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Electric Power Quality and Reliability and What to Do About It
by
David P. Cunningham, P.E.
Copyright 1999-2003
The subject of this article is electric power. Yes, the stuff that
comes through the wires and into your antiques mall so reliability
that we tend to forget about it. Our businesses couldn't exist
without it. Fortunately, it isn't that often that we are forced to
do so. Usually, interruptions are a result of isolated causes
which can be fixed within a reasonable period of time. While it is
a somewhat rude shock when you discover that you have no
electricity available, it usually isn't not too long until it is
there once again.
Typically, a rare unavailability of electric power isn't too much
concern to an antique mall or any other small business. What is a
concern is the generally poor quality of the electric power which
is available. The effect upon your antique mall can range from the
subtle to the serious. Some of your equipment and systems are much
more susceptible to damage than others. The number of poor power
quality incidents is expected to increase as power systems age and
demand increases.
There are four major types of electric power problems: brownouts
and sags; blackouts; noise; and surges and spikes. All are things you
would expect to see in a third world country but are surprisingly
common throughout the United States.
A brownout occurs when the utility lines have insufficient voltage
to provide the minimum voltage required by your machinery and
equipment. A brownout can be regional or local depending upon its cause.
That is, a brownout can occur in a multi state region,
state, county, city, or even in your antique mall. Brownouts
typically occur when the demand for electric power is greater than
the ability of the distribution system to deliver it. They can
occur due to heavy air conditioning demands,electric heating
requirements, sudden increases in industrial use or even, in your
mall, due to inadequate wiring. Power utilities will often stage
rotating blackouts to help resolve brownouts and prevent a
cascading shutdown of the entire power grid. Low voltages are
frequently following by spikes and surges.
Blackouts occur when the electric power is completely shut off.
This can happen in numerous ways, including power utility
shutoffs, accidental tripping of switches and breakers and
even outright sabotage. Lightning storms, ice storms and wind
felled trees are also major sources of blackouts. In any case, the
sudden and unanticipated disruption of electric power can have
really nasty consequences. When power is restored, there can be
severe surges and spikes which can create significant damage.
Line "noise" refers to electrical signals and fluctuations that
are carried along with the AC electrical current in power lines.
Line "noise" can result from arc discharges, high powered radio
transmitters, RF generators, and nearby indirect lightning
strikes. We have seen extraordinarily annoying and confusing
results from "noise" generated from these sources. Another
notorious source of line "noise" is laser printers which should be
electrically isolated from other signal sensitive equipment, such as
computers, by high quality surge suppressor/line conditioning equipment.
Electric power surges frequently occur immediately after brownout
conditions. They also reflect the effect of a sudden withdrawal of
heavy electrical loads. Surges do not occur as often as sags or
momentary brownouts, but have the capability to create substantial
damage in sensitive equipment such as computers. Direct lightning
strikes result in very large surges which can severely damage
sensitive equipment and literally destroy intervening surge
protectors.
OK, this all sounds pretty serious. What does it mean to me and my
antique mall ?? Some of your equipment is sensitive to the impact
of the four major types of electric power problems. Some of it is
not. Your lighting is not particularly vulnerable to these
problems. Any electronic equipment and particularly computer
equipment, or any equipment containing microprocessors, is very
vulnerable to all four major types of electric power problems.
Computers are designed to operate within a particular voltage
range. If the electric power voltage is too high, too low, has
spikes and surges, is turned off, or is noisy, there can be
adverse reactions. Memory can be damaged, hard disks corrupted and
destroyed, or data scrambled. Keyboards can freeze, funky results
can occur and motors can fail. Our experience is that there are
two types of computer users, those who have experienced electric
power problems and those who will.
Fine! I'm convinced. What do I do about it? Really high quality
surge suppressors, especially those capacities in excess of 400
joules, will help but they are only part of the answer. All computer
equipment and relatively low wattage equipment containing
microprocessors should be protected with devices called
uninterruptible power supplies (UPS). A well selected UPS system
works very well and provides years of protection. A UPS stores
electricity in a low voltage battery and filters the incoming line
current to provide a clean noise free electric power supply. If the
voltage is too high, it is reduced to an appropriate level. If it is too
low, it is increased to an appropriate level. When the power to the
UPS is interrupted, the backup battery and an inverter takes over
supplying electric power to the equipment connected to it and an
alarm sounds. Any other sensitive electrical equipment deserves a
high quality surge protector.
Software Gallery is located where our electric power is provided
by a member owned cooperative which sends our electric power to us
over a mountain pass. Our electric power availability is
reasonably good except from late spring through late summer when
electrical storm activity is at its peak. During that time anything can
happen as a result of lightning strikes. Throughout the year we see
many electric power related problems that manifest themselves as
sags, spikes and line noise. We protect ourselves in every practical
way we can because we have so much computer equipment and make
our living with it. You can and should protect yourself in a similar
manner because no part of the country is immune to these issues.
Here is what we did:
• Power company installed heavy duty meter base surge protector
• Installed surge protectors on all sensitive, non computer
equipment such as microwave oven, laser printer (which draws
too much power for a UPS)
• Installed lightning arrestors on all incoming phone lines
• Uninterruptable power supply installed on telephone controller
• Installed three high capacity UPS for our computers
• All other printers protected with surge protectors/line
conditioners
The result is we haven't had any equipment fail and we haven't
detected any problems which we could trace to electric power
sources. This is in spite of a significant number of occurances of
electric power quality problems. We recommend, unless your are
personally proficient, that you find a reliable, honest local vendor to
assess your needs. They can provide an appropriate solution for
your specific situation and be available to troubleshoot when
needed.
Now, not when you need service, is the time to establish this
essential relationship. Its really good, cheap insurance. While
you are at it establish the same kind of service relationship for
your computers and supporting hardware. To find the appropriate
person or firm ask around among your fellow small business owners.
Our experience is that one or two good choices will eventually
float to the top.
Our personal experience is with both APC and Tripplite UPS and
surge protection/line conditioning equipment. Both have worked
well for us although most of the equipment we currently use was
provided by APC.
Copyright Notice: Copyright 1999-2003 David P. Cunningham, P.E.
All rights reserved in all media.
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