You Be Doing Electrical Preventive Maintenance? You Bet!
By Matthew T. Glennon, P.E.
AVP, Electrical Loss Control
Preventive maintenance is not a new concept. People have been doing precautionary work
on motors, engines, and other mechanical systems for decades. But when I suggest doing
preventive maintenance on electrical distribution systems, I am often met with incredulous
looks and the repeated question, "What for? Nothing moves what could go
Preventing Electrical Failure
A great deal can go wrong if an electrical distribution system is not adequately
maintained. As electrical loads cycle between high and low demand, thermal expansion and
contraction cause connections to loosen. Electrical panels that are never cleaned
accumulate dust and dirt that deposit on these connections. The loose and dirty
connections provide a high resistance path that are directly responsible for more than 30
percent of electrical failures. Another 17 percent of electrical failures are attributed
to live electrical components being exposed to moisture.
With a comprehensive electrical preventive maintenance program, both of these
conditions which account for almost half of all electrical losses can be
corrected. (See Table 1 below).
|Loose connections / parts
|Line disturbance (other than
|Defective / inadequate insulation
|Foreign objects / short
|Overloading / inadequate capacity
|Accumulation of dust, dirt and
|All other causes
TABLE 1: Top Causes of Electrical Distribution System
Failures Based on Hartford Steam Boiler Claims Data
According to the Institute of Electrical and Electronics Engineers (IEEE), the failure
rate of electrical components is three times higher for systems where preventive
maintenance is not performed. This tells us that electrical failures, for the most part,
can be avoided. But what does an electrical preventive maintenance (EPM) program entail?
There are five points to consider:
It is important that the people who perform your EPM program be properly trained to
work on the specific equipment being maintained or tested. This includes understanding the
functionality of the equipment, both electrically and mechanically, and having a thorough
knowledge of electrical safety practices and procedures. Special training is required for
high-voltage equipment and protective relay devices, so this should not be overlooked.
- Regularly Scheduled Inspection, Testing, and Servicing of Equipment
An EPM program should be performed on a regular basis. The period between work
depends on the environmental conditions, the importance of the equipment and its loading
and use. However, EPM should be performed at least once every three years and more
often for critical components.
The first step in an EPM program is a complete thermographic inspection of all
electrical equipment prior to the scheduled outage. This survey is a non-invasive method
of identifying high temperature excursions which indicate potential problem areas due to
loose or dirty connections, load imbalances, or improper installation of equipment. This
initial step helps in determining the resources you will need during your scheduled outage
to perform EPM. Ideally, a thermographic inspection should be done during peak-load
conditions by a certified, experienced thermographer.
Plans should be made to have all circuit breakers and disconnect switches repeatedly
opened and closed during the shut-down period to ensure proper operation. In addition,
protective relays and circuit breaker trip devices need to be tested and calibrated on a
regular basis. Different test sets are often required for the various equipment depending
on the manufacturer and the age of the devices. Therefore, ensure that the people doing
this work have the proper equipment, experience, and training to perform these functions.
Oil-filled transformers, circuit breakers and disconnect switches should have samples
of the insulating oil screen-tested as a means of identifying potential problems with
those components. Transformer oil should also undergo dissolved gas analysis to identify
specific adverse conditions present inside the unit. Equipment insulated with SF6
gas should be inspected and leak-tested to ensure the integrity of the gas system.
- Sound Judgment in Evaluating Results
It is imperative that the person reviewing the test reports of the thermographic
inspection or the equipment tests have a thorough understanding of the specific subject
matter. This is important so that informed, responsible decisions can be made on how best
to correct the conditions found. For example, the results of transformer oil testing may
indicate the need to take action such as reclaiming or replacing the oil. The decision as
to which alternative to take needs to be made by an informed individual.
- Perform the Necessary Work
This seems like an obvious point, but often it is not done. It does little good to
have testing and inspection done to identify problem areas if you have no intention of
fixing the problems. Preliminary testing and inspection help to focus your resources on
the critical tasks, but ultimately you need to have scheduled outage to perform the
The fundamental concept of EPM is simple: Keep it clean, dry, and tight.
Be sure to inspect all equipment for evidence of deterioration, exercise mechanisms to
ensure proper operation, and clean and tighten all electrical connections and equipment
- Concise and Complete Record-Keeping
This is the most overlooked aspect of EPM. However, a clear record-keeping system
will help keep the EPM program cost-effective by ensuring that all the work is being done
when it is supposed to be. In addition, tracking of test results over time can often
identify a potential failure that can be corrected before it happens.
EPM Is Cost-Effective
Electrical preventive maintenance is cost-effective in several different ways. First,
it is cheaper to make repairs to equipment before it fails. When electrical equipment
fails, particularly protective devices like circuit breakers or relays, there is usually
subsequent damage to other components in the system. Often the equipment cannot be
repaired and must be completely replaced. New equipment does not always replace the failed
component in-kind and may require other modifications to make the system whole.
Failed equipment results in unplanned outages that can be very costly when replacement
equipment cannot be easily found. Instead of having a planned system outage for EPM at the
most convenient time for your operation, equipment failures are always at inopportune
times. Emergency repairs are very costly due to the urgency of the situation where
temporary work is required before a permanent repair can be done.
In addition, an effective EPM program will improve equipment efficiency and reduce
utility bills. A loose or dirty connection has increased resistance which results in
higher power losses. By simply tightening and cleaning electrical connections, you can
lower these energy costs. When considered over a period of time, these energy losses can
add up to quite a significant amount of money.
If you have been taking your electrical distribution system for granted, its
probably time for you to implement an EPM program. But dont wait until after the
first electrical failure happens you may not have a system then.
If you would like more information on implementing an EPM program, call Hartford Steam
Boilers Fax-On-Demand information hot line at 1-800-716-7874. Follow the directions
to access the HSB Electrical Preventive Maintenance standard (Document #420).
Matthew Glennon is a registered Professional Engineer in New Jersey with over 12 years
of experience in electric power engineering and construction. He is a magna cum laude
graduate of Manhattan College where he earned a Bachelor of Engineering degree in
electrical engineering. In addition, he holds a Master of Engineering degree in electric
power engineering from Rensselaer Polytechnic Institute (RPI) in Troy, N.Y. and an MBA in
Finance from Rutgers University. He is a member of IEEE, NFPA, and the National Society of
Professional Engineers (NSPE), as well as a Correspondent to the National Academy of
Forensic Engineers (NAFE).