The only thing worse than having a system failure is not knowing what caused it. With PQ monitoring, though, you can eliminate some of your troubleshooting headaches.
It would be nice to go to bed at the end of the day and know that you're going to be able to sleep through the night. It would be nice to know there isn't a possibility you'll get a phone call just as you finally fall asleep. If you're a plant engineer or technician, though, you know you'll never enjoy these happy fantasies. But you also know that being roused from your slumber in the middle of the night by a phone call informing you that production has unexpectedly stopped at your facility is nothing compared to the waking nightmare you'll encounter if you can't explain to management why it happened and more importantly, why it won't happen again.
The cause could be one of any number of things, but you don't have the rest of the week to troubleshoot the entire plant — this work stoppage may have already cost the company thousands of dollars in lost materials and production downtime. You could try to diagnose the problem on your own, but unless you're an expert in power quality — and you probably aren't — your hunches and predictions won't carry much weight. Of course, none of this would be a problem if you had a power quality monitoring system. If you did, at the same time that phone call woke you up and alerted you to the problem, you could have received a page informing you that a voltage sag a voltage sag occurred on the motor circuit serving the conveyor line at 1:32 p.m., stopping production for 15 sec. But you don't have a PQ monitoring system — you're going to have to go to the plant manager empty-handed and buy yourself some time until you can troubleshoot the system and pinpoint the problem. Be sure to pack an extra bottle of Pepto Bismol in your lunch pail tomorrow.
According to a recent study conducted by independent research firm Frost & Sullivan, the total revenues of the North American power quality test and measurement equipment market topped out at $274.2 million in 2001. Thanks to technological advances that will allow manufacturers to put more features in smaller and less expensive equipment, the study predicts revenues will increase to more than $500 million by 2008 (Figure). More than 50% of those revenues will come from permanently installed monitors and instruments.
PQ monitoring devices come in a variety of shapes and sizes. Hand-held and portable instruments have made great improvements in testing capability in recent years and can be helpful in uncovering small, localized problems, but only when you're troubleshooting after an event has taken place. It's the permanently installed, full-system monitors, strategically placed on pieces of equipment throughout your facility, however, that let you know what happened and where it happened, as soon as it happened. Although you still won't receive the information about what caused your process to shut down until it's too late to stop the disturbance, you won't have to waste time troubleshooting the entire facility to find the culprit.
Vishal Sapru, a research analyst in the power supplies and battery group at Frost & Sullivan, says although permanently installed monitoring systems are considerably more expensive than hand-held devices, the investment will be worth it down the line. “Looking at the overall nature of this equipment, it's expensive, but in the longrun it's not expensive,” he says. “Portable and transportable devices will be cheap, but the amount you spend each time in using one in the same location, it ultimately multiplies. In the longrun, you end up spending more than you would have actually paid for a permanently installed monitor and instrumentation.”
It's too late now to think about what you could have done to prepare for the event that took place last night, so it's time to start thinking about what you can do to get ready for the next one. Without a degree in advanced mathematics, characterizing and understanding power quality events can be a daunting — and time-consuming — task.
There are those who are trying to simplify the identification of power quality problems, though. IEEE Standard 1159, “Recommended Practice for Monitoring Electrical Power,” places most disturbances into one of five categories and characterizes their durations and rms variations (Table. Having at least a rudimentary understanding of what can happen to your facility's electrical system is the first step in selling management on the benefits of a PQ monitoring system.
But before you run out and burn up what little money your company can afford right now on capital expenditures, heed the advice of industry experts who warn that you shouldn't let your emotions get the best of you just because your facility encountered a hiccup in the electrical supply. “As a practical matter, what seems to happen is that plant engineers sell upper management on [PQ monitoring] immediately after there's been some crisis related to electric power,” says Alex McEachern, president of Power Standards Lab, Emeryville, Calif. “And at that point, upper management is generally very upset if there was a problem and nobody can tell them what the problem was. Now it's not at all clear to me that the economics are there even in that case.”
After more than 20 years in the business, McEachern knows a thing or two about diagnosing and solving power quality problems. As the founder of BMI, Edison, N.J., which has since become Dranetz-BMI, and the former president of Electrotek Concepts — sister companies that specialize in PQ monitoring equipment and services — he's considered by many of his colleagues to be a power quality guru. Yet despite that experience, he admits even he gets stumped when trying to come up with justifications for investing in such a system in some cases. “The additional information [a PQ monitoring system can give you] has some value,” he says. “But identifying that value is really tough. I think that's one of the fundamental issues in the whole power quality monitoring industry. You could end up spending $20,000 to $30,000. How do you justify that?”
As with so many other capital expenditures, justification ultimately becomes a matter of the bottom line. If an industrial facility continues to experience power quality problems that carry real and perceived costs in terms of lost materials and downtime, it's only a matter of time before investing in a monitoring system will make financial sense. “It's a pain threshold for a customer,” says Chris Melhorn, engineering manager for EPRI PEAC, Palo Alto, Calif. “If they perceive that they've lost enough money because of an interruption in their process, then they want to get that fixed. And monitoring plays a part in it.”
And although he admits business has been down in the last year, Mike Hillhouse, president of Hillhouse Power Systems, a Mandeville, La.-based supplier of power quality monitoring equipment and services, believes the market will come back when plant and facilities managers begin to take a different approach to monitoring. “The mindset of the customer has to be that it is a cost of doing business,” Hillhouse says. “A lot of customers don't view it that way right now. They're saying, ‘Well, if we haven't had failures in the past, then why buy it?’”
The typical continuous PQ monitoring system consists of several monitors installed in a facility at various points on the electrical system. Potential and current transformers are used to measure voltage and current levels throughout the system. The instruments can even be connected to the facility's computer network, where the results of that monitoring can be observed on-site in real time or transferred via a modem and phone line to an outside service provider's server. The system will also store event data for future reference. Most monitoring services will offer notification via e-mail or pager whenever an event of unacceptable size or duration occurs on your system.
If that sounds rather basic and run-of-the-mill, it is. Gathering the data isn't the difficult part. Putting it into a form that you can understand and use to solve your power problems is. Monitoring instruments can typically produce more data in one day than an engineer or technician could be expected to review in one month, and unless an event occurs on the system, that could amount to pages and pages of perfect sine waves — not exactly exciting reading material. “We've developed power quality instruments that can provide so much information that it's just overwhelming,” McEachern says. “So people stop using them. The information that comes out of the more complicated instrumentation needs to provide useful information, not pictures of waveforms, for heaven's sake, but something that says, ‘This is what the problem is.’”
Melhorn agrees. For him, moving from reams of data to concise and valuable information entails not only telling the customer what happened and where it happened, but also what they can do to prevent it from happening again. “[Plant personnel] know when their process trips — they don't need a monitor to tell them it happened,” Melhorn says. “If you can get in there and show them that if they can install some sort of mitigation device, they wouldn't have those interruptions every month.”
Hillhouse and others who provide PQ monitoring services make that data more easily digestible by sending out monthly or quarterly reports that outline the number of power quality events a facility may have endured in that time and whether those events approached acceptable limits defined by the customer. “The advantage, of course, would be that not only do you get event notification, but you get long-term historical information that could be used to analyze data over a long period of time to determine what's going on,” he says.
Thanks to the Internet, all of that information can be offered online on dedicated, password-protected Web pages set up by the service provider. Those quarterly or monthly reports will show up online with the accompanying charts and graphs plotting actual events against accepted normal values. In the end, however, you're still only getting a bunch of numbers that explain in great detail what happened without telling you what to do to prevent it from happening again.
In fact, monitoring services can be useless if the data you receive isn't presented in a form you can use, Melhorn says. “I would ask the service provider if you're going to get a nice, detailed report that cuts through all the thousands of wave forms that were downloaded and maybe provides you with some recommendations on where the problems are on the system and ways to correct those problems,” he says. “[Using that information, facilities managers] can start correlating events. They can get that information and start determining what type of events caused their facility to trip off line. It's not every event that caused it, but at least they can have some record of when it happened and they can get their equipment operators to keep a log of when the equipment shut down. Then they can start correlating system events or internal events to equipment misoperation.”
Ironically enough, the most valuable information you may get out of a PQ monitoring system could be no information at all. Power quality problems are popular scapegoats, but they're not always the cause of a work stoppage issue. Faulty system hardware and software can be just as disruptive. With a monitoring system in place, however, you can rule out a problem with the quality of your electrical supply system. The alternative leaves you without an educated guess as to where to begin your troubleshooting. “If you don't have a power quality monitoring system, you have to lump power in with software bugs and loose cables and bad supplies,” McEachern says.
Knowing where the problem originated can also be helpful in reducing the amount of money you spend on outside service organizations or troubleshooting specialists. By being able to diagnose your problem as power-related, you eliminate the need for a field service engineer to visit your site and possibly charge you for unnecessary repairs. “It's a fairly well-established fact that in the field service industry, engineers who don't find problems still replace stuff,” McEachern says. “They've traveled all the way out there, and it would be embarrassing to say to a customer, ‘I don't know what it is, and I'm not going to change anything.’”
Aside from the reactive components of PQ monitoring like the identification of sags and swells, these systems can also provide a proactive service in lowering your utility bills. Power quality events may only occur at your facility once every six months, turning your monitoring system into a rarely used, and expensive, dust-collector, but Hillhouse says it can help reduce or eliminate penalties on your company's energy bill for things like demand charges and low power factor.
In addition to providing you with the details of transients and harmonics on your system, monitoring can help you identify your continuous electrical demand, allowing you to adjust your daily operations and lower your monthly energy bill.
Hillhouse also predicts that as deregulation of the utility industry slowly opens up the retail access market, PQ monitoring will come in handy for reducing power factor charges. When a utility customer's total load has a higher reactive component, it causes the voltage at that facility to go down. As a result, the utility has to add capacitance to its system to hold the voltage at an acceptable level. If your utility charges you for having a low power factor, being able to monitor your power and make the necessary adjustments on your system to avoid this situation can save you hefty penalty fees.
Regardless of your reasons for purchasing a monitoring system, the idea is to make the investment before it's too late. Don't think that just because you haven't had power quality problems in the past you won't have them in the future. At the very least, it will save you some sleepless nights.
Sidebar: Principles for Monitoring Systems
To effectively monitor compliance and reduce unnecessary data, a PQ monitoring system should be all of the following:
Distributed — The intelligence to evaluate disturbances according to compliance standards should be distributed amongst various components of the monitoring system.
Scalable — Power monitoring instruments, communication components, and software must be capable of growing to systems consisting of hundreds of points without becoming unmanageable.
Open — Compliance information should be widely available to other systems and end users.
Flexible — A PQ monitoring system must be flexible enough to adapt to evolving standards and user preferences.
Source: “Pass or Fail: The Future of Power Quality Monitoring,” by J. Sheppard, A. Tisot, and J. Yeo — Power Quality 2001 Conference Proceedings