to selectively coordinate breakers and limit any outages to small sections of a building instead of having an entire building go down. “The time delay eliminates power transience when switching large inductive loads.” UPS In 2004, Cushman & Wakefield, a major commercial real estate broker company, began a project to replace antiquated UPS systems in its St. Louis location. The company wanted a scalable system and started with two 500-kVA 9900B series Mitsubishi UPS systems. “Then it grew to three and from that relationship, we started utilizing Mitsubishi UPS at many of our locations, primarily for its reliability and secondarily around the fact that on the market at the time, it was the most efficient unit for the highest power factor,” notes Sid Eli, account director for Cushman & Wakefield at Anthem. Reliability, power efficiency, and cost competitiveness are the three driving factors for incorporating the Mitsubishi UPS systems, says Eli. The systems have “performed admirably” through various power outages experienced at the buildings, he notes, adding that “reliability and uptime for a financial institution is huge. Typically, they’re your first line of defense and hold critical load until other systems, such as backup generation, can come on,” he says. “In considering how a system or data center works in a power outage, it typically takes between nine and 26 seconds for generators to start paralleling gear to then switch from the utility feed to a backup generation feed.” Another factor in favor of the Mitsubishi systems is the front access for repair, which is a big benefit for space conservation, he adds. No matter how stellar a machine’s reputation, one can get lulled into a false sense of security, explains Eli. “All machines can break. With a decade worth of high reliability, it’s very surprising and unexpected when we have a component malfunction in the Mitsubishi UPS.” To that end, regular maintenance is critical, and Cushman & Wakefield outsources that task. “If you manage and maintain any machines according to the manufacturers’ specifications, you’re going to get the best life out of the product and that’s been the case with our entire line of Mitsubishi products,” says Eli. “We have retrofitted older Mitsubishi products and then redeployed them to less critical locations. That speaks volumes to the return on investment if after 10 years are able to retrofit or redeploy—you get that much more out of a particular purchase.” Another benefit is power conditioning, he says. “A lot of people think about reliability, the total cost of ownership, and the longevity of capital items that they put into play, but I haven’t found on the market a platform that power conditions better, meaning utility power isn’t very clean. That’s a little shocking to people. Home systems are designed to work with a range of ambiguity in the power, but data center infrastructure and critical systems infrastructure requires very, very clean power.” In order to clean power, Mitsubishi uses single-pass and double-pass inverters on its newer products. “The last thing you want to do is hit your batteries and go on inverter,” says Eli. “Their boxes stand out to me in the sense that they can take a wide range of incoming power fluctuations and a wide range of inconsistencies in power correct without having to go to battery, therefore diminishing their life.” Mitsubishi’s 1-MW (1.05-MVA) 9900C online double conversion UPS is designed to deliver up to 97% efficiency and be easily scalable up to eight units for N+1 redundancy or N capacity, the three-phase UPS incorporates Digital Signal Processor, and Direct Digital Control. Additionally, three-level conversion design increases capacitor life, allowing Mitsubishi to offer a 15-year warranty on the capacitors. The unit also provides a variety of open architecture communications methods as well as an intuitive LCD touch panel to quickly access system status, monitoring, and control. Eli adds that there are situations where Cushman & Wakefield have other products in place where the capital investment is as such where it is not time to change to Mitsubishi products. Carol Brzozowski specializes in topics related to energy and technology.
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