We are increasingly dependent on electrical and
electronic equipment in our everyday lives. The proper functioning of
this equipment depends on a good supply of electricity. Unfortunately,
many people wrongly assume that the only time to worry about the
effect of power on computer and other electronic equipment is when
there is a total power cut. Of course this kind of protection is
essential and one must never underestimate the effect total power cuts
can have on a business and on our lives. However, nowadays power cuts
in the western world are very infrequent and what has the greatest
impact on businesses are the fluctuations and disturbances in mains
power, which are unseen. Companies need to rid themselves of the risk
of the chance that a power disturbance or blackout could interrupt
their business and yet figures still show that many organisations fail
to protect their business with the correct UPS back up solution.
What a UPS does is not only provide back up power
in the event of complete power failure but also takes the input
electricity, cleans it up and outputs what is called 'pure sinewave'.
For the most part this solution works well for those seeking reliable
power protection and is highly recommended for industries running any
kind of mission critical systems.
PARALLEL UPS SYSTEM: WHY DO WE NEED IT?
How critical to an organisation's survival that
failure due to power problems cannot be tolerated. Organisations such
as banks, Internet Service Providers, telecommunication companies and
anyone surviving in the thriving e-commerce industry cannot afford to
have their business to go down at anytime. If it does it can lead to
loss of profits and loss of customers perhaps the most damaging effect
For peace of mind they need to know that their
chosen back up solution can never fail. They need to know that if
anything goes wrong with one UPS then another takes over at once.
Organisations need redundancy. And the solution? To run a parallel UPS
WHAT IS A PARALLEL UPS SYSTEM?
Put simply a parallel UPS system means the linking
together of two or more UPS units in parallel so that in the unlikely
event one fails the other can automatically take up the load. When
buying a UPS in a situation that requires a redundant solution there
are two types to investigate. You can install a parallel redundant
system or an isolated redundant system.
Redundancy in an isolated (or standby) system
configuration depends completely on the on the successful transfer of
the load by the on-line (primary) UPS to its bypass and the graceful
acceptance of that load by the stand-by (secondary) UPS.
Theoretically, it could be a 100% load step, which is a serious
To successfully obtain a transfer it requires the
following four step procedure:
The primary unit must recognize that a transfer is
The primary unit must ensure that the transfer is
- Bypass source is available
- Bypass source is in sync
* Voltage is within accepted limits
* Frequency is within accepted limits
The actual transfer action has to take place:
- Static switch must turn on
- The primary unit's inverter must disengage
- If there is a wrap-around breaker, it must close successfully.
The secondary UPS must accept the load step and
maintain a voltage variation within limits that are acceptable to the
critical load. Actually, since the secondary unit is not supporting
any load, one cannot be certain it is operational and will accept the
transfer at all until it is attempted. What a time to find out there
is a problem!
These four steps are in series. If any one of the
four steps fail, the transfer fails and the load will be dumped.
Remember, this is an emergency situation. There is no room for a slip.
If the reason for transfer is a faulted bus, the transfer must take
place twice before the load bus is attached to a power source capable
of clearing the fault (through the bypass of the secondary UPS). If
the reason for transfer is a failed primary UPS, the module cannot be
isolated for repair because the secondary UPS is feeding the load
through the bypass of the primary UPS. If there is a maintenance
bypass, the load can, of course, be transferred to it but if
unprotected power is acceptable, why spend the money for redundancy?
A parallel redundant systems, and the systems which
Powerware Power Systems strongly supports, has a number of advantages
that increase the availability of protected power to the load and
gives the customer fewer things to worry about where support of the
critical load is concerned.
With a parallel redundant system the following six
points outline the advantages:
1. The two
most critical elements in the isolated redundant scheme are
eliminated: Execution and Acceptance of the load transfer
Qualification stage is minimised because the normal operation of a
parallel redundant configuration is for the modules to share the load,
which means they must be in sync for both voltage and frequency.
3. If a
module is taken off line for maintenance, the remaining module at
worst will suffer a 50% load step, which substantially reduces the
risk of voltage variations outside the limits of the critical load
(its safe to say the risk is eliminated). You can be sure the on-line
module is operational and will accept the transfer because it is
already sharing the load.
4. The unit
that is off-line is isolated so maintenance can be performed.
power to the load is maintained by the on-line unit and automatic
transfer to bypass is still an option if necessary.
6. If a
faulted bus occurs, only one transfer is required to reach a power
source (the feeder bus) capable of clearing the fault.
To make a parallel system work you will always rely
on the transfer to bypass happening successfully with the secondary
module always accepting the load gracefully. But if it doesn't you are
back to where you started. A parallel redundant system eliminates the
possibility of this happening.
HOW TO PARALLEL? REDUNDANCY AND CAPACITY?
When installing a parallel redundant system, in
other words to get two or more units to run parallel and share the
load the units must be locked to exactly the same phase. You must then
synchronise the modules, connect them together through the collective
buses of the system thus allowing them to share the load between them.
The system is now ready to achieve redundacncy. Load the system with
power equal to the total demand of all the loads minus the demand of a
least one module. This ensures that failure of any one UPS wil not
corrupt the power, will allow one to isolate the damaged module whilst
the functioning UPS modules seamlessly take over without the load ever
noticing the transfer.
Doesn't all this sound great. However, we still
have one problem. Traditionally a parallel redundancy configuration is
achieved by having a common paralleling logic circuitry in the system.
This logic circuitry gives out individual commands to all the
different units. Unfortunately this can lead to a single point of
failure for the whole system because if the logic circuitry system
fails the whole UPS system will be in trouble. And so what you are
left with is a very complicated configuration that at the end of the
day and whilst this gives you a 98% solid power protection it does not
eliminate the risk of a single point of failure keeping you from
receiving 100% peace of mind.
That is exactly why the Powerware Hot Sync
technology was developed. An industry leading paralleling technology
in its own right, the patented Hot Sync enables you to set up a
parallel redundant system giving you 100% conditioned power at all
times. Its unique digital design eliminates the system-level single
point-of-failure inherent in traditional parallel UPS modules and
exponentially increases the reliability of the overall system.
HOW DOES IT WORK?
Hot Sync allows two or more UPS units to cover the
same load in parallel and redundant configuration, by working in
complete synchronisation without being wired together. No common logic
is needed in this patented design. It provides automatic load sharing
and module level redundancy with nothing other than the power
connecting the modules.
Hot Sync does not require any centralised commands
to function. All units are able to function on their own and make
decisions simply by looking at their own output, the UPS modules do
not need any communication between them to load share or to remove a
faulty module from the load bus. If one module fails the other or
others continue supplying the load and the failed UPS module is
immediately isolated from the critical bus while the other UPS takes
over the full load. This means there is no single point of failure, no
crashes and most importantly no downtime. In short the critical load
remains 100% UPS protected.
It manages to share the load by making minute
changes to the output phase angle 1000 times per second. If one of the
UPS modules detects that it is getting ahead of the other it will push
its extra load back to the other module until finally the load is
evenly shared. If the load changes all UPSs will see it
instantaneously and in the same way. That's why an even load share is
maintained even if the load varies.
Phenomenal growth of super-servers,
telecommunication switching centres, and other large, centralised
computing operations, has created a market need for extremely large
power solutions. This need typically exceeds the capacity of a single
UPS module. To address this shortfall, Hot Sync enables UPS modules to
be tied together to create a UPS solution that protects the entire
system, and allows additional modules to be added as capacity needs
grow. It allows customers to expand effortlessly from a single-module
system to a two-module redundant system and, potentially, to an
eight-module system. The scalability of this system provides customers
the flexibility to add the power protection as their application
grows. And it also makes redundancy for these very large systems a
reality, increasing system availability and overall reliability.
A globally recognized industry leader for more than
40 years, Powerware designs and manufactures a full line of
Uninterruptible Power Systems (UPS), DC power systems, power
management software/connectivity products. Powerware products are
typically used in networking, PC, financial, medical, industrial,
voice and data communications, military and aerospace applications -
wherever continuous power is essential to daily operations. Powerware
is headquartered in Raleigh, NC, and is part of Eaton Corporation.
The company offers a full range of UPSs ranging in
size from 300 volt-amperes (VA) for personal computers to greater than
1,000 kilovolt-amperes (kVA) for mission-critical applications
including data centers, Internet service providers, and server farms.
Network-connectivity devices, extended battery cabinets, power
distribution modules and other power-related devices further enhance
Powerware UPS hardware offerings. The Powerware product portfolio also
includes a full line of DC Power Systems ranging in size from mini
systems for roadside cabinets or customer premises equipment to large
systems for major switching installations. Power management software
and IT infrastructure management software complete the company's
product line. Basic power management software provides
industry-standard monitoring, alarm and shutdown capabilities. More
advanced software packages offer expansive data archiving, trending
and regression analysis tools with predictive capabilities. With
innovative software that can predict the type and timing of possible
future events, Powerware is leading an industry shift from reactive
power protection to proactive power management.
Eaton Corporation is a diversified industrial
manufacturer with 2003 sales of $8.1 billion. Eaton is a global leader
in fluid power systems and services for industrial, mobile and
aircraft equipment; electrical systems and components for power
quality, distribution and control; automotive engine air management
systems and powertrain controls for fuel economy; and intelligent
drivetrain systems for fuel economy and safety in trucks. Today, the
company classifies its business into four distinct segments, which
are, by size: Fluid Power, Electrical, Automotive and Truck. Eaton has
51,000 employees, 207 manufacturing sites and sells products to
customers in more than 100 countries.
GemNet is a power solutions company, providing
quality power products and services. Our philosophy has always been to
combine its local expertise and commitment with quality products,
technical competence and the support of its principal. Since
inception, it has been our goal to build deep and long lasting
relationships with our customers and alliance partners by providing
them top-quality power products and services. This has been the single
most important success factor for GemNet, earning it the reputation as
one of the leading and most professional power products and solutions
companies. Today, GemNet enjoys an established track record of
excellence with its customers in Pakistan and the United Arab
Emirates. GemNet is the authorized distributor for Eaton Powerware's
range of AC and DC Uninterruptible Power Systems, and offers a large
range of specialized power related products and services. The company
has local offices in Karachi, Lahore and Islamabad (GemNet Pvt.
Limited) and Dubai, United Arab Emirates (GemNet Gulf).
AREAS OF EXPERTISE:
* Service plans to fit the clients needs, including
plans that cover the client's existing Power Systems and UPSs.
* Services also include: Needs Analysis,
Comparative Product Analysis, Cost Justification, End-User Training,
Maintenance, After Sales Support, Data/telecom center electrical
contracting and site preparation
* Power Consulting & Critical Environment Site
Audit (CESA): Audit of existing UPS and recommendation of a power
solution. Analysis of the quality of power feeding the systems.
Facility/Site inspection, identification and correction of the