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May 25, 2007 A Penton Media Publication Vol. III No. 10



CONTENTS
Maintenance and Energy Savings

Electrical Troubleshooting Quiz

Energy Repairs

NEC at the Facility

Confined Entry Attendants

Let's Go Racing! Win a free Road America race weekend for two.

Answer to Electrical Troubleshooting Quiz


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MRO Insider addresses topics such as:

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    Maintenance
    Maintenance and Energy Savings
    Which maintenance practices can you use to reduce energy waste? A good place to start is your electrical service. In analyzing what to do, it's helpful to break the service down into its major systems or equipment types, as follows:
    • Service transformers. Begin with an oil analysis. This will tell you a great deal about the health and efficiency of your service transformers. It's not unusual to find severe problems in transformers that haven't had regular testing performed. It's also not unusual to see big efficiency gains once the problems are corrected. Ask a qualified testing firm which tests are recommended for your particular installation. If the utility owns your transformers and is responsible for their maintenance, don't be penny wise and dollar foolish. Have this maintenance performed, even if you must pay for it. The energy savings alone will probably pay for the maintenance. More importantly, a lack of this maintenance can result in a costly and extended outage.
    • Service conductors. If the cables are accessible, begin with infrared testing to reveal energy losses in the form of heat. Hi-pot testing will show the insulation integrity (or lack thereof), but you have to de-energize the service conductors for such a test. If you don't have a maintenance bypass system, that means shutting down power to the facility. However, it's better to schedule a shutdown than for one to occur due to conductor failure. Several tests can indicate voltage loss or current leakage from live service conductors, but only a qualified person can conduct those tests. These tests cannot replace standard cable tests (which require de-energization via shutdown or bypass).
    • Service disconnects. Infrared will show energy loss at poor connections. Infrared testing is dangerous, because covers are removed while the testing is in progress. Only qualified personnel wearing the appropriate PPE (e.g., blast suits) should perform infrared testing.
    • Switchgear. Doing the manufacturer's recommended switchgear maintenance per the manufacturer's schedule provides energy savings and reliability. Conduct infrared tests on the connections at buses and breakers, as well.
    • Cables. Small leaks in many cables can add up to considerable energy losses. This alone justifies cable leakage tests. Serving the larger purpose of keeping your facility running reliably means you should include cable leakage tests in a larger cable maintenance program.
    Don't forget power quality. Rarely does the grid provide "bad power," but it does happen. Your power monitoring system can tell you when a power event occurs in the supply. Usually, you can trace supply power glitches to specific events -- such as an across the line start of a big motor at a neighboring facility.

    Maintenance for energy efficiency is really a subset of thorough maintenance for reliability. Review your power supply maintenance program to ensure it's complete, and you'll have both bases covered. Once you've eliminated energy losses in your power supply, you can turn your attention to saving energy in your power distribution system. This topic will be addressed in the next newsletter.


    Repair
    Electrical Troubleshooting Quiz
    Your power monitor is set up to show the voltages at the load end of each feeder. Your supply is 484V. You have 10 feeders. All of them are within 2% of supply voltage, except two -- those are at 448V and 443V. What might be the cause?

    The answer to this question appears at the end of this newsletter.


    Energy Repairs
    Transformer replacement offers potential energy savings. Before ordering a replacement transformer, calculate the total load. Use the method appropriate for the type of circuits being supplied (service, feeder, branch). Then, select the transformer size that most closely optimizes efficiency.

    Characterize the load -- is it mostly linear or nonlinear? Would it make sense to split some of this load up and buy two transformers? You might want to do this if, for example, 20% of the load consists of resistive heaters and 80% consists of motors.

    These are just some of the considerations in proper transformer selection. Careful selection can turn an equipment failure into energy cost-savings.


    Operation
    NEC at the Facility
    You might be surprised if you inspect your bottom-fed panels. Anytime a raceway enters a switchboard, floor-standing panelboard, or similar enclosure, it has to allow sufficient space for NEC-compliant installation of the conductors.

    If raceways enter the enclosure below the busbars (or their supports or other obstructions), they must allow conductor clearance of 8 inches for insulated busbars and 10 inches for uninsulated busbars. In any case, raceways can't rise more than 3 inches from the bottom of the enclosure [408.5].


    Confined Entry Attendants
    Remember the old Maytag repairman commercials? That's kind of what a confined entry attendant's job is like, most of the time. This can lead to some false assumptions.

    The attendant may falsely assume that the attendant job involves doing nothing, or that the work inside the confined space is just routine. Either assumption can lead to inattention and poor preparation.

    The person going into the confined space may assume the attendant is familiar with the permit, but this may not be the case. Always review the permit with the attendant. Note if extraction gear is required, what monitoring duties the attendant has, and what the communication means are.


    Show & Events
    Let's Go Racing! Win a free Road America race weekend for two.
    EC&M magazine and Generac Power Systems have teamed up to offer an expenses-paid weekend (August 10-12, 2007) featuring two of the world's fastest racing series. The third annual Generac Power Weekend is one thrilling day of American LeMans series racing (the Generac 500) and an equally exciting day of Champ Car racing at its finest (the Generac Grand Prix). It's your chance to see both series compete in a single weekend at one of North America's most beautiful tracks. Located in the hilly heart of Wisconsin's scenic Kettle Moraine area, Road America is a 4-mile permanent road course that tests drivers with 14 challenging turns.

    Enter by July 10, 2007. Visit the Generac Power Systems virtual booth at the EC&M E-Tradeshow. Full contest rules are available online in the Generac E-Tradeshow booth. For more information about the Generac Power Weekend, go to www.roadamerica.com.


    Quiz Answers
    Answer to Electrical Troubleshooting Quiz First, you'll need to perform voltage drop calculations. Voltage drop is the calculated (not measured) loss due to resistance of the wire over a distance. If your calculations show excessive voltage drop (see 215.2(A)(3) FPN No. 2), you need to replace the cables with larger ones and/or distribute at a higher voltage for a longer distance.

    If you have a large difference between the calculations (voltage drop) and measurements (voltage loss), you have either cable leakage or a potential across connections. You can use infrared, split cable tests, or other methods to locate bad cable sections or bad connections. It's more efficient to test an entire feeder and repair all problems than to shut down and repair just the worst connections or cable sections. But time and money may constrain you to do only partial repairs.



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