In the previous issue, we discussed opportunities to
reduce energy waste in feeder systems. It became clear that infrared
(IR) testing is critical to realizing those opportunities. Be sure to
look at current IR testing techniques and test equipment, so this can
done efficiently. But don't stop there.
Make hi-pot (high-potential) testing the partner of IR testing in
your feeder maintenance program, if it's not already. Hi-potting allows
you to determine insulation integrity (or lack of it). The downside is
you have to de-energize conductors to hi-pot them, so you'll be opening
breakers and shutting down production equipment. However, it's better
schedule a shutdown than to let conductor failure cause one.
Several types of live conductor tests can supplement IR and hi-pot
testing. For reasons of test validity and safety, only qualified
(as defined in NEC Art. 100, specifically for the tests and equipment
involved) should conduct those tests. Consult a qualified testing firm
to determine which tests make the most sense for you.
A couple of other considerations:
No test will tell you that no problems exist. A test will tell you only
whether what you are testing for is within acceptable limits. That's
you need a full battery of tests, performed by qualified personnel
the current generation of test equipment.
- For energy savings and reliability, maintain distribution
equipment to at least the level recommended by the manufacturer.
IR tests on the connections at buses and breakers, and on the exposed
parts of feeders.
- Many small leaks in cables can add up to considerable energy
This alone justifies cable leakage tests. More importantly, these tests
can prevent catastrophic failures and "surprise" shutdowns. Include
cable leakage tests in your cable maintenance program.
Don't Miss InfraMation Hosted by FLIR!
Register by July 31st for InfraMation, the world's largest
infrared camera applications conference, and receive 3 free hotel
and a guest pass. Hosted by FLIR, InfraMation will happen on October
15-19, 2007 in Las Vegas. InfraMation features sessions on condition
monitoring and predictive and preventive maintenance, as well as IR
clinics on electrical applications. Visit www.inframation.org, or call
The overloads for a 200-hp grinder motor trip several
times per week, but the feeder breaker doesn't trip. A quick review of
Art. 430 shows that we are looking at excess current draw (430 Part
III), not fault current (430 Part V).
Here are some preliminary findings:
- A power monitor reveals many bouts of overcurrent in recent months,
tracking perfectly the nuisance trips that began in April. The
are behaving correctly.
- The motor went to a motor repair shop, which conducted a battery of
tests and found nothing wrong with the motor.
- Load problems have been ruled out (for example, the scrap is within
recommended limits, and the augur is sharp).
This is one of those cases where it makes sense to (temporarily) set
aside standard troubleshooting methodology and go directly to a
suspected cause. Do you know what that cause might be? If that cause
isn't it, what should you do next?
The answer to this question appears at the end of this
Summer affects your repair environment. Consider these
- Hot parts brought into an air-conditioned space may be damaged
condensation. If that problem isn't accounted for, you may end up
installing a new part that already needs to be replaced.
- Repairs take longer. Unlike heat stroke, heat fatigue isn't
recognized as a health concern. Nevertheless, it is a productivity
concern. During extreme weather, people tend to make more mistakes
and/or work at a slower pace. If you need a 90-minute repair window
under normal conditions, you might need two or three hours in extreme
weather. Assess conditions, and adjust accordingly.
- A blackout shut down much of the Eastern Seaboard in the summer
2005. Packages slated for overnight delivery sat idle for days. If
you're planning a shutdown for repair and replacement, the Just-In-Time
(JIT) method may prove to be the "just-too-late" method. Order parts
with enough lead time to allow for contingencies. Don't forget that
summer storms can also wreak havoc with airlines, delaying the arrival
of key personnel.
Can you think of other repair complications that arise in summer?
Have your team make a list, update it as new concerns develop, and
on solving the top three problems each week.
NEC at the
The one factor that is constant in facilities is that
things will change. Keep this in mind when planning power distribution
panel layouts. A panelboard is limited to a maximum of 42 overcurrent
protection devices [408.35] (not including the mains). Allow room for
additional breakers in a given panel, and allow space for an additional
panel or two on a given wall.
Eye protection violations seem to be more common in the
summer. Partly, it's because people prefer the styling of their
sunglasses to that of their safety glasses. Visibility is also a
A lens scratch can create a glare effect that you don't get with
In addition, people are increasingly aware of eye cancer risk and
want the protection provided by UV-rated sunglasses. It's also true
many safety glasses aren't ergonomic and may feel uncomfortable.
Fortunately, there are many choices in safety glasses to solve these
problems. The days of clunky black frames with clear flat lenses are
gone. Safety glasses are available that look better than many
and offer superior UV protection and comfort.
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
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 four-mile permanent road course
that tests drivers with 14 challenging turns.
Enter by July 10, 2007. Visit the Generac Power Systems virtual
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
go to www.roadamerica.com.
Where do you turn when you need accurate information on
changes to the National Electrical Code? Acknowledged as the leaders in
providing information on the NEC, EC&M magazine and EC&M
Seminars have been the preferred sources of this information for more
than 60 years. Seven Code change conferences have been scheduled in the
fall of 2007. Host cities include: Atlanta, Boston, Dallas, Orlando,
Philadelphia, St. Louis, and Seattle.
As an approved provider with the National Council of Examiners for
Engineering and Surveying (NCEES), through its Registered Continuing
Education provider Program (RCEPP), professional engineers attending
of our 2008 Code change conferences will receive Professional
Development Hours (PDHs), a requirement for re-licensing in many
The conferences are also approved by every state that has a continuing
education requirement for contractors and electricians.
For additional information on the dates and locations of these
Electrical Troubleshooting Quiz
The nuisance tripping started in the spring -- when
ceiling temperatures began to rise. That's a good clue.
As temperature rises, ampacity drops. This why you have temperature
adjustment factors [310.10] and why voltage drop calculations factor in
temperature and conductor size.
A portion of the feeder probably runs through a ceiling cavity that
traps heat due to insufficient airflow or is just hot to begin with.
Sizing that portion of the feeder for the correct ampacity will solve
the voltage drop that is causing increased current demand.
Read through NEC Annex D, Example D3(a) to understand the solution
IR readings can quickly reveal if you have an "Example D3(a)
situation." If you don't, you've easily ruled out a likely cause. Your
next step would be to start standard motor troubleshooting (begin with
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