Dan Rafter 2017-03-01 15:16:34
You already know how important it is to perform regular preventive maintenance on your onsite power system. It doesn’t pay to install a backup generator to protect yourself from a failing public grid if that onsite system doesn’t work when called upon. So you regularly test your onsite power system. You schedule regular inspections from licensed professionals of your gensets. And you do what you can to keep your backup power system clean and properly fueled. But what about your switchgear equipment? It’s easy to overlook these key components of an onsite power system. But if switchgear fail, so will your onsite power system. And that means that your hospital, factory, bank, or data center could find itself without power. And that, even if it’s a power failure of just seconds, could prove catastrophic. The reason for this is simple: Switchgear, while often overlooked, play an important role in any power system. Distributed Energy recently spoke with officials with switchgear manufacturers about the importance of maintenance, the most common causes of switchgear failure, and the steps that building owners can take to make sure that their equipment operates effectively and efficiently. They had plenty to say about this key topic. “Swtichgear equipment is essentially a container for interrupting and switching devices and their controls,” says Harsh Karandikar, vice president of product management with the Lake Mary, FL, office of ABB Inc. “The principle function of the switchgear is to distribute and then control the flow of electricity and, in doing so, protect the components that are involved in ensuring this flow.” If switchgear equipment fails, building owners could find themselves facing a loss of significant dollars. Even though the country’s economy is still on a steady increase, that doesn’t mean that companies can afford any big hit to their bottom-lines. “A malfunction of switchgear, while rare, can interrupt the flow of electricity, thus causing production downtime in industrial plants and a loss of economic activity in commercial installations,” says Karandikar. “It can create a condition in which the safety of the operations and maintenance personnel can no longer be ensured.” Gabriel Paoletti, technical application engineering manager with the electrical engineering services and systems division with Eaton, agrees that a switchgear failure could prove disastrous for building owners. “Since switchgear is a critical part of the power-distribution system, a malfunction can be catastrophic,” says Paoletti. “A failure can prevent power flow to both critical and non-critical loads, since switchgear exists even in the emergency power supply coming from backup generators.” Switchgear failure can also cost businesses a significant amount of wasted time. Repairing failed switchgear can be a complicated process, one that can keep businesses from focusing on what should be their top priority: making profits. “The time required to repair or replace the switchgear can be extensive,” says Paoletti. “A switchgear assembly contains the copper bus, connections, and control wiring of the individual circuit breakers. So while an individual circuit breaker can be replaced by a spare in 30 minutes, the entire switchgear assembly can require weeks for repair or replacement.” Switchgear failures can also spread throughout a power distribution system. That could cost business owners even more money and wasted time, Paoletti says. “Should a switchgear malfunction cause damage to the outgoing or incoming cables that connect to the switchgear, this damage can result in additional equipment, labor, and most importantly, time to repair or replace,” he says. “A building’s electrical system is often taken for granted, and switchgear seems to run without any attention.” The message here then is simple: When building owners, supervisors, and managers are crafting preventive maintenance programs for their onsite power systems, they can’t afford to forget about switchgear. Taking care of these components is a key step toward guaranteeing that onsite generators actually provide backup power when business and building owners call upon them. Fortunately, it’s not overly difficult—or time-consuming—to make sure that switchgear are operating properly. In fact, it takes just the most basic maintenance to keep these components in good operating condition. Why Preventive Maintenance Matters Karandikar says that one of the most common types of switchgear failure is an arc fault, a potentially deadly error that Karandikar says can result from a breakdown of a switchgear’s insulation over an extended period of time or from bus joints that have worked themselves loose. These are problems that facility managers and maintenance personnel should catch and rectify if they are following a preventive maintenance program designed to keep their switchgear equipment operating properly. “An arc fault can cause loss of life or serious injuries,” says Karandikar. “At a minimum, there is significant equipment damage, resulting in long downtimes.” To decrease the odds of an arc fault or other type of switchgear malfunction, building owners and facility managers should follow the recommended maintenance schedule created by the manufacturers of this equipment. Karandikar says that most manufacturers of switchgear have different recommendations for an annual, two-year, and five-year maintenance schedule. In general, the owners of onsite power systems need to make sure that all the mechanical interlocks of their systems’ switchgear work and are properly lubricated. They should also check to make sure that there hasn’t been any breakdown of the insulation protecting this equipment. Another key move is for owners to ensure that all of the bus joints of their switchgear are tight. It’s equally important for facility managers to make sure that breakers are cleaned regularly as a way to remove the dust and dirt that can accumulate in them. Maintenance personnel needs to inspect all the mating parts of breakers for wear. Those mating parts that do show signs of excessive wear should be replaced. Karandikar says that most of the maintenance above applies mostly to spring-actuated breakers. These breakers have several moving parts. Because of this, it is important for facility managers to make sure that these parts are always properly lubricated and that the movement of these parts is not hampered. Some onsite power systems, though, feature magnetically actuated breakers, Karandikar says. These breakers come with far fewer moving parts and actually need much less maintenance. This makes these breakers a good choice for facility managers or building owners who might not have enough maintenance personnel to focus on keeping breakers in top working order. “Based on the data we have, our estimate is that maintenance tasks on a spring-actuated breaker take almost two-and-a-half times more time, than for a magnetically actuated breaker,” says Karandikar. Because they require less maintenance, magnetically actuated breakers are less expensive over their lifetimes, Karandikar says, even if they might cost more in upfront dollars. Karandikar says that ABB studied the lifespan of a standard 11-frame switchgear lineup with 15 breakers. Officials with ABB estimated that a lineup of spring-actuated breakers would cost 12 times as much in maintenance costs, as would a lineup of magnetically actuated breakers. Initial Steps Before facility personnel perform any maintenance on switchgear equipment, building owners or facility managers must first order what is known as an arc flash study, Paoletti says. Such studies usually involve an outside engineer who studies a building’s entire electric system, looking for possible areas where arc flashes are a significant risk. Secondly, every building needs an updated electrical, single-line diagram—a blueprint for a facility’s entire electrical system—Paoletti says. These steps are both necessary for a simple, but important, reason: the safety of maintenance workers. “Without these two, the operation, maintenance, and trouble-shooting of equipment can put individuals at risk,” says Paoletti. Paoletti also recommends that either factory-trained or independently certified individuals perform the more technical aspects of switchgear maintenance and inspections. Again, it comes down to safety. Personnel who don’t understand the intricacies of switchgear technology run a very real risk of suffering serious injuries should they attempt maintenance on their own. With the basics addressed, building owners then need to set up what Paoletti refers to as a “three-tiered approach” to switchgear maintenance. The first tier is an important one. Paoletti says that building employees should complete weekly inspections of their facilities’ switchgear rooms to make sure that there are no water leaks, that the gear is not exposed to the outside atmosphere, and that the room is generally clean. They should make sure, too, that the room boasts easy access to all equipment and exit doors. The second tier involves an annual opening and closing of circuit breakers and an inspection of all system cubicles, Paoletti says. “The failure of a circuit breaker to property interrupt a fault can lead to a complete switchgear failure,” says Paoletti. “Some circuit breakers will not be exercised—opened and closed—for many years during typical operations, which could result in deteriorated lubrication of moving parts and the possible welding together of overheated contacts.” Paoletti also recommends an infrared survey, also known as a heat-sensing survey. In such a survey, a trained person observes switchgear equipment with an infrared camera to detect any loose, corroded, or deteriorating equipment. These surveys require the removal of rear doors or covers, which Paoletti says can be risky. That’s why he recommends that building owners request the installation of infrared windows. These windows allow inspectors to complete their infrared inspections without having to remove any doors or covers. Paoletti’s third tier of maintenance might be the most time consuming, but is also the most important. He recommends a complete shutdown of switchgear equipment every three to five years. During this shutdown period, usually on weekends, qualified individuals can conduct a detailed cleaning of the entire switchgear assembly. They can also conduct simulated load-testing of the circuit breakers and the relays that control the trip circuit of a circuit breaker. “Simulated load testing helps ensure that the circuit breakers will operate properly under a fault condition, versus failing to interrupt the fault and resulting in a potential complete switchgear failure and shutdown,” says Paoletti. “Testing of circuit breakers and relays for proper tripping times also supports a properly coordinated electrical distribution system.” Don’t Forget to Test Your Equipment As Karandikar says, switchgear are made up of several types of electrical equipment all installed within an enclosure. This includes instrument transformers, protective relays, control switches, metering instruments, and power circuit breakers. Because so much goes into switchgear equipment, it is key for building owners and facility managers to regularly test all of the components of this equipment to make sure that the entire switchgear system will work properly when needed. Karandikar says that how often you’ll need to test the components of your switchgear systems depends on the environment and operating conditions they face on a daily basis. He points to the National Fire Protection Association’s guidelines, which recommend that owners and managers test their switchgear components more often if the switchgear in question are providing a critical service. For instance, you might schedule more frequent tests if your switchgear will help ensure that a hospital building won’t ever suffer a power blip. The same might be true if your switchgear are helping to ensure backup power to a data center that can’t afford to lose power for even a second. “No fixed rule can be given when it comes to testing,” says Karandikar. The Fire Protection Association, though, does recommend that owners order inspections of their switchgear equipment soon after it is installed to make sure all the parts are connected and installed properly. Owners and facility managers can then schedule inspections at regular intervals after this, depending on the recommendations of the equipment’s manufacturers. Karandikar says that it is impossible to provide a blanket rule for how often building owners and managers should test or inspect their switchgear equipment. That’s because each switchgear setup is unique, each commercial building is also unique, and each switchgear installation requires its own particular maintenance, inspection, and testing schedule. “Considering that there are almost limitless possibilities for various combinations and types of these components available in a switchgear lineup, having an accurate requirement for testing and inspections can only be determined with each customer project,” says Karandikar. “For the switchgear bus and enclosure themselves, not considering all the other components, switchgear inspection is based on time, environment, operational use, and other factors such as fault events.” Karandikar says, though, that switchgear should always be inspected immediately after malfunctions such as an arcing fault. These types of faults are especially troublesome, as they usually cause damage to other pieces of equipment. Building owners need to inspect switchgear after such faults to make sure that they don’t occur again. Karandikar says, too, that switchgear that are placed in areas with high vibrations should have more frequent inspections, inspections that focus on items such as how tight bus hardware is. Switchgear that do operate in high-vibration areas are more likely to be plagued by hardware that has worked itself loose. And switchgear that operate in harsh environments and are exposed to caustic or corrosive conditions should have more frequent inspections too, Karandikar says. Facility managers need to also test their circuit breakers and relays for proper tripping times. This is important: If a feeder circuit breaker is feeding a fault, it should switch into operation before the main circuit breaker operates. If it doesn’t? There have been cases where an entire building is shut down because internal circuit breakers are not interrupting a downstream fault in the proper amount of time, Paoletti says. Why Do Malfunctions Occur? Paoletti says that he recently completed an analysis of switchgear failure data generated by the Institution of Electrical Engineers as well as from responses to customer surveys. He found that the most common switchgear failures could be controlled—and even largely eliminated—by proper maintenance. These failures can be broken into three main categories: humidity and internal arcing, dust and surface contamination, and overheating as the result of either overloaded equipment or deteriorated connection points or electrical contact areas. These preventable causes of failure? Paoletti says that they account for more than 50% of all switchgear malfunctions. That’s a strong argument for how important regular maintenance is—maintenance that can help reduce or eliminate these major reasons for switchgear failures. There are also outside factors that can cause switchgear failures. Lightning strikes, for instance, can damage switchgear equipment. Regular maintenance might not be able to stop a lightning strike, but it can prevent damage from some outside forces. Consider rodents. Rodents with their sharp teeth and persistent nibbling can easily damage switchgear. But if building facility workers perform regular monthly inspections to make sure that there are no open locations where rodents can enter switchgear installations, they can then dramatically reduce the odds that these creatures can damage circuit breakers and other components, Paoletti says. What other causes can result in switchgear malfunctions? There are plenty of primary possible causes, including defective components, overheating, and of course, unpredictable outside forces. But Karandikar, like Paoletti, says that some of the main culprits in switchgear malfunctions can be traced directly back to human error. And many of these causes can be eliminated if facility managers schedule regular maintenance, testing, and inspection of their switchgear. For instance, Karandikar lists improper application, handling, and installation as primary causes of switchgear failure. He also points to inadequate maintenance and improper operating procedures as two other common reasons for switchgear to malfunction. Again, with regular maintenance and inspections, these problems can be identified quickly and fixed before switchgear fail. This leads to the big question: Do facility managers and building owners take good care of their switchgear? Do they schedule regular maintenance and inspections? The answer, not surprisingly, is a solid “sometimes.” “The evidence we have covers the full spectrum,” says Karandikar. “Many customers religiously follow the manufacturers’ recommended maintenance practices. On the other hand, many conduct no maintenance at all, and run the equipment to failure while keeping suitable spares. When a breaker fails, it can be simply taken out of service and replaced.” Some customers ask for infrared windows on the rear of the switchgear to be installed in their facilities. These can be important tools, as maintenance personnel can use them to periodically monitor the temperatures of the critical joints inside a switchgear system without first having to power it down. It’s important that facility managers and maintenance personnel quickly identify switchgear temperatures that are higher than normal. These higher temperatures can indicate a loose joint, which could eventually cause an arc fault. And no building owner or manager wants an arc fault—a switchgear malfunction that can shut down their facilities and injure their workers. Paoletti says, also not surprisingly, that some building owners do a better job than others when it comes to the maintenance needed to keep switchgear equipment operating properly. If a building contains what Paoletti refers to as mission-critical equipment—such as a data center—then a maintenance program is normally in place and followed. This isn’t always the case, though, in more standard commercial buildings. “For typical commercial buildings, the electrical system can be somewhat taken for granted,” says Paoletti. Sometimes facility personnel neglect electrical systems because it is simply easier to do so. As Paoletti says, electrical equipment doesn’t have moving parts and requires less maintenance than, say, a facility’s HVAC systems. As more complicated building systems take the attention of maintenance personnel, switchgear, circuit breakers, and other pieces of electrical equipment are increasingly ignored. The good news is that switchgear technology has advanced enough so that switchgear are less likely to fail even if maintenance staffers are less than perfect when it comes to maintenance. Karandikar says that new tech supports new approaches to maintenance. Owners can approach maintenance on condition-based terms rather than time-based. So instead of scheduling inspections after a certain number of months or years, no matter what, owners with newer switchgear equipment can adjust their maintenance schedules depending on the severity of conditions in which their equipment is operating. Karandikar says that he expects switchgear technology to continue to improve to make it easier for owners and facility managers to keep these key pieces of equipment operating efficiently and effectively. He points to the improved monitoring capabilities that building owners and managers already have as an example of how switchgear maintenance continues to evolve. “The availability of cost-effective, online temperature monitoring and partial-discharge monitoring technologies allows a user to monitor the health of the switchgear and its components and take mitigating measures when required,” says Karandikar. Paoletti says that new technology allows owners to monitor the internal temperatures of their switchgear remotely. They can also use remote monitoring to determine whether there has been too much buildup of dust on their switchgear equipment, whether there is too much humidity built up in switchgear equipment, or whether floor water can be a problem. “But the application of these new technologies does require the building manager to first consider the proper maintenance requirement of the electrical system, or just hope that a failure does not occur on their watch,” says Paoletti. DE Dan Rafter is a technical writer and frequent contributor.
Published by Forester Media. View All Articles.