POWER SOLUTIONS: Power struggle

Power outages, whether because of a general power failure or a failure of the
backup systems, can be tolerated to a certain level in a number of industries,
however the same can not be said of telecom services. As far as power failures
go–telecom services must be a zero tolerance zone. While even a millisecond of
outage is unacceptable in the Internet Data Center (IDC) business, services like
cellular telephony, fixed phone services and Internet services too, would prefer
uninterrupted power supply. But how do you ensure a 24 hour and seven days a
week power availability in a country like India where power outages are not
uncommon? And where even if availability is not an issue, the power input leaves
much to be desired because of surges and wide voltage fluctuations. The solution
definitely lies in deploying an adequate and efficient power protection system
that has availability and reliability as its most important attributes.

Reliability and Efficiency Issues

What They
Actually Need: Cellular Operators and
Fixed Service Providers

Cellular services

A cellular network usually has a base station which
covers a number of Basic Telecom Shelters (BTS). BTS are pre-fabricated
systems and require air-conditioning running on AC or DC power. Telecom
equipment, generally run on DC power (-48 V DC level). BTS are usually
unmanned and their air-conditioning has to be of high reliability, as BTS
have to be up and running seven days a week and 24 hours a day, without
any break. Besides, cell operators need power backup to run their billing
systems, here the power solution could not be termed as a pure telecom
application but a major requirement. Erratic running of billing systems
might have repercussions for customer relationships.

This could be the typical power backup requirement of a cellular
operator in a city. For a bigger area like a cellular operation spread
over many cities, towns and villages, cell operators have a backbone.
There the biggest challenge is the service support capability of power
solutions vendors. Service outposts after every 3 Km is not possible, so
mobile service centers like Tata Liebert has done, have come up. TL has
such service backup for its customers Tata Teleservices and Birla
AT&T. "We have service franchisees after every 100 Km. Each
service franchisee has mobile support. We charge for this but that’s not
our core area of function", says Harshesh Malhotra of Tata Liebert.

For a base station, precision air-conditioning and AC power is required
all the time because cost of downtime–both tangible and intangible–could
be very high. Usually a 40 KVA UPS support is required. BTS can run
without precision air-conditioning at most for 30 minutes. So you need a
backup generator. Not everybody has backup generators though. Even if a
BTS stops for 30 minutes, cell phones in its area would stop working, an
operator would lose a lot in terms of airtime revenue and customers. Even
its market image would take a beating. For these two reasons, service
providers need reliable backup.

Fixed Service Providers

A typical main switch center of a fixed service provider requires lots
of precision air-conditioning and lots of power. Besides, there are
billing computers also, which need to be fed with power backup. Typically,
the basement of the MSC is full of batteries. MSC works on DC power with
backup time of eight hours and —48 volt DC, with a capacity of 6,000 to
10,000 ampere. A large number of small exchanges are connected to the MSC
through fiber optic links. These small exchanges too require DC power and
precision air-conditioning.

Some FSPs have fiber optic connectivity, say, between
Mumbai and Delhi. After every 70-80 Km, there would be fiber optic
repeater stations. These repeaters, too, require DC power and precision
air-conditioning. The power backup requirement of FSPs beyond the city
limits are similar to that of a cellular backbone.

For telecom service providers, getting any power backup solution or
uninterruptible power supply system would not be a difficult task–they are
abundantly available. But getting a system that fits into their requirement may
be an issue of concern. Besides that, the service providers also need to ensure
that the backup solution, they deploy, meets the most stringent of availability
and reliability conditions (remember the best systems could fail at times as
happened with Exodus Communications some time back). On 7 May 2001, Exodus, one
of the largest hosting services providers, suffered an hour-long power outage at
one of its data centers in Sunnyvale, California because its backup systems
failed to neutralize a power blackout leading to the interruption of services.
This affected service to Exodus customers such as Yahoo, whose web site and
messenger service went out of service for some time.

The incident germinates the need for not only a highly reliable backup system
but also something called ‘parallel redundant operation solutions’.
“For services like IDCs, just having a backup system is not enough. While
on one hand, no shutdowns are allowed at IDCs, on the other, they need regular
maintenance to avoid possible problems. And you just cannot carry out a
maintenance without a shutdown”, points out Harshesh Malhotra, divisional
manager, Tata Liebert Ltd, a leading supplier of power protection solutions to
the Indian service providers. The solution, Malhotra says, lies in deploying a
system that combines availability with maintainability allowing maintenance and
upgradation without shutdowns. ‘’Ad hoc systems like placing one UPS to back
up another won’t work in a data center like operation. What data centers can
do is to set up a parallel system that is intelligent enough to take over even
if there is a slightest failure”, adds Malhotra. While Malhotra said this
in the context of IDCs, the same could be true for fixed and mobile service
providers as also ISPs. An unreliable power system could leave customers
dissatisfied, mar the image of the company and ultimately even destroy all

However, reliability of a power system will not be a function of the system
alone–a lot would also depend on the kind of environment in which a power
system has been deployed. Ashwini Kumar, general manager and country head, Tyco
Electronics Systems India, lists bad input light condition leading to surges and
wide voltage fluctuations, as a major threat to the reliability of power
protection equipment. Given this, it becomes important for service providers to
give careful consideration to the immediate operating environment of the power
systems, before they grade the reliability of their system. Adds Ponam Monga, a
regional sales manager with Powerware International Ltd, “To counter
spikes, surges and fluctuations, you need a UPS with wide voltage
variations”. He says that it also means that the power system should have a
technology that takes care of these anomalies in the electricity input.

Energy being a major cost input in any service provider’s operations and
also a scarce commodity, efficiency of power conversion and power protection
system could be another priority area. There is a significant potential for
energy wastage in DC standby power supply, which powers the telecom or network
equipment and which is actually the major consumer of electricity at any telecom
site. This calls for an efficient power system. But, as Kumar puts it, there are
limits to efficiency. “They are governed by things like the topology of
assembly and deployment of the power system”, he adds. What Kumar says
could be an issue with many service providers in India, as not only, the AC-DC
conversion process is itself less than 100 percent efficient, but DC systems
often run at far less than full load. “The design of UPS is important as at
100 percent load, the maximum efficiency that can be achieved, is 94-95 percent.
The average efficiency levels however, do not go beyond 87-90 percent”,
says Monga.

Service provider networks are expandable–as the network grows so would
power requirements. IDCs often keep adding new servers and other equipment to
meet customer demands. All this means that a power protection system must be
scalable enough to cope with increasing loads. Contingency should be in-built in
an UPS. An ideal way of meeting a contingency would always have a UPS with a VA
rating of at least 1.5 times the total VA ratings of the telecom and network

How does the Indian Market Look?

Power solution providers got good business during 2000-2001 from ISPs and
data centers. Even though some players believe that ISPs continue to have
further business potential, business from the IDC segment has almost dried up as
most ISPs have withheld their business plans owing to a downturn in their

Company info on the web


“ISPs are a huge market for power solution providers. As most ISPs use
routers and servers, they all use AC power for which UPS and precision
air-conditioning is required. Besides, a number of ISPs have their own gateways
for which they need DC power”, observes Malhotra of Tata Liebert. His
company sold UPS solutions worth Rs 15 crore to the IDCs in 2000-01.

Some players expect phenomenal growth from cellular services. With cell
operators adding close to two lakh subscribers a month, their optimism may not
be off the mark. As subscribers grow so would the number of base stations, and
each new base station is a new business opportunity. Moreover, power solution
providers are looking at the new cell networks (fourth license) for more
business this year. Fixed service providers like Hughes Tele.com, HFCL, Shyam
Telecom and Tata Teleservices offered good business last year. Their expansion
plans could be another new business opportunity. Besides, the
upcoming fiber optic backbones are also expected to bring good business.

That the telecom services segment is getting lucerative can be concluded from
the fact that a number of UPS manufacturers like DB Power Electronics, APC, Next
Generation Business Power Systems. TVS Electronics ,
Numeric Power Systems etc are concentrating on the ISP, telephony and data
centre services for new businesses.

Ravi Shekhar Pandey

Building Power Systems for Telecom Networks

Building Power
Systems for Telecom Networks
The reliability of the power system including
batteries determines the reliability of the entire network, in a sense.

Practically, all telecom equipment work with DC power. The voltage
levels are generally 48V or in a few cases 24V. Since a battery bank is
floated across the DC bus, to provide battery backup, the working voltage
is in reality the float voltage of the battery. For VRLA batteries, the
float voltage is typically 2.25V/cell or 54V for a 48V system and 27V for
a 24V system. The positive in a 48V system is grounded whereas in a 24V
system, the negative is grounded. This difference is due to the practice
adopted by the pioneering telecom equipment manufacturers, which is
continuing today.

When it comes to data communication equipment, one has a choice of AC
or DC powered systems. AC powered systems are used because of the
availability of uninterrupted AC power source, but in application where
reliability is the paramount consideration, as in data centers, DC powered
equipment are preferred.

  • What should service providers look for in a power system?

The reliability of the power system including
batteries, in a sense, determines the reliability of the entire network.
Irrespective of the technology encompassed in the telecom equipment it
powers, if the power system is not engineered correctly or lacks a high
degree of reliability, the telecom network is doomed to failure. Hence, it
makes a great deal of sense for service providers to pay attention to the
quality of the power system they buy and also the service objective of the
organization they buy it from.

Both power plant and battery technology have made rapid
advances in the recent past. Switch Mode Power Systems (SMPS) have become
the norm, as have Valve Regulated Lead acid (VRLA) batteries. Both these
technologies make for a far more compact power plant design, modular
approach and low maintenance. Power plants are made up of rectifier
modules, controller, input ac distribution, load distribution and battery
connection modules. In addition to the important electrical parameters
like efficiency, power factor, input voltage window, EMI specifications,
etc, the best in class power plants would exhibit the following

  • High power density leading to compact footprint.
    Higher the footprint, greater is the money spent on floor space for
    equipment rooms or shelters.

  • Full front access with true hot plug-in connected
    rectifier modules. This reduces the risk of downtime and also
    increases the efficiency of the service personnel. Increasingly,
    pressures from customers and competition will force the service
    providers towards higher revenue per operating staff.

  • Buy as you grow–easy expandability of modules,
    shelves, distribution and frames in live condition, help to keep the
    costs commensurate with the stage of growth of the network.

  • Digitally controlled modules with digital user
    interface, which eliminate the need of manual adjustments by trial and

  • Integrated input and output distribution–allows
    for ease of maintenance and also keeps the footprint low.

  • Facility for remote monitoring and remote control.
    As networks increase in size, the requirement of centralized and
    remote monitoring surfaces, as it helps in lowering the cost of
    operation and maintenance. In India, operators have not yet started
    buying remote monitoring and control options, but it is important that
    the systems they buy should have this option so that when the need is
    felt, it is possible to upgrade the system.

  • What are the other site preparation issues?

The power line condition in our country, poses
challenges of its own because of surges and the wide voltage fluctuations.
In addition to the care taken in selecting the power system, service
providers would do well to protect the power system from power line and
lightning surges. While the power plant may have internal surge
protection, this is at best of equipment level. Surge protection also
needs to be provided at the building entry level. What is most important
here is the coordination between the equipment level surge protection
device and the entry-level protection.

HSeveral service providers use servo stabilizers to
provide regulated ac input to the air-conditioning equipment as well as
the power system. While the servo stabilizer is effective at providing a
tightly controlled voltage at its output, it is extremely lethargic in
doing so. Typically, the correction factor of these servo-stabilizers is
of the order of 25 V/sec. Hence, a voltage swing of 60V at the input would
take over a second to correct the output. In the meanwhile, a magnified
voltage swing is delivered at the output. The components are subjected to
recurring stresses and result in premature failure. So, while the servo
stabilizer may be good for the air conditioning equipment, it ends up
doing more harm than good to the power system.

Earthing is another area that merits attention. Most
service providers prefer to have several earth pits for different kinds of
earthing. The result is that differences in earth resistance of the pits,
results in huge potential differences between the various earths in the
condition of a fault or surge. This could result in fault currents taking
inadvertent paths to ground, as they try to seek the path of least
resistance. An effective antidote to this is to connect all the earth pits
together at the pit level. This will not only eliminate the possibility of
multiple earth potentials, but also help in lowering the overall earth

Appropriate selection of the generator too requires
care. Transient voltage drop and rise, and also the crest factor, are two
issues that are often missed while specifying generators. While buying
power systems, the limit for these parameters must be specified taking
into consideration its effect on the DC power system. Typically, the crest
factor should be as close to 1.414 as possible and transient voltage
dip/rise should be within ± 20 percent of the rated voltage.

Perennial Debate

Make or buy is one managerial decision that is often
revisited. Service providers always have this question before them: Should
they instal and manage the power and associated infrastructures like air
conditioning, generators shelters, earthing, fire and security systems
themselves or entrust it to the telecom equipment vendor or should they
entrust it to yet another specialist vendor?

Each service provider has his own approach that has
undergone a change as they mature with experience. As they rollout new
networks, they should limit their own resources to ensure low cost. Most
of the telecom equipment vendors are down financially and they may not
dole out vendor finance as liberally as in the past. The third route of a
specialist vendor may now look as an attractive option.

Ashwini Kumar,
General Manager and Country Head,
Tyco Electronics Systems India

Leave a Reply

Your email address will not be published. Required fields are marked *