Troubleshooting power quality problems with today's power monitoring equipment
Several years ago, when Anthony Beckers worked as the subject matter expert, or as he calls it, a “glorified field engineer,” for a UPS manufacturer, one of his customers, a Richmond, Va.-based nationwide CATV and telecommunications provider, was experiencing a recurring power quality problem. More than a year after its installation and energization, one of the client’s 2kVA outdoor CATV UPS units kept having several standby events every day. The company’s engineers attempted to troubleshoot the problem but could not pinpoint it. They even replaced the entire system — UPS unit, batteries, enclosure — twice with no improvement.
The engineers then called the electric utility and requested an investigation into the matter. The utility’s technician did not find any power problems and told the company that the UPS equipment must be at fault. That’s when Beckers, currently a technical operations/engineering electrician on the critical infrastructure team at Time Warner Cable, San Diego, performed his own inquiry into the situation. He found that the UPS would have as many as 50 events a day. “It was going in and out on battery several times a day,” says Beckers. “They were logging many, many events.”
Beckers also learned that the electric utility’s technician and the client’s engineers used only a digital multimeter (DMM) to analyze the events. “The electric utility technician looked at it with a basic meter and said everything looked okay,” says Beckers. “So then the engineers came back to us, the UPS manufacturer, and said the problem is with your UPS.”
Beckers suspected that the events were power related, even though the power appeared normal on a DMM. “It was either an obvious problem with the power supply or the UPS, but they had already replaced the UPS,” says Beckers, explaining that a DMM was all the client’s engineers had available to them. “It was still doing the same thing, so I knew it had to be site specific and would likely be power related, such as grounding or something to that effect. That’s what led me to bring out the power analyzer.”
Using a portable power quality analyzer, which he set up and left overnight, Beckers uncovered a second, unknown signal near the zero crossing, which would appear intermittently. The client’s engineers and Beckers took their finding to the electric utility, which identified the signal as one used in a two-way automatic communication system (TWACS). “They explained that this TWACS was a form of communications ‘riding’ on the powerline,” says Beckers. “It’s a system that electric utilities use to remotely monitor substations and other sites within their system. It’s very similar to X10 technology.”
To confirm the TWACS signal was the cause of the events, the electric utility turned off the system in that area for a few days. As a result, the standby events stopped. Upon further investigation, the electric utility’s engineers then found the TWACS was out of adjustment and made the necessary repairs. “It was all on the electric utility side of the meter,” says Beckers. “When the TWACS got out of adjustment, it appeared as though the frequency were shifting because it caused a second zero crossing. So the bottom line is the UPS did what it was designed to do because it couldn’t differentiate between the power fundamental and the data signal. As far as the UPS was concerned, the two crossings were a significant frequency change, which triggered it to go on battery operation.”
DIY Power Quality
During the course of his troubleshooting, in addition to the power quality analyzer, Beckers used a portable oscilloscope, which also revealed the second signal. According to Bruce Lonie, president and co-founder of PowerCET Corp., a Santa Clara, Calif.-based power quality consulting, education, and training firm, monitoring devices such as these have improved greatly in the past few years, fostering a DIY atmosphere of diagnosing the simpler power quality problems. “Monitoring equipment is better today and easier to use,” says Lonie.
PowerCET’s general training business, what the firm calls its “knowledge-based training” in topics such as power quality, harmonics, and grounding, used to bring in between $600,000 to $700,000 a year. Last year, the training classes brought in only $100,000. “As far as putting on those seminars, I think that part of the business is over,” says Lonie. “Clients aren’t spending as much time in classes.”
Although a few clients still bring PowerCET trainers in-house for programs, most of the training has switched to online training, particularly for equipment operation, what PowerCET refers to as operational skills. The firm bundles online training with sales of monitoring equipment.
PowerCET sells all the major brands of monitoring equipment, so it remains brand neutral. “If you talk to a specific manufacturer, obviously the best meter for your application is one of their meters. Well, that may be true. However, it also depends on what you want to do.” Companies like PowerCET enjoy the position of being unbiased and offer a broad array of options to their customers (see Choosing the Right Meter).
A simple energy audit using a power quality analyzer or data logger can bring significant savings to a facility, according to Randy Barnett, certified energy auditor for NTT Workforce Development Institute, Denver. “You can set a data logger up for a 30-day period on the equipment and discover that the larger equipment is operating at lower power factor or that there’s a large air compressor that’s consuming a lot more kilowatts than it should.”
For example, by monitoring energy usage on a 200-hp air compressor and fixing any problems it may have, a facility can save up to $20,000 a year. “That’s pretty significant savings,” says Barnett.
In Barnett’s experience, often the power quality issue is coming from within the facility and not the electric utility. “The cases I look at are trouble with the drive or some problems with equipment on the plant floor,” he says.
However, it’s best to first isolate the problem and rule out the electric utility, if possible. “You’d better check yourself out,” says Barnett, who advises starting with a data logger at the point of service, just downstream from the main breaker. “Start there, and see where the problem is appearing. If it’s coming from the electric utility, then depending on the type of problem, the further downstream you go, the problem lessens.”
Many times, even if the problem has been isolated to the incoming power supply, the electric utility denies the problem. “Ideally, a facility’s engineer would find out what information is available from the electric utility in regard to power quality, and if the utility is having any problems on its system.”
Tom Mason, P.E., has experienced power quality problems coming from the electric utility. As an electrical engineer for a large oil company, he was called in to troubleshoot a problem with the company’s central data processing department. The credit card billing system was experiencing computer failures at 5:30 a.m. every morning. “I have always caught the oddball problems, and this was an oddball problem,” says Mason. “It didn’t fit into any category. This was the financial side of the business and had nothing to do with oil company operations or engineering. It was credit card payments.”
After documenting the daily failures, Mason was finally put in contact with a district maintenance superintendent of the electric utility. According to Mason, the superintendent checked around and discovered that the electric utility had suffered problems with some of its automatic capacitor switching equipment and were “temporarily” switching all banks simultaneously at 5:30 a.m. When they were reprogrammed, the problem went away. “We had to identify the pattern of what was happening, before we could solve the problem,” says Mason.
After witnessing the “blip” in the lights at the same time for three days in a row, Mason knew it was a problem with the power being supplied to the building. “It was identical, to the nearest second, exactly the same time every morning,” Mason continues. “Finally, I was able to break through the hierarchy of the electric utility and find someone to research the problem and solve it. The superintendent was happy to correct it after it had been identified, but there’s an awful lot of inertia you must overcome within an electric utility. One customer’s problem is not a big problem,” says Mason. “They won’t talk to you unless you have hard measured data.”
Still, even with measured data, maintenance technicians may have to come up with their own creative solutions to solve power quality problems. For example, when Mason worked for a consulting firm on a project to replace the main switchboard of a high-rise senior citizens’ housing apartment, he learned from the custodian who let him into the electric room to take measurements that his big problem was replacing light bulbs in the stairways. They kept burning out, and residents kept stealing replacements because their reading lamps also kept burning out. “He was buying case quantities of incandescent lamps,” says Mason.
With his own meter, Mason measured 135VAC at the receptacle in the electric room, so he left a voltage logger there for a week. The delivered voltage never dropped below 125V for the week the logger was installed. “I wondered if I just happened to have a real bad moment when they were boosting the voltage,” Mason says. “But from the data logger, over a 24-hour period, it never dropped below 125V.”
Unable to get a favorable response from the electric utility, Mason gave the custodian ordering information for 130V-rated incandescent lamps. “Changing the model number for the lamps they were ordering solved the problem,” says Mason.
Do you feel lucky?
In a time of tightened budgets, monitoring equipment and support are a bargain compared to a more comprehensive preventive maintenance schedule. “The big issue is that companies are just simply not getting done what would normally get done in better times,” says Barnett.
Lonie agrees that the recession has caused a deferral of preventive measures. “Budgets have been tight, so we’re still seeing a lot of deferred maintenance,” Lonie says. “Facilities are pretty much operating in a reactive mode. I’d like to say that I’m seeing a major trend in the other direction, but with budgets as tight as they’ve been, very few companies that I work with are being proactive.”
The only regular maintenance tasks being performed are those dictated by the insurance companies, such as thermographic infrared surveys. “Companies are still doing those, although they delay them to the extent they can,” Lonie says. “If their insurance company allows them every other year instead of every year, they do that.”
Unfortunately, deferred maintenance can come at its own cost. “They’re still in the mode of reacting to problems, which is too little too late for too much,” says Lonie.
Notwithstanding the recent economic downturn, according to Lonie, in both recession and boom times, the problem is that power quality is not a major issue until facilities experience a power incident. “Then it rises to the top,” he says. “But a week later — that’s about the half-life of a power quality problem — it’s still somewhere on the radar, but not very close by. Then within two weeks, they’re focused on some other problem. Yet, in the back of their minds they’re thinking ‘maybe we’ll be lucky, and it won’t happen again before I retire.’”
Lonie calls this mindset the “Dirty Harry syndrome,” when facilities engineers and maintenance technicians are asking themselves: “Do you feel lucky?”
Barnett blames maintenance deferral on a lack of understanding of the issues of power quality. He says it’s a matter of “out of sight, out of mind.” Because a facility has never had a fire, many facilities technicians don’t believe there is the presence of third harmonics in their neutral. “They don’t pay any attention to what’s going on, and yet their system is inefficient,” says Lonie. “They could be losing money, and there are potential dangers that they just don’t pay attention to because they really don’t understand the problems.”
The science of power quality isn’t a part of the training curriculum for an average electrician, says Barnett. “It’s just not part of the training, so they’re not aware of it and don’t test for it,” he says. Often, some symptoms of power quality issues go right by electricians because they’re not aware of what is causing the problem.
Some of the types of problems that occur from lack of routine maintenance are usually within the facility engineers’ or technicians’ existing capability to resolve, says Lonie. “If they’re not testing the circuit breaker — and then all of a sudden they have problems with it — they can mess around with it for a little while and then finally decide to change it out or something like that,” he says.
Yet, there are still some cases too difficult for facilities engineers to take on themselves. “A lot of what we see are complex problems facilities engineers just aren’t able to solve,” says Lonie.
PowerCET recently worked on a large harmonics study for a major hospital that involved 10 simultaneous monitors. Another recent harmonics study involved a wastewater treatment plant where the measurements had to be taken indirectly. “We had to make two sets of measurements, and then use software to subtract the waveforms to get a resultant waveform that was representative of the load we were trying to measure,” he says. “It was the first time I’ve done something like that, but it actually worked out quite well.”
SIDEBAR: Choosing the Right Meter
Choosing a power monitor to buy can be a long, frustrating, and complex process, according to Bruce Lonie, president and co-founder of PowerCET Corp., a Santa Clara, Calif.-based power quality consulting, education, and training firm. The number and variety of available monitoring equipment can be overwhelming. Therefore, Lonie offers the following advice for choosing the right one for your applications.
- Needs assessment: The first step in the process is to determine your power monitoring needs. A “do-everything” system is much more expensive than an energy logger/recorder. Also, there are differences in devices for single-phase and 3-phase monitoring/recording, real-time and long-term recording, logging and event capture, and the number of locations/activities requiring power monitoring.
- Features and specifications: The user’s needs assessment will drive the feature set. Generally, the more features and capabilities a meter/recorder/analyzer has, the more expensive the device. Some of the basic features include integrated display, memory storage, networking, mounting/installation, other I/O capabilities, extended operating temperature, current channel interface, internal battery run/recharge time, input channels, sampling rate, high-speed sampling, and event triggering.
- Measurement capabilities: The required measurement capabilities depend on the application and use. Simple energy logging applications will require fewer capabilities than an event recorder/analyzer. Some basic measurement capabilities and concerns include standards, sampling or digitizing the voltage and current waveforms, event recording, and variable pre- and post-event trigger capture.
- Accessories: Many models of power monitoring/recording equipment include an extensive selection of accessory items. Some “must-have” accessories, according to Lonie, include fused voltage probes, current probes appropriate for the application, carrying/shipping case, extra memory cards, and a universal voltage adapter.
- Programming and setup: The ability to successfully program and install the monitor will determine the success of the monitoring activity. Some devices have a longer learning curve than others. Determine how much time you are willing to invest in learning to set up and become proficient with the meter.
- Software and post-processing capabilities: The more capabilities a software program has, the more complex it is likely to be. Determine want you want to accomplish with the software.
- Support: Monitoring equipment can come with different levels of support. Things to look for in an after-sales support program include ongoing applications support, repair, calibration, and updates.
Source: Bruce Lonie, PowerCET, “Common Mistakes Made in Selecting & Using Power Monitors”