Advances in electrical systems maintenance technology
For the last 20 years, Randy Barnett, director of curriculum development, American Trainco, Englewood, Colo., has been keeping his clients — mostly in-house maintenance personnel in the manufacturing, institutional, and health-care markets — up-to-date on innovations in plant maintenance. “As technology gets more sophisticated, the basic maintenance person is expected to know more and do more,” says Barnett. “I tell the electricians in the class — some who've been on the job for 20 years — that what they've done in the past just isn't good enough anymore.”
To drive home the point, he often asks attendees at his onsite seminars about their own buildings. “I ask them, ‘How old is the building?’ They might say 30 or 40 years, so then I ask them, ‘How many computers, copy machines, laser printers, variable-speed drives, and programmable logic controllers (PLCs) did you have in this building then?’ ” he says. “They just laugh.”
Barnett then ticks off how much of this equipment he passed by on his way to the training room. “We now supply digital loads, and, of course, that's what causes our problems,” he says. “Even little things, like compact fluorescent lighting in the commercial buildings and office areas, cause the electricians to look at their power quality meters and say, ‘Holy cow, where are all of these harmonics coming from?’ The electrician of tomorrow is going to be just as familiar with his infrared camera and power quality analyzer as the old electricians were with the Simpson 260 multimeter.”
According to the Standards Review Council at the InterNational Electrical Testing Association (NETA), Portage, Mich., test equipment continues to evolve, providing more data, automated operation, archiving, and comparison of test data (see New Test Methods). This, of course, says the organization, comes at a fairly steep price. To remain in accordance with ANSI/NETA MTS-2007, “Standard for Maintenance Testing Specifications for Electrical Power Distribution Equipment and Systems,” published by NETA and approved as an American National Standard by the American National Standards Institute (ANSI), Washington, D.C., in July of 2007, facilities must decide either to invest in equipment and training for their in-house electrical maintenance staff or rely on independent service providers.
Have your cake
In recent years, several studies have predicted double-digit increases in the number of plants outsourcing maintenance and testing services to independent contractors. However, many plants have struck a healthy balance between hiring out for non-core tasks and keeping/training a full-time crew (“Outsourcing Options,” EC&M August 2006). At Janos Technology, Keene, N.H., Christopher Cake, maintenance supervisor, is responsible for keeping the equipment that manufactures infrared optical fabrication equipment running smoothly, as well as a variety of polishers, generators, and machine shop equipment. Cake rarely calls in outside vendors — usually the equipment manufacturer — and then only for major repairs or troubleshooting problems on electronic-controlled equipment. The majority of maintenance tasks are performed in-house. “If we're doing major improvements to the building, we'll sub it out,” he says. “General work on equipment is done in-house.”
Proponents of in-house maintenance argue that bucking the outsourcing trend may actually reduce downtime. “The critical systems are too important,” Barnett says. “You can't afford to lose power to them. It's an overall advantage to develop sophisticated diagnostic testing expertise in-house.”
Although employed by an independent testing company, Wally Vahlstrom, director of technical services for Electrical Reliability Services, Pleasanton, Calif., a subsidiary of Emerson Process Management, agrees there are specific instances that call for an in-house diagnostic protocol. “The impact of an unplanned outage on that company cries out for that company to have its own maintenance and testing group,” Vahlstrom says. “For the initial response, they can't wait to call a service provider in the middle of the night. If they have their own people, they might even have them onsite performing various routine tasks, and then they're there if a failure occurs. They can perform initial diagnosis and any needed switching. They are in a good position to know who to call for any special expertise needed. Farming out the service and having no onsite maintenance or testing personnel may result in slower response to emergencies.”
Many plants may also be reluctant to let go of staff members who are most familiar with their equipment and systems. “Folks who are responsible day-in and day-out for a facility know it better than any service provide company can,” continues Vahlstrom. “Their people can work along with the service provider during shutdowns, or turnarounds, or when the services of a specialist are needed.”
Barnett agrees. “You need somebody who knows the system,” he says. “It's somebody who really understands that system and knows what's been going on with it over the years.”
However, new equipment for advanced tests may come with a high price tag and a steep learning curve. “If the equipment fails, it's the contractor's problem and not the company's maintenance problem,” says Harley Denio, level III certified infrared thermographer, licensed supervisor electrician, and president of Oregon Infrared, Aloha, Ore. “Repairs are costly.”
Inexperience is also an issue. NETA's Standards Review Council points out that a problem with maintaining a trained staff — particularly at facilities with long intervals between available outages — is the staff rarely has a chance to practice what they've been trained to do (see Practice Makes Perfect ). OSHA requires that a person be retrained if he or she has not used the particular skill within a year.
Barnett has been called in for training after some unsuccessful in-house attempts at power quality analysis when owners who have finally accepted the need for power quality analysis have handed over sophisticated equipment to their electrical maintenance staff. Barnett believes this problem can be easily overcome with training and is, in effect, an inevitable progression of the modern maintenance worker. “We're teaching them what power quality is and how to use the test equipment to find and fix their problems,” he says. “This is what you're going to see if you look into the future in the world of electrical troubleshooting and diagnostics. It's a lot more critical that they be able to troubleshoot to a different level they could not previously.”
And eat it too
Some facilities may not be up for the investment and want to leave it to the professionals. “When you hire a contractor, you're hiring a person who does that work exclusively,” says Denio. “Maintenance employees have so many other duties, from fixing boilers to hanging bulletin boards. So even if you give him a camera, maybe once or twice a year they'll go through and do the route. So they have a lack of experience because they don't get to do it very often. A contractor does it all the time. The experience that comes with a thermographer is huge for being able to know what they're looking at.”
According to NETA, most facilities hire outside testing firms to perform much of the condition assessment. The organization says that by doing this, the facility does not need to have trained and qualified test technicians on staff. Nor do they need to ensure that employees receive ongoing training for new techniques. This also eliminates the cost associated with owning and maintaining the specialized test equipment required for this type of testing.
Currently, there are several diagnostic methods that are largely outsourced. Despite a rising interest in training seminars about these topics, Barnett says most facilities subcontract out power quality studies and infrared thermography, both the routine data gathering and the annual survey (see Tips for More Accurate Infrared Electrical Scanning). Up-to-date drawings and one-line diagrams are also mostly outsourced. “You need the drawings for arc-flash studies,” Barnett says. “But usually, you don't have the engineers on staff to do all of that.”
Testing that must be performed while equipment is de-energized is frequently outsourced. Power factor testing of transformers, offline testing of cables, breaker injection testing, and contact resistance testing must all be performed on de-energized systems.
“Most of the tests that are listed in either NETA or NFPA can only be done while the equipment is de-energized,” says Vahlstrom. “Those are some of the things that you would call in an outside service company for.”
In addition, most facilities don't keep enough workers on staff to perform a scheduled shutdown or turnaround, which could take up to as many as 300 workers, depending on the facility. Most facilities may also hire outside help for equipment upgrades and changing out the electromechanical relays for electronic relays, as well as replacing bushings on transformers, replacing breakers, and performing acceptance testing.
Try before you buy
Whether facilities use third-party testing firms or rely on internal staff for electrical maintenance testing, all testing should be performed in accordance with the ANSI/NETA MTS-2007, “Standard for Maintenance Testing Specifications for Electrical Power Distribution Equipment and Systems.” These specifications cover the suggested field tests and inspections that are available to assess the suitability for continued service and reliability of electrical power distribution equipment and systems. According to the NETA Standards Review Council, the purpose of these specifications is to assure that tested electrical equipment and systems are operational and within applicable standards and manufacturer's tolerances and that the equipment and systems are suitable for continued service. One of the most widely used sections of this document is Appendix B, The Frequency of Maintenance Tests matrix.
The organization stresses that end-users, contractors, engineers, testing firms, and inspectors can all benefit from using the ANSI/NETA MTS as a reference in their work. NETA actively participates in the development and maintenance of other industry standards. This ensures NETA standards and specifications are as accurate and up-to-date with the latest in testing technologies as possible.
NETA remains grounded in the belief that new methods must be proven effective over time before they warrant inclusion in the standards and specifications. With each new technique or proposed advance in any technique, it must be proven that the new method is at least as useful as the former, according to the organization. While the impact on formerly popular techniques is difficult to assess, it appears, for the most part, that the former techniques are still useful. For example, in the case of monitoring the gas-in-oil of the liquid-filled transformer, oil samples should still be taken to make a more complete evaluation of the oil. Cable testing has changed dramatically over the last few years. High potential testing with DC is still used for new medium-voltage extruded dielectric cable and for acceptance and maintenance of laminated insulation, such as PILC. Alternative maintenance tests, such as partial discharge, overpotential, and power factor with VLF or 60-Hz sources, are being used for extruded dielectric cable.
In addition, the Electric Power Research Institute (EPRI), Palo Alto, Calif., found that DC hipot testing damaged field-aged extruded cables and scanning of bolted connections has decreased the need to torque and tighten to some extent. “But the main advantage of new techniques is that they provide condition assessment info,” says Vahlstrom. “That helps improve reliability.”
Sidebar: New Test Methods
Some of the new diagnostic tools allow the equipment to be evaluated to some degree while in operation (online), while others are for use when the equipment is de-energized (off-line). The following are examples of recent innovations in diagnostic techniques.
- Partial discharge monitoring
Partial-discharge testing of motors and generators has been around for about 50 years in the field, according to Wally Vahlstrom, director of technical services for Electrical Reliability Services, Pleasanton, Calif., a subsidiary of Emerson Process Management. However, testing on cable and switchgear has only recently — within about the last five years — been performed in the field. “New equipment that's coming available on the market will enable these kinds of tests to be made,” he says. “Previously, these techniques were for the most part only available in the laboratory where their environment was very tightly controlled, but new test methods are being developed and standards are being written that provide for field testing.”
The monitoring equipment can be permanently mounted on rotating machinery, switchgear, transformers, or cables to periodically evaluate insulation condition. Partial discharge can also be detected by ultrasound detectors sensitive to frequencies generated by partial discharges.
- Tan-Delta testing
A form of power factor testing, Tan-Delta condition assessment has been more popular in Europe than in the United States in recent years. It is used to detect a form of deterioration in EPR and cross-link polyethylene insulated cables called “water treeing,” which is not detectable with any of the conventional test methods.
Water treeing makes weak spots in the cable that don't cause partial discharge, according to Vahlstrom. “During an overvoltage, such as may be caused by a lightning or switching surge, the worst of the water trees can convert to what's being termed ‘electrical treeing,’ which emits partial discharges and quickly deteriorates the cable from that point forward,” Vahlstrom says. “Tan-Delta testing seems to be the only way to detect whether a cable has a lot of water treeing and whether it's time to replace it or not.”
- Capacitive and ultrasonic testing of transformers
Both of these methods test for partial discharge occurring in the transformer. “They're both emerging as off-the-shelf techniques,” says Vahlstrom.
- Gas-in-oil monitors
Gas-in-oil monitors are available for liquid-filled transformers. Some can be programmed to alarm for certain levels of various gases that may indicate low level internal faults.
- Infrared thermography
Infrared thermographic testing is a heat detection and recording service that can identify developing and hidden problems not visually apparent to the eye. “There's no question when there's heat,” says Harley Denio, level III certified infrared thermographer, licensed supervisor electrician, and president of Oregon Infrared, Aloha, Ore. “A picture speaks a thousand words. You can stand back with an infrared camera and look at an entire panel with one little swipe of the lens and see if there's a problem without having to go to the length of testing with multimeters.”
Emerging in the early 1980s, infrared thermography at that time was a bulky process. “You had to carry the thing up on your shoulder and pour argon or liquid nitrogen into the machine to keep the internal electronics cool,” says Denio. Recent advances have made it streamlined — lighter and smaller. The cameras are also completely electronic, with chips to dissipate the heat. Now that they're getting close to high-definition (HD) models, the imagery is also getting better.
Sidebar: Tips for More Accurate Infrared Electrical Scanning
Recent technological advances have greatly improved thermographic data gathering and processing, making it easier to perform with more accurate results. However, there are still several common mistakes made in the process of gathering accurate data. “Every time a thermographer goes out into the field to perform a survey, the conditions are different,” says Harley Denio, level III certified infrared thermographer, licensed supervisor electrician, and president of Oregon Infrared, Aloha, Ore., a full-service infrared service provider. “Every situation requires the thermographer to look around at the surrounding environment and make a judgment as to what special conditions might exist, and how to gather the data accurately.”
Denio offers the following expert advice on how to successfully avoid common mistakes made while gathering data through an infrared thermography survey specific to electrical systems:
When scanning highly reflective (low-emissivity) targets, such as bus bars, be sure to change your angle to eliminate the reflections on the image. The reflection could be from your body heat or some other heat source in the area — a piece of machinery, light bulb, or a transformer. Reflections will give you incorrect data in the thermal image and, if not understood, constitutes a data error.
- Mismatched and wrong-size fuses
Sometimes in facility maintenance work, a piece of equipment will cause a fuse to fail and it needs to be up and running right away. Maybe it continues to fail regularly and becomes a nuisance. Often, the repair personnel will rummage through a box of spare fuses and install a fuse of the same size amperage rating, but of a different brand and fail setting. Also, when a piece of equipment fails regularly, the maintenance person might install a fuse of the next size up in amperage rating from proper rating, just to make the problem go away. Fuses installed this way have a particular heat signature and can be found with infrared thermography. If the fuse is too large, it will read cool as compared to the others in the group. If it's too small, then it will read warmer than the group. If there is a different trip setting in the mismatched fuse, it will have yet a different heat signature.
- Trip sensors
Trip sensors are electric devices in breakers that measure temperature or amperage in the device. When it reaches above the set limit, the breaker trips. These devices put out a particular thermal signature. It is common data error, often misdiagnosed as an internal problem inside the breaker. GFCI breakers and GFCI receptacles also have a similar heat signature.
- Bad photo angle
When taking thermal images, make sure there is sufficient view of the surrounding area to help find what component is being identified for attention. Always take the thermal image and visual image from the same angle and distance. This will help the end-user return to the same place when repairs are to be done.
- Outside scanning
The weather affects all forms of infrared thermography. A big issue in electrical scanning is the effect that different ambient conditions and solar loading has on the components. Move around to note solar reflections. If it is windy and a fuse disconnect enclosure is opened, there is little time before the convective cooling effect of the wind cools the connections and accurate temperature data becomes elusive. Be ready in front of the component, camera running, in focus and imager settings set before opening the box to be sure to gather the most accurate temperature data.
To read the full text of Denio's article, originally published in Uptime, Fort Myers, Fla., visit Oregon Infrared's Web site athttp://oregoninfrared.com/Infrared-Thermography-Data.pdf.
Source: Uptime, Fort Myers, Fla.
Sidebar: Practice Makes Perfect
One of the most popular classes at Englewood, Colo.-based American Trainco is electrical troubleshooting. “The electricians already know how to do basic troubleshooting, but we see cross-training for maintenance people who do not have a strong electrical background,” says Randy Barnett, director of curriculum development for the seminar-based training company. “There is still a need to teach the basics. That's not going away. But to the electrician in the field, the guy who already has the basics, he moves up to the next rung on the ladder.”
However, like any skill, troubleshooting requires practice, and without the added pressure of the costs of downtime. Yet, troubleshooting practice can be especially hard to come by. Planned downtime is only an absolute necessity for maintenance operations, and your employer may not want you experimenting on its expensive equipment anyway. One way to gain the skills you need could be to purchase separate equipment for troubleshooting. It can even be designed with built-in defects, but this can be expensive.
Another option gaining in popularity is computer-simulated troubleshooting. These simulations can be fairly realistic, and they allow maintenance workers to troubleshoot in a controlled environment. They can be much less expensive than shelling out money for dummy equipment that takes up space, and they can be used at any workstation. Some programs offer a grading system for the troubleshooter's skill level and provide feedback and a printable record.