One has to consider how the UPSs are to be monitored
By Jorma Mannerkoski
Director of Product Marketing
July 30 - Aug 05 , 2001
The world has become totally electronic and digital.
Every device from the personal computer on your desk to the lift which
carries you up to the office each day depends on electric circuitry
which in turn relies on electrical power.
The power supply in the majority of countries in the
western world is fairly stable and power outages are fortunately a rare
occurrence. However, there are variations in power supply and quality
which can affect the operation of sensitive electronic equipment. It has
been estimated, for example, that some 60% of all computer problems can
be traced back to electrical supply problems. Within an office building
there are many things which occur to affect the power supply such as
lifts can momentarily drain the power load so that the current reaching
your equipment is lower than it should be. Moreover adverse weather
conditions such as storms, lightening and snow falls can also impact
upon the power supply.
Choosing the right power protection solution can be a
confusing business. There are a number of different types of UPS each
offering different levels of protection. Moreover, one has to consider
how the UPSs are to be monitored and controlled with the correct
software and what level of support and advice can be expected from your
supplier. The aim of this article is to provide a brief guide through
the power protection maze to enable you to select the best solution for
Power problems fall into nine basic categories as
Power failure is defined as a zero voltage condition
that lasts for more than two cycles. It may be caused by the tripping of
a circuit breaker, power distribution failure or utility power failure.
This condition can lead to data damage, data loss, file corruption and
Power sags involve voltages 80 to 85 percent below
normal for a short period of time. Possible causes are heavy equipment
being turned on, large electric motors being started, and the switching
of power mains (internal or utility). A power sag can have effects
similar to those of a power surge such as memory loss, data errors,
flickering lights and equipment shutoff.
A power surge takes place when the voltage is 110%
above normal. The most common cause is heavy electrical equipment being
turned off. Under this condition computer systems may experience memory
loss, data errors, flickering lights and equipment shutoff.
Undervoltage is a steady lower voltage state. An
example of undervoltage happens during peak electrical demands in the
summer, when utilities can't always meet the requirements and must lower
the voltage to limit maximum power. When this happens. computer systems
can experience data corruption, data loss and premature hardware
Overvoltage occurs when there is a sudden, rapid
voltage peak of up to 6,000 volts. These spikes are usually the result
of nearby lightning strikes, but there can be other causes as well. The
effects on vulnerable electronic systems can include loss of data and
burned circuit boards.
Switching transients take place when there is a rapid
voltage peak of up to 20,000 volts with a duration of 10 microseconds to
100 microseconds. They are commonly caused by arcing faults and static
discharge. In addition, major power system switching disturbances
initiated by the utilities to correct line problems may happen several
times a day. Effects can include memory loss, data error, data loss and
Electrical line noise is defined as Radio Frequency
Interference (RFI) and Electromagnetic Interference (EMI) and causes
undesirable effects in the circuits of computer systems. Sources of the
problem include electric motors, relays, motor control devices,
broadcast transmissions, microwave radiation, and distance electrical
storms. RFI, EMI and other frequency problems can cause data error, data
loss, storage loss, keyboard lockup and system lockup.
A frequency variation involves a change in frequency
from the normally stable utility frequency of 50 Hz or 60 Hz, depending
on the geographic location. This may be caused by erratic operation of
emergency generators or unstable frequency power sources. For sensitive
electronic equipment, the result can be data corruption, hard drive
crash, keyboard lockup and program failure.
Harmonics are distortions of the normal line waveform
and are generally transmitted into the line by nonlinear loads. Switch
mode power supplies, variable speed motors and drives, copiers and fax
machines are examples of non-liner loads. Harmonics can cause
communication errors, overheating and possible hardware damage.
So how can you protect electronic equipment from
these power problems. The answer is to use a UPS or Uninterruptible
Power System. At its most basic level the UPS will provide power to your
equipment in the event of a total power failure giving you time to save
data and shut down files. At a more sophisticated level the UPS actually
conditions and filters the electrical supply so that the power reaching
your equipment is 'pure'.
UPS units vary in size from small desk top systems
which can protect a single PC to very large UPS which can provide power
to a entire building. Almost every type of organisation has a power
protection requirement from companies with computer networks to
hospitals, airports, oil rigs. In fact, anywhere where continuous power
There are three types of UPS technology — off-line,
line-interactive, on-line. Off-line, sometimes called standby, is
designed to protect a single PC or workstation. It is normally the most
inexpensive UPS and only offers back up in the event of a total power
cut and does not incorporate any significant power conditioning
facility. It is called off-line because the UPS circuit only comes on
stream when there is a power outage. Such units use a mechanical switch
to transfer over to battery power when the voltage drops below a certain
level. This causes a delay of two to three milliseconds but generally
most computers are able to ride this out. An inverter inside the UPS
changes the DC power from the battery into AC which can be used by the
computer's power supply.
Line-interactive is a hybrid technology which offers
better protection than off-line but at a lower cost than full on-line.
It offers protection in the event of an outage but also line
conditioning which smoothes out peaks and troughs in the power supply.
For example, if the voltage drops below a predetermined level the UPS
will "boost" it back to normal. This type of design works by
operating the inverter in reverse during times when the input AC power
is normal to charge the battery. If the power fails a transfer switch is
triggered and the battery power flows to the UPS output to power the
equipment. Line-interactive UPS is best used where power conditioning is
not crucial to effective operation of the equipment.
On-line is widely recognised as the best type of UPS
where mission-critical applications are being protected. Although more
expensive than the other two technologies such systems ensure there is
never a break in the power supply. It does this by what is called a
double-conversion technique which continuously converts the AC mains to
DC runs the input via the battery and then through an inverter to
transform it into AC for the equipment load. The ideal situation is to
have electricity as a pure sinewave (see Fig 1). When raw power comes in
from the mains it will inevitably be corrupted and have irregularities.
What an on-line system does is clean and filter the power so that pure
sinewave electrical power is being output to the equipment. With online
systems switchover should be almost instantaneous and the effect of
spikes and surges in supply can be completely eliminated.
In terms of the nine types of power problem outlined
earlier the different types of UPS solution will protect your equipment
from the following problems:
For mission-critical applications on-line technology
is the best power protection solution available. However, it can be
further enhanced with the addition of UPS monitoring software. There are
various levels of sophistication of monitoring software. An IT manager
will want to know immediately of any potential power problems which
could affect the operation of his network. Power management software can
carry out a number of functions including:
• Detailed monitoring of the utility power supply
to detect spikes, brownouts, sags and other variations.
• Controlled shutdowns of critical equipment including selection of
specific load segments of the network which need to be kept running
longer. Users are normally told via a broadcast message on screen that
they have X minutes to shut down their applications and save data.
• Maintenance checks of UPS equipment including status of batteries
and readiness of the equipment to take over in the event of a power
• Recording a log of events so that a pattern of power problems can be
• Automatically alerting those responsible for the network by pager or
e-mail that there is a power problem.
Some of the more sophisticated power management
software suites also allow remote monitoring of the UPS from anywhere on
the network to analyse the performance of the UPS and carry out
preventative work. This is done either through serial port
communications, SNMP (Simple Network Management Protocol) software or
increasingly via the Web. This means the IT manager in London can
control and monitor UPSs on the network wherever they are in the world.
Whatever technology is employed the crucial fact is that the UPS should
be regarded as an integral part of the network. The majority of
businesses, no matter what size, rely on a computer network of some
sort. When a power failure occurs many businesses without adequate
protection are paralysed because not only do they cease to function but
valuable data may have been lost and cannot be recovered.
Installing a UPS on the network requires careful
thought and planning. Many network managers feel that it is enough to
protect the main server. However, they often neglect the routers,
bridges and hubs which carry data traffic. Likewise there may be certain
users processing data locally on their PC who require the added security
of an individual UPS.
Ideally UPS should be considered when an IT
installation is being planned or a building is first being constructed.
Power protection specialists can advise on what equipment is needed to
protect the load and any special considerations which need to be taken
into account. For example, networks running a Unix operating system need
to be shutdown in a specific order otherwise it could take IT staff days
to reboot the system and recover files once power is restored.
In organisations which need to guarantee continuity
in the event of prolonged power outages, such as hospitals or financial
institutions, the autonomy time of a UPS (typically 10 minutes to two
hours) is not enough. In such cases a back up generator is required.
However, even here a UPS is essential as there is always a time lag
before the generator reaches sufficient output to produce the required
current and a switchover to emergency power can be implemented.
Companies like Powerware have many years experience
of recommending and installing power protection solutions which are easy
to use and manage yet effective in ensuring business continuity and
Powerware is a part of Invensys Power Systems, a
global provider of premier power systems, integrating a full line of
uninterruptible power systems (UPS), telecom power systems, software,
turnkey integration and 24/7 maintenance services. Customer applications
include critical network and communications facilities requiring maximum
availability such as IT networks, data centres, fixed line and wireless
telephony and other critical applications. Powerware products are used
in networking, PC, financial, medical, industrial, voice and data
communications, military and aerospace applications — wherever
continuous power is essential to daily operations.
Invensys Power Systems, headquartered in Raleigh,
North Carolina, USA, is a US$2.6 billion leader in total power solutions
for the IT, telecom and industrial markets. The parent company Invensys
plc, headquartered in London, is a US$12 billion global leader in
intelligent automation, controls, power systems and drive systems.
Invensys Power Systems leads the world in power control and energy
storage products for IT, telecommunications and industrial applications.
Comprised of five product groups — Energy Systems, Energy Storage,
Power Conversion, Distributed Solutions and Teccor — Invensys Power
Systems provides customers with a single source for critical elements of
their power systems.
GemNet is the authorized distributor for Powerware
Corporation (formerly Exide Electronics), and offers a large range of
specialized power related products and services. The company has local
offices in Pakistan (GemNet Private Limited) and Jebel Ali, Dubai, U.A.E.
(GemNet Gulf). GemNet offers Powerware's entire range of products
including technical and after sales support.
GemNet's target markets are the emerging markets, and
it's activities are currently focused in South Asia, and the Middle
East. Since inception, it has been GemNet's goal to be a leading
supplier of it's power protection product range in the markets in which
it is present. To this end, GemNet has been focused on getting a
detailed understanding of these markets, building relationships, and
setting up the required infrastructure to support such an operation.
Service and Support:
• Qualified team of engineers provide quality
installation and after sales service.
• Service contracts that provide for loaner equipment if repair time
is to be more than 24 hours.
• Custom tailored service plans to fit the clients needs, including
plans that cover the client's existing UPS equipment.
• Services also include: Needs Analysis, Comparative Product Analysis,
Cost Justification, Consulting, End-User Training, Maintenance and After
Hardware Audits: Audit of existing UPS,
Recommendation of a Power Solution.
Quality Analysis: Analysis of the quality of power feeding your
systems, Improvements in the powertrain system.
Solutions Consulting: Inspection of your complete facility,
Identification of the solution, Correction of the Problem.